retrofit passive house guidlines

Sustainable Energy Ireland (SEI)

Sustainable Energy Ireland was established as Ireland’s national energy agency under the Sustainable Energy Act 2002. SEI’smission is to promote and assist the development of sustainable energy. This encompasses environmentally and economi-cally sustainable production, supply and use of energy, in support of Government policy, across all sectors of the economyincluding public bodies, the business sector, local communities and individual consumers. Its remit relates mainly to improv-ing energy efficiency, advancing the development and competitive deployment of renewable sources of energy andcombined heat and power, and reducing the environmental impact of energy production and use, particularly in respect ofgreenhouse gas emissions.

SEI is charged with implementing significant aspects of government policy on sustainable energy and the climate change

abatement, including:

• Assisting deployment of superior energy technologies in each sector as required;

• Raising awareness and providing information, advice and publicity on best practice;

• Stimulating research, development and demonstration;

• Stimulating preparation of necessary standards and codes;

• Publishing statistics and projections on sustainable energy and achievement of targets.

It is funded by the Government through the National Development Plan with programmes part financed by the European

Union.

© Sustainable Energy Ireland, 2009. All rights reserved.

No part of this material may be reproduced, in whole or in part, in any form or by any means, without permission. Thematerial contained in this publication is presented in good faith, but its application must be considered in the light of

individual projects. Sustainable Energy Ireland can not be held responsible for any effect, loss or expense resulting fromthe use of material presented in this publication.

Prepared by SEI Renewable Energy Information Office and MosArt Architecture.Cover images courtesy of Cooney Architects.

i

FOREWORD (i)

SECTION ONE:The ‘Passive House’

Passive House and the Passivhaus Standard 1Definition of the Passivhaus Standard 1Technical definition of the Passivhaus Standard for Ireland 2Applications of the Passivhaus Standard in the EU and Ireland 3Evolution of retrofitting dwellings to the PassivhausStandard in Europe 3Application of the Passivhaus Standard in Ireland 3Dwelling Energy Assessment Procedure 3Building Energy Rating 4PHPP and DEAP 4

SECTION TWO:Review of Building Stock in Ireland

Energy efficiency and dwelling age 7Fuel poverty source: Healy and Clinch (2002) 8

SECTION THREE:Principles of Passive Houses

Passivhaus Planning Package 2007 - An essential design tool 11Passive house certification 12Building envelope insulation 12Optimising passive solar gain 12Thermal bridging 13Structural airtightness and draught proofing 13Internal heat gains 13Passive House building systems 13What happens in the event of a power failure? 13Back-up heating system 14Domestic hot water production 14

SECTION FOUR:Typical Phases of Retrofitting

Survey 17Initial PHPP calculation 17Changes in layout/design 18Upgrade thermal envelope 18Insulation 18Internal insulation 19External insulation 20Insulating the roof space 20Wall cavity insulation 20Windows and doors 21Airtightness 21Thermal bridges 22Upgrade ventilation and heating system 22Ventilation system 22Recommended ventilation rate 22Mechanical heat recovery ventilation (MHRV) system 23Insulation and positioning of duct work and vents 23Heating system 23Water to air heat exchanger 23Compact unit with electrical heat pump 23Wood pellet / Wood pellet stove / Wood log boiler 24Integrated controls for heating in a Passive House 24Individual room temperature control 24Site supervision 24

SECTION FIVE:Upgrading of Typical Construction Types

Walls 29Random rubble and hollow block wall 29Cavity walls 29Timber frame 35Floor slab 37Roof 42Cold Roof / insulated at ceiling level 42Sloped roof 43

SECTION SIX:Case Study Retrofit Building - Theoretical

Dwelling description 49Current heating and DHW system 50Use of PHPP and DEAP to prepare retrofitting strategy 52Preparing a retrofitting strategy 52Measures in detail 53Thermal insulation 53Windows and doors 53Thermal bridges 53Airtightness 53Ventilation heating system 54Cost of retrofitting 54Passive house verification 57

SECTION SEVEN:Case Study of Completed Retrofitted Project

Case study of completed retrofitted project 61

Table of Contents

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ForewordThe Sustainable Energy Authority of Ireland, SEI, operatesprogrammes and activities to advance the Government’s ambition forIreland to become a world leader in sustainable energy as part of ourtransition to a low carbon economy. Thus, we seek to accelerate thedevelopment and deployment of cost effective low carbontechnologies. Following the implementation of the EU EnergyPerformance of Buildings Directive, recent substantial improvementsin Building Regulations energy standards and requirements for theuse of renewable energy systems, we have seen substantialimprovement in the energy performance required of new buildings.

For several reasons, attention mustfocus now on our existing buildings.The recent extension of the BuildingEnergy Rating to all buildings beingsold or rented coupled with theintroduction of a national residentialenergy efficiency programme, and theknowledge that cost-effectiveopportunities to reduce greenhousegas emissions are most readily foundin buildings are all combining toprovide an extraordinary impetus tohome energy saving.

The PassivHaus standard isrecognized in Europe as a progressiveand advanced benchmark forbuilding energy performance. In 2008SEI published ‘Guidelines for theDesign and Construction of PassiveHouse Dwellings in Ireland‘ whichhave been very well received, withsome 5,000 copies now in circulation.These companion guidelines‘Retrofitted Passive Homes -Guidelines for Upgrading ExistingDwellings in Ireland to the PassivHausStandard’ extend the availablesupport and information for theupgrading of existing dwellings toachieve the ambitious PassivHausStandard.

There has been a noticeable increasein the number of successfully

retrofitted PassivHaus projects incontinental Europe in the past three tofive years and it is expected that thistrend will carry over to Ireland.

These guidelines provide sound andpractical advice on how theretrofitting of older buildings couldpotentially achieve a standard whichwill greatly increase comfort, cutenergy costs dramatically, and offer ahome which is far more “futureproofed”. There are over 1.5 millionhomes in Ireland that could eachbenefit from implementing evensome of the measures contained inthis document.

Professor J Owen LewisCEO, Sustainable Energy Ireland

SECTION ONE

The ‘Passive House’

The ‘Passive House’

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1.1 Passive House and thePassivhaus Standard

A passive house1 is an energy-efficientbuilding with all year-round comfort andgood indoor environmental conditionswithout the use of significant active spaceheating or cooling systems. The spaceheat requirement is reduced by means ofpassive measures to the point at whichthere is no longer any need for a conven-tional space heating system; the airsupply system essentially suffices todistribute the remaining space heatrequirement. A passive house provides avery high level of thermal comfort andwhole-house even temperature. Theconcept is based on minimising heatlosses and maximising heat gains, thusenabling the use of simple buildingservices.

The Passivhaus Standard is a construc-tion standard developed by thePassivhaus Institut in Germany(http://www.passiv.de). The standard canbe met using a variety of design strate-gies, construction methods andtechnologies and is applicable to anybuilding type.

This publication outlines the require-ments in applying that standard to retro-fitting dwellings in Ireland and in allcases when referring to a passive houseis describing a house upgraded to therequirements of the PassivhausStandard. These guidelines should beread in conjunction with the Guidelinesfor the Design and Construction ofPassive House Dwellings in Irelandpublished by SEI in July 2008(www.sei.ie/phguidelines).

1.1.1 Definition of the PassivhausStandard

The Passivhaus Standard is a specificconstruction standard for buildingswhich results in good comfort condi-tions during winter and summer,without traditional space heatingsystems and without active cooling.

The primary focus in building to thePassivhaus Standard is directed towardscreating a thermally efficient envelopewhich makes the optimum use of freeheat gains in order to minimise spaceheating requirement. Structural air-tightness (reduction of air infiltration)and minimal thermal bridging are essen-tial. A whole-house mechanical heatrecovery ventilation system (MHRV) isused to supply controlled amounts offresh air to the house. The incomingfresh air is pre-heated, via a heatexchanger, by the outgoing warm staleair. If additional heat is required, a smallefficient back-up system (using a renew-able energy source, for example) can beused to boost the temperature of thefresh air supplied to the house.Renewable energy sources are used asmuch as possible to meet the resultingenergy demand (PEP, 2006), includingthat required for the provision of domes-tic hot water (DHW).

The energy requirement of a houseretrofitted to the Passivhaus Standard is:

■ Annual space heating requirementof 15 kWh/(m2a) treated floor area;

■ The upper limit for total primaryenergy demand for space and waterheating, ventilation, electricity forfans and pumps, household appli-ances, and lighting not exceeding120 kWh/(m2a), regardless of energysource; and

MosArt Architecture

MosArt Architecture

MosArt Architecture

■ Additionally, the air-leakage testresults must not exceed 0.6 airchanges per hour (ac/hr) using 50Pascal over-pressurisation andunder-pressurisation testing.

In order to maintain high comfort levelsin any building, heat losses must bereplaced by heat gains. Heat lossesoccur through the building fabric dueto transmission through poorlyinsulated walls, floor, ceiling andglazing as well as from uncontrolledcold air infiltration through leakyconstruction and poorly fitted windowsand doors. In a passive house, the heatlosses are reduced dramatically(through better insulation and airtightdetailing) so that internal gains andpassive solar gain contribute arelatively high proportion of the totalneed. As a result of this, a smaller spaceheating system is therefore requiredcompared to that needed in a conven-tional poorly performing dwelling.

A semi-detached, two storey Irish housebuilt in the mid 1970’s before the intro-duction of thermal insulation standardswould be expected to have a spaceheating requirement of over 200kWh/(m2a) and to have a total primaryenergy demand of over 400 kWh/(m2a)for all applications. The equivalenthouse built to the requirements of TGDPart L 2007 would be liable to use 40-50kWh/(m2a) delivered (useful) energy forspace heating and 90-95 kWh/(m2a)primary energy. The PassivhausStandard requirement for space heatingis 15 kWh/(m2a). When compared to ahouse built in the mid-1970’s, with littleor no insulation and poor performingglazing, a house retrofitted to thePassivhaus Standard thus represents asaving of more than 90% on the spaceheating demand.

One of the key benefits of a passivehouse is that it becomes affordable toprovide thermal comfort conditionsaround the clock at much reducedenergy consumption. This is a verypositive aspect of passive houses that isoften forgotten. The energy consump-tion for heating an existing housearound the clock would be significantlyhigher and much less affordable.

1.1.2 Technical Definition of thePassivhaus Standard forIreland

In Table 1 a range of U-values is specifiedin order to meet the PassivhausStandard of annual space heatingrequirement of 15 kWh/(m2a) for theIrish climate. Specifying U-values isdependent upon many variables and theeffect on energy performance can onlybe verified through testing the perform-ance of the dwelling design in thePassive House Planning Package (PHPP)software. In a typical retrofit situation,Passivhaus principles such as orienta-tion, position of glazing, thermal bridg-ing and compactness will generally nothave been considered in the originaldesign. For that reason, the required U-

values for retrofit projects will often befar lower than for buildings that were,from the very outset, designed in strictaccordance with the PassivhausStandard. The U-values included inTable 1 have been tested for the casestudy house presented later in Section 6.This case study house is a terraced twostorey house of compact form and withoptimal (rear) façade orientation ofdirectly south. A detached bungalowhouse of sprawling form would likelyrequire even lower (better performance)U-values than those specified in thetable above in order to meet thePassivhaus Standard. Readers familiarwith the SEI (new-build) Passive HomesGuidelines will recognise that the U-values listed in the table above areconsiderably lower (better performance)

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Measure/Solution Retrofit Passivhaus Standard for the Case StudySemi-Detached House in the Irish Climate

1. Super InsulationInsulation Walls U ≤ 0.10 W/(m2K)Insulation Roof U ≤ 0.09 W/(m2K)Insulation Floor U ≤ 0.10 W/(m2K)Window Frames, Doors U ≤ 0.8 W/(m2K)Window Glazing U ≤ 0.6 W/(m2K)Thermal Bridges Thermal bridges with a linear heat coefficient Ψ ≥

0.01 W/mK will be very common in most retrofitprojects and will require calculating

Structural Airtightness n50 ≤ 0.6 ac/hr @ 50 Pascal

2. Heat Recovery/ Air QualityVentilation counter flow Heat recovery efficiency ≥ 85%air to air heat exchangerMinimal Space Heating Post heating ventilation air/ Low temperature

heatingEfficient small capacity heating system Biomass compact unit, gas etc.Air quality through ventilation rate Min 0.37 ac/hr or 30m3 /person/hrVentilation Supply Ducts Insulated Where applicableDHW Pipes Insulated Where applicable

3. Passive Solar GainWindow Glazing Solar energy transmittance g ≥ 50%Solar Orientation Minimal glazing to north where possibleThermal Mass within Envelope Recommended

4. Electric EfficiencyEnergy Labelled Household Appliances A-Rated appliancesHot water connection to Recommendedwashing machines/dishwashersCompact Fluorescent or LED Lighting RecommendedRegular maintenance ventilation filters RecommendedEnergy Efficient Fans/ Motors Recommended

5. On-site RenewablesDHW Solar Heating Area to be dictated by house size and occupancyBiomass system RecommendedPhotovoltaics Application in a case by case basisWind Turbine Application in a case by case basisOther including geothermal Application in a case by case basis

Table 1. Technical Definition of the Passivhaus Standard for the Case Study Project Presented in Section 6Source: MosArt Architecture

than those specified for the prototypehouse in those guidelines. The reason forthis is that there are often numerousthermal bridges that have to becompensated for in retrofitting an olderdwelling compared to new-build. Thecase study dwelling is also partly shadedwhich reduces passive solar gain, requir-ing a better insulated envelope.

1.2 Applications of thePassivhaus Standard inthe EU and Ireland

1.2.1 Evolution of RetrofittingDwellings to the PassivhausStandard in Europe

The Passivhaus Institut(http://www.passiv.de) was founded inDarmstadt, Germany in 1996 by Dr.Wolfgang Feist as an independentresearch institute. Since then, it has beenat the forefront of the Passive Housemovement in Germany and has beeninstrumental in disseminating thestandard throughout Europe andoverseas. The Institute developed the"Passivhaus Projektierungs Paket" (PHPP- Passive House Planning Package), anExcel worksheet used to determine theenergy supply / demand balance forpassive buildings (available in Irelandfrom SEI Renewable Energy InformationOffice (www.sei.ie/resourcecentre).

Since completion of the first certifiednew-build passive houses in Darmstadtin 1991, there has been an emergingtrend in recent years of retrofitting build-ings to the Passivhaus Standard.

1.2.2 Application of PassivhausStandard in Ireland

The Kyoto Protocol came into force in2005 and the proposed targets of reduc-ing greenhouse gas (principally CO2)emissions by 8% compared to 1990levels by the period 2008-2012 becamelegally binding for EU Member States(UNFCCC, 1997). Within the EU burdensharing agreement in this regard,Ireland's target limit of 13% above 1990levels had been reached in 1997, and it islikely that the limit will be overshot byup to 37% by 2010. The EC Green Paperon Energy Efficiency (EU, 2005) statesthat it is possible for the EU-25 MemberStates to achieve energy savings of 20%by 2010, and sees the greatest propor-

tion of these savings (32%) coming fromthe built environment.

In 2006, the residential sector accountedfor 25% of primary energy consumptionand used 2,990 ktoe of final energyrepresenting 23% of Ireland's Total FinalConsumption. With regard to CO2

emissions, the average dwelling wasresponsible for emitting approximately8.1 tonnes of CO2. A total of 4.8 tonnesCO2 (59%) was from direct fuel use, theremainder being the result of upstreamemissions from electricity usage.

Examining CO2 emissions per dwelling,the average Irish dwelling in 2005emitted 47% more CO2 than the averagedwelling in the UK. Emissions were 92%higher than the average for the EU-15,104% more than the EU-27.

Following the Government’s WhitePaper ‘Delivering a Sustainable EnergyFuture for Ireland’ (DCMNR, 2007), andthe subsequent Programme forGovernment, the Building RegulationsPart L in respect of new dwellings havebeen strengthened to bring a 40%reduction relative to previous standardsin respect of primary energy consump-tion and associated CO2 emissionsarising from space heating, waterheating, ventilation, associated pumpsand fans, and lighting energy usage.These provisions apply to dwellingswhere planning permission was submit-ted after July 2008. This policy hascommitted to a further review in 2010with the aim of extending that improve-ment to 60%.

It is clear that the performance of bothnew build and existing housing stockmust be addressed if we are to achievethe objectives set out both at Europeanand national level. The energy require-ment of a house retrofitted to thePassivhaus Standard is even lower thanthe 40% improvement that applies to allnew dwellings in Ireland from July 2008.As inefficient existing dwellings repre-sent the majority of the building stock,the retrofitting of existing stock to thePassivhaus Standard represents a greatpotential for reducing energy consump-tion.

From January 1st 2009, all existingdwellings which are offered for sale orrent must undergo a building energyassessment and have a Building Energy

Rating certificate. This requirement,perhaps above all other initiatives, islikely to result in a rapid and dramaticappreciation by homeowners of theimportance of energy efficiency in olderdwellings.

The EU Parliment has proposed abinding requirement that all new build-ings needing to be heated or cooled beconstructed to a ‘passive house’or equiv-ilant standard from 2011 onwards (refer-ence European Parliament resolution of31 January 2008 on an Action Plan forEnergy Efficiency: A6-0003/2008). As theenergy efficiency of new-build dwellingssteadily improves, there may well beincreasing pressure to reduce the energyconsumption of older homes in orderthat they can compete for buyers atten-tion on the open market.

Minister Gormley announced in July2008 his ambition that all new domesticbuildings be constructed to a ‘carbonneutral’ standard by 2012 or 2013. Sucha move will likely result in a significantincrease in the market penetration ofrenewable electricity generatingtechnologies which will, inevitably, spillover in terms of application to thesecond-hand housing sector.

Lastly, there are several grant schemesavailable through Sustainable EnergyIreland at present which are focusedtowards building energy efficientdwellings and the deployment of renew-able energy technologies including theGreener Homes Scheme and the LowCarbon Homes Scheme. In addition theWarmer Homes Scheme tackles the issueof energy efficiency in low income, olderdwellings and is of potential relevance tothese Guidelines. In 2003, SEI estimatedthat approximately 220,000 householdsin Ireland live in either persistent or inter-mittent fuel poverty.

1.3 Dwelling EnergyAssessment Procedure

1.3.1 Dwelling Energy AssessmentProcedure

The Dwelling Energy AssessmentProcedure (DEAP) is the Irish officialprocedure for calculating and assessingthe energy performance of dwellings.The procedure takes account of theenergy required for space heating,

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ventilation, water heating, associatedpumps and fans, and lighting, and alsotakes into account savings from energygeneration technologies. The DEAPcalculations are based on standardisedoccupancy and the procedure deter-mines annual values for deliveredenergy consumption, primary energyconsumption, CO2 emissions and costs.These values are expressed both interms of annual totals and per squaremetre of total floor area of the dwelling.

As the national methodology, DEAPserves two primary functions. The first isto demonstrate compliance with certainprovisions in the Building Regulationsand the second is to produce a BuildingEnergy Rating (BER) for a dwelling.

1.3.2 Building Energy Rating

A BER is an objective scale of compari-son for the energy performance of abuilding ranging from A1 to G (seesample label below). Essentially a BER isan asset rating, based on a standardisedoccupancy and usage pattern, and iscalculated for a dwelling using DEAP.The rating is the annual primary energyconsumption of the dwelling expressedin terms of kWh per m2 of floor area. TheCO2 emissions associated with thisenergy consumption are also reportedon the BER certificate and expressed interms of kg of CO2 per m2 of floor area.

1.3.3 PHPP and DEAP

Whereas DEAP is the mandatory methodfor both producing a BER and fordemonstrating compliance with certainaspects of the Irish Building Regulations,the Passivhaus Standard and the associ-ated PHPP is a voluntary design standardfor achieving low levels of total energyconsumption within a dwelling.

While it is to be expected that a dwellingconforming to the Passivhaus Standardwill comply with Irish BuildingRegulations Part L, a separate calculationusing DEAP will be required to demon-strate both this and to determine its BER.

The Passivhaus Standard can be metusing a variety of design strategies,construction methods and technologies.In general, the low energy consumptionrequired to meet the standard will resultin a dwelling achieving a favorable BER,provided that attention is paid to theadvice outlined in later sections of theseguidelines.

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Additional Reading

European Commission (EC), 2005.“Green Paper on Energy Efficiency”.[Internet] EC. Available at:http://ec.europa.eu/energy/efficiency/index_en.html

European Commission (EC), 2006. “Promotion of European Passive Houses(PEP)”. [Internet] PEP. Available at:http://www.europeanpassivehouses.org/html

Government of Ireland, Department ofCommunications, Energy and NaturalResources (DCMNR), 2007. Government“White Paper Delivering a SustainableEnergy Future for Ireland”. [Internet]DCERN. Available at:http://www.dcmnr.gov.ie/Energy/Energy+Planning+Division/Energy+White+Paper.html

O’Leary, F., Howley, M., andO’Gallachóir, B., 2006. “Energy inIreland 1990-2004, Trends, issues,forecast and indicators”. Dublin.Sustainable Energy Ireland.

O’Leary, F., Howley, M., andO’Gallachóir, B., 2008, “Energy in theResidential Sector: 2008 Report”.Dublin. Sustainable Energy Ireland.

United Nations Framework Conventionon Climate Change (UNFCCC), 1997.The Kyoto Protocol. [Internet]. UNFCCC.Available at: http://unfccc.int/resource/docs/convkp/kpeng.html

Guidebook on Energy IntelligentRetrofitting, Published by IntelligentEnergy Europe Agency, February 2008.

Building Energy Rating Label.Source: Sustainable Energy Ireland.

References1 A passive house is a building, for which

thermal comfort (ISO 7730) can beachieved solely by post-heating or post-cooling of the fresh air mass, which isrequired to fulfill sufficient indoor airquality conditions (DIN 1946) - without aneed for recirculated air. Source:http://www.passivhaustagung.de/Passive_House_E/passivehouse_definition.html

SECTION TWO

Review of Building Stock in Ireland

An overview of the current buildingstock in Ireland is provided below inorder to gain some impression of thepotential application of these guide-lines.

There were an estimated 1.46 millionpermanently occupied dwellings in theState at the end of 2006. The mostcommon house type in Ireland in 2006was the detached house whichaccounted for 42.8% of the total,followed by semi-detached houses at27.2% and terraced houses at 17.6%2.

In 2006, the majority of dwellings (75%)were either owned outright or were inthe process of being purchased(mortgaged) representing a slightdecrease on the 1991 proportion of 79%.

There have been historically high levelsof ownership in Ireland compared toother European countries. For examplein Austria the proportion of owneroccupied dwellings was 51% in 2004and for the UK it was 69%.

Dwellings in Ireland are graduallyincreasing in size. For example, theaverage floor area of new housesgranted planning permission grew from130m2 in 1990 to 161m2 in 2007 (anincrease of 24%). In 2006 the averageannual spend on energy by households

was €1,767, an increase of 4% on 2005and 70% on 1990 (3.4% per annum onaverage) – this increased to approxi-mately €2,000 in 2008.

In 2006 the residential sector accountedfor just under a quarter of all energyused in Ireland and after transport it wasthe second largest energy using sector.The sector was responsible for 25%(11,896 kt CO2) of energy related CO2emissions. In 2006 the 'average' dwellingconsumed a total of 25,304 kWh ofenergy based on climate corrected data.

This comprised 19,713 kWh (78%) in theform of direct fossil fuels and the remain-der as electricity.

Putting Irish dwellings into an interna-tional context. Examining CO2 emissionsper dwelling, the average Irish dwellingin 2005 emitted 47% more CO2 than theaverage dwelling in the UK. Emissionswere 92% higher than the average forthe EU-15, 104% more than the EU-27.

Focusing on the quality of the buildingstock in Ireland, The Economic andSocial Research Institute (ESRI)completed a study in 2002 titled ‘IrishNational Survey of Housing Quality 2001– 2002 (NSHQ)’ on behalf of theDepartment of the Environment,Heritage and Local Government

(DoEHLG). At the time of the survey, 57%of all dwellings had been built beforethe introduction of the first Irish BuildingRegulations which came into force in1991. Approximately 750,000 homeswere built prior to any thermal insula-tion requirements (introduced 1979) butthe survey indicates a degree of energyimprovement across the older housingstock. Nevertheless, in 2001 24% of allhouseholds surveyed had no insulatedwalls (equating to 63% of pre-1940 builthouses), 18% had no insulated roof (40%of pre-1940 built houses) and 31% hadno double glazing (49% of pre-1940built houses).

The percentage of dwellings with centralheating had increased from 52% in 1987to 91% in 2005.

Energy efficiency and dwellingage

Pre-1940 dwellings were mainly solid-wall construction, while during the1940s through to the 1970s, cavity-wallconstruction was implemented. Duringthe 1980s, improved U-values for bothwalls and attics were introduced invarious building regulations, increasingthe thermal efficiency of dwellings, andthese U-values have since been furtherenhanced with the introduction of morestringent building regulations.

Review of Building Stock in Ireland

In terms of real numbers, it isestimated that 930,000 houses inIreland were built before the first everbuilding regulations in 1991, withapproximately 1 million homes builtbefore the 1996 Building Regulations.350,000 houses in Ireland have nowall insulation, 200,000 houses haveno roof insulation and 350,000 houseshave single glazed windows.

Stock of Private Households in Permanent Housing Units - Types of Accommodation

DWELLING TYPE

Detached HouseSemi-Detached HouseTerraced HouseFlat / Apartment[1]Bed-sitNot StatedTotal

2006 number

625,988398,360257,522139,8728,75131,8031,462,296

2006 % of Total

42.827.217.69.60.62.2100.0

Source: SEI

The graph across highlights the trendfrom 1972 to 2010 in terms of energyefficiency of dwellings in Ireland. Themost significant improvement in thisperiod was post 1979, when the firstBuilding Regulations were introduced. Itwould appear from this data, therefore,that dwellings built pre-1979 wouldbenefit most from retrofitting to thePassivhaus Standard (amounting toapproximately 750,000 dwellings).

Fuel Poverty SOURCE:HEALY AND CLINCH (2002)

The study by Healy and Clinch highlightsthat older dwellings are more likely to beoccupied by those experiencing fuelpoverty than newer dwellings, with thehighest absolute numbers found inhomes built in the 1940s-70s, wheresome 111,000 households are affected.As might be expected, those in newerhomes experience a lower level of fuelpoverty. Retrofitting older dwellings tothe Passivhaus Standard would there-fore assist in addressing the issue of fuelpoverty in Ireland.

Summary

It is likely that dwellings which are olderthan 30 years and have had little or no

prior upgrading are most suited to retro-fitting to a significantly higher energyperformance standard (such asPassivhaus Standard) given theircompletion prior to introduction ofthermal insulation standards in the late1970’s. Further, due to the age of thesedwellings, they may well require signifi-cant upgrading of the building fabricwhich often provides a stimulus toupgrade energy performance.

In short, the older the building the moreeffective would be retrofitting to thePassivhaus Standard.

0

50

100

150

200

250

300

350

400

1972 1979 1982 1992 2002 2008 Regs 2010est.

Energy rating of Irish housing:Indicative Trends over 4 decades

Construction standard/year

PrimaryEnergykWh/(m2a)

References

2 Energy in the Residential Sector, 2008Report, by Fergal O’Leary, Martin Howleyand Dr. Brian Ó Gallachóir

Source:MosArt Architecture

SECTION THREE

Principles of Passive Houses

The principles of passive houses will beoutlined below in brief. More detailedinformation is provided in Chapter 2 ofSEI’s Guidelines for the Design andConstruction of Passive House Dwellingsin Ireland (www.sei.ie/phguidelines).

The building envelope consists of allelements of the construction whichseparate the indoor climate from theoutdoor climate. The aim of retrofitting tothe Passivhaus Standard is to upgrade thebuilding envelope in order to minimiseheat loss and optimise solar and internalheat gain to reduce the space heatingrequirement to 15 kWh/(m2a).

The following parameters are funda-mental in this process:

1. Well insulated building envelope

2. High energy performing windowsand doors

3. Minimised heat loss through thermalbridging

4. Significantly reduced structural airinfiltration

5. Optimal use of passive solar andinternal heat gains

6. Introduce renewable energytechnologies such as solar thermal

Passivhaus Planning Package2007 – An Essential DesignTool

The Passivhaus Planning Package 2007(PHPP) is a software package based on aseries of extensive and interlinked Exceldata sheets which collectively allowbuilding designs (including retrofitstrategies) to be verified against thePassivhaus Standard. The latest version

of the PHPP software can be purchasedfrom SEI’s Renewable EnergyInformation Office (www.sei.ie/resource-centre). The verification requires theinput of very specific and detailed dataabout the building design, materials andcomponents into the PHPP spreadsheetsand is then related to the climate datafor the region in which the house wouldbe retrofitted. The validity of the resultfrom this process is of course highlydependent upon the validity of the dataentered.

Some of the principal datasheetsincluded in the software are listedbelow, along with their main functions:

■ Climate data – it is possible tochoose the climate for which thepassive house is being designed.This has a potentially significantimpact on the U-values required toachieve the threshold annual heatrequirement.

■ Verification – this sheet collates theresults of the overall evaluation ofthe building including the SpaceHeating Requirement, SpecificPrimary Energy Requirement, HeatLoad and Frequency of Overheating.The user can see at a glance on thissheet whether or not the buildingcan be certified as a Passive House.

■ U-value – this sheet enables theassessor to specify the constructionof all the opaque (ie. does notinclude windows) elements of thebuilding envelope for the purposesof calculating the U-values of thoseelements. The sheet requires theinput of the thermal conductivity (λ-value) of the building materialsproposed as well as their thicknesses

and the proportion of insulationoccupied by structural elements.

■ Windows – the orientation and sizeof all windows are entered into thissheet, along with the U-values of theglass and frames as well as othertechnical specifications.

■ Annual Heat Requirement – thisvalue is calculated by determiningthe heat losses through transmissionand ventilation and subtracting thetotal solar and internal heat gains.The annual space heat requirementmust be less than 15 kWh/(m2a).

■ Heat Load (W/m2) – the building’sheat load is based on energy balancecalculations estimated by subtract-ing the minimum solar gains andinternal heat sources from themaximum transmission and ventila-tion heat losses.

The PHPP software is comprehensiveand detailed and therefore requiressome training prior to embarking onpractical application to a real project.However, the software is also quite userfriendly and the verification pageenables the user to check whether or notsuch thresholds as space heatingrequirement are met. In the event thatthe key Passivhaus Standard criteria arenot met, for example, the assessor willfirstly have to check to see if there areany fundamental errors in terms of dataentry. If this is not the cause of theproblem, then the retrofitting strategywill likely have to be modified in order toachieve the required standards. In aretrofit situation, this will typicallyinvolve improving the U-values of thebuilding envelope.

Principles of Passive Houses

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Extracts from the PHPP software areincluded later in Section 6 pertaining tothe retrofit case study house.

Passive House Certification

At the time of writing these Guidelines, apassive house in Ireland can be certifiedby the Passivhaus Institut in Darmstadt,Germany (http://www.passiv.de) orcertifying body approved by thePassivhaus Institut. For further informa-tion on certification of passive houses inIreland contact SEI’s Renewable EnergyInformation Office or the PassivhausInstitut directly. The evaluation criteriafor the certification (Source: PHPP 2007,pp.23) are:

- Specific Space Heat Demandmax. 15 kWh/(m2a)

- Pressurisation Test Result n50max. 0.6 air changes per hour

- Entire Specific Primary EnergyDemand max. 120kWh/(m2a) includ-ing domestic electricity.

The above criteria have to be verifiedwith the PHPP 2007, and the required listof documentation for the passive housequality approval certificate, constructiondrawings and technical specificationwith product data sheets, must besubmitted to the certifying party(including PHPP calculations). Also,verification of the airtight buildingenvelope according to IS EN 13829, a

record of adjustment of the ventilationsystem, declaration of the constructionsupervisor and photographs of thecomplete building must also be submit-ted. Upon examination of receiveddocumentation the applicant receivesthe results of the examination from thecertifying party. If the necessary verifica-tions have been found to be correct andthe above criteria have been met the‘Quality Approved Passive House’ certifi-cate is issued (PHPP 2007, pp.28).

A wider European passive house certifi-cation scheme was developed within theIntelligent Energy Europeproject (2005-2007) “Promotion ofEuropean Passive Houses, PEP”(http://www.europeanpassivehouses.org).This certification scheme is applicable to‘an emerging market scenario’ (i.e.countries with a small number of passivehouse buildings), aims to ensure that thedesign of a particular passive house candeliver the specific energy requirementsin accordance with the PHPP andconfirms the airtightness of thecompleted building. This certificationscheme involves the verification of the'as built' design (i.e. that reflects theactual construction, incorporating anymodifications made during construction)in accordance with the PHPP and confir-mation of the airtightness of thecompleted building by a fan pressurisa-tion test performed in accordance with ISEN 13829.

Building Envelope Insulation

There are several different methods andmaterials available to upgrade theperformance of the building envelope indwellings to the Passivhaus Standardand the most typical scenarios likely tobe encountered are illustrated in thenext Section. Continuous insulation ofthe entire thermal envelope of a build-ing is the most effective measure toreduce heat losses in order to meet thePassivhaus Standard. Achieving this in aretrofit situation is more challengingthan for a new-build.

Insulation of the building envelope canbe divided into four distinct areas: exter-nal wall, floor, roof and windows/doors.Existing passive houses in Central andNorthern European countries have been

achieved with U-values for walls, floorsand roofs ranging from 0.09 to 0.15W/(m2K) and average U-value forwindows (including glazing and windowframes) in the region of 0.60 to 0.80W/(m2K). Typically triple glazed windowunits are used in passive houses inCentral and Northern Europe.

These U-values are far below (i.e. betterthan) the limits set under the IrishBuilding Regulations.

According to the current TechnicalGuidance Document Part L 2007 therequired U-values are 0.27 W/(m2K) forwalls, 0.16 – 0.22 W/(m2K) for roofs, 0.25W/(m2K) for ground floor slab, 0.15W/(m2K) for ground floor slab with underfloor heating and 2.0 W/(m2K) forwindows, rooflights and external doors.

Optimising passive solar gain

The optimal approach to the design of apassive house is to avoid an excessivearea of north facing glazing and placerelatively large windows facing south.This is in order to minimise heat lossesthrough the north facing elevation,which receives no direct sunlight duringmost of the heating season, whilemaximising ‘free’ solar heat gains on thesouth. Achieving the optimal distribu-tion of glazing when dealing with exist-ing dwellings will often be verychallenging and in many instances it willsimply not be possible to increasepassive solar gain due to the aspect ofthe dwelling. A detached house in itsown grounds might provide some scopefor alteration and provision of south-facing windows, but an east-west facingmid-terrace house will not have thesame scope. The PHPP software can beused to determine whether or not thePassivhaus Standard can be reachedwith any given aspect and it will typicallybe possible to compensate for lack ofpassive solar gain by increasing the levelof insulation of the building envelope.

Extensive areas of glass on the southfacing façade in a well insulated and air-tight dwelling might well lead tooverheating on warm sunny days. ThePHPP software will alert the designer toany risk of overheating by calculatingthe frequency of overheating andexpressing this as a percentage of the

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Passivhaus Institut Certificate example, QualityApproved Passive House.Source: Passivhaus Institut, Germany.

year in which the internal temperature inthe house rises above 25 degrees C.

Thermal Bridging

Thermal bridging (i.e. un-insulated jointsbetween walls, floors/ walls, ceilings/adjacent walls, windows/walls etc) areweak points of thermal resistance in thebuilding envelope and cause unwantedlosses of energy. A thermal bridgeincreases heat loss through the struc-ture, and in some extreme cases thismay cause surface condensation orinterstitial condensation in the structure.Surface mould growth or wood rot maybe the consequences of a thermalbridge. Special care must be taken toensure that retrofit measures do notincrease the likelihood of creating suchproblems which can affect the healthand longevity of the building.

The Passivhaus Standard for linearthermal transmittance should notexceed 0.01 W/(mK). This requires thebuilding designer to identify and locateall potential thermal bridging in theconstruction, applying careful specifica-tion and detailing of those elementsproviding where possible a continuinglayer of insulation as well as taking careto execute those elements on site as perdesign details. The impact of thermalbridging can be tested and verified inthe PHPP software as the design of theretrofitting scheme is being developed.

Structural Airtightness andDraught Proofing

Building an airtight or leak-free structureis imperative to achieving the PassivhausStandard. If there are gaps in the build-ing structure then uncontrolledamounts of cold external air can infil-trate the building. Achieving a high levelof air-tightness eliminates cold draughtsand associated comfort losses. It alsoprevents condensation of indoor moist,warm air penetrating the structure, andpossible structural damages due todecay, corrosion and frost. The air tight-ness of a building can be accurately (ISEN 13829) measured by carrying out ablower-door test and the PassivhausStandard is reached when there are lessthan or equal to 0.6 air changes per hour@ 50 Pascal pressure.

The airtight construction requiredshould reduce the penetration of radonin to the building. Radon which can stillbe detected inside of the building will bepartly contributed from outside air aswell as off-gassing from building materi-als. To mitigate against effects of lowradon concentrations recommended airchanges of 25 to 30 m3/person providedby a mechanical ventilation system aresufficient3.

The Radiological Protection Institute ofIreland (RPII) (www.rpii.ie) and the IrishBuilding Regulations provide adviceabout the treatment of radon in the builtenvironment.

Internal Heat Gains

A passive house is very efficient at utilis-ing ‘free’ internal heat gains from domes-tic household appliances, kitchen andutility equipment, electronic equipment,artificial lighting, and occupants. Heatlosses from stoves or boilers alsocontribute towards the overall spaceheating requirement as long as they arepositioned within the building envelope.Occupants of the building alsocontribute to meeting the heat load; atypical adult human continuously emits100W of heat when stationary. A familyof five persons, therefore, can emit up to0.5 kW of heat. This may seem like asmall amount but it equates to approxi-mately two thirds of the total space heatload for the case study passive houseretrofit project presented in Section 6.

Passive House BuildingSystems

As indicated earlier a passive house doesnot need a conventional space heatingsystem of radiators or underfloorheating to maintain a comfortableindoor climate. Instead, due to the smallspace heating requirement involved, thefollowing building services are sufficientin a passive house:

■ Mechanical ventilation system withheat recovery which provides mostof the space heat requirement.

■ Back-up system capable of heatingthe air passing through the dwellingvia mechanical ventilation to meet

any auxiliary space heating needs,expected to be small. Typical fuelsources for the back-up systeminclude biomass, heat pump, gas,and in some instances electricity (forexample ‘green electricity’ fromrenewable sources). The back-upsystem is also used to provide hotwater, either throughout the year orduring winter if a solar water heatingsystem is used during summer.

An airtight house requires a well-designed mechanical ventilation systemto provide good indoor air quality. Apassive house is ventilated using amechanical system which incorporatesair to air heat recovery (mechanical heatrecovery ventilation, or MHRV). Exhaustair is extracted from rooms that typicallyproduce heat, moisture and unwantedsmells such as kitchens and bathrooms.Before this air is expelled to the outsideit passes through a heat exchangerwhere the heat is transferred to theseparate stream of incoming fresh air,thereby eliminating the need tocompletely heat the fresh air as it entersthe building.

It is important that attention is paid toregular replacement of air-filters for bothincoming and exhaust air. Filters areused not only to provide clean air for theoccupants but also to ensure that theheat exchanger is not clogged with dustand other matter. If the filters are notregularly replaced (for example every sixto twelve months) and become cloggedwith dirt the MHRV will have to workharder to provide the same volume of airto the house, thereby increasing thespeeds of the fans and, ultimately, usingmore energy. In retrofitting a dwelling toinclude MHRV, occupants will likely haveno experience of the maintenancerequirements involved with the system.

What happens in the event ofa power failure?

If there is a loss of electricity (and thedwelling has no back-up generator) theventilation system will stop working andthe supply of fresh air will be cut off. Ifpower is lost for a short while (forexample a few hours), then there is likelyto be no noticeable difference in indoorair quality. However, if the loss of power is

prolonged, the simple solution is to openthe windows and to create natural crossflow ventilation through the building.

Additional details on MHRV aspects areprovided in SEI’s publication Guidelinesfor the Design and Construction ofPassive House Dwellings in Ireland.

Back-up Heating System

As previously highlighted in theseguidelines, the space heating require-ment in a passive house is so low thatthere is no need for a traditional spaceheating system. Space heating demandin a passive house is typically metthrough passive solar gains (40 – 60%),internal heat gains (20 - 30%) and theremainder (10 - 40%) needs to beprovided from building systems. Theoptimal way to transfer the smallamount of required heat throughout thehouse is through the mechanical ventila-tion system.

The PHPP software will accuratelypredict the following two measure-ments for each retrofit passive housedesign:

■ Annual Space Heat Requirement –this measures the amount of energythat is needed to maintain acomfortable indoor temperature,specified in kilowatt hours persquare metre of treated floor areaper year, or kWh/(m2a).

■ Heat Load – this measures thecapacity of the space heating systemrequired to maintain comfortableindoor temperatures at any onetime, specified in Watts per squaremetre of treated floor area, or W/m2.

For the retrofit case study the annualspace heat requirement (without lossesof the heating system) is 15 kWh/(m2a)reduced from an initial 214 kWh/(m2a).Including the losses the so called finalenergy (post retrofitting) is 30kWh/(m2a) equating to approximately2,490 kWh over an entire year (the housemeasures 83m2 in treated floor area).Annually, this would equate to 230 litresof oil, 240 m3 of mains gas or 450 kg(0.45 tonne) of bagged wood pellets.

The heat load, on the other hand, hasbeen reduced from 80 W/m2 (6.64 kW for83m2) to 9 W/m2 (0.74 kW for 83m2). Thisamount of energy could be provided bya very small wood chip / pelletboiler/stove compared to what might betypically required in a family home.

The most common method of ‘heating’in a passive house is by post-heating thefresh air after it has already beenwarmed by the exhaust air in the MHRV.There are a number of ways in which thetemperature of the air can be boosted,including:

■ Water to air heat exchanger;

■ Compact unit with electrical heatpump; and

■ Wood pellet/wood log boiler/stovewith integral back boiler.

An overview of the typical back-upheating systems used in passive housesto provide thermal comfort3 is providedin Section 4.4.

Domestic Hot WaterProduction

As in any type of dwelling, the passivehouse requires a system that providesdomestic hot water (DHW). As withspace heating, it is important that thesystem is energy efficient, wellcontrolled and has an adequate capacityto meet demand. Generally the DHWsystem in a passive house is combinedwith a heat source such as a wood stove,solar thermal collector, compact unit orheat pump for space heating. Mostpassive house examples encounteredhave utilised solar thermal collectors asthey reduce the use of primary energyand CO2 emissions. It is important tonote, however, that the PassivhausStandard is indeed achievable withoutsolar based water heating. The introduc-tion of the BER system as an indication ofthe energy performance of dwellings inIreland, together with the mandatoryrequirement in the Building RegulationsPart L 2007 in relation to renewableenergy provision is likely to increase theinstallation of solar technologies.

In terms of specifying a solar collectorsystem, the following outline guidanceshould be considered:

■ The optimal orientation is due southand deviation from this will reducethe contribution of the collectors toDHW production. In places wherethere is no south facing roof, thenexpected orientation losses can beovercome by increasing the collectorarea.

■ The optimal tilt of the solar panelsfor DHW is approximately 45degrees. (In a pitch that is greaterthan 45 degrees the potential annualoutput is compromised somewhat).

■ There are two main types of solarcollectors typically used, namely flatplate panels and evacuated tubes.

Primary energy, in kWh/year: Thisincludes delivered energy, plus anallowance for the energy “overhead”incurred in extracting, processing andtransporting a fuel or other energycarrier to the dwelling. For example,in the case of electricity it takesaccount of generation efficiency atpower stations. SEI, Dwelling EnergyAssessment Procedure (DEAP), 2008version 3, pp. 31.

Delivered energy, in kWh/year: Thiscorresponds to the energy consump-tion that would normally appear onthe energy bills of the dwelling for theassumed standardised occupancy andend-uses considered.

References

3 Translated from Protokollband Nr. 30,Lueftung bei Bestandssanierung:Loesungsvarianten, Dr. Wolfgang FeistPassivhaus Institut

SECTION FOUR

Typical Phases of Retrofitting

4.1 Survey

A detailed survey of the building to beretrofitted is an important basis for agood low-energy design.

The existing build-up (in terms of materi-als, performance and dimensions) of thedifferent elements of the thermalenvelope and details of junctions, possi-ble thermal bridges, windows and doorshave to be accurately recorded. In manycases, the precise build-up of theenvelope will not be known to theowner of the dwelling (for examplewhether external walls are of cavityblock, hollow block or solid block) and inthese situations it will be necessary tocreate an inspection opening to clarifythe construction type.

Details of the heating and DHW systemas well as data on energy consumptionover a three year period are also criticallyimportant as a means of verifying thethermal performance of the existingbuilding fabric. In parallel with this, it isalso important to consider the comfortlevels experienced by the dwellingoccupants. Low energy bills could bemisinterpreted as a reflection of anefficient dwelling when in fact theoccupants might have been living insome considerable discomfort duringthe heating season due perhaps to lackof resources (fuel poverty) or malfunc-tioning heating systems.

A blower door test would be helpful toascertain the current level of airtightnessand to identify where cold air may infil-trate the building fabric in the heatingseason. The Passivhaus Standardrequires an airtightness performance of0.6 air changes per hour measured at 50Pascal pressure and the majority of older

dwellings will perform considerablypoorer than this.

The National Standard Authority ofIreland (NSAI) recently introduced aregistration scheme for service providersinvolved in the Air Tightness Testing ofDomestic dwellings to IS EN 13829:2000.This scheme should ensure highstandards in terms of independence andquality of testing and evaluation.

The use of a thermal imaging cameracan also be very helpful in locating weakpoints in the thermal envelope but sucha procedure is not necessarily manda-tory especially if the survey and assess-ment is being undertaken by someonewith experience in retrofitting.

Given the importance of maximisingpassive solar gain, the overall aspect ofthe building facades as well as area andorientation of glazing is important to

note. It will also be necessary to ascer-tain the extent of the shading surround-ing the building by surveying theposition, shape and height of adjacentobstacles such as buildings and trees.

Lastly, the completion of a detailedsurvey will provide the opportunity tolocate potentially harmful or toxicsubstances such as asbestos. Thesesubstances should be replaced withmore suitable material during the build-ing process.

Initial PHPP Calculation

It is recommended to do a PHPP calcula-tion of the existing building and tocompare the ‘theoretical’ with the actualenergy consumption. If there is a consid-erable difference between bothestimates (for example greater than10%), it would first be important toverify the comfort levels of theoccupants.

The initial testing of the dwelling in thePHPP software will quickly determine itscurrent performance compared to thePassivhaus Standard and will provide agood indication of the extent of upgrad-ing works that would be required. Forexample, the current space heatingrequirement of the case study retrofit

Typical Phases of Retrofitting

Blower door airtightness test.Source: MosArt Architecture

Thermographic ImageSource: GreenBuild Building Information Services

house presented in Section 6 wasestimated in the PHPP as 214 kWh/(m2a)which is approximately 14 times lessefficient that the 15 kWh/(m2a) requiredby the Passivhaus Standard.

4.2 Changes in layout/design

In some cases, it might be possible toalter the dwelling layout and / orarrangement of glazing in order toincrease overall energy efficiency. Giventhat the existing building is alreadymodelled in the PHPP, any changes thatare being considered to the buildingform and orientation of glazing can betested during the design process regard-ing the effect on energy performance aswell as the risk of overheating (whichmight arise if a dwelling has an excess ofsouth-facing glazing without a screen tokeep the high summer sun out).

When considering a major retrofitproject, the owners might also considerusing the opportunity to extend theirhome or to modify the internal layout orarrangement of rooms. In suchinstances, it should be remembered thatlarger homes, no matter how energyefficient, will undoubtedly consumemore energy than smaller houses of asimilar specification. There has been atendency for dwellings in Ireland tobecome larger over the years andhomeowners should consider verycarefully the extent of space that theirfamilies really need. Minimising the areaof extended floor space will reduce buildcost and perhaps leave additional fundsfor enhancing the overall retrofit specifi-cation.

If it is proposed to change the overallform of the dwelling, care should betaken to bear in mind the importantprinciples of achieving compactness(reducing the surface to volume ratio),maximizing the proportion of exposedglazing to the south, east and west (tobe tested and verified in the PHPP), andavoiding unnecessary recesses andprojections that might cause shading.An iterative process should be estab-lished between the architectural re-design of the dwelling and cross-check-ing the overall energy performance inthe PHPP. For instance, existing windowsto the south, east and west of the build-ing could possibly be enlarged in orderto increase solar gain and therebyreduce the space heating requirement.

4.3 Upgrade Thermal Envelope

As highlighted earlier, a key perform-ance threshold given by the PassivhausInstitut is the maximum specific spaceheat requirement of 15 kWh/(m2a). Forall retrofit projects (and especially forolder dwellings), it will inevitably berequired to significantly upgrade theinsulation performance of the thermalenvelope and install highly efficientwindows and doors and mechanicalheat recovery ventilation system in orderto reach the above threshold.

The heat recovery system will bediscussed in Section 4.4. If no heat recov-ery is included in the retrofit scheme, theenergy savings that it would havebrought to a project would have to becompensated for by an even moreefficient building fabric.

Guidance on upgrading the perform-

ance of the thermal envelope isprovided below, considering the follow-ing aspects:

■ Insulation (internal and external);

■ Windows and doors;

■ Airtightness; and

■ Thermal bridges.

4.3.1 Insulation

One of the key challenges in upgradingoverall insulation levels in dwellings is tochoose from the wide variety of materi-als available on the marketplace. Aboveall, the insulation has to be appropriateto its application. Some insulationproducts are suited to use for fill in cavitywalls, for example, whereas others arenot. Some are load-bearing for useunder concrete floors whereas othersare ‘soft’ and better suited to fitting inthe attic space. Some products have verylow thermal conductivity values ((λ)lambda values) - which means they havehigh insulating properties and canprovide a higher level of insulation for agiven thickness compared to lesserperforming products. Insulation typeswill also vary on price, fire safety issuesand amount of processing and / orchemicals involved in their manufacture.

Different thicknesses and thermalconductivities of insulation products caneasily be tested in the U-value sheet inthe PHPP. Dependent on the overallretrofit strategy, the additional insula-tion might be placed on the outside ofthe structural building shell (sometimesreferred to as ‘outsulation’), the inside(so-called ‘dry-lining’) and/or within theconstruction envelope (eg. filling thecavity space created by two leaves of

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APPLICATION OF DIFFERENT INSULATION TYPESRoof Ceiling Floor Wall Façade Perimeter

Mineral wool x x x x xPolyurethane x x x x xPolyisocyuranate x x x x xPhenolic x x x x xEPS x x xXPS x1 x xWood fibre x x x x xWood wool x x xCalcium silicate x2

Cork x xCocos fibre x xFoam glass x3 x x x xCellulose x x x x

Notes: 1 Cold roof construction, 2 Internal insulation, 3 Flat Roof, Sedum Roofs.Maximise passive solar gainSource: MosArt Architecture

external and internal blockwork or, inthe case of timber frame between thewall studs).

Ideally, the insulation layer should becontinuous all around the buildingfabric without any breaks. While this isrelatively easy to achieve with a new-build project, avoiding breaks in theinsulation layer is considerably morechallenging when retrofitting.

The location of insulation relative to thestructural envelope can have a signifi-cant influence on thermal bridges.External insulation, for example, istypically the most effective in reducingthermal bridges, whereas internalinsulation would be the least effective.

In every case, it is critically importantthat the retrofit designer makes surethat the proposed insulation strategywill not cause more interstitialcondensation in the structure that canbe evaporated to the exterior over thecourse of one year. The amount ofcondensate that can potentially build upwithin the envelope of a building is influ-enced by climate (temperature andhumidity) and internal air conditions(high or low occupancy, internal averagetemperature and humidity). All calcula-tions in these Guidelines are based on (a)climate conditions for Dublin and (b) lowoccupancy (according to BS EN ISO13788, Annex A). ). The danger of inter-stitial condensation is that it is, by defini-tion, hidden within the structure andtherefore may be reducing the thermalperformance of the envelope unknownto the homeowners, potentially causingstructural defects in the medium to longterm as well as health risks from result-ing mould growth. There is free softwareavailable which can be used to test therisk of causing interstitial condensationwith different insulation strategies andapplication of such tools is stronglyrecommended herein.

4.3.1.1 Internal Insulation

There are advantages as well as disad-vantages of internally insulating thebuilding envelope which need to beconsidered at an early stage of the retro-fitting strategy.

In terms of advantages, the followingattributes are highlighted:

■ The external facade of the buildingwill remain untouched by theupgrading works which would bebeneficial when dealing with certainexternal finishes which homeownersmight be reluctant to cover withexternal insulation, such as tradi-tional brick, or natural stone.

■ Internal insulation may be cheaperwhen compared to external insula-tion because of certain savings, such

as not having to use scaffolding andnot being dependent on reasonableweather to carry out the works.

■ In terms of thermal comfort, a roomwhich is internally insulated willtypically heat up much quicker dueto the avoidance of having to heatup massive external walls.

Considering disadvantages, the follow-ing are highlighted:

■ Internal insulation will reduce theusable net floor area of rooms withexternal walls. In the case of thesemi-detached retrofit housepresented later, this reduction wouldbe approximately 20% (300 mminsulation) of the total net usablefloor area for insulation with athermal conductivity value of 0.035W/mK (such as mineral wool or cellu-lose) and 14 % for an insulation witha thermal conductivity value of 0.025W/mK (such as polyisocyuranate).Related to this, any surface mountedservices located on the internal faceof external walls, such as electricalswitches and sockets, will have to bere-mounted on the new surface.

■ Inevitably thermal bridges will becreated for example atexternal/internal-wall-junction orexternal-wall/ceiling-junction. As aresult of this, additional insulationmay be necessary along internalelements such as walls and ceilingsto reduce the effect of the thermalbridges with all details having to bestudded very carefully to avoid anycondensation in joints.

■ Usually there has to be a vapourbarrier on the warm side of theinsulation. When fixing paintings orcupboards with nails or screws thisvapour barrier could be penetratedwhich would compromise itsperformance and result in a higherrisk of mould growth and damagesin the wall construction throughcondensing water. A service cavitymay be necessary to avoid penetra-tion of the vapour barrier. This againreduces the treated floor area.

Internally insulating on the top of anexisting concrete floor slab would createa number of practical knock-on-effects.For example, the clear height of internal

page 19

In the top diagram, the risk of creating a thermalbridge is greatly reduced using external insulation.Source: MosArt Architecture

Testing of various insulation strategies for risk of creating interstitial condensation.Source: MosArt Architecture

OUTSIDE

INSID

E

OUTSIDE

INSID

E

and external doors and windows wouldbe compromised by the higher finishedfloor level, the balustrade height ofwindows or railings might be too low andthe height of the lowest riser of an inter-nal staircase might not be consistent withthe height of the other risers which wouldbe unacceptable from a health and safetypoint of view.

4.3.1.2 External Insulation

External insulation is typically used withmasonry construction types but mightalso be considered as an option forupgrading timber frame dwellings. Thekey principle behind this insulationmethod is to completely wrap aroundthe entire structural building envelopethereby significantly reducing thermalbridges which can otherwise arise whereexternal walls and foundations connectto internal walls and the floor slab. Ifexternal insulation is being proposed fora cavity wall construction, then it wouldbe imperative to also fill the cavity withinsulation in order to avoid thermallooping occurring from the ‘cold’unheated cavity through the internalblock leaf to the inside of the dwelling.This would also reduce the visible thick-ness of insulation required externally.

There are two options of external wallinsulation, as follows:

■ The so-called ‘composite system’ or‘single-skin system’ is where insula-tion is either stuck or mechanicallyfixed directly to the external face ofmasonry wall, reinforced with forexample a plastic or glass fibre meshand then rendered. To avoid compli-cations regarding damages orwarranty it is important to usecomponents of one building systemonly. This composite system is usedwidely on Continental Europe as atechnique to upgrade existing build-ings to the Passivhaus Standard.With this single skin constructiontype, care should be taken that thesystem has Agrement Certificationfor insurance purposes.

■ The second system is where instead ofthe above single-skin system a venti-lated cavity is created between theexternal cladding and the insulation,the latter of which is otherwise fixedto the exterior of the existing walls in asimilar manner to the other option.

Insulating the Roof Space

When considering insulating the roofspace, the first decision to make is todetermine the position of the thermalenvelope of the dwelling. In mosthomes, the thermal envelope will be onthe horizontal and just above theplastered ceiling comprising of insula-tion rolled out between the roof joists. Inother situations, such as where there is avaulted ceiling for example, the thermalenvelope will be within the sloping roofcomprising of insulation fitted betweenthe roof trusses. In the case of where theformer scenario exists, it might be worthconsidering changing the position of theinsulation to the sloping part of the roofwhich would result in extending theheated volume of the dwelling. This hasthe advantage of creating a heated atticspace into which it might be possible toposition some of the service equipmenttypically found in passive houses, includ-ing a large solar hot water tank as well asthe mechanical heat recovery ventila-tion equipment. By positioning thisequipment within the (extended)thermal envelope, transmission heatlosses will be minimised. Furthermore,not having to lay thick insulation withinand above the roof joists might facilitateplacing a floored surface in the atticwhich would provide additional storagespace for the homeowners. A leaky attichatch would also be avoided when thesloped section is insulated.

Shifting the thermal envelope to thesloping roof should be verified in thePHPP software and the load-bearingcapacity of the roof trusses should bechecked prior to placing additionalloads thereon.

In dwellings where sloping ceilings arefound, the implications of placingadditional insulation underneath theroof trusses should be evaluated withrespect to clear head height. There maybe insufficient space internally to placeadditional insulation, in which case itmight be required to place the insula-tion externally (above) the roof trusses.This is only likely to be economicallyfeasible if the roof coverings (tiles orslates) are in very poor condition andneed upgrading or replacing.

To externally insulate a ground floor slabwould require completely removing theexisting concrete slab and more than

likely the hardcore there under beforeplacing a damp-proof membrane, a layerof insulation and a new floor screed. Justas externally insulating a roof, this wouldbe costly, hugely disruptive forhomeowners and might not be justifi-able in terms of cost and return oninvestment.

If it is decided not to excavate theground floor slab to provide an insula-tion layer, some compensation will beprovided by externally insulating theexternal walls down as far as the founda-tion. Externally insulating external wallsas far as the foundation will marginallyreduce the heat loss from internal floorsas well as marginally reduce thermalbridges emanating from the rising walls.

4.3.1.3 Wall Cavity Insulation

Cavity wall insulation in Ireland is nowcommonplace and involves filling thecavity between the inner and outer leafof concrete blocks with appropriateinsulation material. It is quite likely thatinsulating the cavity alone, however, willnot be enough to achieve the requiredU-values for the Passivhaus Standard. Insuch cases, cavity insulation will have tobe combined with internal and / orexternal insulation to achieve thetargeted U-value identified in the PHPPsoftware.

The proper installation of cavity insula-tion can be proven by using a thermalimaging camera which will immediatelyhighlight parts of the construction thathave not been fully insulated due to

page 20

Source: MosArt Architecture

External insulation should befitted to run past the level of theinternal floor slab in order tominimise thermal bridging(lower sketch)

their detection as being colder than thefully insulated areas.

4.3.1.4 Windows and Doors

The greatest heat losses in a dwellingtypically occur through windows anddoors. The better the thermal perform-ance of these elements, therefore, theless insulation will be necessary in walls,floors and roofs.

There is a growing range of windowsand doors available in Ireland which aresuitable for passive house design. Manyof these will have insulation integral tothe frame so that thermal bridging fromthe exterior to interior surface isminimised. Specifiers and homeownersshould be aware that mullions andstanchions (glazing bars) will reduce thearea of glass and, accordingly, the

amount of solar gain.

It also should be considered that as theU-value of the glass components, e.g.double glazing / triple glazing improve,the glass will let through less solar andlight gains in addition to reductions dueto increased frame, mullion andstanchion proportions. However,improved U-values will provide a netdecrease in energy consumption.

The joints between windows and doorsto walls and floors have to be sensiblydetailed. Ideally, an external insulationlayer would be used to overlap thewindow or door frame by at least 65 mmin order to reduce potential thermalbridges to a minimum. Furthermore theabove joints have to be vapour proof onthe inside and weather proof externally.

To prevent overheating in summer itmight be worth considering shadingdevices such as overhangs, balconies orbris soliel which block direct sunlightwhen the sun is high in the sky in thesummer time. In winter, when the sun islower in the sky, passive solar gain willbe provided by the sun’s rays passingunderneath the shading device.

4.3.1.5 Airtightness

The Passivhaus Standard requires amaximum hourly air change rate of 0.6at an under and over-pressure of 50Pascal. That means the entire air volumeof the dwelling changes through gaps,cracks and other openings in the build-ing fabric at a maximum of 0.6 times inone hour at an air pressure of 50 Pascal.

Compared to the current Part L, this levelof airtightness is quite a high perform-ance standard but is neverthelessachievable when both design detailingand site operations have been wellexecuted.

The airtight membrane or layer shouldalways be located on the warm side ofthe insulation and should be continuousaround the building fabric without anybreak. In masonry buildings, theplastered internal face of walls isregarded as the ‘airtight’ layer, whereas aseparate membrane would be requiredif the wall construction is comprised oftimber or steel frame.

Different construction configurationswill require different strategies with

regards to protection from the dangersof interstitial condensation. For example,in certain instances a vapour checkmembrane with a relatively low resist-ance factor might be sufficient (i.e.,allowing some moisture to pass throughthe wall), whereas in other situations, acomplete vapour barrier might berequired which totally prevents anymoisture entering the construction.There are currently vapour membranesavailable on the market which are so-called ‘intelligent’ insofar as their vapourresistance can change depending on therelative difference in vapour pressurebetween internal and external environ-ments. They can thus ‘close’ or ‘open’ as

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DEFINITION OFVAPOUR BARRIER AND

VAPOUR CHECK/ VAPOURCONTROL LAYER:

µ value is the vapour resistance factorof a material (see also IS EN 12524)d is the thickness of a layersd is the equivalent air layer thicknessi.e. a vapour barrier with an sd of 1500m is equivalent to 1500 m thickness ofstill air in terms of vapour resistanceand is calculated as follows :sd [m] = µ x d [m]vapour check: 0.5 m < sd < 1,500 mvapour barrier: sd > 1,500 mBRE IP 2/05 Modelling and ControllingInterstitial Condensation in Buildings.

Source: Passivhaus Institut

Use of rubber gasket to seal a penetration of theairtight membrane. Source: MosArt Architecture

Externally insulated window frame reducing heat lossSource: Optiwin GmbH

Traditional sash window with mullions and stanchionswhich reduce solar gains and create a thermal bridgefrom outside to insideSource: MosArt Architecture

appropriate. Whichever membrane isused, it must be remembered that it willfunction as the airtight layer and mustbe treated with great care during theconstruction process.

The timing of carrying out an airtight-ness test (commonly referred to as a‘blower door test’) is very important inthe overall retrofit procedure. It is impor-tant to carry out the test prior to thecompletion of final finishes so that if thetest fails then any gaps or cracks in theairtight layer can be precisely locatedand accessed for repairs. The use ofsmoke puffers / pencils / sticks can bevery useful to precisely identify leakswhile the building is pressurised or de-pressurised. The test should ideally becarried out once the airtight layer hasbeen completed but while it is stillexposed, including most especially thetaped joints between the windows anddoors to the building envelope as well asjoints between different elements of thedwelling (ceiling, walls and floors). Allpersons working on the site must makesure not to subsequently compromisethe airtight layer which can easilyhappen, for example, where servicessuch as cables or pipes have topenetrate the barrier.

4.3.1.6 Thermal Bridges

The concept of thermal bridges hasbeen introduced earlier in Section 3.

There are two types of thermal bridgesof interest to these Guidelines, namely(a) repeating thermal bridges and (b)linear thermal bridges.

Repeating thermal bridges wouldinclude studs or rafters in the insulationlayer or indeed wall ties in masonry

construction. This kind of thermal bridgecan be calculated in the PHPP by enter-ing the percentage of the insulationlayer occupied by the material (such astimber studs) as well as the thermalconductivity of that material. Repeatingthermal bridges are thus accounted forwithin the normally quoted U-values forwalls, roofs and ground floors. An extractfrom the PHPP software is includedbelow to illustrate how repeatingthermal bridges can be calculated.

Linear thermal bridges, on the otherhand, can be found at junctions of inter-nal and external walls, at the eaveswhere there is little or no space forinsulation and even around opes forwindows and doors. These bridges werenot accounted for at all until they wererecognised in recent versions of thebuilding regulations. The calculation ofthermal bridges is a specialist field thatwill probably require assistance from aprofessional.

The linear thermal transmittance (ψ)values have to be verified in accordancewith EN ISO 10211. The ψ values forseveral products certified by thePassivhaus Institut can be found on theirwebsite (www.passiv.de) or on theirproduct certificates.

4.4 Upgrade Ventilation andHeating System

The upgrading of the ventilation andheating system is the second step inretrofitting dwellings to the PassivhausStandard.

Ventilation System

The dwelling to be retrofitted might be

ventilated in a number of ways, includ-ing through controlled means by extractfans, vents in the wall with adjustablegrills and openable windows or bysimply by uncontrolled means throughdrafts and leaky construction. Ashighlighted in the previous section,however, it is vital for the PassivhausStandard that a very high level ofairtightness is achieved in order tominimise heat loss. Airtight construc-tion, in turn, is accompanied in thePassivhaus Standard with mechanicalheat recovery ventilation systems. Thisnext section of the guidelines willprovide an outline of considerationsnecessary in planning such a system inthe context of retrofitting a dwelling.

Recommended Ventilation Rate

According to the Passivhaus Institut, theappropriate air change rate for dwellingsis between 0.3 and 0.4 times the volumeof the building per hour at normalpressure, with a general recommenda-tion of leaning toward the lower rate.This maintains high indoor air qualitywhile ensuring a comfortable level ofhumidity and maximizing energysavings.

Compliance with the Irish BuildingRegulations Part F might require moreair changes per hour than the PassivhausInstitut recommends. It is possible toenter a higher air change rate into thePHPP which consequently leads to aslight increase of the energy consump-tion.

The PHPP software suggests that 30m3

per person per hour should be providedto dwellings to ensure good air quality.These two measurements can be usedto choose an appropriately sizedmachine for different dwelling designs.Taking the retrofit case study presentedlater in Section 6 as an example, anoccupancy of 2.4 persons would require71 m3 of fresh air delivered to the houseper hour. In terms of extract, the PHPPsoftware uses the following rates fordifferent room types as default values,kitchen = 60m3/h, bathroom = 40m3/h ,shower = 20m3/h and WC = 20m3/h. Inthe case study house these total 100m3/h which is close to the supplyvolume which will ensure that thewhole house system will be balanced.The supply and extract volumes can be

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accurately set by using a digitalanemometer and adjusting the valveson the vents in each room as required.

Mechanical Heat RecoveryVentilation (MHRV) System

The efficiency of the heat exchanger inthe MHRV determines the amount ofheat that can be recovered from theexhaust air and, therefore, has a verysignificant influence on the additionalspace heating that may be required in apassive house. The efficiency of sensibleheat recovery should exceed 75% for thenominal range of flow rates specified forthe unit when measured in terms of thesupply-air side temperature ratio asdescribed in IS EN 13141-7:20044.Specifiers and designers should be waryof products claiming extraordinaryefficiency rates of 95% or higher. Thesafest route is to install equipment thathas been independently tested andverified by such bodies as the PassivhausInstitut.

(See www.sap-appendixq.org.uk).

Current accreditation testing proceduresfor mechanical ventilation systems oftenproduce unrealistically positive testresults. If reliable measured values arenot available, or a certificate is notpresented, then the values are calcu-lated by subtracting 12% from accredita-tion test results.

In DEAP a default efficiency of 0.66 isassumed for mechanical heat recoverysystems and the default Specific FanPower (SFP) is assumed to be 2W/[l/s].This default value is considerably lessthan is achievable in practice (as verifiedby institutes such as the PassivhausInstitut).

The Passivhaus Standard can beachieved without a heat recovery systemas well. However, when eliminating theMHRV system the savings foregone inrecovering the thermal energy have tobe compensated by other measures suchas additional insulation of the thermalenvelope. This could turn out to be a falseeconomy, therefore. As a practicalexample, if a MHRV system was omittedin the case study building (Section 6), thespace heating requirement woulddouble the maximum allowed by thePassivhaus Standard.

Insulation and Positioning of DuctWork and Vents

It is very important to adequatelyinsulate the air ducting so that there isminimal loss of temperature in deliver-ing warm air around the house. Thethickness of insulation generally used inpassive houses is between 6 cm and 10cm for ductwork. It is also preferable tolocate the ducting within the thermalenvelope and to keep pipe runs as shortas possible by ideally positioning theMHRV unit in the centre of the house.

Vents are normally placed in the ceilingbut can also be placed in the wall ifnecessary. The air inlets are typicallydesigned to spread the air horizontallyacross the ceiling, minimising downwarddraughts. There should be a gap (10mmis sufficient) either under or over thedoor of each room to enable the easymovement of air from one room to thenext. If doors are fitted tight withoutsuch a gap, rooms with exhaust ventswould be under negative pressure androoms with supply air would be underpositive pressure.

There are a number of MHRV productsavailable on the market that have beenspecifically developed for retrofitting tothe Passivhaus Standard.

Heating System

The most common method of ‘heating’in a passive house is by post-heating thefresh air after it has already beenwarmed by the exhaust air in the MHRV.There are a number of ways in which thetemperature of the air can be boosted,including those listed below:

■ Water to air heat exchanger;

■ Compact unit with electrical heatpump; and

■ Wood pellet/wood log boiler.

These three options are explored inoutline only below with additionaldetails provided in SEI’s Guidelines onPassive Homes. It may well be possibleto continue to use the existing heatingsystem in the dwelling (for example, oilboiler with radiators) albeit in manycases it might not be an efficient modeland might be at or near the end of itsuseful life. In addition, the design outputof the heating system is likely to be too

large for the retrofitted dwelling whichcould have a heat load demand of lessthan 20% of that of the original need.Another strategy would be to retain thepipes and radiators already existing inthe dwelling but to replace the olderlarger boiler with a smaller and moreefficient one that can serve not onlyspace heat requirements but alsodomestic hot water production. Oneadvantage of keeping the radiatorsresults in the homeowner being able tocontrol individual room temperatures byadjusting the valves manually to suittheir needs or using ThermostaticRadiator Valves (TRV) to set the roomtemperatures. Even if the original radia-tors are being retained as the primaryheating system, there will still be a needfor a MHRV system which will now notonly supply fresh pre-heated air to thedwelling but will also distribute the heatgenerated by the radiators throughoutthe house. A further issue to consider indebating whether or not to retain theoriginal radiators is the fact that they willprobably have to be moved if internalinsulation is proposed for the dwelling.

Water to Air Heat Exchanger

This method involves using a heatingdevice placed immediately on the freshair supply outlet of the MHRV. If thehouse needs additional heat (which isdetermined by a thermostat) then hotwater is circulated through the device,hence the title of ‘water to air heatexchanger’. The hot water is heated, inturn, by using a number of energysources including a stove or boiler (for alarger house) in combination with solarhot water panels or evacuated tubes.

Compact Unit with Electrical HeatPump

This system is so-named as it incorpo-rates all of the technology required for apassive house in a relatively small unit,namely the MHRV, the DHW and theheating power for the home, in this casepowered by an electrical heat pump. It istherefore very suited to smaller homeswhere space might be limited for largetanks, stoves and storage for wood. It isimportant to use a heat pump with thehighest possible efficiency (coefficient ofperformance or COP).

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A 3D model of a typical compact unit isillustrated below.

Wood pellet/Wood pellet stove/Woodlog boiler

A boiler is typically located in a separateplant room whereas a stove is located inan internal room for example a livingroom. Wood pellet stoves/log boilers canserve as an auxiliary or back-up source ofheat as well as for domestic hot waterproduction. The following issues shouldbe remembered when consideringinstalling a wood stove or boiler:

■ Pellet boilers are available in typesloaded automatically or manually,whereas wood log boilers and woodpellet stoves for domestic use areonly manually charged.

■ The equipment must be sized appro-

priately to the heat load of thehouse. This will be defined by the‘Verification page’ in the PHPPsoftware. Taking the prototypehouse presented in these guidelines,a stove of just 7 kW output would besufficient for all space heating andDHW needs.

■ An independent combustion airsupply must be provided to anystove or boiler in a passive housebearing in mind the level of airtight-ness that has to be achieved. It isimportant to check if your chosenproduct can accommodate directconnection to the external air.

■ Most wood boilers/stoves are highlyefficient (up to 80 – 90%) and whenburning pellets there is very little ashremaining following combustion. Aflue will be required to take exhaustgas emissions safely away from thehouse, as with any typicalboiler/stove. This flue must complywith Part J of the building regula-tions.

■ A stove or boiler that directs most ofthe heat output to the DHW tank isessential if the hot water is to beused to heat the ventilation air asdescribed above. If there is a need toback-up the MHRV the stored hotwater will be used to re-heat thefresh air.

■ As previously indicated, it will oftenbe logical for such units to be usedfor not only auxiliary space heatingbut also for auxiliary water heating.

■ Although the demand for wood fuelwill be low, a dry space for storagehas to be provided. Wood (whetherlogs, chipped or in pellets) is bulkyand a considerable volume isrequired for storage especially if it ispurchased in bulk to keep costs to aminimum. Storage underground isalso possible in special containers.Wood pellets need to be kept dryerthan chips or logs.

Integrated controls for heating in aPassive House

Heating systems in Ireland have tradi-tionally been simple, with among themost common boiler based systemsbeing a timer and a cylinder thermostat,and with sometimes even room thermo-stats being absent. However, theBuilding Regulations Part L requireminimum levels of control, installingequipment to achieve the following:

■ Automatic control of space heatingon the basis of room temperature;

■ Automatic control of heat input to

stored hot water on basis of storedwater temperature;

■ Separate and independentautomatic time control of spaceheating and hot water;

■ Shut down of boiler or other heatsource when there is no demand foreither space or water heating fromthat source.

The above levels of control should beincorporated into any dwellings retrofit-ted to the Passivhaus Standard.

Additional control features can be incor-porated to a heating system so the overallsystem performance improves. Oneexample is the ‘weather compensation’feature, which is the ability to adjust theoutput of the system based on themeasured external temperature. The mainadvantage of using weather compensa-tion is that the heating system closelymonitors external temperature trends andadjusts the output accordingly.

The preferred internal temperature canbe set using an internal thermostat. Ifthe internal temperature goes below thethermostat setting, the system willautomatically start to heat the fresh airpassing through the ventilation equip-ment.

Individual Room Temperature Control

Different rooms may have differenttemperatures due to solar gains, occupa-tion and internal heat loads. Roombased temperature controls for temper-ature differentiation between differentrooms may be necessary if individualcomfort requirements are set for differ-ent rooms. In a centralised ventilationheating system, however, the supply airtemperature is relatively constant (20degree C) for the whole house and thiswould be typical for most houses retro-fitted to the Passivhaus Standard.

DHW is produced typically by the back-up heating system, supported by solarcollectors. Hot water can also beproduced electrically but this willincrease the primary energy consump-tion and therefore adversely affect theBER.

4.4 Site supervision

An overview of the various worksrequired to achieve the Passivhaus

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Water to air heat exchanger unit. Source: MosArtArchitecture

Compact unit including ventilation heat recovery andair to water heat pump. Source: Drexel und Weiss

Standard has already been provided,including emphasising the differentinsulation methods that could be used,the importance of minimising thermalbridges, the risks associated with unwit-tingly creating interstitial condensationand the need to achieve a high level ofairtightness. It is vitally important thatboth the contractor(s) carrying out thework as well as the energy advisorinspecting the works must be suitablyexperienced in all of the above issues inorder that a successful result is achievedfor the homeowner.

There is a rather high margin for error inretrofitting to the Passivhaus Standardand care should be taken at every step ofthe way.

During the construction while openingwall, floor or ceiling constructionsharmful substances (Asbestos, pollutantemitting materials, respirable glass fibre

…) may appear. The opportunity shouldbe taken to remove these and replacewith harmless materials.

For further information on asbestosremoval - www.epa.ie.

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References

4 IS EN 13141-7:2004, Ventilation forbuildings/ performance testing ofcomponents/products for residentialventilation. Performance testing of amechanical supply and exhaust ventila-tion units (including heat recovery) formechanical ventilation systemsintended for single family dwellings.

SECTION FIVE

Upgrading of Typical Construction Types

This section illustrates many of the mostcommon construction types in Irelandand various means of upgrading theirperformance to the PassivhausStandard. It must be appreciated thatthere are many different constructiontypes as well as numerous techniquesand materials available to reducethermal losses and to deal with all thepermutations and combinations wouldnot be possible within these Guidelines.It is hoped that the variety of examplescovered below, however, provide asuseful guidance for most scenarios thatwill be encountered by persons inter-ested in retrofitting.

It must be stressed that readersshould not copy techniques fromthese guidelines without checking thesuitability of the building beingupgraded! For all parts of the thermalenvelope, the risks of interstitialcondensation have to be calculatedand verified. Furthermore, there maybe other issues such as structuralstability and fire safety considera-tions to be considered.

Retrofitters should only use IABapproved products with installation byspecialist contractors only to ensureinsurance by Home Bond.

5.1 Walls

The following Section explains how toupgrade different wall constructionswhich are common in Ireland.

For all construction types care has to betaken when externally insulating at thebase of walls. The insulation here shouldbe a type of material which is suitable for ahumid environment. Furthermore thedetail has to be developed in that way sono moisture can infiltrate the construction.

Readers should also note that a changein external finishes may require planningpermission.

5.1.1 Random Rubble and HollowBlock Wall

Walls constructed of random rubble orhollow block are often found in very olddwellings and, accordingly, are often notinsulated.

If the stone used in the dwelling isexposed and of high aesthetic quality,homeowners might well be reluctant toclad over this with external insulationwhich would completely alter thecharacter of the building. In situationswhere this is not the case, however,external insulation might be considered.

When insulating externally there are twopossible options, either using a looseinsulation type with a ventilation cavityor using a single skin insulation type.Using loose external insulation typicallyrequires a substructure comprisingwooden battens which are fixed to thewall and bear the load of the newfaçade. Depending on the thickness ofthe insulation required, it might benecessary to counter batten externallyto the first layer of battens to provideenough depth. An oriented strand board(OSB) or a wood fibre board is then fixedto the external side of the battensfollowed by a breather membrane.Thereafter, a ventilation cavity is formedwith vertical battens which can be cladwith appropriate materials.

The other option is to insulate externallywith insulation boards which create asingle skin structure (ie. no ventilationcavity). In this case, the insulation ofrequired thickness can be mechanicallyfixed to the structural wall and thereafter

plastered with an approved rendersystem.

In many situations, random rubble wallsor hollow block walls will already beinsulated internally (commonly referredto as ‘dry-lining’). If the wall is already drylined, the plasterboard and plastic sheet-ing should be removed in order to checkthe condition of the timber or metalstuds as well as the existing insulation. Ifthese are not in good condition, theyshould be replaced or upgraded andclosed with OSB and an airtight layer/vapour control layer. As has beenstressed earlier, great care has to betaken when insulating internally in orderto avoid causing interstitial condensa-tion. A membrane with a high vapourresistance (vapour ‘barrier’) may help toprevent the build up of condensation,but this should be proven by calculation.

It is recommended to create an insulatedservice cavity for cables and pipesrunning along the external walls in orderto protect the vapour control layer frombeing penetrated by nails or screws.

It is possible to mix both external andinternal insulation techniques but thereis likely to be more costs involved due toadditional labour and materials.

A number of 3D images are provided toillustrate different possible approachesto significantly upgrading the energyperformance of random rubble andhollow block walls. These sketches arenot exhaustive. Rather, they serve asexamples of the kind of approach thatmight be used.

5.1.2 Cavity Walls

When dealing with cavity walls, it isusually best to full-fill the cavity with

Upgrading of Typical Construction Types


Existing Standard Random Rubble Exterior Wall

Random Rubble Exterior Wall Upgraded to Passivhaus Standard - Internal “Loose” Insulation

Note: Only the use of IAB approved products are premitted and installation by specialist contractor only


Dry Lined Hollow Block Exterior Wall Upgraded to Passivhaus Standard


Dry Lined Hollow Block Exterior Wall Upgraded to Passivhaus Standard - External “Loose” Insulation



Existing Standard Hollow Block Exterior Wall


Hollow Block Exterior Wall Upgraded to Passivhaus Standard - Internal “Loose” Insulation



Existing Standard Hollow Block Exterior Wall

Hollow Block Exterior Wall Upgraded to Passivhaus Standard - External “Rigid” Insulation

insulation in order to reduce the thick-ness of the additional insulation that willinevitably be required. This is normallydone by injecting suitable insulation(such as beads) into the cavity.

Make sure when filling the cavity thatthe insulation material does not transmitwater coming from driving rain to theinner leaf (there is a variety of certifiedproducts available on the market soplease ensure the installer is IAB certified(Check www.nsai.ie).

As for the random rubble and hollowblock wall, there are two means of exter-nally insulating, namely with a (new)ventilated cavity construction or as asingle skin construction. It is likely thatthe insulation layer does not have to beas thick as for the random rubble orhollow block wall because of the betterthermal performance of the cavity wall.

If it is decided that the wall should beinsulated internally, care should betaken that potential interstitial conden-

sation is considered in the detailing anddesign. As before, it is recommended toremove existing insulation and airtightlayers where they exist and upgradethese in best practice manner includingservice cavity as described in Section4.3.1 and 5.1.1.

5.1.3 Timber Frame

Typically in Ireland, the structural part oftimber frame constructions is built withOSB on the outside, insulation in



Existing Standard Cavity Exterior Wall

Cavity Exterior Wall Upgraded to Passivhaus Standard - External “Loose” Insulation


Cavity Exterior Wall Upgraded to Passivhaus Standard - External “Rigid” Insulation


Existing Standard Cavity Exterior Wall

between the studs and a layer ofpolyethylene on the inside. It is morethan likely that the polyethylene sheet-ing will not have been installed as anairtight layer. Therefore the sheeting hasto be taken off and the condition of theinsulation checked and possiblyreplaced by a better performing type.Opening the wall will also provide agood opportunity to check the condi-tion of the studs as there might bedamage caused over the years bypenetrating water. In the worst-casescenario parts of the structure may haveto be changed.

The existing cavity (between the timberstructure and the external concreteblock leaf ) should be filled with insula-tion to reduce the inevitable additionalinsulation that will be required either on

the internal or external face of theconstruction.

Only certified insulation systems whichdo not transmit water from the outer tothe inner leaf should be used.

There are again the same possibilities toupgrade the timber frame constructionto the Passivhaus Standard externallyand internally as mentioned above forthe masonry wall constructions. Some ofthese options are illustrated below.

Another option to upgrade a timberframe construction is to remove theouter leaf of concrete block or brick andinsert a new insulated timber frame wallin its place. The principal advantage ofthis approach is that large parts of thewalls can be pre-fabricated and there-fore produced with a much higher

accuracy than on-site assembledconstructions. Another advantage is thatthe footprint of the building would notextend as much as it would if theconcrete leaf was retained andadditional insulation were placedexterior to that. Such considerationsmight be important with buildings thatare very closely spaced. This option isnot illustrated below but the build upwill be similar as for external upgradewith loose insulation material. A disad-vantage that must be considered is thecost and waste associated with remov-ing the outer masonry leaf.

5.2 Floor Slab

Floor construction types in Irelandtypically comprise of either a suspendedtimber floor, power floated concrete

Existing Standard Timber Frame Exterior Wall

Timber Frame Exterior Wall Upgraded to Passivhaus Standard - External “Loose” Insulation



outside

inside



Timber Frame Exterior Wall Upgraded to Passivhaus Standard - External “Rigid” Insulation





Timber Frame Exterior Wall Upgraded to Passivhaus Standard - Internal “Loose” Insulation

floor or concrete floor with a screedfinish. The thermal performance of theseis typically not sufficient to achieve thePassivhaus Standard and will thusrequire upgrading. Unfortunately, floorconstructions are difficult to upgradebecause most often the finished floorlevel cannot be changed (consideringclear heights at doors, first steps at stairs,height of balustrades etc.).

For bungalows it is worth thinking abouthigh performance vacuum insulation(see performance details below) plus anew build up on top of the screed. Theknock-on effects of rising the finishedfloor level has to be considered verycarefully. Internal doors may have to becut at the bottom and special detailingwould be required at the threshold ofexternal door(s).

Suspended floors are the easiest to deal

with and can be upgraded by removingthe floor covering, insulating betweenthe joists, fixing a vapour control layerand covering this with a new floor finish.Make sure that the vapour control layeris not penetrated.

An option of upgrading concrete floorslabs with a screed finish is to take offjust the screed and insulation andexchange the existing insulation with abetter performing insulation. Vacuuminsulation, for example, has a thermalconductivity (λ) value of 0.004 W/mK, i.e.approximately 10 times more efficientthan either mineral wool or cellulose.For more information please visit thefollowing website: http://www.vip-bau.de/e_pages/start_e.htm

Vacuum insulation has to be handledwith extraordinary care (like glass). If thefoil wrapping of the boards is penetrated

the thermal conductivity will increase upto approximately 0.02 W/mK. It shouldbe noted that at the time of print thisproduct does not have Agrment certifi-cation.

If the U-value of the above upgradeoptions is still not low enough (as deter-mined by the PHPP software) or if thereis a power floated concrete floor slab it isworth thinking about completely replac-ing the floor construction with highlyinsulated floor slab as described inSection 4.3.1.2.

The installation of a radon barrier shouldcompleted in accordance with the IrishBuilding Regulations.


Existing Standard Suspended Timber Ground Floor

Suspended Timber Ground Floor Upgraded to Passivhaus Standard


Note: Excavation Required to allow for additional Thicknessof Insulation to Engineers Detail.

Note: Only the use of IAB approved Products are Permitted& Installation by Specialist Contractor Only

Existing Standard Concrete Ground Floor

Concrete Ground Floor Upgraded to Passivhaus Standard

5.3 Roof

5.3.1 Cold Roof / Insulated atCeiling Level

Where there is a cold unused attic spacethe insulation will typically be foundwithin the joists just above the plaster-board ceiling to the attic.

As suggested earlier, in the long termthe homeowner might consider convert-ing the attic space to a living space ormight be used to locate some of thepassive house mechanical plant whichshould be sited within the thermalenvelope, such as the ventilation system.In these cases it is recommended interms of cost and good building practiceto create a ‘warm’ attic which means thatthe sloped section of the roof isinsulated (see Section 5.3.2).

Usually the airtightness layer (or ratherthe vapour control layer) - if existent –will not be installed correctly to achievethe Passivhaus Standard. For example,the joints between different sheets willtypically not be taped. The first task,therefore, is to remove the existingplasterboard and exchange it with alayer of OSB. On the internal face of theOSB a vapour control layer has to befixed. Installing this vapour control layeris difficult work as the membrane needsto be seamless under the entire insula-tion layer. In the case of houses withmasonry internal walls, each room canbe sealed individually as the membranecan be taped to the four walls which are,themselves airtight. In situations wherepartition walls are constructed of timber,however, the creation of a full seal ismore challenging. The membranes in allindividual rooms need to be properly

connected – otherwise, while each roomitself might have a sealed ceiling, thepartition walls will severely compromisethe overall airtightness of the dwelling.Alternatively, it might be possible toinstall the airtight layer on top of thejoist which is an easier option. If choos-ing this option, however, be aware thatthe insulation must be installed abovethis membrane which will reduce theavailable head height in the attic space.

A service cavity should thereafter ideallybe created by battens and plasterboardon the internal side of the airtight layer.This will lower the ceiling height,however, and it has to be clarified by thedesigner if this is acceptable to theoccupants.

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Existing Standard Ceiling to Attic Space with Insulation on the Flat

Ceiling to Attic Space with Insulation on the Flat Upgraded to Passivhaus Standard

Note: Excavation Required to allow for additional Thicknessof Insulation to Engineers Detail.

Note: Only the use of IAB approved Products are Permitted& Installation by Specialist Contractor Only

5.3.2 Sloped Roof

If it is necessary to insulate the slopedsection of a roof there are two options,either insulation on top of the rafter(externally) or below the rafter (inter-nally).

If the roof slates or tiles as well as exter-nal weathered parts of the roof construc-tion are in poor condition it is probablywise to replace these as part of theupgrade. In this case external insulation

is recommended. The rafters have to beincreased in size by adding anotherrafter on top of them. On top of that anOSB or wood fibre board is fixed andthen battens, counter battens and slatesare added.

Insulation will also be placed betweenthe rafters and internal to this will be anOSB layer, vapour control layer, battensto create a service cavity and, finally,plasterboard.

When the external parts of the roof arein good condition the insulation couldbe added to the inside. The build up is inprinciple the same as the external insula-tion except that there is no OSB or woodfibre board on top of the rafter. Note thatan additional internal build up willreduce the clear head height and with itthe usable floor area.

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Existing Standard Pitched Roof With Insulation on the Slope

Pitched Roof with Insulation on the Slope Upgraded to Passivhaus Standard

Note: Ceiling Heights may Restrict this Build Up

The thermal performance of buildings isnot only dependent on carefullydesigned build up of walls, roof and floorslab. When retrofitting buildings to thePassivhaus Standard the correct designof junctions in terms of insulation,thermal performance, airtightness and

costs also have to be considered. Thereare many options and strategies that canbe used to retrofit to the PassivhausStandard and to show every singleoption for the upgrade of the buildingenvelope would go beyond the scope ofthese guidelines.

The following two sections show possi-ble solutions for the upgrade of a blockwork and timber frame wall construc-tion.

page 44


Additional insulation appliedin attic space and ventilation tile installed.

Airtight layer sealed to wall.

Existing windows removed and replacedwith new tripled glazed thermally brokenwindows.

Existing conc. window cills removed andreplaced with pressed metal cills with external insulation returned to underside of cill.

Additional insulation applied using‘beads’ to create a full fill cavity.

Airtight layer to continue throughfloor cavity.

External insulation fixed to existing render returned to meet the windowframe.

External windows removed and replacedwith new tripled glazed thermally brokenwindows.

Existing conc. window cills removed andreplaced with pressed metal cills withexternal insulation returned to undersideof cill.

Airtight layer to be sealed at floor slab.

Addition of perimeter insulation from rising wall to underside of external insulation to reduce impact of cold bridging.

NOTE:Only the use of IAB approved products is permitted & installation by specialist contractor only.

Standard Cavity Wall Construction Retrofit for Cavity Wall Construction

Source: MosArt ArchitectureNOTE:Only the use of IAB approved products is permitted & installation by specialist contractor only.

Additional insulation appliedin attic space and ventilation tile installed.

Airtight layer sealed at all joints and to allwalls, floor and external opes.

Additional insulation applied using newinternal stud work and returned to meetwindow frame.


Existing conc. window cills removed andreplaced with pressed metal insulatedcills and 2 No. courses of brick laid tomatch existing.

Optional service cavity.

Insulation fitted into floor cavity with airtight layer continuing through.


Existing conc. window cills removed andreplaced with pressed metal insulatedcills and 2 No. courses of brick laid tomatch existing.

Additional insulation applied using newinternal stud work and returned to meetwindow frame.

Airtight layer to be sealed at floor slab.

Floor screed cutback to allow additionalfor insulation.

Addition of perimeter insulation at risingwall to reduce impact of cold bridging.

Standard Timber Frame Construction Retrofit for Timber Frame Construction

SECTION SIX

Case Study Retrofit Building - Theoretical

This Section will illustrate a theoreticalcase study in how to approach theupgrading of a semi-detached house tothe Passivhaus Standard. A descriptionof the construction type and thermalperformance of the property will first beprovided. Thereafter, it will be shownhow the specialist software PHPP wasused to determine such critical issues asthe level of insulation required for thePassivhaus Standard along with sizing ofmechanical systems and prediction ofannual space heating requirement.Schematic drawings are included inorder to illustrate various means ofachieving a highly efficient thermalenvelope as well how to deal withchallenging issues such as thermalbridging and excellent air-tightness. Anapproximate estimate will be providedof the projected savings in terms ofenergy for both heating and DHWproduction.

Dwelling Description

The dwelling chosen as a case study is asemi-detached / terraced house built inthe late 1970’s and located in northCounty Dublin.

The house comprises three bedroomsand one bathroom upstairs with anentrance hall, sitting room, kitchen anddining area at the ground floor level. Thetotal accommodation comprises 83m2.In addition to this is an unheated, exter-nally accessed, single storey, flat roofedgarage attached to the western side ofthe dwelling.

In terms of aspect, the front of the housefaces north and the rear of the housefaces south. There are no east facingwindows but three windows which facewest.

The construction of the walls, floor andceiling is summarised in the Table below.The windows were replaced in 2004from single glazed units with woodenframes to double glazed PVC. Atticinsulation was also fitted in 2004 whichadded considerable comfort to thedwelling.

Thermographic images of the housewere taken at pre-dawn in lateSeptember 2008, with an outsidetemperature of 11 degrees C and aninternal temperature of 18 degrees C.The low energy performance of thebuilding fabric can be easily appreciatedfrom these images, highlighting uninsu-lated external walls with thermal bridg-ing, heat loss through ventilation grills,uninsulated external door, poorlyinsulated hot water pipes connecting toradiators and inadequately sealed attichatch.

A blower door test was also carried outon the same day to determine the levelof airtightness of the dwelling. The resultof this test was 6.39 air changes per hourat 50 Pascal, or 6.6m3/(hm2). The principalweakness of the envelope in terms ofairtightness is the ground floor, compris-ing wooden flooring on timber joistsover a ventilated void. According to theoccupant, there are often severe drafts

Case Study Retrofit Building - Theoretical

CURRENT BUILDING ENVELOPE DETAILS (FROM INTERIOR TO EXTERIOR)Walls Floor Ceiling Windows and Doors

100mm inner 25mm wooden 12mm plaster concrete block floor covering board

40mm cavity 150mm joists 100mm ceiling joistuninsulated uninsulated with 100mm mineral

wool insulation

100mm exterior 150+ mm open concrete block ventilated space

Overall U-value Overall U-value Overall U-value Overall U-value of = 1.69 W/(m2K) = 1.47 W/(m2K) = 0.43 W/(m2K) windows = 1.85

W/(m2K) and doors = 3.0 W/(m2K)


blowing up from the open space belowthe ground floor creating severe thermaldiscomfort. A number of the windowsand both external doors are insuffi-ciently sealed as can be seen from thesmoke test carried out during the blowerdoor test. Other weaknesses includewiring which passes from the first floorthrough to the attic space as well as apoorly sealed attic hatch.

Current Heating and DHW System

The house is currently heated using arelatively new natural gas boiler ofapproximately 80% efficiency. The boilerheats six radiators (two downstairs andfour upstairs) which are controlled by athermostat located in the kitchen. Thereis also a wall mounted electrical heaterin the upstairs bathroom and a portableelectric heater in the living room.

The house currently has no DHW tank.Hot water is provided on demand at thekitchen sink (using electricity) and in theupstairs bathroom with an ‘electricshower’. The primary control for heatingaside from the kitchen thermostat is atime clock.

page 50

Front (north) elevation illustrating significant heat lossthrough the upstairs front bedroom external wall(Bedroom 2). The red glow located between the twowindows is created by heat loss from a wall mountedradiator at that position. Source: GreenBuild Building Information Services

Rear (south) view of Bedroom 3 highlighting in redsignificant heat losses through the uninsulated exter-nal wall from a wall mounted radiator positionedunder the window. Source: GreenBuild Building Information Services

Heat loss depicted in blue colouring created by cold airentering the corner of a bedroom through a ventilationgrill.Source: GreenBuild Building Information Services

Heat loss depicted in black and blue colouring createdby an uninsulated front door. Note how the coldmigrates inward along the floor. Source: GreenBuild Building Information Services

Heat loss (depicted in grey line) from an under floor hotwater pipe feeding a radiator. Source: GreenBuild Building Information Services

Poorly sealed attic hatch displaying heat loss aroundthe perimeter (in dark blue colouring).Source: GreenBuild Building Information Services

Smoke test clearly highlights poorly sealed windowsSource: MosArt Architecture

Smoke test illustrating air leakages below a window sillSource: MosArt Architecture

Leaky floor constructionSource: MosArt Architecture


page 51

Use of PHPP and DEAP to PrepareRetrofitting Strategy

All the relevant details concerning theexisting building dimensions, thermalenvelope performance, level of airtight-ness, orientation and shadowing as wellas electrical elements, heating systemare entered into both the PHPP and theDEAP software.

As can be seen from the Table above, thedwelling as it is currently constructedhas an annual space heating require-ment of approximately 14 times that ofthe Passivhaus Standard. Further, withan existing BER of E2, there is consider-able scope for improvement to bring theoverall energy efficiency to what wouldbe required by the revised 2008 Part LBuilding Regulations (a BER of approxi-mately B1).

Taking the current annual space heatingdemand and multiplying this by gas andelectrical prices, it should, theoretically(according to the PHPP), cost the ownerin the order of €900 per year on gas and€570 per year on electricity, totallingapproximately €1,500 per year. Thisestimation is very close to the actualamount spent on heating by theoccupant of the house as determinedfrom a review of their energy bills.

Preparing a Retrofit Strategy

There are quite a number of aspects ofthe current dwelling that cannot bealtered to any significant degree, includ-ing, for example, orientation and surfaceto volume ratio. Other aspects thatmight be improved, albeit with somedifficulty and therefore relatively highcost, include thermal bridges andamount of south facing glazing. Themost cost effective means of makingconsiderable improvements to overallenergy performance include (a) signifi-cantly upgrading the insulation value ofthe entire thermal envelope, includingwindows and doors, (b) considerablyimproving the level of airtightness, (c)installing a mechanical heat recoveryventilation system and (d) fitting renew-able energy technologies such as solarcollectors for DHW and improving theefficiency of the gas boiler.

The steps used to gradually upgrade thecase study dwelling are detailed in thetable on page 55. A summary of the

overall result of the upgrading strategyis provided hereunder:

■ The space heating requirementtarget of 15 kWh/(m2a) has been

met, reducing the current energyuse by 93% from the current level of214 kWh/(m2/a) according to thePHPP calculations. Referring to DEAP

PERFORMANCE OF THE EXISTING DWELLING ACCORDING TO PHPP AND DEAP7

PHPP DEAP

Annual space heating 214 KWh/(m2a) 160 KWh/(m2a)requirement

Annual primary 441 KWh/(m2a) including 356 KWh/(m2a) (only includes energy use all household electricity electricity for lights, pumps & fans)

Building Energy Rating N/R E2

CO2 Emmissions 94 KgCO2eq/(m2a) 37 KgCO2eq/(m2a)

Space Heat Requirement

0 50 100 150 200 250

0

1

2

3

4

5

6

kWh/(m2a)

Primary Energy Requirement

0 50 100 150 200 250 300 350 400 450 500

0

1

2

3

4

5

6

kWh/(m2a)

Heat Load

0 10 20 30 40 50 60 70 80 90

0

1

2

3

4

5

6

W/m2Source: MosArt Architecture



Retrofit Step

sRetro

fit Steps

Retrofit Step

s

the ‘heat use’ has been reduced from160 kWh/(m2a) to 9 kWh/(m2a) (also areduction of 93%)

■ Achieving the Passivhaus Standardrequired very significantly upgrad-ing the U-values of the buildingenvelope. The poorest performingelement of the dwelling is the walls(U-value of 1.69 W/(m2K)) whichwould need to be upgraded to 0.10W/(m2K). The windows and doorswould have to be replaced with highperformance triple-glazed elements,airtightness improved from 6.39 airchanges per hour at 50 Pascal to 0.6air changes per hour, use of a MHRVsystem with an efficiency of 85%,increasing the area of south facingglass from 7.38m2 to 9.05m2 andreplacing the gas boiler with a unitwith 90% efficiency and installing5m2 of solar collectors (flat plate orevacuated tube) on the south-facingroof.

■ The primary energy demand includ-ing for DHW, heating, cooling, auxil-iary and household electricity wasreduced in the PHPP analysis from457 kWh/(m2a) to 105 kWh/(m2a) andin DEAP from 375 kWh/(m2a) to 55kWh/(m2a)

■ The heat load for the dwelling wasreduced by 90% from the currentsize of 80 W/m2 to 9 W/m2. Takingthat the dwelling is 83m2 in size, thesize of boiler required for spaceheating alone could be reducedfrom 6.6 kW output to just 0.8 kW.

■ Frequency of overheating remainsunaltered at 0%.

■ Referring to the CO2 calculations inDEAP, the CO2 emissions have beenreduced from 160 kgCO2eq/(m2a) to12 kgCO2eq/(m2a), representing a93% reduction. In real terms, giventhe house size of 83m2, there wouldbe an annual saving in CO2emissions of over 12,000 Kg, orapproximately 12 tonnes. In 2004,the ‘average dwelling in Ireland wasresponsible for emitting approxi-mately 8.2 tonnes of CO2. If the casestudy house was retrofitted to thePassivhaus Standard, it would emitjust 1 tonne per year. It is estimatedthat approximately 750,000 housesin Ireland were built before the firstever Building Regulations. If 25% of

those were upgraded to thePassivhaus Standard, there would bea reduction in annual emissions ofCO2 by 2MTCO2eq/(m2a).

■ Lastly, the Building Energy Rating ofthe case study dwelling in achievingthe Passivhaus Standard would bean A3, a very significant improve-ment from its E2 BER.

Measures in Detail

As mentioned above all proposedmeasures have to be checked and beapproved for each individual project.

Thermal Insulation

The existing house was built in tradi-tional un-insulated cavity wall construc-tion, with a U-value calculated at 1.69W/m2K. A 40 mm fulfilled cavity withblown insulation beads and rendered300 mm EPS insulation on the outer leafwill bring the U-value down to 0.10W/m2K. As shown in Section 5 there are anumber of options available to upgradea wall such as that described above.

The flat ceiling to the attic has to beinsulated with 100 mm mineral woolbetween the joists. Additional insulationwill be required, however, in order toachieve the target U-value (if usingmineral wool insulation, for example,400 mm would be required. If otherinsulation products with lower thermalconductivity (λ) values are being consid-ered, less depth would be needed). Inorder to keep the attic accessible, itwould be advantageous to construct araised floor above this additional insula-tion using OSB, for example.

The existing ground floor slab is asuspended floor construction and itwould have been extremely difficult toreduce the U-value down to the required0.10 W/m2K. It was decided, therefore,that the best option in this case wouldbe to remove the existing floor andconstruct a new 150 mm concrete floorslab with 300 mm insulation under-neath.

Windows and Doors

In terms of glazing, it is proposed to usetriple glazed windows with an averageU-value (glass and frame) of Uwaverage=0.9 W/m2K and doors with a U-value of Ud=0.8 W/m2K. The windowsand doors should be installed in the

same layer as the cavity to continue theinsulation layer.

Thermal Bridges

In general thermal bridges are reducedby using external insulation. Perimeterinsulation should be continued on theouter face all around the buildingapproximately 500 mm to 1,000 mm intothe ground, dependent on the depth ofthe foundation. Furthermore, the framesof windows and doors should beoverlapped by the external insulation (atleast 60 mm thickness) to reducethermal losses.

The most significant thermal bridgeswould occur at the concrete canopy overthe front door, the concrete columns oneither side of the front door and at thejoint of wall and roof of the adjacentgarage. It would probably be best toremove the existing concrete canopy aswell as the columns. If there is still a needfor a canopy it could be constructed as-new, yet structurally separated from thehouse.

The uninsulated cold wall of the garageshould ideally be disconnected from thehouse and the resulting gap insulated(some means of structurally anchoringthe garage wall back to the house willlikely be required). The roof of thegarage is easier to deal with as it ismainly made from timber and thereforeits thermal conductivity is not that high.Besides, additional insulation can easilybe fitted above and under the rafters toreduce the thermal bridges.

Thermal bridges can also be created atthe party wall with the neighbour if theydo not insulate their building. Thesethermal bridges can be reduced byinsulating internally.

Lastly, the hatch to the attic has to bewell insulated and sealed airtight.

Airtightness

A continuous airtight layer has to becreated in the building. As render isairtight, there is typically no difficulty inachieving airtightness over wall areas.Windows and doors should be tapedairtight with a suitable tape to the wall.Following that the reveals can to beplastered.

The layer of foil underneath the concretefloor slab serves two purposes.

The first duty is to prevent the concreteseeping into the gaps between theinsulation boards while pouring it. Thesecond function is to create the airtightlayer. This foil has to be taped airtight atthe edges to the walls.

All joints of joists or rafters to walls haveto be taped airtight to the walls. If thereis no render in the ceiling level at thewalls these spaces have to be renderedor spanned with a vapour barriermembrane.

Underneath the insulation of the firstfloor ceiling a vapour barrier has to beinstalled. It is very important to carry outa blower-door-test before the closingthe access points to joints and junctions.It will typically happen that the first testresult exceeds the 0.6 air changes perhour. During the test leakages can belocated and sealed.

Ventilation Heating System

In the case of the example dwelling, theventilation system and heat recovery

unit are located in the ‘box room’ on thefirst floor. The ventilation ducts arepassed through the ceiling void andsupply the fresh air to the habitablerooms such as bedrooms and down tothe ground floor in two shafts to thefamily and living room. The air isextracted in the kitchen, hall, box roomand bathroom.

The heat recovery unit is calculated withan efficiency of 85% and as a ‘back-upheating’ the existing heating systemwith radiators is retained.

Room temperatures are controlled withtime control, external temperaturesensors and thermostats.

Cost of Retrofitting

The cost of the above proposed workshas not been estimated for this ‘theoret-ical’ case study. However, experience onContinental Europe suggests that retro-fit costs to the full Passivhaus Standardtypically equate to approximately 60%of what it would cost for to build the

same dwelling completely from new. Itmust be stressed that such works aremost economically viable when dealingwith an old dwelling which, irrespectiveof energy performance, needs to becompletely upgraded. The case studydwelling presented in the followingchapter is an example of where such anoverhaul was needed. In that case, theextra over costs to reach towardsPassivhaus Standard (i.e. over the abovecosts of new kitchen, extension, conven-tional builder’s work and so forth) was inthe region of 14%.

Until such time as more projects getunderway in Ireland, it is difficult toestimate what retrofit costs will be.

PHPP CALCULATIONS DEAP CALCULATIONSStep Description Space Heat Primary Heat Load Frequency of Primary Heat use CO2 Building

Requirement Energy (DHW, Overheating Energy (Space Heat emissions Energy RatingHeating, Cooling, Requirement)

Auxiliary and Household Electricity):

Units of Measurement kWh/(m2a) kWh/(m2a) W/m2 % kWh/(m2a) kWh/(m2a) kgCO2eq/(m2a)

Passive House threshold 15 120 10 10 - - - -

Current performance 214 457 80 0 375 160 79 E2

1 Insulation of building fabric 49 178 26 4 177 51 39 C2(walls, ceiling, floor), reduction of thermal bridges - improve U-value walls from 1.69 to 0.10 W/(m2K), U-value ceiling from 0.43 to 0.09 W/(m2K), U-value floor from 1.47 to 0.10 W/(m2K)

2 Change from double to triple 35 154 20 5 153 38 34 C1glazed windows, change doors -improve average U-value windows from 1.85 to 0.91 W/(m2K), U-value doors from 3.00 to 0.80 W/(m2K)

3 Airtightness - improvement from 6.39 29 145 13 15 125 22 28 B3to 0.6 airchanges per hour @ 50 Pascal

4 Balanced whole-house-ventilation system, 16 126 9 0 108 9 25 B2with Heat Recovery Unit, efficiency 85%

5 Increase window sizes of south facing 15 126 9 0 108 9 25 B2windows,from 7.38 to 9.05 m2

6 Condensing Gas boiler for heating 15 105 9 0 55 9 12 A3and DHW- efficiency of 90%, DHW not electric anymore, 5 m2 Solar panels, 300 l hot water storage


0

50

100

150

200

250

Current SpaceHeat

Requirement

Part L 2005 Part L 2007 RetrofittedPassivhausStandard

kWh/(m2a)

Space heating energy comparison, Current use in case study dwelling, Building Regulations (TGD) Part L 2005 and2007 and the Passivhaus Standard. Source: MosArt Architecture


Externally Insulated Building Envelope and Heat Recovery Venilation System in Retrofitted Dwelling

Copy of the PHPP 2007 verification sheet for theoretical case study pre retrofitting

Copy of the PHPP 2007 verification sheet for theoretical case study post retrofitting

SECTION SEVEN

Case Study of Completed Retrofitted Project

Case Study of Completed Retrofitted Project This project is one of the first in Ireland inretrofitting a conventional built dwellingtowards a Passivhaus Standard. Theclients visited MosArt's demonstrationpassive house ‘Out of the Blue’ in 2006and were inspired to convert their hometo the same standard of comfort andenergy efficiency.

The existing external walls wereconstructed as a standard cavity wallwith a 100 mm brickwork outer leaf, 100mm cavity and 100 mm concrete block-work inner leaf. Upon inspection thecavity was found to have no insulationinstalled and the walls had been drylined internally with timber studs withrock wool insulation between, polyethyl-ene vapour barrier and plasterboardwith skim finish.

As the exterior leaf was brickwork wewere restricted in how we couldupgrade the fabric to the PassivhausStandard. We achieved this by fully fillingthe cavity with blown in insulation, theexisting dry lining was removed inter-nally and replaced with larger timberstuds and higher density insulationbetween, a higher quality airtightvapour barrier was installed and tapedon all joints with specific care taken tojunctions at floors, ceilings and aroundwindows and doors and new plaster-board and skim finish was installed. Allexisting wall vents were blocked upinternally and a MHRV unit was installedthroughout the house.

The existing double glazed windowswere replaced with thermally brokentriple glazed windows throughout andtriple glazed roof lights were installed inthe roof.

The existing roof was a standard tiledroof with pre-fabricated timber trusseswith insulation on the flat. As the alter-ations to the existing house included anadditional bedroom in the roof spacethe insulation had to be changed to onthe slope to accommodate this.Additional timber rafters were installedto accommodate additional higherdensity insulation in the roof spacebetween the timbers, airtight vapourbarrier was added and new plasterboardwith skim finish.

The existing heating system wasreplaced with a MHRV unit and heatpump with a gas condenser boiler asback-up and solar collectors to the rooffor hot water supply.

It is important to note that theprogramme for a passivhaus build differsto that of a conventional build. Timeshould be allowed for the installation ofthe airtight layer, this airtight layershould then be tested (blower door test)for leaks prior to any plasterboard beinginstalled. Should any leaks be detectedthey should then be rectified and theairtight layer should be re tested untilthe required level of airtightness is

achieved. Testing with a thermalimaging camera is also available. Thiscan detect any cold bridges in the exter-nal fabric of the building. Strict on sitesupervision is required throughout theconstruction works by the designer. Thesite foreman or main contractor shouldalso be made aware of the importance ofstrict on site supervision by them of alltrades to achieve an airtight building. Oncompletion the house should have onefinal blower door test.

The retrofitted building was occupied inMay 2008 and at the time of print, theheating season is approximately 50%complete. The actual annual energyconsumption cannot be verified beforeMay 2009 at the earliest. A comparisonbetween the modelled and achievedimprovement of the energy perform-ance of this project is yet not possible,therefore it is anticipated that the annualspace heating requirement will bereduced by 80%.

The extra-over cost to achieve thePassivhaus Standard according to thecost plan on this project was 14%. Itshould be borne in mind that this houseunderwent a major retrofit and exten-sion programme and thus the abovepercentage extra over costs should in noway be taken as a general guide forretrofit projects.

Case Study of Completed Retrofitted Project

Envelope elements Pre-retrofit U-values Post retrofit U-valuesExternal cavity wall 0.28 W/(m2K) 0.19 W/(m2K)Floor slab 0.58 W/(m2K) 0.18 W/(m2K)Roof 0.13 W/(m2K) 0.11 W/(m2K)Windows 2.90 W/(m2K) 0.81 W/(m2K)

Improvement of U-values

All proposed retrofit measures must be properly detailed to enableconstruction and well as to verify performance in the PHPP software

Before commencingany retrofit works, a fullsurvey will be requiredto establish currentinsulation standards

While the red brickfacade remaineduntouched, all the windows were upgrad-ed to triple-glazedPassivhaus Standardunits (U-value of 0.81W/(m2K) for entire window)

These special tripleglazed roof lights wereused on the south facing rear elevation (U-value of 0.91W/(m2K) for entire window)

Retrofitting to reduceenergy consumptionalso provides a valuableopportunity to enhancethe aesthetics of theinterior

The mechanical heatrecovery ventilation system was installed inan accessible part ofthe warm attic space

This water to air heatpump is connected to alow-temperature under-floor heating systemand is anticipated toprovide 85% of thespace heat requirement(COP = 3.4)

The existing buildingenvelope was dry-linedinternally with high performance insulation

Locations such as thiswhere large servicesexit the building envelope are very difficult to seal properlyin terms of airtightness

The south facing rear ofthe house on comple-tion, with 15m2 of flatplate solar thermal collectors which areexpected to contribute65% of DHW demand

Sustainable Energy IrelandRenewable Energy Information OfficeUnit A, West Cork Technology ParkClonakiltyCo CorkIreland

T. +353 23 8863393F. +353 23 8863398

[email protected]

SEI is funded by the Irish Government under theNational Development Plan 2007 - 2013 with programmes part financed by the European Union.

retrofit passive house guidlines

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