sustainablewall_systems

8/7/2019 SustainableWall_Systems

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Hemcrete, BioBric & Poroton

Sustainable & SolidWall Systems with Ecological Materials

In the context of radical environmental requirements and dramatic energy savings thefuture of human habitat will have to combine sustainable, dense mixed urban

neighbourhoods, Eco-Towns with solid, durable and healthy Eco-Homes.

Ecological systems depending on high technology and energy consumption cannot

anymore be relied upon as sustainable and viable options for future building types and

will remain complementary and experimental endeavours. We will more likely have

to generalize and optimize passive systems allying natural materials, renewable

resources, regional economies and local skills. We will more likely adopt smart and

timeless solutions adapting from past vernacular traditions and adapting to best new

scientific and technical knowledge.

A Typical Cavity Wall Construction

The cavity wall and other hybrid wall structures present shortcomings and liabilitieswhich will increase with new legal requirements regarding carbon emissions and

energy efficiency. They also present a growing degree of complicatedness and

dependence on fossil based resources and apear less and less convincing and losing

ecological, economical and technical credibility.

In order to comply with modern regulations and in the context of the Eco-Housethe cavity wall has to increase its cavity almost to a breaking point of structural

consistence and stability. This creates additional complication, reassessment of skills,

longer building times and higher costs. Both cavity wall and sandwich wall need to

increase their wall thickness and reschedule their components to achieve both energy

savings and required carbon footprints. Eventually some wall systems are growing

quite thick with substantial layers of insulation without however being able to take

advantage of solar gains and benefit of thermal mass. Most conventional systems are

voracious of novelties, of specialisation and innovative materials and membranes,

either natural or chemical. The building process is turning into an absurdlycomplicated technical assemblage. Not only is this frustrating, expensive and time


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taking in the reality of the building process, but it is also highly antagonistic to the

original purpose of sustainability, ecological comfort and good practice.

The Cavity Wall, the Imperfect Remedy

The paradoxical purpose of the Cavity Wall is Separation and Isolation

The illogical and unhealthy Schizophrenia of the Cavity Wall


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The Traditional Solid Wall, a Sustainable Alternative

The logical Beauty of the Sustainable Solid Wall: Articulating Exterior & Interior

42,5 cm aerated clay block Wall rendered with Lime Mortar (outside) and Marmorino

Plaster (inside). Base, sill and door frame in local limestone.

The simple and quick building process allows to dedicate more time to details and ornament!

(Wall Building Experiment during The Princes Foundation Summerschool in Lincoln, 2008)


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The Ecological Complexity , Evidence & Simplicity of the Aerated Brick Wall

The Better Way to Build

Building single leaf, load bearing and rendered walls with fired, aerated clay blocksallows for a quick, cost efficient and extremely simple building process. The clay

blocks of various producers have achieved a degree of complexity and of excellence

after at least 20 years of experience in Continental Europe.

The efficiency of the system is due both to 1) the nature of the clay blocks: extrudedwith vertical perforations and aerated by a micro-porous structure, the clay blocks

maintain a good thermal mass with less density and higher insulation values. And, 2)

the building technique of accurate thin bed joints and interlocking vertical joints

(eliminating maximum of thermal bridges through mortar joints) . As the building

process is virtually dry the wall is immediately ready for finishing without the risk of

long-term drying out shrinkage.

The walls are weather and air tight, very vapour permeable (avoiding condensation),

excellent for thermal insulation. They offer an efficient protection against Summer

over-heating and temperature breaks in winter. They are fire resistant and have good

acoustic qualities.

They can carry loads from concrete floors and can also be used as infill panels inframed buildings. They can also be used below dpc level with tanking to build cellars.

U _ Values*The U_Values indicated for various types of aerated clay blocks are consistently

around 0,25/0,26 W/mK for a 365 mm wall and 0,22 W/mK for a 425mm wall.


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*U_Value is the coefficient of heat transmission through the materials composing the

envelope of a building. The lower the U-Value the less heat is uselessly escaping, and

the less the building is affected by either cold or hot exterior temperatures.

New Opportunities for Crafts in Sustainable Construction & Ecological Materials

Crafting and Rendering the Cornice with Lime Mortar

(All photos taken during the Princes Foundations Summerschool in Lincoln, 2008)The Prince of Wales Crafts Aprrentices


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Aerated Clay Block Wall built during the Summer School in Lincoln:

An Opportunity for Sustainable Crafts & Architecture

This wall was built and rendered in less than a week by some craftsmen andapprentices of the Summer School. Rather than spending their time in complicatedand laborious building activities most of the available time could be used to design

and produce in refined detailing and some ornament. The almost dry and efficient

building system of aerated clay blocks not only creates a more comfortable working

context, but speeds up construction time to twice or three times (with crafts people

trained and familiar with the system) the time needed to build cavity walls!


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The blocks are extruded with vertical perforations. Sawdust which is mixed in with the clay

matrix, burns away during firing to give a micro-porous structure.

There are various types of Aerated Clay Blocks available on the European building market,

and often produced locally in Germany, Austria, France, Italy, Spain, etc. During the Lincoln

Summerschool the Princes Foundation used BIOBRIC, a French block imported into the UK.

Presently the Aerated Clay Blocks are produced under licence in the UK. POROTON, (an

invention from 1958 by a Swedish engineer), is a popular and affordable building materialthroughout Northern Europe.


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Most of the aerated clay block producers offer a full range of standard blocks and specials,

corner blocks, reveal blocks, make up blocks, insulated clay lintels, blocks for ring beams,

etc.

Environmental & Ecological Considerations

Ecologically Friendly Construction1. Relation with the surrounding environment

2. Low environmental impact in the manufacturing process

3. Low degree of nuisance during construction

Energy managementHigh level of continuous thermal insulation reduces energy demand in heating. Thermal bridges values are also

much lower than conventional construction.

MaintenanceNo maintenance required.

Humidity and condensationHigh protection against dampness penetration and the formation of condensation.

Acoustic InsulationGood results are easily achieved.

Quality of living environmentHealthier living environment is assured by the lack of dampness, the good insulation values and the resistance

against biological growth.


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Air qualityThe clay blocks do not contain pollutants such as fibres, organic airborne materials (benzene, toluene, solvents,

ethers), formaldehyde and so on (there are about 100 possible pollutants in organic airborne materials such as

PFA). No fungicides or insecticides are present and no radioactive components.

Water purityNo adverse effect on the water table.

Water and Waste managementNo effect on domestic water consumption and in waste management

RecyclabilityThe aerated clay blocks are totally recyclable.

In case of fireMasonry clay blocks are totally fire proof (class A1). Furthermore no toxic gases will be released when exposed to

fire.

In case of floodingProlonged exposure to water will not alter the structure of the clay blocks and their mechanical and thermal

characteristics will be the same once dry.

In case of earth tremorsExcellent behaviour in seismic areas. The holding structure, with reinforcing rods contained in the column blocks

and continuous lintels at each floor level is very efficient. The only recommendation is seismic areas is to fill the

perp joints, an operation not necessary in other areas.

In case of pests and insects presenceThe blocks cannot be attacked by pests and insects.

(quoted from theBouyer Leroux BioBric website: www.clayblocks.co.uk/index.php

Timber Frame ConstructionConventional timber frame systems which should be more sympathetic because of their

interesting carbon footprint fail however often to satisfy thermal mass and energy efficiency

issues. Their design is often dictated by the insulation industry or the component suppliers.

They suffer also from an excessive complicated layering of various components and

membranes, many of which are not renewable and fossil-fuel based.


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The Unsustainable Complication of the Framed Sandwich Wall

The Better AlternativeHemp Lime Technology

Tradical Hemcrete is a unique, highly sustainable construction product for the

creation of insulating walls as well as insulation layers for floors and roofs.Hemcrete

is a blend of specially prepared hemp shiv (Tradical HF) and special lime based

binder (Tradical HB). Together these products form a bio-composite building material

that can be used both for the creation of buildings that have excellent thermal and

acoustic properties as well as creating a healthy living and working environment.

Properties ofTradical Hemcrete

Low Density,-High Thermal Insulation, High Sound Insulation, High Thermal Inertia, Good

Vapour Permeability, Good Flexibility, Fire and Pest Resistant, Significant Reduction of CO2

Emission, Air tightness, Recyclable and Renewable, Non Toxic, etc.


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Walling with permanent internal Formwork for Spray Application

The Carbon Balance

The combination of patented, UK produced air-lime based binders and the woody

core of the UK grown industrial hemp plant results in construction products that

achieve the capture of significant amounts of carbon from the atmosphere.

Calculations show that approximately 110 kg of CO2 per m3 ofHemcrete walling

material is sequestrated more for roof insulation.

The construction of buildings are responsible for approximately 50% or more for theCarbon Dioxide Emission in the UK. The impact of reduced carbon footprints in thebuilding industry would be immediate and sensational. Current Government

regulations ask a 1 Ton CO2 reduction by year and Zero Carbon by 2016! Tradical

Hemcrete built houses can do much better: they have a negative Carbon footprint.

With 5000 Hemcrete houses among the 250.000 to be built annually, the Government

CO2 reduction targets would be met!

A typical house built in Tradical Hemcrete = minus 40 Tons to 50 Tons of CO2

The approximate U_value for a 400 mmHemcrete wall is 0,20 W/m2K


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Various Wall Systems & Finishes

There are various possibilities to buildHemcrete walls with rendering, boarding orbrick cladding finishes. The walls can be sprayed or cast depending on the wall type

and building site logistics, but can also be done with prefabricated blocks or panels.

Tradical Hemcrete can be used to build various types of framed wall systems. Intimber frame buildings it provides the wall form, the racking strength and the

insulation and forms a integrated solid system. In steel and concrete framed buildings

it provides the wall form and insulation in one monolithic product.

The excellent vapour permeability protects the timber from deterioration mechanismsand extends its longevity.


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The high thermal performance and air tightness allow for efficient single skinstructures without additional insulation.

Hemcrete offers a substantial thermal mass despite the lower density and weight

Hemcrete is a quite flexible material with relatively constant qualities in a variety ofgeographical and climatic situations. Its compact porosity offers both a breathable,

airtight and vapour permeable structure and reacts well in humid and damp situations.

Hemcrete has however to be absolutely protected against durable water exposure

either up from the ground or from the top. It needs a carefully executed lime render,

sufficient overhangs and correct gutter detailing, and cannot of course be built inflooding areas.


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Building of the 2x4 Timber Frame, Brick Base and Shuttering Board for a 400 mm Hemcrete

Wall at the Summer School in Lincoln

An Opportunity for an affordable, healthy and sustainable ArchitectureThe finished Hemcrete Wall Structure at the Lincoln Summer School


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Tradical

Hemcrete

for better than zero carbon buildings

Lhoist UK has developed a lime based binder that works with industrial hemp to form a

building material called Tradical

Hemcrete

. The carbon footprint of Tradical

Hemcrete

is actually negative. The plant material (Tradical HF) absorbs carbon through

photosynthesis as the plant grows and the carbon emission of the lime based binder

(Tradical HB) is low enough that the net carbon footprint is still negative in the combined

product. The carbon remains in the Tradical Hemcrete bound by the lime based binder.

Tradical Hemcrete therefore has the ability to lock sequestered carbon into the fabric of

buildings whilst delivering highly insulated, quick to construct, comfortable, healthy,

sustainable and durable buildings.

The product has excellent insulation and acoustic properties and has been in use in France

for over 10 years in niche market new build and renovation on a small scale and has been

selected in the UK in the last two years for major new build projects including the Adnams

Distribution Centre in Suffolk and the CAT WISE project in Wales, as well as a number ofhousing and extension projects around the UK.

Tradical Hemcrete is used as a solid wall form in combination with a structural building

frame, commonly timber, to build all types of building. It can also be used with other frame

materials and can be used in roof and floor insulation. Insulating plasters have also been

developed in France and retrofit insulation to existing buildings has also been carried out.

The net carbon saving effect, taking account also of the avoidance of using high embodied

energy materials, can be as much as 50 Tonnes of CO2 equivalent for a typical new build

house at construction stage. The excellent insulation performance of Tradical Hemcrete

alone would also deliver the opportunity to achieve very low or zero carbon emissions from

the buildings in use and, combined with the inherent carbon capture at the construction stage,can provide the key to achievingbetter than zero carbon buildings. Certainly, Code for

Sustainable Homes Level 3 is readily achievable and designers are currently working on

Level 5 and 6 designs incorporating Tradical Hemcrete.

In addition the vapour permeability of Tradical Hemcrete provides a healthy environment

that building occupants and users should benefit from in the long term and Tradical

Hemcrete delivers very comfortable, warm in winter, cool in summer buildings assisted by

the buffering effect on temperature changes that the product exhibits through its

hydrothermal characteristics.

Lhoist UK has responded to the increasing demand for sustainable and low carbon

construction products by bringing together a team of partners to deliver Tradical Hemcrete

as a building product available to mainstream construction. Lhoist has teamed up with Lime

Technology Ltd. to blend and package the products; with Hemcore Ltd. the principal

industrial hemp processing business in the UK to supply construction grade hemp; and with

Castle Cement Ltd. to provide access to a nationwide distribution network of over 1000

builders merchants.

(Press Release provided by Tradical)


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CONCLUSIVE NOTES

Hemcrete and Aerated Clay Blocks (Biobric, Thermoplan, Poroton, etc.) can be used

to reasonably build buildings up to 4 floors, though Hemcrete has eventually beenused in buildings up to 6 floors in France.

The Aerated Clay Block can be used as a frame infill, both in new and old buildings,

and both materials have good credentials in both new buildings and conservation

projects.

Both systems can be combined in various manners, either by adding aHemcrete

Panel or Render to the Aerated Clay Block Wall or by building a Clay Block Cellar or

Ground Floor with aHemcrete Upper Floor, etc.

A very promising system is a combined aerated clay block andHemcrete wall system

where U-values of 0,15 could be achieved in less than 500 mm walls. TheHemcrete


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is directly sprayed on to the Aerated clay blocks. The maximum depth of the

Hemcrete is 500mm and there is no need for framing or ties!Hemcrete can then

additionally be used also to have thermally efficient floors and roofs.

One can also imagine a scenario with a more formal Clay Block Building facing the

street and a more vernacularHemcrete structure as a Back Building or a MewsBuilding, etc.

1) Both Aerated Clay Blocks andHemcrete perform exceptionally in terms ofenergy efficiency, insulation, thermal mass, vapour permeability, acoustic

comfort, etc. The required wall thickness for both has to be a minimum of

400mm.

2) Hemcrete achieves a quite good 0,20 W/m2K U_value for a 400 mm wall andeven 0,15 W/m2K for a 500 mm wall.

3) The Aerated Clay Blocks achieve approximately between 0,22 and 0,26W/m2K for a 400 mm wall depending on the various block types and qualities.

4) Hemcrete performs spectacularly in terms of Greenhouse impact by lockingup 40T/50T CO2 house, whereas the Aerated Clay Blocks perform relatively

well by having a 30% lower CO2 footprint than comparable cavity walls.

5) Both Aerated Clay Blocks andHemcrete need to be rendered.Hemcrete needsa special attention regarding water exposure whereas Aerated Clay Blocks do

not suffer from water exposure.

6) Hemcrete is a wet building process and the wall take some time to dry outsufficiently, whereas Aerated Clay Blocks is a dry building system allowing

for a more discontinuous building process.

7) Hemcrete is a relatively soft material unlike Aerated Clay Blocks and needeither to reinforce edges, projections and corners or soften them intochamfered or rounded ones. This softness is also an issue regarding the

hanging and application of fixtures and needs to be addressed as an important

issue. One has to evaluate also the capacity of theHemcrete wall to cope with

later alterations, perforations and refurbishments and additional service

conduits. Quite positively though any wall damage or conduit can be repaired

or respectively filled in or insulated by eitherHemcrete or special light lime

mortar.

Hemcrete Project for a Development in Stamford (UK) (The Princes Foundation 2008)


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Two Sustainable Wall Structures at the Summer School in Lincoln

This paper has been produced by Lucien Steil at the Princes Foundation for the Built

Environment following up on the Residential School of the Prince of Wales

Building Crafts Apprentices in Lincoln in 2008 (The Summer School was planned,

coordinated and directed by Ben Bolgar and Lynette Green).

The findings of the paper were used to prepare the brief of The Natural House

project to be built at the Innovation Park at BRE (Building Research establishment)

by the Princes Foundation for the Built Environment.

http://www.bre.co.uk/page.jsp?id=2075
http://www.bre.co.uk/page.jsp?id=2075http://www.bre.co.uk/page.jsp?id=2075http://www.bre.co.uk/page.jsp?id=2075

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