Mind the Gap

What can Passive House design teach us about closing the building performance gap?

Elrond BurrellUK Registered Architect

Certified Passive House Designer

VIA-architecture.net

If you don't measure results, you can't tell success from failure

David Osborne and Ted Gaebler

Let’s talk about:1. What is the building performance gap?

2. Why does it matter?

3. Reasons for the gap

4. Passive House design

5. Results

1. What is ‘the gap’?When building performance in use doesn’t match design predictions

1. Energy Consumption

2. CO2 emissions

3. Health and wellbeing• Comfort• Hygiene• Indoor Air Quality

What is the gap?When building performance in use doesn’t match design predictions

1. Energy Consumption

2. CO2 emissions

3. Health and wellbeing• Comfort• Hygiene• Indoor Air Quality

Health and WellbeingComfort• Air temperature, surface temperatures, temperature

asymmetry, draught-free, relative humidity

Hygiene• Condensation, mould

Indoor Air Quality• Fresh air, odours, CO2 levels, moisture

2. Why does ‘the gap’ matter?People see sustainable design as:• Woolly• Well intentioned, but . . .• Expensive / luxury• An add-on extra• Pointless

They are right . . .. . . while there is a performance gap.

Climate Change

Is sustainable design mitigating climate change?

Not (much) while there is a performance gap

Close ‘the gap’ and . . .

Sustainable design is• Not woolly: clearly defined outcomes• Not just good intentions: delivers on promises• Not luxury: what educated clients demand• Not an add-on: integral to design• Not pointless: relevant

AND genuinely helps mitigate climate change

3. Reasons for ‘the gap’1. Design

2. Construction

3. Commissioning

4. Occupation

Design• Designers don’t know the impact of decisions• No modelling• Wrong / unknown modelling assumptions• Wrong assumptions about how people behave• Designs unbuildable

Construction• Drawings / documentation not followed• Changes made during construction• Lack of quality control

Commissioning• Not done• Incomplete• Wrong

Occupation• Complex systems that people don’t know how

to use• Not educated in using a building efficiently• Don’t care?

4. Passive House design• Clear performance requirements• Rigorous non-prescriptive design methodology• Modelling integral to the design process• Design QA• Construction QA• Rigorous 3rd-party verification process• Accountability

A focus on what matters1. Insulation

2. Airtightness

3. Heat Recovery Ventilation

4. Thermal Bridges

5. Windows & Doors

How Airtight?

4.5X

plu

s

0.6 ach 5.0 ach

HRV vs Windows

3X p

lus

Window ventilation only82% efficient HRV

Why is PHPP so accurate?• A design tool• Instant• Transparent• Parametric• Useful

• Simplified• Steady state• Only what’s needed

• Detailed

• Verified• Dynamic simulation• Real world results• Constant improvement

How detailed?

U = 0.86 W/(m²K) U = 0.84 W/(m²K) U = 1.22 W/(m²K)

From the Pwassivhaus Institut

Exampleswww.passivhausprojekte.de

5. ResultsEnergy Consumption / CO2 Emissions• Heating• Energy

Health and Wellbeing• CO2 levels• User comfort / satisfaction

Heat Loss• 12

PHEv

eryt

hing

else

Co-heating test resultsCentre for the Built Environment, Leeds Metropolitan University

Heat Consumption• 12

Measured heat consumption from four housing estateshttp://passipedia.org/

Wilkinson Primary School

Architype (UK)

Energy ConsumptionkW

h/sq

m /

yea

r

0

50

100

150

200

250

2013 2014 2013 2014 2013 2014 2013 2014 2013 2014

CIBSE CIBSE TM46 BREEAM2Very2Good BREEAM2Excellent Passivhaus Passivhaus Passivhaus

Typical Good2pracGce

Median Willows St2Lukes Oakmeadow Bushbury Wilkinson

70+

% re

duct

ion

CO2 levels

Camden Passive House

bere:architects (UK)

Comfort / Satisfaction

Wimbish Social Housing

Parsons + Whittley (UK)

Comfort / Satisfaction

Takeaways: to close the gap• Clear measurable targets

• Model accurately and often to measure design

• Measure completed buildings and learn

• Accountability throughout the process

VIA-architecture.net