Passivhaus in the UK

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Passivhaus in the UK - are we making
progress? Liz Reason, Director, CarbonLite

CarbonLite
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The UK government has ambitious ambitions

• Targets for new buildings
• zero carbon homes by 2016
• zero carbon non-domestic buildings by 2020
• the Eco-Town Challenge
• reducing CO2 emissions by 80 across
  developments as a whole
• making it possible for residents to live within
  a 2 tonne CO2 budget

DECC Department of Energy and Climate Change
Government is consulting on a strategy to reduce
CO2 from existing buildings by 80
Zero carbon schools
Zero carbon colleges
A 60 cut in carbon footprint
11/20/2009
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And has devised the Code for Sustainable Homes
for starters
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The first officially PH certified UK building -
training centre/ offices, Machynlleth
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Private house, Stroud
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Social housing, Ford Farm, Plymouth
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Denby Dale, West Yorkshire
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Disability Essex, Rochford
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Lound Hall, 38 room nursing home, Suffolk
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Refurbishment of a community centre, London
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Gentoo Housing Association - Racecourse Estate
Houghton-Le-Spring, Tyne and Wear
25 homes
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Victorian Cottage, Hereford
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We need a clear pathway to the destination of low
energy buildings

• Know where youre going
• Understand energy in buildings
• Adopt the best components, tools and techniques
• Measure how well you did
• Close the feedback loop

These are the principles adopted by CarbonLite
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Three standards underpin CarbonLite
They provide clear CO2 and energy targets
These are domestic sector figures based on a 80m2
semi-detached house
The standards are all based on the Passivhaus
standard and associated software
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Why model CarbonLite standards on Passivhaus and
PHPP?

• The standard
• A carefully developed low energy building
  standard
• Promotes design of cost-effective energy
  efficiency solutions
• Focuses on getting the fabric right
• Performance-monitored
• Gaining credibility throughout Europe and beyond

• PHPP (PassivHaus Planning Package)
• Two specific energy targets
• space heating 15 kWh/m2.yr
• primary energy 120 kWh/m2.yr
• Models buildings as a system and encourages low
  energy solutions throughout
• Optimises passive solar gain
• Promotes and assists designers to achieve low
  energy solutions
• Provides reasonable predictions of energy use for
  meeting CarbonLite standards

But it was not possible accurately to model in
SAP a super-insulated dwelling with passive solar
gain
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In the first instance, the UK regime differs in
key respects from the Passivhaus standard

• The UK
• A CO2 target
• prompts carbon-saving solutions which tend to be
  expensive kit
• Expressed as a target reduction against a
  notional building whose parameters are not fixed
• It is possible to achieve compliance by worsening
  the base case
• Focuses on the fabric standard but is ambivalent
  towards non-fabric energy
• Compromises the fabric standard

• Passivhaus
• Two energy targets
• space heating
• primary energy
• Specific energy targets
• 15 kWh/m2.yr space heating
• 120 kWh/m2.yr primary energy
• Focuses on fabric standard and applies and
  accounts for low energy design at the whole
  building

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The comparison of SAP and PHPP

• The key findings
• When modeling well-insulated low energy
  dwellings, we found
• PHPP tended to predict higher heating
  requirements than SAP
• SAP predicted no heating at all (where in
  practice some heating is needed)
• Because there are no fixed energy limits,
  inefficient built forms are favoured rather than
  penalised
• SAP indicates that carbon savings can only be
  delivered by expensive kit before using useful
  energy efficiency measures

• Our approach
• We set up a PHPP model of a standard UK developer
  3 bed semi-detached house, altered to meet the PH
  standard
• We then set up a SAP model of the same house and
  found differences
• Where assumptions in the two models differed, we
  introduced the SAP assumptions into PHPP

So whats going on?
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We explored six possible differences
kWh/m2.yr
NB These differences are cumulative
These differences are not exhaustive - more
analysis could be undertaken
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And heres what we found
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Energy balance - the big difference is in the
gains .
No heating needed
And heres why
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but not the only one

• Ventilation losses overestimated
• Fabric losses underestimated

Solar gains underestimated
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PHPP looks daunting but accounts in detail for
energy use

• PHPP
• uses frames and glazing of individual windows,
  accurately measures shading, calculates window
  installation thermal bridges
• assumes low gains from hot water, lighting,
  appliances and occupants
• A appliances and 100 low energy lighting are
  required
• hot water systems required cylinder insulation,
  insulated primary pipe lengths, and dead leg
  volumes
• these are used to accurately estimate the actual
  hot water energy consumption
• MVHR test procedures produce a conservative power
  consumption figure, by testing at 100 Pa external
  and around 75 maximum flow rate of the unit
• calculates the heat absorbed by cold water lying
  in pipes and toilet pans

• SAP
• uses homogeneous window characteristics
• assumes business as usual on household energy
  efficiency, and continues to expect tungsten
  lighting to be used
• does not reward design of efficient hot water
  systems
• MVHR Appendix Q test procedures do not replicate
  the design of real systems

With a 15kWh/m2.yr space heating limit, every kWh
counts
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We need to change UK culture

• Weve
• been too relaxed about energy in buildings
• muddled our metrics
• oversimplified SAP to make it accessible to a
  broad range of users
• used fudges without understanding the
  implications and incentives they create
• undervalued energy expertise and divorced it from
  design
• failed to exploit the energy expertise we do have

So what do we need to do?
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Set up a new organisation

• To focus on the Passivhaus standard and
  methodologies
• To provide leadership
• To build capacity in people and products
• To expand the market

WATCH THIS SPACE
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CarbonLite www.carbonlite.net