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Colin Powell from GCP Architects outlines the concept and challenges of PassivHaus, a design standard for producing buildings with very low energy demand.
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PassivHaus - the solution for low energy building?
Colin Powell BA(Hons) DipArch Msc RIBA
gcp : architecture : energy : sustainable design
Content • PassivHaus primer – a brief outline • (why) Do clients want PassivHaus • The problems for PassivHaus design – myths and reality • Knowledge based design – don’t be frightened by numbers • Challenges for the designer • Engaging the user – achieving performance in use
gcp : architecture : energy : sustainable design
gcp architecture : energy : sustainable design
Effective sustainable design requires a detailed knowledge of building science, technology and construction Our core skills as architects provides our clients with a depth of understanding that informs our advice on energy and sustainability Our consulting business provides the specialised knowledge of sustainable and low energy design needed to help our clients achieve their ambitions
i n t r o d u c t i o n
gcp architecture : energy : sustainable design
PassivHaus is a design standard for producing buildings with very low energy demand Developed in Germany in 1991, now being used around the world as a tried and tested standard Not only applicable to housing, it can be used for large and small buildings and refurbishment
q u i c k o u t l i n e
gcp architecture : energy : sustainable design
Standard applicable to all building types PassivHaus focusses on building energy calculated through a rigorous calculation method Not only applicable to housing, it can be used for large and small buildings EnerPHit standard applies PassivHaus principles to refurbishment and retrofit
offices
schools
housing
student residence
q u i c k o u t l i n e
gcp architecture : energy : sustainable design
• Exceptionally high thermal insulation
• High performance triple glazed windows
• Thermal-bridge-free construction
• Very low air permeability – airtight building envelope
• Comfort ventilation with
highly efficient heat recovery
continuous thermal insulation typically >300mm thick
larger windows to the south for beneficial solar gains
continuous air barrier To prevent air leakage
ventilation system delivers fresh air to main activity spaces
ventilation with Heat recover to save energy
q u i c k o u t l i n e
gcp architecture : energy : sustainable design
Govt. Agenda for Carbon Reduction – Climate Change Act 35% Reduction in CO2 by 2020 Increasing energy costs and prospect of increasing energy instability Planning and statutory targets for energy and carbon
l e g i s l a t i v e a g e n d a f o r c h a n g e
DECC – monthly retail price indices
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1992
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2004
2005
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Fuel price indices in the domestic sector in real terms 1992 to 2012
Coal andsmokeless fuels
Electricity
Gas
gcp architecture : energy : sustainable design
Clients want reliable solutions that deliver real benefits Suspicion of complex renewable technologies that may not deliver reduced energy Resistance to sustainability measures that are counter-intuitive Need for solutions that are simple and robust
We are increasingly finding that sustainability is an important driver to occupiers and investors; • Occupier concern over energy use and running cost • New taxation (e.g CRC) • Sustainable buildings give occupiers tangible costs
savings (£5.2m saved in past 4 years) • Holds long term property values with investors • Now a contractual requirement for our whole supply
chain
(Sarah Cary – Sustainable Development - British Land)
r e a l - w o r l d i s s u e s In our previous offices, energy costs were over £23,000 per annum and rising fast. Energy costs in the new office are projected to be a credit of £2,000 per annum and rising in line with energy costs, representing a £25,000 per annum saving on the old office. (John Walkerdine - Interserve )
gcp architecture : energy : sustainable design
Stable internal temperatures without cold surfaces or draughts Reduced risk of overheating Controlled ventilation can reduce the risks of respiratory disease Thermal performance and air-tightness through rigorous quality control at design and construction stage
Image courtesy of International PassivHaus Association
I t s n o t j u s t a b o u t m o n e y “We think each person lifted out of fuel poverty will save the health service about £250 a year. Data suggests there are 20% more deaths in Oldham in winter than in summer because of extra respiratory illnesses and heart problems [linked to cold homes]. If you get a cold winter and people cannot heat their homes, you get more people suffering and turning up in A&E” (Guardian Nov.13 – ‘Actively cutting energy bills in Oldham – Welcome to the Passivhauses’)
gcp architecture : energy : sustainable design
Exeter City Council Hastoe Housing Group Interserve University of East Anglia Leicester City Council Circle Housing Gentoo Diocese of Worcester University of Bradford London Borough of Tower Hamlets Carmarthenshire Council East Midlands Housing Association Raynsway Properties Estimated over 500 completed projects by end 2013 a rate of growth consistent with Germany 20 years ago (NHBC Foundation July 2012)
W h y a r e c l i e n t s c h o o s i n g P a s s i v H a u s ?
“healthy buildings”
“addresses fuel poverty”
“reduced management & maintenance”
“future proof”
“not eco-bling”
“demonstrates CSR”
“fabric first”
“massive cost saving”
“tried & tested”
“opportunity for higher revenue”
“right thing to do”
gcp architecture : energy : sustainable design
M y t h s a n d R e a l i t y
You can’t open the windows
PassivHaus needs no heating
Sealed buildings are unhealthy
Mechanical ventilation wastes energy
PassivHaus overheats in summer
PassivHaus are too complex
PassivHaus are too simple
Windows can be opened for comfort and cooling, buildings will recover more quickly after closing
PH do need heating – just very little – a single towel-rail or perhaps a big dog?!
Proper ventilation is designed-in and works even in cold months when you want to keep the windows closed
Efficient, well-designed Heat Recovery Ventilation saves 10 times the energy it uses
Shading and cooling are key parts of the design process and certification criteria
PH often use less technology and simpler systems
Sometimes you just can’t win! (there are plenty of examples to refute this)
gcp architecture : energy : sustainable design
M y t h s a n d R e a l i t y
You can’t open the windows
PassivHaus needs no heating
Sealed buildings are unhealthy
Mechanical ventilation wastes energy
PassivHaus overheats in summer
PassivHaus are too complex
PassivHaus are too simple
Windows can be opened for comfort and cooling, buildings will recover more quickly after closing
PH do need heating – just very little – a single towel-rail or perhaps a big dog?!
Proper ventilation is designed-in and works even in cold months when you want to keep the windows closed
Efficient, well-designed Heat Recovery Ventilation saves 10 times the energy it uses
Shading and cooling are key parts of the design process and certification criteria
PH often use less technology and simpler systems
Sometimes you just can’t win! (there are plenty of examples to refute this)
gcp architecture : energy : sustainable design
The energy we use is affected by different factors • Age of the building
E n e r g y i n b u i l d i n g s – u s i n g n u m b e r s t o i n f o r m d e s i g n
62% 19%
13%
3% 3%
Home Energy
HeatingHot WaterAppliancesLightingCooking
Energy use – average all UK homes
gcp architecture : energy : sustainable design
The energy we use is affected by different factors • Age of the building • Lifestyle • Purchasing decisions
E n e r g y i n b u i l d i n g s
32%
22%
29%
9% 8% Home Energy
HeatingHot WaterAppliancesLightingCooking
Energy use – new home to current regulations
E n e r g y i n b u i l d i n g s – u s i n g n u m b e r s t o i n f o r m d e s i g n
gcp architecture : energy : sustainable design
Heat loss from the building has to be balanced with energy (heat) in to maintain comfort We can calculate where this heat is lost by modelling
S o w h e r e d o e s a l l t h e e n e r g y g o ?
gcp architecture : energy : sustainable design
Heat loss from the building has to be balanced with energy (heat) in to maintain comfort We can calculate where this heat is lost by modelling
S o w h e r e d o e s a l l t h e e n e r g y g o ?
walls 13.2
roof 9.2
floor 4.0
windows 24.2
ventilation 48.0
Current Regs - elemental energy loss – kWh / m2
Therm. bridges
2.7
gcp architecture : energy : sustainable design
Heat loss from the building has to be balanced with energy (heat) in to maintain comfort We can calculate where this heat is lost by modelling
S o w h e r e d o e s a l l t h e e n e r g y g o ?
walls 13.2
roof 9.2
floor 4.0
windows 24.2
ventilation 48.0
Current Regs - elemental energy loss – kWh / m2
Therm. bridges
2.7
gcp architecture : energy : sustainable design
• Understanding from elemental analysis enables optimises solutions
• Implications for building design from site layout to construction
U n d e r s t a n d i n g t h e n u m b e r s h e l p s i n t a r g e t i n g s o l u t i o n s
walls 8.4
roof 5.2
floor 3.3
windows 13.7
ventilation 5.6
Therm. bridges
0.0
PassivHaus - elemental energy loss – kWh / m2
gcp architecture : energy : sustainable design
• Increased cost for construction is invested in the building fabric and insulation
• Typically 5-10% more expensive (recent studies show this reducing)
• Payback period around 20 years (but energy costs increasing)
• Protection against fluctuating fuel costs and future uncertainty
Illustration of energy cost savings for a 3-bed detached house
A n d p r o v i d e s c o m p e l l i n g a r g u m e n t s f o r c l i e n t s
gcp architecture : energy : sustainable design
• Understanding the main factors that influence performance
• Site factors are significant and need to be considered
• Building form can make life easier – or more difficult
• Complex buildings may need more complex solutions – adaptive buildings that adjust with occupancy
C h a l l e n g e s f o r t h e d e s i g n e r
gcp architecture : energy : sustainable design
• Construction type needs to be considered from the outset
• Traditional construction is possible – but will demand new understanding from constructor
• New materials and constructions may be worthwhile
• Clear coordination between design and construction team is vital
C h a l l e n g e s f o r t h e d e s i g n e r
gcp architecture : energy : sustainable design
• Success of the project will rely on a good briefing for the end-user
• PassivHaus needs to be ‘driven’ and will take time to acclimatise - the user and the building
• Explaining the reason for controls is as important as knowing what they do
• Understanding seasonal variations will ensure comfort in different conditions
E n g a g i n g t h e u s e r
On hot summer days keep the
windows closed !
Heating by towel rails – press boost if you need some
extra warmth
Keep the ventilation on
auto and press boost if things
get steamy
The boiler is small and won’t be
running very much – don’t worry it’s
not broken!
gcp architecture : energy : sustainable design
PassivHaus are too simple