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Passivhaus, If you think it will cost more it willInaugural South Pacific Passive House ConferenceAuckland 2015
Nick GrantElemental SolutionsUK Passivhaus Trust@ecominimalnick
Deja vu
1997
Suggests cost/performance correlation
Deja vu
2003
Market transformation in 6 years
Vienna - mature market
Constraints“Here is one of the few effective keys to the design problem — the ability of the designer to recognize as many of the constraints as possible — his willingness and enthusiasm for working within these constraints. Constraints of price, of size, of strength, of balance, of surface, of time and so forth.”
“I have never been forced to accept compromises but I have willingly accepted constraints.”
— CHARLES EAMES
FormDoes a cost effective Passivhaus have to look like a Passivhaus?
Value Engineered(3.5 billion year design time)Why do they always look like birds?
What can we guess about this bird just by looking at it?
Design freedom As free as a bird
Freedom of choice
Form factor double whammy
• = Heat loss area/useful floor area
• Higher FF = more wall and roof = more cost
• Higher FF = more insulation = even more cost
• More insulation = thicker walls = bigger footprint = even more cost
• Before we even think about complexities of build, shading etc
Passive House Design, Vallentin & Gonzalo
Compensating for too compact a form by adding
fins
Guess where this owl lives?
Form & heatloss
Irony is allowed in nature(within natural constraints)
Punch
Length
DepthHeigh
t
Roof pitch
Natural selection is slow & expensiveWe can model
PHPP Tools Simple scenario tracker
© Elemental Solutions
Structural strategy• Easy to make airtight?
• Easy to avoid thermal bridges?
• Cost efficient?
• Perhaps part of the aesthetic?
• Using available materials?
• etc
Beyond Biomockery
www.fishing.net.nz
warm blooded animal has structure on inside
cold blooded animal has structure on outside
if you want to build an insulated building, where
does the structure go?
As in nature:structure
air barrierinsulation
wind and weatherexternal structure
Image Nick Grant
Not like theseGreen style over function
Image Nick Grant
Image Nick Grant
This is good
Image Nick Grant
Mike Whitfield super-insulated traditional cruck frame extension
This is good
Image Nick Grant
Sjölander da Cruz
This is good
This is goodCavity wall, (or ICF) floor joists don’t penetrate plaster air barrier
Image Nick Grant
Wall/floor junctionAdding complexity to standard detail to reduce
heat loss
Image Nick Grant
Simpler
Image Nick Grant
Structural slab
Air tight layer
Load
Image: ArchitypeSimpler still
Fenestration(Sorry! Northern hemicentric)
Larger windows with low frame factor, all the same size.
Image Nick Grant
Fenestration
Smaller windows have more frame and less glass.
Image Nick Grant
44
Windows - performance
44
Uwindow=1.8 W/m2K
Poor Installation;Traditional mullions
Installation free of thermal bridges;Simplified design Uwindow=0.8 W/m2K
For UK Building Regulations, the performance of these two windows can be considered the same:
But with Passivhaus, you have to calculate them individually
How could you optimise the window performance through design?
Passive Solar;What does free heat cost/kWh?
Image Nick Grant
Gains 4000 kWh/a - losses 1863 kWh/a Window area 36m2
= 59 kWh/m2.a
- About £6‘saved’ per m2 window per year @ 80p/kWh*
- Gets worse the more glass you add! (utilisation factor, solar shading, additional mass - all cost)
- BUT, free if you needed the window area anyway.- *(3% discount rate, 20 year life, £400/m2 window cost, 100% utilisation – YMMV)
MK9 2HPMK9 2HP
Larger overhang to shadeMay need external blindsStructure more challengingDifficult cill detailExtra thermal bridge at cillDirt from splashLoss of wall space
Glass to floor
Image Nick Grant
Glazing to ground omitted• More daylight• Better summer comfort• More useful space• Big cost & time savings• Architect likes it!
Image Nick Grant
Image Juraj Mikurcik Architype
Design out mechanical shading (UK climate)
Image Nick Grant
m2 window cost in UKDouble Passivhaus Overcost/m2
Floor areaAdditional Build
costPVC High Quality £180 £240 £12 + 1%?
Timber High Quality £230 £310-450 £16-£43 + 1-3%
Calculation based on a current Passivhaus Project, Cae Duff26m2 windows and doors134m2 TFA (PH methodology so c.a. 150m2 GIFA)
No mullions large fixed
Hi drama, low cost
Passivhaus by Bjørn Kierulf, Createra, Slovakia
Fixed glazing c.a. 30% cheaper than opening windows, much cheaper than sliding doors.
Maximum utility
Image Nick Grant
However:• Add 50% glazing area• Add extra shading to deal with subsequent overheating of
extra glass.• Add sliding doors (tilt&slide +55%, lift & slide +105%)• Add steel structure to accommodate sliding doors• Make all windows opening even if not required (c.a. 30%
cheaper for fixed depending on manufacturer)
Result: + 10 to 15% on total build cost?
Simple Services
Alan Clarke
Thermal store
Solar pump
Stove pump
Heating pump
Heating manifold
Pipes to gas boiler
Solar controls
Under-floor controls
DHW pump
Alan Clarke
Typical Green Building Services
All that kit: £20,000
Life of 20 years: £1000/year + fuel + maintenance.
Heat + hot water: 5,000kWh/yearGas @ 6p/kWh: £300/year☹ Slide courtesy Alan Clarke, UK Passivhaus Conference 2013
Passivhaus heating conclusion:
Expensive fabric = cheap heating
Slide courtesy Alan Clarke, UK Passivhaus Conference 2013
Heating• Radiators
Bushbury Passivhaus School
Simple radiators with thermostatic valves, one per room, not all rooms.Image Nick Grant
Boiler for 2,400m2 school
You sure this is right?
Image Nick Grant
Housing Examples
m2 build costs in UKSelf build costs Homebuilding & Renovating Mag from RICS 201491-160m2 house in East of England, NW, SW or Scotland
Builder/subbies Main contractorStandar
d Good Excellent
Standard Good Excellen
t£960 £1164 £1514 £1010 £1226 £1593
Passivhaus projects that I knowDenby Dale 1186*Wahrunga 1570Clehonger 1400
Borth 1400Lancaster 1505
*Excluding fees
N.B. The basis area and what is excluded varies by project
Denby Dale
Image Green Building Company
Lancaster Cohousing Project
Passivhaus Community Housing Project
Andrew Yeats ( Eco Arc Architects ) & Alan Clarke
International Passive House Conference 2014
Photo Lancaster Co Housing
Based on Denby Dale/AECB Gold details
Image Nick Grant
Post occupancy evaluation, Lancaster Co-Housing co-heating tests etc by Sheffield University
Passivhaus LedburyBuilt by Mike Whitfield
Image Nick Grant
Passivhaus Ledbury
Image Ruth Busbridge
Glasgow-marble floor/foundation
Image Ruth Busbridge
Image Ruth Busbridge
Image Nick Grant
Passivhaus ClehongerBy Mike Whitfield
Image Nick Grant
Image Nick Grant
Image Nick Grant
Passivhaus & artist’s studio In Wales
Image Nick Grant
Air barrier outside structure
Image Nick Grant
N50 = 0.36 achImage Nick Grant
Image Rob Davies
Image Rob Davies
Image Nick Grant
Image Nick Grant
Borth Passivhaus
£1400/m2 without plot, landscaping and furniture.
Housing Lessons
• Keep the thermal envelope really simple• keep the services really simple• Glaze for daylight not ‘free heating’
– ‘Free’ solar gains cost about $1/kWh– Staying warm is easy, staying cool is harder
• Timber works great• Masonry also great
SummaryUnless you laugh in the face of physics or blow the budget, it won’t not look like a Passivhaus - deal with it
