Passivhaus, If you think it will cost more it will

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

OK, not all birds look so bird like . . .

kiwibird.org

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