1.
Passivhaus, a step too far?
Isn’t pretty good, good enough?
Inaugural South Pacific Passive House Conference
Auckland 2015
Nick Grant
Elemental Solutions
UK Passivhaus Trust
@ecominimalnick

2.
2 common criticisms
• It’s not economic in our mild
UK/ Californian/New
Zealand/Australian climate.
• It’s not economic in our cold
Swedish/ Maine/Russian
climate.

3.
Our Self Build
Best Practice Assumptions 1995 (Year 12BP -
UK)
• Straw cheap and excellent U value.
• If maxing U values no point in modelling energy
• Wood is a cheap zero carbon fuel (just don’t want to
spend every weekend cutting it).
• Use natural vent, crazy using electricity to save firewood
with HRV.
• Double glazing had similar U value to Triple.
• Install windows in plane of rain screen for robust water
tightness, must open out.
• Need a porch and sun space as buffer zones.

4.
1.3 ach without tapes or
membranes
100mm EPS considered extreme!
Thermal bridge free
foundation slab
DIY roof trusses

5.
Built by a Sheila
Images Nick Grant

6.
Image Nick Grant

7.
Image Nick Grant

8.
Drawn; Jon Broome
The Green Self Build Book
Basic construction proved sound
and has formed the basis for
many projects since:
Almost a Passivhaus?
A pretty good house?

9.
Retrospective PHPP
Missed Passivhaus by a factor of 6!
• 91kWh/(m2.a) v 15 PH
target!
• Form factor about 5
• Bump-outs shade the
windows in winter.
• No HRV
• High spec’ double
glazing in plane of
rain screen


10.
EnerPHit with PH components?
• Same energy use as now but better comfort.
• EnerPHit refurb £50k? House cost us £40k to build
• Crippled by poor form factor (about 5)
before After EnerPHit?

11.
Why Passivhaus?
• Is the 10 W/m2 or 15 kWh/(m2.a) arbitrary?

12.
Physics definition
“A Passive House is a building, for which thermal
comfort can be achieved solely by post-heating
or post-cooling of the fresh air, which is required
to achieve sufficient indoor air quality – without
the need for additional recirculation of air.”

13.
Are we tunnelling through the cost-benefit barrier?
Passive House Design, Gonzalo & Vallentin
?

14.
Supply air heating?
• In the UK it costs more
– Special fan coil
– Buffer to stop tank-less heater cycling
– Doesn’t work with simpler cascade vent approach
– Ducts need insulating - cost & space
– Still need towel rail circuit unless electric
• Not good for large houses and non domestic
• Complicated to make some rooms warmer or cooler
• Extra heat tends to go upstairs
• Weather data & design critical . . . . etc.

15.
So Why 10W/m2 –15kWh/(m2.a)
• Inspired by a brilliant thought experiment that
changed the industry
• It works and seems about right!
• If you don’t aim for something, you’ll fall for
anything – a slippery slope
• We don’t have to decide the optimum standard for
every component on every job
• It is easier to hit a target that isn’t moving
• It forces us to do sensible things:

16.
16
Via Graham Irwin, Inhabit

17.
The real savings of going far enough
• Forces us to radically simplify
– We can’t just add some insulation & better windows
• Forces us to sort the form factor
• Forces us to consider fenestration carefully
• Forces us to design for airtightness
- We can’t just spend more time chasing leaks
• Forces us to prioritise what we spend the budget on
• Simplifies controls
• Simplifies heat distribution
• Guarantees comfort and air quality
• Avoids the ‘comfort take’ rebound effect

18.
It can stop us making expensive mistakes over and over!
Image Nick Grant

19.
Non-Standard Buildings
“A Passive House is a building, for which thermal
comfort can be achieved solely by post-heating
or post-cooling of the fresh air, which is required
to achieve sufficient indoor air quality – without
the need for additional recirculation of air.”
Once again:

20.
Non-Standard Buildings
• Archive - insufficient ventilation to deliver the
required heat or cooling
• Schools & offices - much more ventilation/m2 but
vent & heat out of sync’
• Care homes etc much higher gains
• Tiny buildings, poor form factor, high gains

21.
Hereford Archive & Records Centre
A very Eco-Minimal passive approach
Image Nick Grant

22.
Key design strategy:
Office isolated from cooler
repository
22°C this
side all
year
14°C this
side is
ideal
Image Nick Grant

23.
Energy balance using PHPP
• Simplest form
• Low IHGs 0.6W/m2
• c.a. 1 air change/day
• No HRV
• RH 40-60%
• RH buffering by contents
• Temp 14°C-20°C
• No cooling
• Supply air dehumidification
• Inspired by Tim Padfield
www.conservationphysics.org

24.
Image Juraj Mikurcik Architype
Usual construction but masonry load bearing
inner

25.
Initial blower door test:
3,532m3 over 3 floors.
C ring too big (85cfm min).
<0.04 ach @ 100Pa
Final test with duct blaster!
Great airtightness details developed with
contractor – their first Passivhaus
Image Nick Grant

26.
Image Nick Grant

27.
27Image Nick Grant

28.
Simplicity; a hard discipline
Archive repository fresh air supply, what we planned:
DX cooling for summer
dehumidification
small fan
filter

29.
Simplicity; a hard discipline
Archive repository fresh air supply, what we got:

30.
Self build ‘Passivhaus’ guitar making workshop
for retired Architect
Image Nick Grant

31.
Quick check in PHPP, just incase!
• 7.7m2
• 107kWh/m2.a??
• Form factor 8.8 (Heat loss area/TFA, <3 is good)

32.
Gains/m2 high
It works!
Image Nick Grant

33.
34
Paper and article available on www.elementalsoutions.co.uk

34.
Why Not Passivhaus?
Crossover climates/lifestyles
But what if we need to keep out the dust?
Laurie Baker, Kerala

35.
Passivhaus Claims
Free download:
www.passivhaustrust.org.uk
Clear & easily verifiable
• blower door
• thermography
• PHPP
• components & materials
Trades description
• fake goods
• consumer law
• annoys those doing it properly

36.
Conclusions
• The Passivhaus Standard makes us go far enough
to get genuine benefits
• Still room for improvement
– simplification & improved robustness not more
complication
• Sometimes Passivhaus doesn’t fit and that’s OK
– It is not the only option and you don’t have to do it