Is the Passivhaus standard too extreme for a mild climate such as New Zealand? Do we really need to do all the modelling and calculations if we max out the insulation and air tightness? Nick Grant's first presentation at the first South Pacific Passive House Conference in Auckland aims to explore these questions.

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

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

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

36. 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

37. 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