1. Passive House
for
Medium Density Housing
in NZ

2. Elrond Burrell
UK Registered Architect (UK)
Certified Passive House Designer
Board member Passive House Institute NZ
via-architecture.net

3. Overview
1. Medium Density Housing
2. Passive House in NZ
3. Passive House MDH
4. Passive House MDH study

4. Housing Crisis

5. Medium Density Housing (MDH)
“BRANZ defines MDH as multi-unit
dwellings (up to 6 storeys)”

6. Category 1
1 – 2-storey attached houses

7. Category 2
2 – 4-storey attached houses

8. Category 3
Apartments
(up to 6-storeys)

9. Passive House in NZ

10. Architype Architects, Dunedin Context Architects, Auckland
Passive House MDH is coming !

11. Passive House MDH examples

12. MDH Category 1
14 Affordable Terrace Houses – Parsons + Whittley, Norfolk

13. MDH Category 1
10 Terrace Houses – Professor Gökay Deveci, Scotland

14. MDH Category 1
14 Semi-detached Houses – Hamson Barron Smith, Norwich

15. MDH Category 2
10 Townhouses - Rook Architects, Frankfurt

16. MDH Category 2
6 Apartments - HCMA Architecture + Design, Victoria BC

17. MDH Category 2
Retrofit of 32 Flats - 2e Architects, Manchester

18. MDH Category 3
Passive House city district in Heidelberg. Photo: Passive House Institute

19. MDH Category 3
53 Apartments – RMA / Architype, London

20. MDH Category 3
21 Apartments - Deimel Oelschläger Architekten, Berlin

21. Main question:
What changes from the NZBC are needed to
meet the Passive House standard?
Focus: Opaque thermal envelope
• Industry often equates R-values with building
performance and energy efficiency
• Passive House often perceived as “super-insulated”
Passive House MDH study

22. 1. Identify a suitable project
2. Model the project
3. Test the model
Passive House MDH study

23. The Project
• A real development (now being
constructed)
• Information readily available (marketing
materials!)
• Project performance irrelevant, NZBC
minimums assumed

24. ‘The Grounds’ Auckland
A theoretical study only, using publicly available information!
Not actually designed or constructed to the Passive House standard.

25. 3 Storeys, typical floor plan

26. Efficient thermal envelope (Form factor 1.4)

27. Efficient treated floor area

28. Modeling parameters
• Main façade faces north
• Thermal bridge free
• All windows and doors fixed units except
opaque entrance doors
• Shading from building geometry, fixed shading
shown on the design and interior blinds on the
north façade
• Ventilation PHPP default HRV unit 75% eff
• Airtightness of 0.6 ach

29. Thermal envelope
NZBC Zone City Required R-value (U-value)
Roof Wall Floor
1 Auckland 2.9 (0.34) 1.9 (0.53) 1.3 (0.77)
2 Wellington 3.3 (0.30) 1.9 (0.53) 1.3 (0.77)
3 Christchurch 3.3 (0.30) 2.0 (0.50) 1.3 (0.77)

30. … but windows
R0.26 = U-value of 3.85 W/(m2K)
Fails comfort criteria, which says something about the NZBC
R0.35 = U-value of 2.87 W/(m2K)
Thermally broken aluminium frames with double glazing (4/12 air /4)
R0.71 = U-value of 1.40 W/(m2K)
Frame U-value 0.75, double glazing (low-E 4/16 Ar /4)
NZBC Zone City Required R-value For PH Comfort
1 Auckland 0.26 0.35
2 Wellington 0.26 0.71
3 Christchurch 0.26 0.71

31. Results
NZBC City Results
Zone Heating
Demand
kWh/(m2a)
Heating
Load
W/m2
Over-
heating
%
Passive
House
?
1 Auckland 13 10 7 Yes
2 Wellington 13 12 3 Yes
3 Christchurch 21 10 2 Yes

32. Results
123
Auckland Wellington Christchurch

33. Conclusion
NZBC required R-values for the opaque
thermal envelope are a reasonable starting
point in these cities for a MDH Passive House
project

34. Caveats !
Simple Study
Ø e.g. Domestic hot water not included. Often critical for
overheating & PE/R in MDH
Ø e.g. No thermal bridges included. Could easy add 2 kWh/(m2.a)
Dependent on other Passive House
requirements being met, even when these
exceed NZBC requirements

35. Discussion
Slab insulation ~50mm EPS
Ø Likely to use thicker EPS or XPS for practical
reasons, therefore better performance
Ventilation 75% efficiency
Ø Likely to be considerably more efficient with
PH certified ventilation systems available

36. Discussion
Aluminium window joinery
Ø Unlikely to install Alu joinery recessed in the
wall, more likely to use uPVC (or maybe
wood) joinery with better performance
Assemblies of R2.0 and lower
Ø Robust PH assembly likely to be better than
R2.0 by default. e.g. 90mm stud framing +
uninsulated 35mm service cavity = R2.1

37. Discussion
Orientation
ü Auckland: Rotate up to 40º east or west OK
✗ Wellington: Rotating even 5º fails
✗ Christchurch: Rotating even 5º fails

38. Let’s build some Passive House MDH
J
Thank you