BRANZ – MBIE workshop on airtightness, ventilation etc.
Starter for ten – Questions to discuss with BRANZ on 10 June 2021
Interstitial condensation in new residential and non-residential buildings
1. What evidence exists on the risk of interstitial condensation in residential and non-
residential new buildings in New Zealand?
2. Is there validated evidence that quantifies the increased risk of interstitial condensation
when increasing insulation levels as per the H1 proposals in the various climates of New
Zealand? Also considering necessary changes to construction, e.g. warm construction.
3. In what situations (e.g. construction types, construction details, climates, internal
environmental conditions, building typologies) does the available evidence suggest that
additional measures are required to mitigate the risk of interstitial condensation? E.g. will
increased insulation require NZ to adopt the widespread use of vapour control layers, if so in
what situations?
4. Which mitigation measures are critical to prevent unintended consequences (and in what
situations)? Which measures are ‘nice-to-haves’ (i.e. beneficial but not urgent)?
5. How could adequate management of interstitial condensation risk be pragmatically verified
during the building design, consent and construction process?
6. Are there any interdependencies between different mitigation measures that need to be
considered?
7. Do any mitigation measures require changes to other aspects of building design and
construction?
8. What can we learn from overseas about what works / doesn’t work and are these learnings
transferrable to New Zealand?
9. What are the gaps in available evidence and how / how quickly could they be addressed?
10. When will the NZ Hygrothermal modelling project be completed (the s 9(2)(a)
draft report from 2016)? We assume the model buildings project is related to this work.
Airtightness and ventilation in new residential buildings
11. What is BRANZ’s position on desirable minimum standards for airtightness and ventilation in
new homes in New Zealand (recap)?
12. On what evidence is that position founded?
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13. Are there alternative ventilation strategies that work? Do different residential building types
or climates require different ventilation strategies?
14. Does BRANZ have a position on ventilation requirements to prevent overheating?
15. What is the problem with current settings and practice (including evidence documenting the
problem(s))?
16. To what extent have the impacts of potentially shifting minimum settings to BRANZ’s
recommendations already been assessed and quantified?
17. What are the interdependencies of potential changes to airtightness and ventilation
settings? E.g. does introducing airtightness standards necessarily require changes to
ventilation standards? What ventilation strategies rely on certain levels of infiltration
(max/min)?
18. What can we learn from overseas about what works / doesn’t work and are these learnings
transferrable to New Zealand?
19. How could BRANZ’s recommended airtightness and ventilation settings be achieved and
verified during the building design, consent and construction process?
RELEASED UNDER THE OFFICIAL INFORMATION ACT 1982
