Page 50 - Build 151

Internal moisture
May need to update Building Code G4
Depending on the results of the occupant behaviour project and given the results from WAVE, we may not be able to rely on the regular opening of windows.
As in ltration is no longer at the level it was previously when it provided a useful amount of dilution ventilation, we are near a point where an update of clause G4 may be needed. Various case studies by BRANZ are beginning to show this (see pages 55–56).
Double glazing misconception
A common misconception is that double- glazed windows x moisture issues since there is a reduction in condensation. However, all double glazing does is raise the temperature of the glass in contact with the indoor air.
This, in e ect, just masks indoor moisture issues and does nothing to help its removal.
What’s next?
A current BRANZ project is looking at estab- lishing a national airtightness database to more e ectively track changes in housing stock. Meanwhile, the energy-e cient venti- lation project will establish a framework for evaluating ventilation system performance in tandem with whole-building energy e ciency.
The outputs from WAVE, along with these two projects, will help provide the evidence necessary to make informed choices around the future of Building Code clause G4. This, in turn, will assist the industry to design and deliver homes that are ventilated e ciently and are warm and dry.
For more Visit www.buildmagazine.org.nz and select moisture in the search box.
BRANZ Building Basics Internal moisture is available from www.branz.co.nz/shop.
48 — December 2015/January 2016 — Build 151
FEATURE SECTION