Page 48 - Build 152

Ventilation
A breath of fresh air
Just what do Kiwis do to keep their homes free from stu y air? BRANZ is using science to nd the answers and aid in the design of better ventilation systems.
BY MANFRED PLAGMANN, BRANZ SENIOR PHYSICIST
ABOUT 2 YEARS AGO, we acknowledged our lack of understanding of what occupants do when ventilating their homes and why they are doing this.
Understanding home occupant behaviour
We wanted to know whether occupants are:
● regularlyopeningtheirwindows
● closinginternaldoors,orwhetherhomesaretrulyopenplan ● usingbathroomexhaustfansorrangehoods.
These questions and others have a large impact on the ventilation that occurs in homes and therefore of its moisture load and general indoor air quality. Ventilation behaviour of occupants also has an impact on the e ectiveness of installed ventilation systems.
As a lack of ventilation a ects health, we need to understand how occupants a ect ventilation and the motivation for their actions.
Balancing cleaner air and energy loss
Why should we worry about the amount of ventilation? As with many aspects of life, there is a trade-o . In this case, it is between cleaner air and energy loss. The recommended ventilation rate is about 0.4 air exchanges per hour to maintain a healthy indoor air quality.
For a 100 m2 home, this means exchanging air with the outdoors at a rate of about 100 m3/hr. If we go much below this, we experience higher concentrations of pollutants, odours and moisture, resulting in potential adverse health e ects and mould growth. If, on the other hand, we overventilate, excess amounts of heating energy will leave the house, resulting in higher than necessary power bills.
Highly effective ventilation systems can be designed, but the e ectiveness of any technical solution largely depends on the actions of the occupant, and these are rarely considered.
New project measuring homes
In March 2015, BRANZ started a new project looking at ventilation- relatedoccupantbehaviour.
46 — February/March 2016 — Build 152
FEATURE SECTION