Day 3 - Australian Climate
Passive House was created in Europe where heating demand far outweighs cooling demand. Undoubtedly Australia is a far hotter climate, in fact it is also the driest inhabited continent. But that does not mean that fundamentals of Passive House do not apply here. In fact the southern states are primarily in heating demand too. Presently a Victorian home will spend 90% of its energy consumption on heating.
Here are some considerations for our climate, based on lessons already learnt;
Thermal mass is not a key factor, likewise for phase change materials.
A super insulated house has the potential for overheating, which can also occur on the shoulder seasons; cross ventilation, minimal east & west glazing, can make a difference.
A small air-conditioner will be required during the hottest of days, however its load will be insignificant compared to our current expectations. A Passive house is calculated on indoor temperature remaining between 20-25 degrees year round. Overheating would be considered at say 28 degrees, so the load on the unit is to only cool by 3 degrees. If only one air conditioner is required, positioning is important.
Getting a bit more technical….
With winter overnight temperatures dropping to around 0 degrees, we have to combat a temperature difference of 20 degrees from the passive house minimum indoor air temp. Insulating against this is much easier than a 30-40 degree difference Northern Europe and North America needs to battle. As a result we can design to passive house standard with 150mm of wall insulation and 200mm of roof insulation. Not as difficult as one would initially assume hey!
There are less than 20 certified passive houses in Australia presently. If you’d like to read more on them please check out the Australian Passive House Association, or keep an eye out for a Passive House Open Day.