Day 8 - heating & cooling
So far I’ve learnt that we can assume a building heading towards passive house standard has the following features;
An improved thermal envelope (good insulation)
An airtight envelope (no drafts and minimal air leakage)
A MHRV system (ventilation for supply of clean fresh air & removing stale air)
High Performance Windows & Doors (quality components and double or even triple glazing)
Controlled solar gains (well designed external shading)
The result is an extremely consistent indoor air environment. The need for heating and cooling has been dramatically reduced. In fact, most days of the year Heating and Cooling simply won’t be required. Especially in the Australian climate.
Let me explain in a little more detail…
For a passive house we can assume that the indoor temperature is to remain between 20-25C year round.
Unless you are in the alpine regions, the most extreme temperature difference from inside to outside will be around 20 degrees. (0/20 degrees in winter, 25/45 degrees in summer). Mitigating that temperature in a house of high performance is actually quite easy to achieve. We simply don’t need the heating and cooling systems that we have grown to accept. Ducted gas heating or Hydronic heating is simply not required in winter, and nor is an evaporative or ducted air conditioning system. We can simply boost the air temperature with one unit, on demand, a single reverse cycle air conditioner.
It is common to place the unit in a living zone and rely on the HRV system to distribute through a house.
It appears that we’ve got to make a mental shift from “I need a bigger air conditioner” or “I never want to be cold so make sure the heater is big enough” to this; “build me a house so that I don’t need constant heating or cooling!”