Australian Passive Solar Home

What temperature range are you happy with in your home? It’s a question fundamental to energy efficient home design, but it is one that seems seldom asked.

Australian software modelling that underpins NatHERS allows a temperature range through the year of 15 deg C (bedrooms at night in winter) to 22.5 – 28.5 deg C (summer, depending on climate zone). To put that another way, NatHERS uses the concept of adaptive temperature, where people’s preferences depend on what is happening outside.

The Passivhaus standard states a range of 20-25 deg C (although the range for Australian Passivhaus for which I have seen logged data tends to be more like 19-26 deg C.) So Passivhaus takes no notice of what is happening outside – the interior temperature is fixed within a narrow range.

Our passive solar house is sitting at 19 – 25 deg C so far this summer (no artificial heating or cooling being used). I thought that was pretty good, and one friend said it was almost ‘thermostat like’ in its small range. He’s from the UK, however another person also watching the house performance closely, but this time from New York State, said a 5 deg C range is way too much for him!

In our high diurnal range climate, north of Canberra, my wife loves throwing open the windows and doors when, after a hot day, the cool gully breezes blow. She’s ecstatic if the temperature inside drops to ambient – say, 15 deg C. Such a refreshing change! In our old house she hated temperatures inside over 25 deg C, but if there was a fan moving air, I am happy with 28 deg C. Conversely, she is unconcerned about interior temps others consider cold.

When I have worked in offices, I have disliked how the inside environment is completely divorced from what is happening outside. In fact, in one building, I had to go outside each lunchtime otherwise I felt slightly claustrophobic. On nice days, many others did the same.

Given that the acceptable temperature range depends so much on psychology, physiology, climate adaptation, wearing of suitable clothing, activity levels (and so on), what do you think is an acceptable temperature range?