Our house – its performance – Australian Passive Solar Home

(Above) The house performance is being logged with a 24-channel system that records many temperatures, in addition to interior carbon dioxide levels and relative humidity. The green line is outside temperature; the blue line inside temperature; and the red line the temperature of the thermal mass (concrete slab).

So how well does our passive solar house perform? I’ll keep this page updated as time passes.

In short, so far the house performance is excellent, achieving measured results that many people claim can be achieved in this climate only with expensive materials and specialised construction techniques (none of which have been used).

Note: We are not yet living in the house full-time – the bathrooms and kitchen are yet to be finished. However, I am working in the house nearly every day, and sometimes we stay overnight. The house is only 100m from our existing house, so that’s easy!

The following measurements are based on datalogging at 10 minute intervals, 24 hours a day, with temperatures shown for the middle of the house. The house is located about 80km north of Canberra.

Spring 2025

Notes: Partial occupancy, rear door sealing and internal thermal mass incomplete for most of the period; southern reflector panel not erected.

Outside temperature varied from 0-32°C.
Without the use of any heating or cooling systems, the house interior stayed at a comfortable temperature (18.5-24.0°C) all the time. Measured interior radiant temperature was always within 1°C of air temperature – and usually within 0.2°C.
On a few days where the dew point was high (e.g. 19.4°C), air movement via fans was needed for best comfort if the occupants were physically active.
CO₂ levels were maintained below 600ppm in all conditions.
Occupant participation including opening and closing curtains some days; occasional opening of windows and doors for ventilation; and very occasional night flush cooling (windows and electric hatches opened, ventilator not powered).

First Part of Summer 2025-2026

Notes: Partial occupancy, southern reflector panel not erected.

Outside temperature varied from 5°C to 40°C.
Without the use of any heating or cooling systems, the house interior stayed at a comfortable temperature (18.0-25.0°C) all the time.
The 18°C interior minimum occurred only once – I opened the house more fully at night when I needn’t have. Excluding this, the minimum temperature was 19°C.
Measured interior radiant temperature was always within 1°C of air temperature – and usually within 0.5°C.
On a few days where the interior dewpoint was relatively high (e.g. 17.5°C), air movement via fans was needed for best comfort if the occupants were physically active.
CO₂ levels were maintained below 750ppm in all conditions and were typically less than 600ppm.
Frequent night flush cooling (windows and electric hatches opened, ventilator occasionally powered) was used.
Net curtains opened only for night flush cooling; otherwise they stayed closed.