On a sunny winter’s day, a bit of solar gain during the day is great, however, if passive solar gain is your primary heating solution, make sure you know what you’re doing.
I took this photo of a north facing window. Notice the nice sunshine streaming through. Also notice the shadow line on the top portion of the window. The top part of the window never sees the sunshine and therefore never supplies solar gain. Given that the window is about 10 times less thermally insulating than the wall, the top portion of the window is permanently a heat loss in winter. The rest of the window is a heat gain during certain hours of the day, depending on cloud cover, but is also a heat loss at all other times. Lastly, every day we suffer from a thing called night-time, and winter nights are long…providing plenty of time for heat loss.
So again, when designing for passive solar gain, you need to understand what you are doing. Shading devices need to be carefully considered as does the strategy of heat retention.
An important question to ask is, ‘Does the solar gain through the window compensate for the heat loss through the window?’ You can check out the answer to this question in my previous post about glazing ratios.
It’s worth knowing that all houses involve ‘passive solar’. Acknowledging this fact and accounting for it in your design will determine if you benefit from it or suffer from it.