Australian Passive Solar Home

Curtains. It doesn’t sound a very interesting topic but in an energy-efficient home, window curtains – and how they are mounted – are important.

As I have written previously, windows are like enormous holes in your walls, letting heat in and out. Double glazing reduces that heat transmission, but far more heat passes through windows and their frames than the insulated walls in which they are located.

Curtains can be part of that heat control.

This pic shows the approach we’re taking in our passive solar home.

The dark curtains are Ikea Annakajsa block-out curtains, being used in a doubled thickness and sewn together at the top. These are the heaviest, densest curtains I could find at reasonable money. They will be closed at night, and my initial measurements show a great reduction in heat transfer through the windows and frames.

The net curtains are again Ikea – Lill this time. They will be kept closed all summer. They are primarily designed to reduce indirect radiant heat gain, and again my measurements show that they do this. They will be open all winter, allowing the direct solar radiation best entrance.

The pelmet serves two functions. It holds the track on which the Annakajsa curtains run (the net curtains move on a separate rail), and it prevents convective heat loss past the top of the curtains. (The curtains also touch the ground for this reason.) I made the pelmets from primed pine – cheap and easy. The pelmet ends go well past the windows, meaning the open curtains obscure little of the window area.

It sounds bizarre but I racked my brains for ages over curtains. The main issue was cost – heavy curtains (e.g. thick velvet or similar) are very expensive. Heavy duty roller curtain tracks are similarly very expensive. But the doubled Ikea curtains are low in cost, the roller tracks came direct from China, and the net curtains and rails are very low cost.

Energy-wise I think that they will work well, and my lovely wife Georgina is happy with the stylistic choices.

As I write, I am finishing making the final pelmet – it’s just under 6m long.