Heat transfer through windows?

27 Jan 2008
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Llanfair Caereinion, Nr Welshpool
United Kingdom
In the summer I want to stop the suns rays heating the room, but in the winter I want the suns rays to heat the room, so how?
Thoughts are.
1) k glass or film which can be reversed summer and winter.
2) shutters.
3) thicker curtains with maybe a white curtain against window side.
But Monday the double glazing man is visiting, we need a new patio door, but we have wooden frames on the windows, would like maintenance free frames, and at least one window cracked, so the gas must have escaped. So the question is what replacement, or addition, secondary double glazing seems a good idea, so can replace glass with fly screens in summer.

But out of my comfort zone, so looking for ideas.
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In a bid to keep the temp down inside the house I was experimenting the other day with our double patio south facing doors, in full afternoon sunshine with the curtains closed (white liner) the temp between the curtain and the window was 34c. I then hung a white sheet on the outside of the window and this dropped the temp between curtain and glass to 29c
I've just fitted a drop arm awning for my main south facing window.

It has made a noticeable difference to the room temperature
I would have preferred a brise soleil, but I haven't found an available DIY option.
....and as it was, this was a really cheap and effective solution! :)
I have a gazebo on our patio to put the windows in the shade.
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as munroast points out
the sun coming through the glass spreads heat in the room on the first surface it touches
shutting the blinds just traps the heat in the void until it leaks away this will be almost all into the room unless the window is open then its a guess if more hot air is getting in than out so a surface outside the window is needed to reflect or hold the heat outside
1) k glass or film which can be reversed summer and winter.
2) shutters.
3) thicker curtains with maybe a white curtain against window side.
Shutters outside to block the heat before it passes through the window.

Curtains will help a bit, but the effect will be far less than shutters or similar on the outside, as the heat will still end up inside, just between the curtain and the window. Curtains across an open window would be better.

K glass doesn't work like that. Even if the whole window could be reversed, it still wouldn't work in the way you want.
It blocks heat passing from the inside to outside due to the longer wavelength of the IR, not due to which side of the glass the coating is applied to.

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