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Renovating - how to keep heat from the sun in the winter, and out in the summer


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I'm buying a new place in the northern hemisphere (49° N) with lots of southern (or rather SES) exposure. I'm putting quite a bit of thought (together with an architect) into how to improve its energy performance. I'm particularly interested in passive heating and cooling. I have actually just written a little simulation that lets me see where direct sunlight will fall at a particular date and time: image.thumb.png.ab5ae55ca55aa7f70d4c7abf65b0f638.png

That's my library (the largest and most important room) at 9:30am in the summer solstice. 

 

Further information: Climate zone Cfb. Heat waves during the summer are a thing; AC is not (and I have no interest in installing it). I'll keep the old radiators but exchange the gas heater for an air-water heat pump.

 

So, we have (at least) two sets of problems:

 

1. Keeping cool during the summer

 

If I understand correctly, once sunlight is in, it's in (except for the small fraction that would be reflect back out of the window - next to nothing during the summer, as I can see from the simulation, in that there will be no direct "bounce" back) and it will be eventually converted into heat. Other than pulling thick shutters all the way down and sitting in the dark (apparently the previous owners' solution), my best bet is some sort of Brise-Soleil or, alternatively, a retractable awning, no? (The idea, in a Brise-Soleil, would be to keep high-altitude-angle sun rays out, and let low-altitude-angle rays in.) Are there other possibilities? (A friend suggests something high-tech.)

 

2. Keeping warm during the winter.

 

It can be rather cloudy during the winter, so it's unclear to me that I will be able to get much passive heating, but every bit is worth considering. Other than "don't have mirrors reflecting light right back out the windows", what would help? One think I can think of is installing reading nooks on the wall opposite the windows, where I would get direct light on winter mornings (see the snapshot above) but not during the summer. Perhaps one can design the surface of said nooks so that they can retain heat for a few hours and then release onto the occupier in the afternoon? What material/shape would be best for that?

 

Anything else I am not think of? I am a newbie at this.

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Speaking of which, here is a picture of a brise-soleil - but obviously, if put on a window, I'd want to it install it the other way around, with the slabs going *inwards* as they go downwards. 

 image.png.eb4578526bcbbed58ffacaefe0eba1ee.png

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The sun is higher in summer than winter so roof overhangs above windows or similar can reduce solar gain in summer and keep it in winter. 

 

I think cladding with a well ventilated void behind also helps reduce heat gain. Bit like putting a large shade over the walls.

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Yes, of course I will insulate, and yes, of course the entire idea is that the sun is higher in summer; the point of the simulation is to show the exact effect. See, e.g.,

 

https://webusers.imj-prg.fr/~harald.helfgott/simulcurie/21_6_2021.html

 

https://webusers.imj-prg.fr/~harald.helfgott/simulcurie/21_12_2021.html

 

for the difference at my place between the summer and winter solstices. (Thanks to the architect for taking the measurements.)

 

To me, the entire idea of a roof overhang with slats is to let low-elevation sunrays in, even through the overhang. That is why I said that setting up one as the above seems completely backwards. This is even clearer in the following picture:

image.png.22721e6dbe188f898b489abab3b38043.png

 

I'd turn this around 180 degrees. Am I missing something?

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