The rub to this argument is - more HOURS of daylight in the summer. This fact coupled with higher outside temps, WILL MAKE A HOUSE WITH SOUTH FACING WINDOWS WARMER IN THE SUMMERTIME THAN A HOUSE WITH NO SOUTH FACING WINDOWS!!!
Please don't yell. It's completely unnecessary. It's not hard to make the south facing windows work. You need overhangs, as pointed out, but the angle of incidence, along with the right kind of glazing makes it entirely possible to restrict heat gain. In Northern latitudes, what may be much worse for causing overheating is large glass expanses in West windows. West windows get little to no heat gain in Winter, but can't be shaded by overhangs in Summer. I've got lots of south window, but it never gets hot in the living room until the sun starts to set.
The problem with that is that it cuts down light too. I prefer to shade with curtains, which are movable.
Mary
I can picture the angles of incidence of the sun varying from winter to summer. I have a covered walkway where I marked "north" by noting the shadow of the support posts at solar noon on a winter day. The sun never shines on that spot in the summertime.
How does one determine the desired eave overhang and angle? I would imagine that different times of day could be selected for the shade needed. Enough shade to shield the house between 10am and 3pm? On June 10th? Those calculations I could make, with input from
I have the same question about my Solar Sponge. It will be fixed to the azimuth of one wall, but I can set it at any elevation that I like. Presuming that it would be most useful before noon, I was going to use suncalc over a 9am-noon period and locate the lowest average variation from sun angle for some fixed panel angle.
The max sun elevation at noon on 12 and 6/21 is 90-lat+/-23.5 degrees, eg 26.5 and 73.5 for Phila's 40 N latitude. You might use simple geometry to make an overhang that admits all winter sun on 12/21 and excludes all summer sun at noon on 6/21, with some blank wall between the top of the glass and the overhang. With more effort, you can make an overhang with a triangular cross section that's reflective beneath and bounces more winter sun into the window and still excludes all sun at noon on 12/21.
Nick
They are - but the heat is already _inside_ by the time the light hits your curtains, so you have potentially lost the battle already.
No it isn't! If our south facing room is hot because the sun is shining in and I draw a curtain it cools perceptively and immediately :-)
I've done it lots of times. The curtain has to be lightproof of course, which can cut down the light but it only has to shade that sunlight which is shining directly into the room.
Thus, when Spouse and I are having breakfast in the bay window of our south facing dining room and the sun's rays are hot we close the curtain behind him in the morning to prevent the south eastern rays coming in and the one behind me in the afternoon to shield those from the south west. At lunch time, for a very short period, we have to close both. The answer would be to have a curtain which would just cover the immediate south facing pane but we can't be bothered :-)
I was once fascinated because on a very hot day the bees in a hive in full sun were flying in a cloud at the front of the hive. I leaned a large slab of stone against the side of the hive where the sun's rays were striking and the bees all went inside and behaved normally from then on. How they knew that the hive had cooled was another matter but my observation was that the effect was immediate.
Mary
Robert Gammon wrote
very much
can't even
FACING WINDOWS
In theory, yes, just because the windows are poor insulation compared with a wall instead.
In practice its a minor effect when I have the doors open while the outside temp is acceptible, for a very pleasant outside/inside effect, and turn the swamp cooler on when the outside temp is higher than is pleasant. A swamp cooler costs f*ck all to run so the theoretical worse insulation with the glass is purely academic and I save because I can have outside air blow right thru the house when the outside temp is acceptible. The house isnt that thick in a N/S direction, mostly only about 20'
Mary Fisher wrote
pointed
No it doesnt when you calculate the eaves properly.
Those are inside, so the heat still gets in.
And you have to fart around adjusting them daily too.
That could work well with a light-colored curtain that reflects shortwave sun back out of the window, which blocks radiation longer than 3 microns, but an outdoor shade can work better. If a dark-colored curtain converts shortwave sun to longwave heat (eg 10 microns at 80 F), the window won't pass it back to the outdoors. The heat will stay trapped inside the house. This is the original "greenhouse effect."
Nick
snipped-for-privacy@XReXXSolar.usenet.us.com wrote
I just used a properly sun angle calculator.
That was in the late 60s, bound to be plenty online now.
All you really need to do is ensure that the sun doesnt enter the doors in summer, and set the eaves overhang to ensure that.
Its a lot simpler with windows/patio doors where you just need to ensure that the sun doesnt enter in summer.
My garage sits facing almost due west. metal door, the garage temp shoots thru the top in summer
Oh for goodness' sake!
I've said that the system I use works. When we bought the curtains we didn't ask the salesman about the physical properties of the fabric!
We don't use any kind of curtains in our greenhouse by the way, that works well too, it doesn't get too hot because of effective and automatic ventilation.
We protect the interior of the car from the greenhouse effect by a plastic sheet over the windscreen when the car is parked in our (south facing) drive. That works too, perhaps you'll be pointing out that it can't.
I know our situation, you don't.
It's mainly a matter of color. Sounds like it's light-colored.
Nick
LOL!
If it's "immediate", then the only thing you're registering is the fact that sunlight is no longer hitting _you_. Which is absolutely true. When you block sun from actually hitting your windows, obviously the only heat that can enter is from the thermal gradient if it's warmer outside than in.
If you allow the light to come through the window, then stop it, _something_ inside has to warm up. Light coloured curtains will certainly reflect a significant amount of the light back outside, but some _has_ to become heat, inside the house. If it isn't apparently heating the room as a whole, it's your curtains. When that happens, they'll radiate the heat and probably half of it will end up back outside - but you still end up with more heat inside the house than you would if the light hadn't penetrated the window in the first place. This is why i said "potentially" - if your home is well designed (or in rainy England :-) ), that may not be too much heat.
Preferably aluminium or reflective mylar - though that might really annoy your neighbours!
They deliberately function as a fan to pull warm air out of the hive, and I expect they simply stop doing that as soon as the air they're moving no longer feels too warm, but that's not the same thing as using the curtain - because the stone kept the sun from ever touching the hive. It's the difference between putting shutters in front of your windows and curtains behind them.
That's right. The radiant heat doesn't heat us.
You don't know bees as I do.
Mary
I may, but that's hardly relevant to the physics behind trapping heat inside your house.
But you said, "They deliberately function as a fan to pull warm air out of the hive, and I expect they simply stop doing that as soon as the air they're moving no longer feels too warm, ... "
I'd said, "on a very hot day the bees in a hive in full sun were flying in a cloud at the front of the hive." not that they were fanning at the entrance.
Mary
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