# Solar gain and South-facing overhangs



## sparticle (Dec 16, 2008)

Hello everyone. This is my first post here. Someone from your forum invited me to come check it out.

Right now I'm in the process of designing a home as green and simple as I know how. So far, I'm still on the drawing it on paper stage. Today my task is overhangs. I drew a little template of the high summer sun angle for my area and in order to keep the sun from entering the house at all, the overhang on the South side at a little over 2.5 feet

Most things I've read show the same drawing of the summer sun high angle and keeping it out of the house. My BF is wondering why you would want to keep all of the high sun out? If the sun came in a foot would that really overheat the house that much? Also, during the summer some sun is going to come into the house before and after the high angle so why all the effort to keep out *all* of the high angle?

I think he just doesn't like such a big over-hang. The primary entrance is on the East side and protected.

Any input? I look forward to checking out more of this site.


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## Tex (Oct 31, 2008)

Doors and windows are you biggest contributor to energy loss. When the Summer sun shines directly on your window, your house can heat up quickly. The key to designing overhangs for energy efficiency is to have enough overhang to block the high Summer Sun, while not having so much overhang to block the beneficial direct contact of a lower Winter Sun on your window. This optimum overhang will vary by your altitude, surrounding terrain, and average temperatures of different seasons in your area. 

You might also consider planting trees by your South facing windows that will provide shade in the Summer and allow Sunlight through in the Winter when their leaves have fallen.

Edit: I just noticed where you live. If Summer's are not usually very warm there, you probably won't need much overhang. Many people have stone or masonry floors and walls near the South facing windows for "thermal mass". The stone heats up during the day and at night, the heat slowly comes out of the thermal mass to heat your home or at least slow down it's cooling.


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## sparticle (Dec 16, 2008)

Thanks Tex. I just moved here from texas last year. I have all my homebuilding books out while I'm working on this and I went through the overhangs section again in all the books I could. All of the books had different ways of calculating overhang. Some were pretty confusing and all were different than the method I found about a year ago which I based my current overhang design on. I did make it through 2 of the methods and was pretty close to what I had figured out (about 2.5 ft).

Then I found this cool website:

sustainable by design :: overhang design

I entered all the info it asked and moved through each month on the date tab. It was great and it'll work just fine. This will be several confirmations and an architect is going to check it. I just want as much as possible to be right.!


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## Tex (Oct 31, 2008)

I like the overhang design tool. I put that in my favorites. Thanks.


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## JeepHammer (Oct 10, 2008)

There is always the greenery solutions too...

Slats that look like ceiling joists over the south facing windows/patio...
Grows vines in the summer, clear in the winter since the vines die out...

(Can't remember what you call that right now...)


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