I am almost exactly 45 degrees north latitude. I am wondering what the angle of the sun is at when I want some passive solar and when I do not?

At the moment I would like to have my passive solar heat come from 10' x10' glass overhead doors, with a dark acid stained concrete floor just inside. And another set of doors without glass on the outside of the ICF wall to close at night.

So what I want to determine, of course, is how much overhang or awning to have above the doors to keep out as much summer sun as possible while letting in as much winter sun?

ICF
The BUILDITSOLAR website has some really cool calculators. One is for overhangs. If you dont mind a consistent color look into having the concrete pigment added during the mixing. For me it was cheaper and alot easier than the staining ive done. I think i paid 10 dollars per yard.

ICF
After checking out your co. webpage i know why your using stain. That is some awesome concrete work.

That website has a ton of info, I will have to check it when I have more time.

Brawler, thank you we do a fair amount of decorative concrete, but it comes second to ICF. Our website is a couple years out of date, I need to work on it.

Here's a formula I use regularly as a basic starting point. To calculate the sun angle anywhere on the planet at solar noon on Summer Solstice, the formula is: 90-Latitude+23.5. The 23.5 number refers to the angle of the earths tilt if you’re curious. So for your location that would be 90-45+23.5=68.5 degrees. For the equinoxes (both spring and fall) the formula is simply 90-Latitude, or in your case 90-45= 45 degrees. And lastly to calculate the maximum sun angle at solar noon on Winter Solstice the formula is 90-Latitude-23.5, or in your case 90-45-23.5=21.5 degrees. In warmer climates I typically design for 100% sun shading at the equinoxes. I recommend sketching a cross-section of the wall/ window area you are trying to shade. Once you sketch the height of your glazed area, you can figure out how deep of an overhang or awning you will need to shade the glass at the equinox sun angle (45 deg in your case). Since you live in a colder climate you would probably want your overhang a bit shorter so you are still getting heat in the end of March and early April. The flip side of the coin is the shorter you make it the more heat gain you will have in August and September.

Hope that helps,

Nicholas

The navy site http://aa.usno.navy.mil/data/docs/AltAz.php also has a good calculator. I usedthe FREE GOOGLE program called Sketch-Up to design my home. You can use Google Earth to place your model on your lot and then use the Shadows tool in sketch-up to see the sun in your home! I tested it and it is spooky how well this works! I also did a ton of reading (solar passive books) and did the math (simple Trig) to back-up the eaves-shadow information Sketch-up was giving me. I found a lot of great information from GOV sites regarding Solar Paths and Solar Azimuths. I have Kerkstra planks in my home that also have another 4" of poured concrete & radiant heat inside that pour. The house gets up to 80 from the sun (If I dont close the shades) and stays warm for a good deal of time after sunset. The only flaw is that Michigan does not get a ton of winter sun (but it isnt too bad either). During the summer I open the basement doorwall, the clerestory windows and the sun is blocked from the 3' eaves & my house stays about 70-75 during blazing hot days. I hardly used my AC this past summer. You can take a look at some of it at www.mrbutka.net/house/house.html Good luck with your design!

Check out the following. Its great.

http://www.susdesign.com/tools.php

The tools listed in the above link are great for designing overhangs for different regions. I like this one and use it often.   http://susdesign.com/overhang/index.php

Love the acit stained concrete and used it for the same purpose on my last project. Take a look at this, most people can't believe it's concrete.


Tom Pittsley
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www.eebt.org