# Setback for Trees from Solar Space/Panels



## Phantomfyre (Jul 1, 2004)

Hi everyone,

First, a belated thank you to everyone who responded on the generator questions I asked a while back - things got nuts around here and I read the responses, but didn't get a chance to post back. Thank you!

Now, the new question!

Our house is just about PERFECTLY situated for passive solar. It's 30x48, with the long side facing due south, on a south slope. Currently is a single-story ranch with a walkout basement - on the south side - so there is a 2-story high wall getting southern exposure right now. Our plan is to add a second story to the house, and add a solar space/greenhouse on the south side, probably the entire length of the house but only 2 stories high (to the height of the current structure) on that. (Also want to incorporate passive cold air draw/flow in the house, a solar array on the house roof, etc., so I'm sure I'll have a million and one questions once we get into the serious planning phase of the house project.  )

Anyway, right now, I have some little seedling oak and maple seedlings I'd like to plant in the yard/pasture to add some shade out there, but I want to make sure I don't plant the trees in a location that's going to interfere with my solar plans later on! How far away from the house should I plant these things, figuring oak and maple will mature at 60-80 feet, possibly 100 feet on the maples. Latitude and longitude are 41.6Â° N 88.6Â° W. I know that shading the west side of the house would be ideal to prevent unwanted solar gain in summer, but I cannot plant anything to the west of the house because the septic leach field and garage are in the way.

Actually, here's a not-to-scale, but reasonable, drawing of the house, garage, proposed sunroom (yellow), proposed mudroom (blue), garden (brown), septic stuff, and existing trees (light green are mulberries, dark green are spruces.)









I appreciate the help!


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## MELOC (Sep 26, 2005)

maybe you could consider awnings or trellised plants to provide shade directly at your house and avoid any conflict between trees and the solar panels?


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## fishhead (Jul 19, 2006)

You could always use vines for providing shade for the house and even the solar panels would provide shade if placed on the wall with a space behind them.

I've got trees in my yard and I really like the coolness they provide.

I think what you'll need to figure out is the angle of the sun at your latitude at the time you expect your solar panels to work. Someone here should be able to provide that info.


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## wy_white_wolf (Oct 14, 2004)

May not be what you wanted to hear.

The trees will have to 25.85" away from the house for every foot in heigth you expect them to grow to keep from shading the house on solar noon the winter soltice at 41.6 degrees lat.

so 100' tall would be @215'
80' tall would be @172'
60" tall would be @129'


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## Phantomfyre (Jul 1, 2004)

Vines are a great idea - especially for that western exposure! Hmm, hop and/or kiwi vines...

Passive solar would obviously be in use fall through spring; the solar panels year-round. We've got our electricity use cut to a level that I *think* we should be able to run here purely on solar, or almost. And our propane useage (heat, hot water, cooking) is less than 500 gallons a year with no supplemental heat source. Obviously, a bigger house will affect our usage, but we're hoping the passive solar will more than offset that.

I should mention that my drawing is not the whole yard, just the area the house is situated in. The road is 100 or so feet to the north of the house/garage, and there are a few trees up there, and the line of spruces continues up the west property line and along the north side by the road (great windbreak). We have a huge granary/corn crib up in the northeast corner of the property, a machine shed 30 or so feet due south of it, and a run-in shed for the horses 20-ish feet due south of that, with a few more trees to the south of the run-in and west of all the buildings. The property is 327' feet wide, and 1300'-something feet deep. (10 acres.) There is horse pasture to the east and south of the house and garden (between the garden and mulberries) now. There's a small creek on the other side of the mulberries that runs west-east across the property, an acre or so strip of woods behind that, a 5 acre hay field, and the back is more brush/woods/meadow with a 2nd, even smaller, creek.

So we have plenty of room to work with - primarily, I'd like those trees to provide shade to the yard and pasture, not so much the house. I just don't want to plant them so close to the house that they'll conflict with the solar plan.

Wind power is also a possible option that can be considered, but we'd have to do a site analysis to determine the real feasibility of that. The best place would be out in the hay field on the hill back there, but then we're running a lot of line ($$$) to service the house...

I think geothermal would be too hard to incorporate into an existing structure?


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## MELOC (Sep 26, 2005)

i think geothermal would depend on the current heat distribution system. if you already have forced air, i bet it would be easy.


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## Phantomfyre (Jul 1, 2004)

WWW, maybe not what I wanted to hear, but precisely what I needed to know - thank you! I wouldn't have thought it'd be quite that far... So no more *big* trees south of the house in the yard! Most of the pasture is to the east/southeast of the house; I might be able to get a couple of the oaks out there if I put them far enough east. Looks like smaller trees will be needed if I want something closer to the house. And I'll have to find a totally different spot for the sugar maples.


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## Phantomfyre (Jul 1, 2004)

Meloc, we do have forced air now. I know *very* little about geothermal, but if it's possible, I'd better read up on it!


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## MELOC (Sep 26, 2005)

lol, i guess what i meant was that incorporating it into your home would be easy. you will still need a pipe field for heat transfer or a well or two depending on what you may choose to do. that part can't be easy, lol.


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## SolarGary (Sep 8, 2005)

Hi,
I'd do this solar site survey -- its easy to do, and it gives you an idea how nearby objects will shade collectors -- it also gives a good feel for the path of the sun around your house (both elevation and azimuth) for the full year. Everyone I've talked to who did the survey said they learned a great deal, and some avoided some serious problems with bad collector locations:

http://www.builditsolar.com/SiteSurvey/site_survey.htm

On the tree distance issue, you can draw in on the site survey diagram the highest elevation angle that you want to tolerate in each direction (for example the elevation at 9am and 3pm), and then figure the distance that the tree has to be away as: 

Distance = (tree height)/(tangent (elevation angle))

This assumes the collector is at ground level -- if its elevated, than this helps.

The suns elevation angle at 42 degree latitude and at noon is:
Fall and spring Equinox: Elevation = (90 -42) = 48 degrees above horizon
Summer Solstice: Elevation = (90 -42) + 23.4 = 71.4 degrees above horizon
Winter Solstice: Elevation = (90 -42) - 23.4 = 24.6 degrees (very low!)

The 90 - 42 is called the Zenith angle (if you point straight up, its the angle between your arm and the sun), and the 23.4 degrees is the tilt of the earths rotational axis to the plane the planets -- this causes the higher sun in the summer and lower in the winter.

But these are at solar noon -- the sun is lower before and after noon, and for good solar collection you really want to be collecting at least 3 hours before noon and 3 hours after noon.
Its really best to do the Solar Site Survey to get the full picture.
Feel free to email me if you have any problems with it.


Gary


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