# angle of roof



## vallyfarm (Oct 24, 2006)

I live in upstate NY near Saratoga Springs. I'm building a duck house and was wondering what would be the best angle to pitch the roof. I would like to add some solar panels at a later date and make it as eeasy to do as possible. Also, should the roof be facing true South, or is there a better position for that too? Thanks for some help, Mike :help:


----------



## ET1 SS (Oct 22, 2005)

The closer to perpendicular to the rays of the sun, the more sun a roof will get. 

With each season the sun's arch moves, so each season has it's own 'perfect' roof angle.

Each location on the planet has it's own Latitude degree, which defines what angle is 'perfect' in the summer. 90 degrees at the Poles means that a vertical wall is parallel with the spin axis of the planet and is fully getting as much of the sun's rays as possible. 0 degrees at the equator means that a flat roof gets the most sun in the summer. What ever Latitude degree your home is located at, defines exactly what angle would be 'perfect' for your location in the summer.

Solar panels to be efficient must be mounted to follow the sun. They must move in one axis of motion during the day to follow the sun on it's arch, and they must be able to change the arch's angle each day to track the season.


----------



## Windy in Kansas (Jun 16, 2002)

A rough general rule of thumb is your area latitude plus 10Âº. 

I don't have a chart handy but there should be plenty on line. Here is one link that says tilt should be latitude plus 15Âº.
http://www.macslab.com/optsolar.html

On page 7 of this solar company PDF a table indicates the degree of tilt depends upon the latitude in general. http://www.campbellsci.com/documents/manuals/msx.pdf


----------



## 12vman (Feb 17, 2004)

I would suggest looking at the best angle for winter and design the roof from there..
~Don


----------



## SolarGary (Sep 8, 2005)

Hi,
The general rule is the tilt should equal latitude for best year round performance.
For best summer performance use latitude minus 15 degs.
For best winter performance use latitude plus 15 degs.

As 12V says, if you want more even year round output, then best to optimize for winter (latitude + 15 degs).

You can see what different angles do for your location with PVWatts:
http://rredc.nrel.gov/solar/calculators/PVWATTS/
They offer a Version 1 and Version 2 -- the Version 1 one seems a lot easier to use to me.

Gary


----------



## vallyfarm (Oct 24, 2006)

Thanks guys! Mike


----------



## Jim-mi (May 15, 2002)

Consider snow fall in your area.
If you have pannels "up on the roof" can you get to them to remove the snow . . .??

In my area I only install PV on pole mounts . . . a long handle soft brush is used to remove snow. Also an advantage of a pole mount is it can be seasonly adjusted for tilt.

And another advantage to a pole mount is that there is NO penetrations of a roof surface . . . .read leaks . . . . . .


----------



## ET1 SS (Oct 22, 2005)

Jim-mi said:


> Consider snow fall in your area.
> If you have pannels "up on the roof" can you get to them to remove the snow . . .??
> 
> In my area I only install PV on pole mounts . . . a long handle soft brush is used to remove snow. Also an advantage of a pole mount is it can be seasonly adjusted for tilt.


???

Heavy snow load = high latitude

If your roof is designed for panels, and you live in the land of snow; then you have a very steep roof.

Snow on steep roofs tends to slough off very easily.


----------



## Jim-mi (May 15, 2002)

OK if your starting from scratch you can design\build say a 12-12 pitch. 
I have encountered none of these in my installs.
Far more common is a 4-12 pitch. Pannels mounted on a single story house roof of 4-12 pitch are going to be very hard to reach to remove snow.
There are darn few "A Frames" around here.

Still the best solution . . . .a pole mount. . . .and its adjustable for summer\winter.


----------



## ET1 SS (Oct 22, 2005)

Jim-mi said:


> OK if your starting from scratch you can design\build say a 12-12 pitch.
> I have encountered none of these in my installs.
> Far more common is a 4-12 pitch. Pannels mounted on a single story house roof of 4-12 pitch are going to be very hard to reach to remove snow.
> There are darn few "A Frames" around here.
> ...


A roof with a 12-12 pitch is roughly a roof set at a 45 degree angle.

As it happens I live at Latitude 45.

So a 12-12 pitch roof would be fine for covering with solar panels. and it would be fairly steep enough to throw off most snow. 

If you want to heat water; then you do need a lot of panels.

If you want to make electricity to operate your home; then you do need a lot of panels.

I generally think of a pole mount thing, as being significantly smaller than the surface area of a house roof.

In this case, smaller equals less. Less panels and thus less ability to do stuff. Less heated water, and/or less generated electricity.

Granted you could mount poles in rows out in a field and you could have as many pole mounts as you wish to have. So by having three dozen pole mounts you may well be able to approach the generating capacity of a roof.


----------

