Roof pitch for solar gain.

[52cents]

Hi,

I'm remodeling an investment property. The roof needs to be completely rebuilt and now is the time if I want to change the pitch. I will have a couple of skylights on the south slope and I'm wondering what the optimum roof angle would be if I live at a 35º latitude. Should I just make the pitch 35º or go steeper to catch more morning and afternoon winter sun?

Any experts out there?

[Mother Fussbudget]

Are you hoping to put photovoltaics (PV) on this roof to generate electricity, solar hot water generation, or purely passive solar?
According to this article http://www.solarpaneltilt.com/#fixed the optimum angle would be 29.7-degrees for PV.  But again, it depends on your goals.

[52cents]

No Solar panels, just skylights. There is too much summer foliage cover to justify panels.

Thanks.

[The Architect]

Hi,

I'm remodeling an investment property. The roof needs to be completely rebuilt and now is the time if I want to change the pitch. I will have a couple of skylights on the south slope and I'm wondering what the optimum roof angle would be if I live at a 35º latitude. Should I just make the pitch 35º or go steeper to catch more morning and afternoon winter sun?

Any experts out there?

IIRC, you loose more than you gain from openings in the roof no matter how you slope it. If it's less than 4:12 already, do a nice 5 or 6:12 and put lots of insulation in there, it'll help more than trying to catch the sun in that way. You could try a clerestory in the new roof for maybe some solar gains and daylighting, but that'd be a 90* wall built onto your new 5/6:12 roof.

Depending on your climate, a cathedral ceiling helps keep things cool and makes the space feel huge. Even a low one will be appreciated by tenants.

[52cents]

 I'm primarily installing skylights for light gain rather than heat gain, so they are going in regardless. I'm just wondering, if I'm going to put holes in the roof anyway, if the pitch would help counteract heat loss in the winter. Yes ,it will be a cathedral ceiling with a SIP panel roof (still researching that though).

[The Architect]

I'm primarily installing skylights for light gain rather than heat gain, so they are going in regardless. I'm just wondering, if I'm going to put holes in the roof anyway, if the pitch would help counteract heat loss in the winter. Yes ,it will be a cathedral ceiling with a SIP panel roof (still researching that though).

More information, albeit not very technical. If you've got summer foliage, ideally put them on the S. side with foliage to block sun in the summer and let it in in the winter. The greater the slope, the less the loss; up to the point where 90* is as efficient as a window can be. If they're for light and you can't screen them in the summer, consider a clerestory (with overhang to block summer sun) or north-facing skylights. They'll be cold, but they won't let the heat in in the summer and you'll get the best light quality.

[52cents]

Thanks for the info, that was helpful. Seems like a 8 to 10 pitch roof will work just fine. Lots of foliage in the summer, so that's not an issue.

[deborah]

You could get things like solartubes rather than skylights. These have a smaller roof penetration, provide more light, and are more energy efficient.

[dragoncar]

You could get things like solartubes rather than skylights. These have a smaller roof penetration, provide more light, and are more energy efficient.

In my experience, these look like crap -- super blue tint (I know the sky is blue, but that's still my subjective impression vs. skylights).  Definitely visit a real installation before committing to these.

[deborah]

You could get things like solartubes rather than skylights. These have a smaller roof penetration, provide more light, and are more energy efficient.

In my experience, these look like crap -- super blue tint (I know the sky is blue, but that's still my subjective impression vs. skylights).  Definitely visit a real installation before committing to these.

The ones I was looking at earlier this year had no blue tint. +1 on visiting a real installation. There are a number of options available now, so it is worth investigating what is actually available for you.

[dragoncar]

You could get things like solartubes rather than skylights. These have a smaller roof penetration, provide more light, and are more energy efficient.

In my experience, these look like crap -- super blue tint (I know the sky is blue, but that's still my subjective impression vs. skylights).  Definitely visit a real installation before committing to these.

The ones I was looking at earlier this year had no blue tint. +1 on visiting a real installation. There are a number of options available now, so it is worth investigating what is actually available for you.

I'm guessing the more expensive ones have better reflective surfaces resulting in better spectrum.  The cheaper ones look like they are just polished conduit (no mirroring per se)