Vent clearance under solar panels

Hi,

I'm planning out my installation, and I have three vents which will have solar panels over them. Two are bathroom vents (metal), and one is a sewer vent (PVC). The panels will be at an angle, and so there ought to be enough room for everything, but I was wondering what kind of minimum clearances I need between the top of the vent and the back of the panel.

Basically, I need to know the minimum distance that the vent has to be above my roof, and the minimum distance that the vent has to be below the panels. Hopefully the sum of these dimensions is less than the distance from the roof to the back of the panels, otherwise I'll have to relocate the vents. Not a huge deal, but just one more thing to worry about. The current vents are about 2 feet high, which seems a little excessive considering that we don't really get much snow here.

Oh, and this is a flat roof with a 3.6-degree pitch, if that makes a difference.

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,814 admin
    Re: Vent clearance under solar panels

    Would you have access to drop a snake down the vents without having to pull up the panel?

    If not, I would really consider moving them to where somebody can put a snake down them if it is ever needed.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • jagecjagec Solar Expert Posts: 157 ✭✭
    Re: Vent clearance under solar panels
    BB. wrote: »
    Would you have access to drop a snake down the vents without having to pull up the panel?

    If not, I would really consider moving them to where somebody can put a snake down them if it is ever needed.

    -Bill

    Yes, I would. Not from DIRECTLY above the vent, but it wouldn't be much of a bend at all from the edge of the panels (certainly much less than any snaking done from under a sink!). The bathroom vents would be somewhat less accessible, but I wouldn't need to get into them anyway. I just want to make sure that I'm code-compliant.
  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Vent clearance under solar panels

    Vent height is regulated not just by snow, but by being high enough to prevent down drafting. Down drafting attic vents are not too much a problem but down drafting pluming vents can be. I have seen cases of traps being sucked dry by excess wind and down draft.

    Consider, if you can get to the attic, relocating the plumbing vents to the other side of the roof. Consider losing the attic vents, and install ridge vents instead.

    Tony
  • mike95490mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Vent clearance under solar panels

    I think the plumbing code requires "so many inches above obstructons"

    Another thing to consder, is consilidate the vents in the attic space, and just run one pipe thru the roof. I cut down 7 vents, to 2 doing that, while building . There are some limits, plumbers know them.
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  • strawbalestrawbale Solar Expert Posts: 31 ✭✭✭
    Re: Vent clearance under solar panels

    jagec, see this very similar thread that I started 14 months ago--

    http://forum.solar-electric.com/showthread.php?t=6293

    I am glad that I took the time to consolidate my vent pipes in the attic/truss area.

    Strawbale
  • jagecjagec Solar Expert Posts: 157 ✭✭
    Re: Vent clearance under solar panels

    The problem is that I don't actually have an attic in my house. It's a rowhouse, where the builders basically constructed a full new wooden frame within the preexisting brick 'shell' that had been there since 1910. The ceiling drywall is directly fastened to the roof joists. As such, if I wanted to relocate any plumbing, I'd have to cut my walls apart, and cut as many 2x4s as needed to add a bend in the pipe. Needless to say, I really don't want to do that if I can possibly help it.

    So am I correct in thinking that the plumbing vent is the only real issue here? The (powered) bathroom vents don't need to worry too much about drafting, after all. Right now I'm thinking that I'll trim the bathroom vents down just a little bit to ensure adequate clearance, and then use maybe a 20-degree elbow to extend my sewer vent out from under the panels without changing its height.
    Like so:
    mounting.png

    Thanks for the link to the other thread, that was helpful.
  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Vent clearance under solar panels

    You could elbow the plumbing vent, above the roof line, and run a run of pipe up the roof pitch away from the panels. I'm not sure it meets the UPC (Pluming code) but I don't see anything wrong with the idea.

    The bath fans are somewhat problematic. I would ensure that there is essentially no restriction on the exhaust of the fans.

    Tony
  • solarixsolarix Solar Expert Posts: 713 ✭✭
    Re: Vent clearance under solar panels

    Check with your building dept. Around here they have a rule preventing any vents beneath solar arrays. (Now with the 3' fire access rule in the 2012 code - we have very little space on many roofs available for solar)
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