Snow loads on Solar panels

[Pluto55]

I need some clarification please; in the 2018 IBC, sec. 1607.13.5.1.1 thru 13.5.4 :: I cannot discern
if a snow drift load is required on solar panels that would be located on the leeward slope of a
gable-roofed house. The house type: CapeCod with a full dormer across the southern side (proposed panel location).
The roof proposed to support the panels has a 5/12 slope and is covered w/ asphalt shingles.
From the south wall to the ridge board is 12 ft.and from ridge to the north wall 12 ft.
The panels will sit only a few inches above the shingles and follow the roof surface.
Does ASCE 7, sec. 7.6.1 and Fig. 7-5 apply to solar panels?
The roof is framed with 2x6 (nominal) rafters spaced approx. 19 inches on center.
Thanks for reading this.

 

[CivilSigma]

Can you share a sketch?

You only consider snow drift if there are nearby structures.
It reads that this is a detached home in some neighbourhood with other detached units? If that's the case then there is no snow drift on the roof structure. And the panels are a few inches from the finished surface, so I would consider normal snow load

 

[Pluto55]

Thanks CivilSigma for taking the time to respond.
[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1612545189/tips/sketch.2021.02.05_rnvaot.pdf[/url]
I think I've attached a sketch (cross section showing framing and an isometric sketch).

ASCE 7, Fig. 7-5, shows a gable roof with a snow drift load (unbalanced load) but does
not specifically make andy reference to solar panels. It seems like the unbalanced (drift)
snow load on the panels (eventually transfered to the rafters) should equal I x p sub ground.

There seems to be a conflict with the codes:: IBC 1607.13.5.1.1.exception.

Once I resolve the snow loading condition, I may have questions on the gable frame analysis.

Thanks again for your thoughts and others are welcome too.
Regards,
Gary C.

 

[CivilSigma]

I don't have access to IBC, but the provisions of ASCE 7 Fig. 7-5 are general design steps for the roof.

I'm not sure how the US system works, but here in Canada, if you are designing a residential building (building area < 600 m^2), you don't need to consider snow drift and unbalanced snow loads. That may be applicable to you?

But I do agree with you, just treat the roof structure as if the solar panels weren't there.
They are installed practically flush with the shingles, and won't interfere or cause additional snow drift to the roof. They will contribute additional DL, so include that in the analysis.


Once you determine the loads acting on the rafters, make sure that the panels are stiff enough to resist the snow pressure.