Fire Rating (was Big PV footprint) [RE-wrenches]

[Joel Davidson]

Wrenches,

I hope this info is useful.

Here are some general PV array descriptions. A direct or integral mounted PV
array can be mounted either in full contact with the roof or can be the actual
roof. A stand-off mount is a structure and roof fastening system for mounting
the PV array above and parallel to the roof surface. A rack mount is a
structural frame and roof fastening system used to mount the PV array above and
at an angle to the roof surface.

The Uniform Building Code (UBC) Roof Class and PV array mounting method
determines the acceptable solar module fire rating. Direct and integral mounted
PV arrays and PV roofs shall meet or exceed the building occupancy group and
construction type. An integral mounted PV array shall use a non-plastic backed
PV module. A PV array on a stand-off or rack mount is roof-mounted equipment and
not the roof itself. Building inspectors allow solar modules with Class C fire
ratings on stand-off and rack roof mounted PV arrays.

Standard solar modules have a glass front and plastic back sheet and have a
Class C fire rating. ASE Americas and some custom solar modules have a glass
front and glass back and may have a Class A fire rating. Solar modules with
glass on both front and back weigh over 4 pounds per square foot and may require
structural analysis and additional roof reinforcement. Powerlight makes a
combination polystyrene insulation and PV laminate (unframed solar module) that
can be mounted directly onto a building’s existing roof. Uni-Solar Standing Seam
Structural Metal Roofing is an example of a roof with an integral PV module.

As Matt points out, there are not a lot of Uni-Solar metal roofing jobs out
there. I encourage you all to seek building integrated PV jobs even though they
will try your patience. Most BIPV projects take 1.8 to 4 years from conception
to completion unless you fall into an installation project that the owner and
architect developed on their own. BIPV is a steep learning curve for you and
your local inspectors, but it's worth the climb. BIPV will be more common ten
years from now.

By the way, the architects might have joked about oak leaves on the roof, but
UL's PV module burning brand and burning roof test is pretty rigorous.

Happy holidays,
Joel Davidson



matthew tritt wrote:

> I've been fortunate in being able to influence the design of several
> high-end homes in this area to include well oriented standing seam metal
> roofing to accommodate Unisolar PVL If there weren't any of this type of
> construction going on, the pikin's would be mighty slim for thin film
> installations indeed.
>
> Regarding the A and C fire rating issues discussed earlier, I brought this
> up with the architects who are doing the design on a resort near here,
> which, thanks to me, includes about 6 kW worth of PVL. Big roof!
> Their comment was pretty straight-forward; What's the rating on a layer of
> Oak leaves? For that matter, I understand that the only PV module with a
> class A rating is ASE, all the rest are C rated. More reasons not to exclude
> thin film from your installation considerations.
>
> Matt

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