Hi,
I talked with the roofer who gave the "Best Roofing Practices for PV"
course at the NW Solar Expo, and at the Oregon Dept of Energy. I then
took his recommendation and ran it by two local roofing professionals,
who similarly approved. They recommended using the EternaBond "Tape"
product. It looks like a 1/4" thick pre-rolled roof caulking. I get it
in 2" wide rolls, or, you may be able to purchase it pre-cut. (It's not
cheap.) You peel off the plastic outer layer and put it on the back of
the L-feet. I put on a double layer. It becomes activated by pressure,
so, when you screw your stainless steel lag bolts (with washers) into
the underlaying rafters, the EternaBond will ooze up in to fill the
cavity between the washer and oval L-foot hole.
I'd recommend that you allow yourself several hours to cut the
EternaBond and pre-apply it to the L-feet before bringing the hardware
on the roof. That way, only the final layer of plastic needs be removed
before screwing the L-foot onto the roof. But, be warned, even with a
top plastic layer on the "tape", the EternaBond will stick to
everything! There is no doubt that this is a much more solid,
waterproof connection than the dollops on caulking around the six screws
that must hold down every boot.
Good Luck!
Laura
--
Laura Uhler, Owner
Solar Ki, LLC
(541) 602-6909
laura.uh...@solarki.com
www.solarki.com
Kelly Keilwitz, Whidbey Sun & Wind wrote:
Wrenches,
We install PV & SHW on a lot of flat-pan metal roofs here in the Great
Northwest. Most of these roofing seams are not amenable to S-5! clips
-- and if they are we can't trust how the roof is held down.
We want to install the supports to best roofing practices. The roofers
that we've worked with use rubber boots that fit over vents and holes,
which seal to the roof with goop and are attached by screwing through
the ring at the base of the boot, through the roofing, into the roof
sheathing.
The flashing boot around the post requires 5 to 9 more screw holes,
depending on the diameter and doesn't conform around the standing
seams very well. Additionally, on roofs with no full sheathing deck --
like with skip sheathing, and horizontal perlins - the boot cannot
attach to the roof very securely.
Although this seems necessary for situations where there is an actual
object going through the roof (e.g. conduit, pipe, and vents), I don't
see how flashing this way will be better than simply using posts
without the boot flashing, or even L-feet, direct to the roof, with an
EPDM gasket, with one or two lag bolts predrilled into the roofing
truss or perlin, and filled with goop 'till it squirts out.
What do you do on metal roofs in these situations?
Thanks,
Kelly Keilwitz, P.E.
Whidbey Sun & Wind, LLC
Renewable Energy Systems
NABCEP Certified PV Installer
WA Electrical Administrator #KEILWKM923RB
987 Wanamaker Rd.
Coupeville, WA, 98239
360.678.7131
sunw...@whidbeysunwind.com
WA Electrical Contractor #WHIDBSW920MS
WA General Contractor #WHIDBSW946M1
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Laura Uhler, Owner
Solar Ki, LLC
(541) 602-6909
laura.uh...@solarki.com
www.solarki.com
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