Reverse tilt kits?

[J.P.M.]

Wouldn't the permit package already have specified some kind of mounting hardware for the reverse tilt? If as-installed system doesn't match what was submitted on the permit application, there could be some 'splainin to do.

If the structural design calcs are required and if external loadings are required to be considered, bolting/attachment details and strength calcs would normally be included and would show suitability for the anticipated loadings. Sometimes things are not considered. There's code enforcement as it is written and then there's code enforcement as it's sometimes practiced.

[J.P.M.]

Wind loading is a real can of worms. The ASTM standards are definitely not done with solar panels in mind. My engineer has software to figure the wind loading and it comes up with stupidly high numbers for the uplift that panels could see (over 150lb per tilted panel on an exposed flat roof). Reverse tilted panels could be way worse. The mounting manufacturers are not going to help you much. Probably going to need to find a local PE to get a building departments approval.

The ASTM standards are done with about any structure in mind. Think of tilted lean-to type walls on flat roofs, or shading/rain covers as an example. Depending on the location and zone, and particulars of the orientation, that 150 #/tilted panel ( ~ 17 ft^2 --->>> 150/17 = 8.8lbf/ft^2 --->> wind vel. ~ 60 M.P.H. doesn't sound too high to me. Still, if and unless the person running the software knows what they're doing and can't get the same result by hand to verify, something may be amiss, but probably w/ the input, not the software.GIGO.

[sensij]

Wind loading is a real can of worms. The ASTM standards are definitely not done with solar panels in mind. My engineer has software to figure the wind loading and it comes up with stupidly high numbers for the uplift that panels could see (over 150lb per tilted panel on an exposed flat roof). Reverse tilted panels could be way worse. The mounting manufacturers are not going to help you much. Probably going to need to find a local PE to get a building departments approval.

Wouldn't the permit package already have specified some kind of mounting hardware for the reverse tilt? If as-installed system doesn't match what was submitted on the permit application, there could be some 'splainin to do.

[solarix]

Wind loading is a real can of worms. The ASTM standards are definitely not done with solar panels in mind. My engineer has software to figure the wind loading and it comes up with stupidly high numbers for the uplift that panels could see (over 150lb per tilted panel on an exposed flat roof). Reverse tilted panels could be way worse. The mounting manufacturers are not going to help you much. Probably going to need to find a local PE to get a building departments approval.

[DanS26]

Dan, looking at the pics in your other thread and I can see why you are concerned.

It is definitely wind loads you should be concerned about but that is only half the battle. The vibrations created by even low wind speeds will be problematic.

IMO you should be more concerned with the attachment point.....a lag bolt sunk into the roof rafter is not enough. I'm thinking a more robust attachment mechanism is needed.

[Amy@altE]

I'll ask IronRidge, standby.

[J.P.M.]

Probably.

[DanKegel]

What solar panel racking vendors provide guidance and support for reverse tilt mounts?
There are a lot of installers who would like to offer those, but lack the engineering expertise to design them from whole cloth; support from the vendor would help those installers do it right.

Unirac specifically advises against it with their products:
http://unirac.com/wp-content/uploads...LICABILITY.PDF

Spice Solar has one drawing with reverse tilt:
http://www.spicesolar.com/wp-content...-TILT-ELEV.pdf

The Australian company Clenergy has the most detailed info I've found so far.
http://clenergy.com/Products/Mountin...ack/Solar-Roof
has an adjustable tilt leg installation guide with a table showing base rail support spacing for reverse tilt based on roof slope, wind zone, and building height:
http://clenergy.com/getmedia/1e86aec..._V3-2.pdf.aspx

I'd love it if y'all could chime in with info about other vendors that support reverse tilt.