Correct I can not find any restrictions on adding solar for an older home with two roof layers. Maybe a better way to ask the question have other installers put solar on a home with two roof layers?
Original Message:
Sent: Apr 10, 2021 10:06 PM
From: Duane Ediger
Subject: Adding solar if a roof has two layers, of a metal roof over shingles
Sounds like the intended S-5! product might be the SolarFoot (https://s-5.com/products/solarfoot/). Their installation instructions say that the brackets "must be mounted directly over and into the supporting structure of the roof, i.e. wood decking, wood or steel purlins, or trusses...." There is no restriction mentioned regarding existing substrates.
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Duane Ediger
Owner
RafterEye LLC
duaneediger@gmail.com
Original Message:
Sent: Apr 10, 2021 05:22 PM
From: David Hrivnak
Subject: Adding solar if a roof has two layers, of a metal roof over shingles
We planned to use a generous amount of S-5 Solar feet. Each one accepts 4 stainless screws that goes into the decking which is 1by planking. The 1.5" screws will securely get into the planking which is in good shape. So I am not worried about pulling out. But my manager says he does not want the liability by going against the conventional wisdom of not installing solar if there is two layers. I have not been able to confirm if that is a hard and fast rule, a typical solar convention or just a local convention. It seems from most of the comments it is not a nation wide convention.
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David Hrivnak
Sales/Engineering
EcoLogical (part time)
dhrivnak@chartertn.net
Original Message:
Sent: Apr 09, 2021 10:58 PM
From: Duane Ediger
Subject: Adding solar if a roof has two layers, of a metal roof over shingles
My best guess would be that a primary criterion would be attachment strength. PV racking is most commonly attached to a steel roof either via clamping hardware on the ribs of the metal material, or with brackets that screw through the metal roof into a structural member (or plywood deck). With clamps, the design wind uplift force per clamp (which would determine the minimum number and maximum spacing of clamps) would be a function of the type and gauge of the metal roof material and the spacing and pullout force of the metal roof fasteners. Penetrating brackets would eliminate the need to account for the likely unknown method of metal roof attachment, but the compressible shingle material between the metal roof and the roof deck may not be allowed by bracket manufacturer specifications -- with standoff instability and leaks being two potential failure modes. If allowable, the installation crew would need to verify proper attachment to the deck or structural members.
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Duane Ediger
Owner
RafterEye LLC
duaneediger@gmail.com
Original Message:
Sent: Apr 09, 2021 05:41 AM
From: David Hrivnak
Subject: Adding solar if a roof has two layers, of a metal roof over shingles
We have an opportunity to install solar on a shingle roof that was covered with a metal roof. I think the default wisdom is if a roof already has 2 layers we are not to add solar. Is that a hard and fast rule or if an engineer looks at it and calculates the loads are OK can one proceed?
Thank you
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David Hrivnak
Sales/Engineering
EcoLogical (part time)
dhrivnak@chartertn.net
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