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Old 09-13-2020, 10:13 AM   #1
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Insulation Under Solar Panels?


Iím wondering if anyone has built a wind barrier around their solar panels and added foam board insulation on top of the roof under the solar panels? My husband is considering doing this, but I canít find any examples of other bus conversions that have done it this way. Iím wondering if there are reasons why it might not be a good idea?

The top of our bus is fiberglass, and heís talking about using fiberglass to mold a wind barrier from the top edge of the bus to the bottom of the solar panels, which would cover up the support structure for the solar panels. He would leave an air gap between the foam boards and solar panels. The roof will also be insulated inside of the bus with spray foam.

Thanks for any input you can offer!
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Old 09-13-2020, 10:21 AM   #2
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Most solar panels are supposed to have a little space under them for air flow and cooling.
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Old 09-13-2020, 10:49 AM   #3
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Good to be concerned with a fiberglass roof, temperatures from undersides' radiation can get super hot.

Air circulation when stationary is critical.

Stopping the panels blowing off comes from the strength of the panel framing rack and its connection to the surface below. Do NOT use the "semi-flex" type, but fully framed glass covered type designed for professional home installs, high voltage and rated for hurricanes.

To reduce lost mpg all that's needed is a front airfoil.

I have seen an "edge lip" all round to make panels less visible basically the panel space is "sunk" into what looks like a shallow pool space.

But that would impede air circulation and be difficult to DIY.

My reco would be using thick layers of very strong and reflective waterproof coating to protect the fiberglass itself, pretend you will be under constant attack by aliens blasting infrared ray guns.

Then thick thermal insulation underside to keep the heat out, maybe even a professional spray foam job.

If you can, attach a strong roof rack to the vertical steel bits, top of the load-bearing posts?

to hold the framed panels at least 2-3" above the roof surface

altogether weighing maybe many hundreds of pounds that may be the biggest challenge.

Or, second choice by far, just use the bare frames with 2-3" spacing brackets, PlusNut'ed to the fiberglass itself.
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Old 09-13-2020, 12:37 PM   #4
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We have put insulation on top of the roof and under the solar panels / spare tire. Planning to do more as time allows.
Probably a little un-convential but it works fine and you do not loose head room. Photos are somewhere in the Dory thread.
We used a lot of small solar panels and are less nervous that they blow out of there frames then with big ones. There is anecdotal stories of people loosing large panels and building a cover around the panels to avoid the wind getting under them.
Good luck,

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Old 09-16-2020, 05:02 PM   #5
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I placed 2Ē foam board insulation on top of my flat roofed Motorhome then covered it with two layers of reinforced plastic then solar panels over the top of that. Itís been on there for 8 years now but some rats gnawed holes in the plastic cover so Iím trying to slide a new layer under the solar panels by jacking up each side of the panels. Not a easy job.
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Old 09-16-2020, 10:54 PM   #6
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Still want an effective air gap under the panels

the cells getting hot reduces output

and longevity
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