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Old 09-19-2019, 08:36 PM   #41
Almost There
Join Date: Jun 2019
Posts: 90
No, and neither is a foamed roof

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Old 09-22-2019, 02:38 AM   #42
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Join Date: Jul 2019
Location: Freedom Field, New Mexico
Posts: 265
Year: 1998
Coachwork: International
Chassis: Amtrans
Engine: 444E
Rated Cap: 84 pas
Just want to address the number of comments about the whole bus being a thermal conductor from the viewpoint of someone who lives in a bus 24/7 in the Chihuahua dessert of New Mexico. The radiant heat from the sun heating the roof was definitely the most prominent comfort issue we had to deal with. We decided to cover the roof with ten 327W solar panels. With an air gap under them. The panels absorb most of the gradient heat from the sun, while the desert breeze moves heated air away from the bus roof.
With no additional insulation a 8000BTU A/C unit augmented with a small reportable swamp cooler kept us 15 to 20 degrees cooler than the desert around us on days where the temp in the shade was 110.
Not our final answer. We followed by insulating the walls with 2"poly board and covering 90% of the windows on the outside with 1/4" plywood +1/8" headboard painted white.
Now the solar panels provide enough power to keep our 600AH battery bank hoped off while keeping us at a chilly 77 degrees, charging our phones, running our 5.0c.f. deep freeze and allowing us to plop in front of the tv.
Comfotable enough for us. I may lift the solar panels and spray the closed cell foam on the roof this winter though. That's a great idea!
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Old 09-22-2019, 09:57 PM   #43
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Location: pa
Posts: 2,142
Year: 98
Coachwork: 1. Corbeil & 2. Thomas
Chassis: 1 ford e350 2 mercedes
Engine: 7.3 powerstroke & MBE906
We insulated a rear section of our roof on the outside with 1/2" aluminum faced iso board. It works good for all the reasons mentioned. Spray foam on the outside would probably do better. You can see some pics in our dory built thread.
We suggested outside roof insulation below the solar panels in our small bus and did not get a lot of response from the forum in that time. Insulation on the outside is better then on the least from an insulation / conductivity/ thermal bridging standpoint.

Later johan
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Old 09-23-2019, 12:29 AM   #44
Join Date: Oct 2015
Location: BC Rockies
Posts: 116
Year: 93
Coachwork: Corbiel
Chassis: Ford
Engine: 5.9 Cummins
Rated Cap: 36 pass
Must say I enjoy reading about alternative ways of doing things. And this talk of utilizing disruptive technology - well- it does appear to be disruptive!
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Old 07-11-2020, 01:40 PM   #45
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Join Date: Jun 2020
Posts: 7
Interesting idea

Originally Posted by Iqinsanity View Post
Iím fine with having to be the first to try it lol, but Iíve seen enough spray foamed roofs with that white paint with those little glass beads in the hottest major city in the country to know that itís far superior to anything else.

Still looking for a bus though, and storage is an issue. So Iím thinking I wonít start for another year on an actual bus, just buying some of the bigger items in advance.
Were you able to make this work into your build? Did you incapsulate the insulation in fiberglass? I get the thermodynamics/stat mech involved here. The only part that's getting me is the high winds at the front edge of the bus. I'm picturing it wearing from the front to the back. If you were able to make it work, I'd love to see it!
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Old 07-11-2020, 02:51 PM   #46
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Join Date: Jul 2020
Location: Sacramento
Posts: 880
Year: 1999
I've seen build videos where people put decks on the roof and insulate under them with foam board.
I have a shuttle bus which has fiberglass insulation in the roof and it looks great, so no reason to remove it, but ADD to the insulation on top. My plan is to put foam board on the roof and then cover it with fiberglass, then add some pet tubing on top of that, and then solar panels on top of that, and then seal all of that with clear resin.
Basically create another sealed second roof layer that generates water cooled solar and hot water heater.

These were the plans for my solar powered catamaran, so have the materials and experience being applied to the rolling tiny home instead of the floating tiny home.
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Old 07-11-2020, 06:33 PM   #47
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Join Date: Apr 2012
Location: So Cal
Posts: 3,063
Year: 1935
Coachwork: Superior
Chassis: Chevy
Engine: 317 ci/tid / Isuzu
"My plan is to put foam board on the roof and then cover it with fiberglass, then add some pet tubing on top of that, and then solar panels on top of that, and then seal all of that with clear resin."

That design will lead to low photoelectric output from your solar panels as you'll see when you read up on solar panels.

Is all that going to go on top of your roof mounted water tanks?
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