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Old 04-09-2014, 08:24 PM   #1
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St. Louis , Missouri
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Question What should we use to insulate underbelly?

Hubby has the belly skins removed from our 1961 Sovereign and the old, nasty, rat poop, acorn crusted insulation cleaned out. He wants to replace it with foam spray insulation --- is that a good choice? I've seen lots of mention in other posts about the aluminum bubble type insulation -- is it better?
Thanks in advance for any advice!
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Old 04-09-2014, 11:08 PM   #2
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1973 27' Overlander
Portsmouth , Virginia
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I've been putting in a double layer of the pink closed cell foam board that you can get at the big box stores. It's used for insulating foundations from the surrounding soil and is rated at R4 for 3/4". I am using it doubled up at 1.5" for R8. Since it is made for contact with dirt, it's doubtful that its going to break down underneath a trailer. I used 2" decking screws with fender washers to hold it up to the bottom of the floor. I taped sections together for the double thickness with standard duct tape. Fairly easy process.

Honestly, I'm not sure how much good the aluminum bubble wrap would work. You're not going to get much benefit from the reflectivity on the bottom of the trailer. And you have to have some method to secure it to the bottom of the floor.

A spray foam would probably insulate very well, my only concern with that would be if water was to leak down from the top, would it have any way to get out or would it be sealed in where it could rot the floor or rust the frame or both. Most of the water damage isnt due to wood and metal getting wet, but from the fact it doesnt get to dry out. That's one of the benefits of the pink foam board, it won't hold in any water. Cost wise, you're probably looking at 15 a sheet, I think I used about 8 to 10 sheets on the whole job.

Here are a couple of pix of my rig:


Ongoing adventures at:
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Old 05-04-2014, 01:48 AM   #3
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1976 25' Tradewind
, Florida
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Sharp looking install on that insulation!
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