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Old 08-22-2014, 05:52 PM   #1
cramar
 
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Installing insulation ABOVE the subfloor

The preferred method for insulating a new subfloor seems to be glueing on rigid foam insulation to the underside of the subfloor between the rails. Oh course the subfloor over the frame gets no insulation whatsoever. I thought in addition to this, why not cover the entire upper side of the subfloor throughout the trailer with 1" foam then install the vinyl flooring on top of the foam? Using the rigid foam insulation that goes under concrete slabs should have adequate compression strength to support people walking on it. The advantages are cushioning and everywhere gets insulation even over the rails. The only downside I see is the floor becomes 1" higher loosing this much headroom. For us this is not a problem. Has anyone done this? Am I missing something?
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Old 08-22-2014, 06:00 PM   #2
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howdy.. yes.. if you get water under, it will not be able to dry out.. otherwise, sounds like a good idea..

also... I would consider insulating the underbelly to keep heat in there to keep freezing to a minimum.
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Old 08-22-2014, 06:09 PM   #3
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You must be short.... I couldn't sacrifice the head room. LOL
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Old 08-22-2014, 06:37 PM   #4
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I dropped my belly pan when I realized that the factory insulation was
a joke (not funny kind).
The plan was to glue new 1" foam as you stated but I got to thinking that
if the floor ever did get wet (as CF mentioned); it could not dry out thus
ensuring mold and rot.
My solution was to cut slightly over size pieces and create a bow in the
styrofoam such that it was held in place by the frames (laterally) and
further create an air pocket which would further insulate.
Was not fun or all that easy but maybe easier than what you are planning.
PS: while I was doing this I completely cleaned and painted everything in sight
under/frames/axels etc so better than new.
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Old 08-22-2014, 08:10 PM   #5
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I don't see the big need to insulate the floor. What kind of weather do you plan on camping in? I took all the old insulation that was full of mice and water and left the underside between the belly pan open. If it is that cold out, keep your socks on and use a floor mat. It works fine for us and we have camped in below freezing weather.
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Old 08-22-2014, 08:31 PM   #6
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I'd tend to agree with Doug on this. I don't think insulating the underside of the sub-floor is worth the time or effort. On the next trailer I do for myself, there won't be any insulation under the sub-floor. A good furnace, warm socks and wool rugs will do you well without wondering if there is water stuck between the sub-floor and insulation rotting away.
You might look into a laminated panel that incorporates a layer of insulation for the sub-floor. If you can find a good floor covering that is warm to the toes, like cork, all the better.
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Old 08-22-2014, 08:47 PM   #7
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Quote:
Originally Posted by cramar View Post
The preferred method for insulating a new subfloor seems to be glueing on rigid foam insulation to the underside of the subfloor between the rails. Oh course the subfloor over the frame gets no insulation whatsoever. I thought in addition to this, why not cover the entire upper side of the subfloor throughout the trailer with 1" foam then install the vinyl flooring on top of the foam? Using the rigid foam insulation that goes under concrete slabs should have adequate compression strength to support people walking on it. The advantages are cushioning and everywhere gets insulation even over the rails. The only downside I see is the floor becomes 1" higher loosing this much headroom. For us this is not a problem. Has anyone done this? Am I missing something?
I use a couple of runners on my vinyl floor. Old Classics, etc. had carpeting with padding installed, THEN they put in the furniture. AWFUL - trapped moisture, smells, was impossible to keep clean, and wear patterns quickly happened. But you could make a template of the entire free area of the floor (do it yourself stores used to sell a heavy paper or Tyvec pattern with 1 foot squares preprinted on it) and cut a piece of carpet and padding to fit. Needs cleaning? Pull it out and scrub it in the driveway. When it wears out toss and get new. Want a different look, toss and get new. Feet are toasty warm and the trailer is quieter. You could leave the bathroom area bare or use bathmats that can be easily hung to dry and washed.

Oh and another disadvantage of raising the floor - all the doors might have to be shortened.

Paula
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Old 08-22-2014, 08:53 PM   #8
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Im of the same school of thought. I'm not insulating my sub-floor. I think the sub-floor plus my flooring material of choice will be fine. Of course I will be sure there are no drafts coming up from under the cabinets, but then throw rugs, socks and furnace will be fine. I come from tent camping and the tent stays warm. I cant see how the trailer would get that cold unless I'm planning on full-timing in extreme temps. And if I'm wrong, it will be a little cold, which I like when I'm camping anyway. However, I'm way more concerned with keeping it cool inside in the not-so-cold times anyway.

My concern was primarily for the floor to be able to dry out when it gets wet anyway. For sure it will get wet. But staying wet is the reason for rot. If it can dry out, there wont be rot. No matter how you insulate the floor, if it gets wet, it will stay wet. The ability to breathe is my primary focus.
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Old 08-22-2014, 09:13 PM   #9
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I am with Mixter, Top and Shacksman and vote for no insulation. Remember that Shacksman lives and camps in Canada. I am much more concerned about the belly pan area being able to dry out when it gets wet. It is not like the floor is open to the outside air. Even though there is no insulation in the cavity, the air in the enclosed cavity is a an insulator.

It might get down to the forties when we camp, and possibly colder at night, but this just means that the furnace will have to run a little longer. If I were really planning on doing some cold weather camping, I would probably install some 2x2 carpet tiles over the cork floor in my Tradewind.

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Old 08-22-2014, 09:24 PM   #10
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If you are talking about the blue ( high density) foam we use for foundation and underslab insulation I don't see an issue with moisture. I think the trade name is Dow Formular. It is designed to buried in the earth. I am 6'-3", it would not be for me but, if the loss of head room is not a concern I would go for it. If you install 1" or 1.5" directly over the framing then screw the plywood through the foam and into the frame it should work fine. Not sure what the fire rating of the foam would be. You would have to design a structural detail at the perimeter since the shell actually bears on the plywood.
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Old 08-25-2014, 09:51 AM   #11
cramar
 
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Still thinking...

Thanks for all the comments. Well, it seems the consensus is that using foam insulation above the subfloor would cause more problems with moisture retention that in would solve. Good point! However I realized that the vinyl plank flooring that we will be installing just might cause the same issue anyway. (Carpeting is not going to happen with a dog that sheds constantly.) So probably the vinyl will trap moisture, so it might not be any worse with foam under the vinyl.

But this has me thinking. I wonder if there is a breathable option? Something like installing RaceDeck Free-Flow above the subfloor and below the vinyl, with strategically spaced vent holes in the vinyl to have an air path to the subfloor.
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Old 08-25-2014, 10:11 AM   #12
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I think the comments are good about keeping things warm rather than trying to keep heat in when there only so much that can be done in the Airstream's floor.

There are 1/4" waterproof insulating backer backer boards for use under in-floor heating mats. R value is a little over 1. About the same as xps foam board.
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Old 08-25-2014, 11:05 AM   #13
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I used two layers of closed cell foam board held underneath with decking screws and fender washers. I don't see that foam holding any moisture in as there is always some bit of a gap between it and the wood itself. Besides that, that space underneath is really in three sections as you go from curbside to street side with the largest in the middle, about 5 feet wide. Water doesnt tend to get to the middle section, it comes down on the sides traveling in between the skins. The Foam board there is only about a foot wide, so again where do you think the water is going to get trapped?

Besides insulating the foam board does serve to protect the underside of the subfloor. Its really not an expensive mod, probably about 200 for materials. If you live down in TX, then maybe it never gets that cold to bother, but farther north, it probably helps some.

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Old 08-25-2014, 11:33 PM   #14
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Installing insulation ABOVE the subfloor

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