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Old 03-14-2014, 02:18 PM   #1
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Installing Prodex under the floor

Does anyone know which Forum had the discussion about using Prodex as a insulator between the floor and belly pan, I have had a moment of can't find nothing. It talked about laying the Prodex on the frame then putting the floor down or something like that. Please help, I am ready to insulate my floor.

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Old 03-14-2014, 07:42 PM   #2
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How much insulation value will the prodex give you on the bottom of the trailer? As a radiant barrier, I can see where it may help under the roof, but under the floor there isn't that much radiant energy to reflect.

I'm finishing up using the pink closed cell foam board under the trailer, 2 layers of for a total of 1.5 inches or R8. Not a perfect solution, but it should keep the floors from getting too cold or too hot.


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Old 03-14-2014, 08:21 PM   #3
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I read about someone using it between their interior skin and the ribs. And the factory used to run fiberglass right over the top of the frame and then screwed the plywood on top - which made a perfect "wick" for moisture to follow.

Anyway, I've read many threads/posts on these forums, and don't recall anyone running prodex or reflectix over the top of the frame - but then again "recalling" things is becoming more and more difficult . . . what was the question?

On a serious note, I believe a radiant barrier works best when there's an air gap on the side that you want to keep cooler. So if you're trying to keep heat from getting in your trailer you don't want the barrier touching the surface towards the interior of the trailer (up against your plywood floor). If you're trying to keep heat from escaping the Trailer then against the surface if fundamentally "OK", however because heat rises AND because the shell and/or your windows are never going provide much insulation value, I do not believe that a radiant barrier in/at your floor is going to be "up to much". Just my 2 pennies worth.

(i also used rigid foam board in my floor, cut to fit between framing members)

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Old 03-14-2014, 08:25 PM   #4
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If you search the forums for the word, you'll find over 100 threads that contain it. It's a little tougher to read through them a to find it :-( but it's only 100 out of many thousands of threads.
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Old 03-15-2014, 07:44 AM   #5
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Here's the big question that was the deciding factor for the route I took...

What happens when water gets in between the wood and prodex, foam board, etc when its fastened to the bottom of the floor?

It is inevitable that water will get there. I think the prodex will trap it badly, and the foam board will too if they are installed up against the floor.

I chose to go without any insulation underneath after reading several threads on the subject. I think my best protection against wood rot is the ability to allow the wood to dry out quickly. I will obtain some element of insulation in the floor through my flooring matieral. However, I'm in a mild climate and can do that.

That said, If I were to insulate the floor underneath, it would be with foam board. I would install it with an air gap so that it is not flat up against the floor, with plenty of ways to drain the water that will inevitably get there. You could do prodex the same way, but my thoughts are the if you lay it across the frame, you wont create the needed air gap for the product to work effectively AND you will create a water pan that your flooring will sit in when it gets wet.

Keep us posted on what you decide to do.
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Old 03-15-2014, 09:22 AM   #6
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Prodex in the floor

Thanks for the replies, looks like foam board would be safer to use with a air gap, don't want the new floor to rot from moisture build up due to Prodex in constant contact with the wood. Thanks again.
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Old 03-15-2014, 10:34 AM   #7
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Whatever you use, make sure water has a path of escape. Some folks used something like RMAX which is foam with Aluminum on both sides which has R-value and also acts like a radiation barrier. I have seen installations with strips of foam to separate the larger sheets from the floor. I used panel adhesive in thick beads to glue mine on and I hope there will be enough gap there for water to drain. I did it in straight lines and I was in a hurry. Most of my floor has no insulation but I put two 1/2 layers on the sections between the frame and the side wraps since I did not plan on having to get in there on a regular basis. I put screws on the center skin section with the intent of insulating later on and having access to that area for inspecting the structure from time to time. I don't like the rivet and forget mentality and I don't like drilling the things out.

The factory used fiberglass over the frame because it was cheap and fast and it compresses where the floor hits the frame. Fiberglass is the worst thing they could have used.


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