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Originally Posted by Zeppelinium
I have looked through all the related threads and I see that foil, supported away from the skins, is a highly effective insulation. However, I don't see any details on whether or not the foil is glued and sealed to the ribs at the edges to create a reasonably air-tight volume. Are the installation details already discussed elsewhere?
What about Andy's comment about foil, breathing, and condensation? Any indication that the "Malconium method" creates condensation or other water vapor problems?
While I'm at it, I'd like to insulate the belly pan with something that's inhospitable to vermin and waterproof. If you put a closed cell foam up against the floor, is there a concern about possibly retaining a thin film of water on top of the foam and against the plywood? If the edges are reasonably tight against the frame members but aren't sealed, would that be enough breathing room?
Someone indicated they would install two layers of foil. Is there any data, subjective or otherwise, on how effective that was?
I also saw that interior skin temps along the ribs was 7-10 degrees different than the skin away from the ribs. Has anyone measured the improvement using either the 3/16" closed cell foam tape or the cork tape (seen in other posts)? Did these methods of insulating the ribs reduce condensation significantly, or change the inside temp (I'm mostly interested in the hot climate results, but the cold climate results should be an indication of similar performance on the hot side, duh).
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You can find some more details about the installation approach that I used along with some photos in the following thread:
http://www.airforums.com/forum...ods-14803.html
I used foam strips around the edges of the cavities to act as spacers to hold the foil in the middle of the cavities. The foam strips are generally tight to the sides of a given cavity and the foil is cut as close as I can to the actual size of the cavity. I glue foam to the outer skin, glue the foil to the outer foam strip and glue the inner foam strip to the foil. The only place where the foam is not tight to the outer sides of the cavities is along the bottom at floor line. I have held the foam back 1/2" or so to create a bit of a channel along the botton. I also drilled holes in the bottom of the wall cavitity and glued screen over them so that there was a path for moisture to get out if any managed to accumulate at the bottom of the wall.
For floor insulation since I am intending to install hot water radient heating on top of the floor I am intending to add a layer of reflective foil on the floor first and put my heat tubing on top of that. I had originally thought of putting a layer of foil under my floor and using some sort of spacer to keep it just below the floor so that I had an air gap between the floor and the foil. The reflective foil seems to be more effective with an air gap and this would provide a little breathing room for the bottom of the floor. In my case I am using Polyboard for the floor so moisture would not have been a problem. I did think though that I might poke a small drain hole in the middle of the foil in each cavity. The slight sag in the foil would cause any moisture to drain toward the hole and out.
I think the idea of glueing foam to the bottom of the floor is a good idea too. The good news is that the floor is the least important place to have insulation so most any solution would work well enough in my opinion. Some forum memebers have even elected to leave the under floor area without any insulation.
Malcolm