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Wabbiteer · 07-29-2010, 04:48 PM

http://www.2hsc.com/residential/manu...vm_physics.pdf

malconium · 08-03-2010, 01:36 PM

The reflective aspect of the foil is extremely important even though the foil is between the skins. While the skins are opaque to radiant energy in the visible spectrum they do let through radiant energy in the invisible spectrum - specifically in the infrared part of the spectrum. Putting an air gap on both sides of the foil reflective surface helps the foil to do a much better job of reflecting radiant energy. This is true whether it is heat that is trying to come in from outside or if it is heat trying to get out from the inside.

I don't seem to have mentioned it here in this thread but I added small drain holes at the bottom of my wall cavities in case water did get into the walls. I drilled one or two holes about 1/4" or so in diameter at the bottom of each cavity and glued some screen over them to keep bugs from being able to crawl in. I have no idea if the technique really works but it seemed like a good idea at the time. This should give water an alternative route to exit the wall other than by running on on the floor.

I actually used Reflectix foil insulation which I believe I bought at Lowes - that's what they carry. I liked the sound of the Prodex variety and would probably consider using it instead if I were to do this again. The principle difference seems to be that there is a layer of foam insulation between the layers of foil rather than a layer of bubbles. That seems like a good idea to me. As I recall one of the forum members found that Prodex could be purchased through the Internet at a better price than what I was paying for my insulation at Lowes. That is a good thing too.

Malcolm

Flysoncloud · 08-03-2010, 08:02 PM

I am all about saving money where and when I can.........I work for Sysco foods and they use a lot of different packing stuff to keep things frozen. The other day the cleaning guys came by my shop and had what looks like buble wrap made of foil and they had a lot of it. Being thrify (cheap) like I am I brought it home with a bunch of 1.5 inch styrofoam. I was thinking (which tends to get me in trouble) why not glue the buble foil to the wall then use the pink stuff then put another layer of the buble foil over the pink. I also thought about using some of the styrofoam too. The only reason I would use it is because its free but I wonder if is a waste even if it is free.
I dont quite understand what you guys mean by "air gap". Would my plan not leave the "air gap"?

malconium · 08-03-2010, 10:02 PM

What I mean by the air gap is that the foil works best when there is space between the foil surface and the inner or outer skin. This keeps the foil surface from being in contact with the skin so that less heat is transferred to the foil by conduction. It also lets the foil do a better job of reflecting the radiant energy. So the idea is to suspend the foil in the middle of the wall cavity and leave an air gap or space on both the inner and outer sides of the foil. This means that the foil is about 3/4" from the outer skin and from the inner skin since the wall cavity is about 1-1/2 in overall size. The narrow foam strips that have been mentioned in this thread are used as spacers around the edges of a given part of the wall cavity to hold the foil suspended at the mid point between the two skins. It is not necessary or desirable to have foam everywhere if that forces the foil to be in direct contact with the inner or outer skins. If the wall cavity is full of foam you might as well leave out the foil.

I hope that helps...

Malcolm

Flysoncloud · 08-04-2010, 04:38 PM

Thanks for explaing the air gap for me. I guess it just makes more sence for me to just use the pink stuff I have laying around already.

VIKING · 08-05-2010, 11:07 AM

Quote:

Originally Posted by uoshane

Thanks for explaing the air gap for me. I guess it just makes more sence for me to just use the pink stuff I have laying around already.

The reason I decided not to use the pink stuff was the amount and smell of the rodent feces contained within it. It's a home for rats, mice and snakes. The foil/ foam/ foil is not hospitable as a nice fiberglass nest is. If money is the concern I can tell you it was less than $350.00 for my safari, and that was with 2 layers of Prodex.
Best to you,
Rich the Viking

Flysoncloud · 08-05-2010, 06:53 PM

Can one of you that used this strip method for the air gap post some pics or post the link of a pic so I can see how you did it? I kinda get the idea by reading but I am better wih pics.
Did you use the Prodex to make the strips?

SilverHoot · 08-06-2010, 05:49 AM

I used 5/8" thick semi-rigid foam insulation cut in about 1" wide strips glued to the subfloor. Have not got to the walls yet will do the same there. Glue the strips to the inside of the exterior skin and the the Prodex to the strips. Very much like Uwe did here, look at post #24 http://www.airforums.com/forums/f39/...n-27759-2.html I have seen where some have actually cut strips of the Prodex to use as the strips, I wanted more air space so chose to use the semi-rigid foam.

Flysoncloud · 08-06-2010, 01:48 PM

Thank you very much! It makes much more sence to me now. I think I will try this method!

tlynn87 · 01-25-2012, 07:34 PM

So after doing lots of reading and researching I have decided to use Prodex too. My question is for malconium. What is the result of all your hard work? Have you had her in the summer heat or the freezing wither weather yet? I plan on full timing in my AS and live in extreme climates!! Also when you install 2 layers of Prodex is there any extra room on the inside? Would I be better installing 3 layers or will that ruin the benefit of the air gap??

Thanks for any replys!

malconium · 01-26-2012, 02:52 PM

Quote:

Originally Posted by tlynn87

So after doing lots of reading and researching I have decided to use Prodex too. My question is for malconium. What is the result of all your hard work? Have you had her in the summer heat or the freezing wither weather yet? I plan on full timing in my AS and live in extreme climates!! Also when you install 2 layers of Prodex is there any extra room on the inside? Would I be better installing 3 layers or will that ruin the benefit of the air gap??

Thanks for any replys!

My Airstream is still a bit of a work in progress but I do feel happy that I added foil insulation instead of the original fiberglass insulation. I have only take the trailer out 2 times so far in weather that has been moderate. I was using a small electric heater at night with night time temperatures down to maybe the high 40's. Much of my recent work has been on my radiant heating system. See the following thread on that topic.

http://www.airforums.com/forums/f163...ion-78761.html

My personal opinion is that two layers would be the way to go for your need. From what I can tell it is a good idea to have at least 1/2" of air gap at the surface of each foil layer. The walls are about 1-1/2" thick which means that using two layers would give you right at about 1/2" of air gap between each layer. You can use 1/2" thick foam to make supporting strips around the edges of each cavity. I also think it is a good idea to add some sort of thermal break between the ribs and the inner skins. I used felt but I do not honestly know if that is better than other alternatives. It was what I could find at the time and installed easily enough.

One type of reflective foil insulation that might be worth looking into - especially from a price point - is the following:

Aluminum Radiant Barrier Insulation | Ra-flect Radiant Barrier

This type has a woven mesh material between the layers which makes it very strong. I am not sure how this behaves instead of a layer of bubble or foam but I think that with two layers of foil the air gap between the two layers is a lot better than any thin foam layer with just one layer. In our application the strength may not be that important either. The price point looks very good compared to what I paid for Reflectix foil. I have purchased some of this product for insulation in a back porch and I used some of it on my Airstream floor too. I wish I had found it sooner.

Malcolm

tahoe_air · 01-30-2012, 12:58 PM

I've been trying to keep up with everyone's insulation types and techniques and have come across some insulation on CL for a good price. Does anyone know about the NASA type foil backed over a thick membrane stuff? Its about 1/2 thick and used in house attacks. I don't think its the same stuff as the Prodex. Sorry if this has been asked before. I tried to find it first before I posted.

tlynn87 · 01-31-2012, 04:21 AM

Thanks for the reply Malcolm!! I still have plenty of work to do before I insulate. I think i am going to use two layers of Prodex though. Good luck with your project

Tlynn87

Tahoe_air

Sorry never have heard of anyone using the stuff before, But sounds good being that it's 1/2 in thick. Good luck

SilverSky · 01-31-2012, 05:39 AM

I finished a second layer of Prodex in my 23' Safari this winter and am very happy with it so far (just putting the inner skins on now). I did .5x1 in foam furring strips glued with liquid nails to the exterior walls for the first layer, then just compression fit the second which went much faster. I didn't do the holes in the floor like Malconium, but I think it would be a good idea in principle. I was almost able to do both layers with one roll of the 48" Prodex (700 sq ft). I was more thrifty with the second layer by foil taping med size pieces for larger areas. I also used some for covering vents and windows to try and stay warm last winter. The other day is was around 30 outside and I had to turn down my little heater, it was very cozy. I actually hate covering up the insulation, I like the way it looks. Even though it is more time consuming, I'm very glad I did this over the pink.

tlynn87 · 02-01-2012, 06:21 PM

Silversky would you please explain what your mean when you say compression fit the second layer??

Thanks

SilverSky · 02-01-2012, 07:11 PM

Happy to explain, esp since I probably misused the term. With the first layer, I cut and glued the Prodex to the furring strips. Then I ran all my electrical wires. The second layer I just cut the Prodex to the shape of the opening and did not use any glue to hold it in. The material keeps it's shape, so it stays in place well. Installing the interior skins will also keep it in place. I have a guaranteed .5 inch air space between the ext wall and the first layer due to the foam spacers, the other layers air space is variable, but I'm not worried about that, just glad to have the second layer. Good luck! HTH, elly

DontBSilly · 02-02-2012, 04:14 AM

I started insulating the underside of my caravel just yesterday. I used strips of 1/2" foam board to surround each cavity and glued them temporarily with some construction adhesive I had left over from putting in the new floor. Just a few dabs on each piece works well. You can actually surround two cavities at once, slipping the strips between the cross brace and subfloor where the subfloor joints are lapped with the second piece of plywood. The 1/2" foam slides in easilly. Then I cut 3/4 in foam about a quarter inch oversize for each cavity. I held the piece up to the floor bolts protruding through the cross brace and made a slice with a razor knife at each bolt, just enough for the foam to slide around each bolt. Then I used a scrap of 2X4 and a hammer to coax the rest of the panel in place. It makes a nice tight fit. I used 1 5/8 drywall screws and roofers tin caps through both pieces of foam and up into the subfloor to make sure that everything stays put. My subfloor bolts are long enough that I can put washers made from tin caps on them and a nut to further ensure that this stuff stays in place. Today I'll tackle the tricky outter curved sections.

Chuck · 02-02-2012, 06:31 AM

pictures....pictures....pictures.

it didn't happen without pictures!

tlynn87 · 02-07-2012, 12:38 PM

Ok thanks for the explanation silversky!! I am going to start insulating soon!! I'm sure I'll have a couple more questions after I start. Thanks for your help

tlynn87 · 02-16-2012, 01:24 PM

malcolm and silversky i have a question. I have just removed all of the old pink stuff and there is a glue with some old pink stuff residue on the aluminum. i was wanting to know if you removed this before you installed prodex or if you just left it on. If you did remove what is the best method of doing so? thanks for your help!!