Foil insulation - observations, tips and tricks

[malconium]

Sorry for the late reply. I have not been keeping up with the forum in a timely fashion lately. I did remove the residue and I did it by using a stiff brush. Mine was actually a wallpaper paste brush but I think other kinds would work as well. Probably even a broom would work. I used my shop vacuum cleaner to pick up the loose pieces.

Malcolm

[SilverSky]

I used a plastic scraper (Pampered Chef's pan scraper) and Mineral Spirits with a rag. I couldn't get it all off, but it was definitely an improvement. I wish I had power washed the inner skins when it was completely empty instead of scraping/washing them by hand. Sorry if this is too late to be helpful.

[tlynn87]

Ok thanks. Its not too late!! I have found my self doing a lot more to this camper than originally planed. I got to get a good look at the frame so now I have to remove all the old subfloor and paint the frame with some por 15. And while I have it all out I'm going to pressure wash the inside walls!! But thanks for the replys! I was thinking today that I am going to be in extreme cold and heat and thought about putting two layers of Prodex together for the first layer next to the outer skin and then one more a 1/2 in away with the spacers. So altogether I would have 3 layers of Prodex but two of them will be sandwiched together to add thickness. I thought about doing this because the Prodex is so thin. Do you think this is a good idea or just a wast of money??

[SilverSky]

I'll leave the answer about the layers to Malconium or others better versed in the insulation performance arena, but please let me/us know what you decide or end up doing. Side note: I didn't start out planning to gut my stream and have a complete shell-off frame restoration (floor and frame thanks to Frank's Trailer Works) either, but now that I did, I feel like this trailer can get handed down to my future grandchildren. Good luck!

[malconium]

Originally Posted by tlynn87

Ok thanks. Its not too late!! I have found my self doing a lot more to this camper than originally planed. I got to get a good look at the frame so now I have to remove all the old subfloor and paint the frame with some por 15. And while I have it all out I'm going to pressure wash the inside walls!! But thanks for the replys! I was thinking today that I am going to be in extreme cold and heat and thought about putting two layers of Prodex together for the first layer next to the outer skin and then one more a 1/2 in away with the spacers. So altogether I would have 3 layers of Prodex but two of them will be sandwiched together to add thickness. I thought about doing this because the Prodex is so thin. Do you think this is a good idea or just a wast of money??

I think the third layer is overkill. The effectiveness of foil insulation is its ability to reflect radiant energy and that is not related to its thickness. It is also best to have an air gap on both sides of the reflective surfaces. For that reason it is better not to have the foil in direct contact with either the inner or outer skin. I suggest the best way is to space one layer 1/2" away from the outer skin and the other layer 1/2" from the first layer. That way you have 1/2" air gaps on both sides of both reflective foil layers.

Malcolm

[ekstarr]

What a great thread! I am definitely copying Malconium for the most part. Been cutting my many, many foam spacers.

Curious how you guys got the Prodex snug against the frame edges? Tape? Caulk? Is it necessary to be snug or is "close enough" close enough?

When cutting the Prodex did you use scissors? Razor? Exact-o? Did you just measure the cavity and cut based on those measurements? I saw Malconiums tip on the oddly shaped cavities - great idea.

Thanks everyone.

[SilverHoot]

I measured each cavity, used scissors to cut and foil tape at the edges.

[Zeppelinium]

Originally Posted by ekstarr

...Prodex snug against the frame edges? Tape? Caulk? Is it necessary to be snug or is "close enough" close enough?...

When it comes to insulation, there is no such thing as "close enough." Any gaps which allow air circulation from one side of the Prodex to the other kills its effectiveness. The only permissible exception might be a small space at the bottom edge to prevent a water leak from being trapped between the Prodex, the stringer at bottom of that cavity, and the exterior shell.

The Prodex is superior to fiberglass batt only when it is installed well. That's why glass matts are popular--it's easy to install and inherently reduces air movement in the cavities. Poorly installed Prodex will still provide good control on heat transfer via radiation, but its total R-value in that case is only about 1/3 of glass matt.

Zep

[ekstarr]

Originally Posted by Zeppelinium

When it comes to insulation, there is no such thing as "close enough." Any gaps which allow air circulation from one side of the Prodex to the other kills its effectiveness. The only permissible exception might be a small space at the bottom edge to prevent a water leak from being trapped between the Prodex, the stringer at bottom of that cavity, and the exterior shell.

The Prodex is superior to fiberglass batt only when it is installed well. That's why glass matts are popular--it's easy to install and inherently reduces air movement in the cavities. Poorly installed Prodex will still provide good control on heat transfer via radiation, but its total R-value in that case is only about 1/3 of glass matt.

Zep

Thanks Zep! I have put in most of my foam spacers (see photo below).

One more question. Clearly it's near impossible to have the Prodex completely flush with the aluminum ribs - due to human error with measuring, tracing, and cutting. So, would it make sense to use reflective tape to seal the gap between ribbing/frame and the Prodex?

I am going to embark on the Prodex installation this weekend and hopefully finish!

[Zeppelinium]

Originally Posted by ekstarr

T... would it make sense to use reflective tape to seal the gap between ribbing/frame and the Prodex? ...

I'm sure aluminum HVAC tape is better than duct tape/Tyvek tape--no anti-conduction R-value, but substantial reduction in radiation transfer.

No matter how perfect the Prodex is fit within the cavity, the edges must be taped to the ribs to prevent air circulation around the edges (except for small gaps at the bottom to prevent condensation/leaks from pooling).

Most tapes will kill the reflective properties of the Prodex, so you'd want to control the width of the tape in order to maximize the Prodex performance. That being said, any loss of reflective performance at the edges would be small compared to the convective loss if you don't tape.

I have only experimented with the Prodex (wow, times have changed! I can now build the whole instrumentation system in a unit about the size of a deck of cards), not installed it in an Airstream. In my opinion, however, you want to cut the Prodex larger than the cavity so that it folds up on the ribs. Then you just run the tape along the rib and you avoid the problem of getting tape on the active face of the Prodex. Much easier to apply the tape that way and you coincidentally control the in-out position of the Prodex at the edges, reducing the amount of foam spacers.

Z

[ekstarr]

Originally Posted by Zeppelinium

I'm sure aluminum HVAC tape is better than duct tape/Tyvek tape--no anti-conduction R-value, but substantial reduction in radiation transfer.

No matter how perfect the Prodex is fit within the cavity, the edges must be taped to the ribs to prevent air circulation around the edges (except for small gaps at the bottom to prevent condensation/leaks from pooling).

Most tapes will kill the reflective properties of the Prodex, so you'd want to control the width of the tape in order to maximize the Prodex performance. That being said, any loss of reflective performance at the edges would be small compared to the convective loss if you don't tape.

I have only experimented with the Prodex (wow, times have changed! I can now build the whole instrumentation system in a unit about the size of a deck of cards), not installed it in an Airstream. In my opinion, however, you want to cut the Prodex larger than the cavity so that it folds up on the ribs. Then you just run the tape along the rib and you avoid the problem of getting tape on the active face of the Prodex. Much easier to apply the tape that way and you coincidentally control the in-out position of the Prodex at the edges, reducing the amount of foam spacers.

Z

wow, that's great advice Z. makes a lot of sense. boy it's tricky to get the insulation to a "gap-less" size. i am pretty much done with my panels, just need to do the tape now.

[malconium]

Originally Posted by ekstarr

Thanks Zep! I have put in most of my foam spacers (see photo below).

One more question. Clearly it's near impossible to have the Prodex completely flush with the aluminum ribs - due to human error with measuring, tracing, and cutting. So, would it make sense to use reflective tape to seal the gap between ribbing/frame and the Prodex?

I am going to embark on the Prodex installation this weekend and hopefully finish!

I have a question for you from looking at your photos. Is your foil touching the outer skin of the Airstream or is it suspended at the halfway point in the wall cavity? I just can't tell from the photos. The cavities look rather deep.

[ekstarr]

Originally Posted by malconium

I have a question for you from looking at your photos. Is your foil touching the outer skin of the Airstream or is it suspended at the halfway point in the wall cavity? I just can't tell from the photos. The cavities look rather deep.

Malconium, the Prodex is suspended halfway in the cavity - and for the most part, does not seem to be touching the outer skin. See the attached photo for a better reference. I can't say for sure that there is not a single place where the foil doesn't touch, but at least 95% of it seems to be suspended halfway through... the remaining 5% may be a little curl that makes contact. I have yet to go through with reflective tape filling any gaps. I also plan to re-cut some Prodex for a snugger fit on some cavities.

The cavities are 1.5" thick. Also, I should mention, this isn't technically an airstream, it's a 1952 Silver Streak Clipper, pretty much identical to the Curtis Wright.

[malconium]

Originally Posted by ekstarr

Malconium, the Prodex is suspended halfway in the cavity - and for the most part, does not seem to be touching the outer skin. See the attached photo for a better reference. I can't say for sure that there is not a single place where the foil doesn't touch, but at least 95% of it seems to be suspended halfway through... the remaining 5% may be a little curl that makes contact. I have yet to go through with reflective tape filling any gaps. I also plan to re-cut some Prodex for a snugger fit on some cavities.

The cavities are 1.5" thick. Also, I should mention, this isn't technically an airstream, it's a 1952 Silver Streak Clipper, pretty much identical to the Curtis Wright.

Nice looking trailer. Not to worry if it touches here and there. The general rule is that the foil works best if there is an air gap on both sides is all - hence my question. I put the first layer of foam strips right around the edges of my cavities attached to the outside body. I then glued the foil to that. I only put foam in the middle in really large areas or on the end caps where the curve was pronounced and the foil seemed to want to sag some. My final strips of foam were usually right around the edges too so the foam went pretty far in sealing up the edges of the foil. Putting the inner skin back in typically compressed the foam and foil sandwich a bit too which probably helps with the seal.

[pinkflamingoes]

Hadsmh

[HiHoAgRV]

I've been happy with Prodex in my '63. I started out glueing it to the skin but in most places, it peeled back and left an airgap. It's easy to tell where that happened (before installing the inner skin, in full sun there it's possible to just touch it and tell a temp difference). Like everyone else said, sealing the edges is the important part.

My second layer is installed OVER the ribs to provide a thermal break. I don't think this is feasible using the factory rivet spacing, I went with a rivet every 2"

I've camped in the upper 20 degree temps with a single electric cube heater and it's just fine. Full sun in Florida and the AC kept us nice and cool. If I had to pick a single thing that prodex does NOT do as well as batt, it would be sound control but that may be just a perception comparing it to my 1991 with smaller windows, more cloth on the interior and heavier interior construction.

[Danny Z]

Wow! This, as have all of the posts I have read, has been so insightful! Thanks so much. I am just about to re insulate and wanted to make sure there have been no updates as to the prodex having issues over an extended time. As well as ask if there has been any new products that one might recommend over prodex? As long as I am here, it sounds like the time investment of foam spacers and prodex is huge compared to going with a batt insulation. In hindsight, is the prodex performance (when installed correctly) worth it, or for the time it takes would you recommend using a batt insulation and calling it done?

[Foiled Again]

Originally Posted by Danny Z

Wow! This, as have all of the posts I have read, has been so insightful! Thanks so much. I am just about to re insulate and wanted to make sure there have been no updates as to the prodex having issues over an extended time. As well as ask if there has been any new products that one might recommend over prodex? As long as I am here, it sounds like the time investment of foam spacers and prodex is huge compared to going with a batt insulation. In hindsight, is the prodex performance (when installed correctly) worth it, or for the time it takes would you recommend using a batt insulation and calling it done?

Have NEVER restored an old Airstream - but am having a foam insulated AVION done partly because it IS well insulated. I Prodexed my hatch on the Eddie Bauer because it was so wretchedly cold this winter.

Let's assume that it costs 4 times as much and takes 4 times as long to use Prodex as batt insulation. The first weekend it's 95 degrees outside and your Air conditioner CAN keep the inside cool... you'll be glad you didn't skimp. Being able to camp in November when the temperatures are in the 40's and not running your propane tanks empty... you'll be glad you didn't skimp. If you keep the trailer as little as 3 years it becomes a no-brainer.

[slowmover]

See jonplayers TRAVELUX restoration on this site at post 240 or so, and his use of Energyshield. Great pics of great work.

[nrgtrakr]

Not to start the anti foam controversy back up, but if I had to do a frame off rebuild I would ...

• Run plasitc conduit for the wiring
• Generously slather all joints and rivets on the inside with TremPro 635
• Put heating pads on the tanks wired to their own breaker and individual disconnect switches
• Place pieces of Reflectix between the ribs and line the underside with it
• Spray with foam and trim slightly deep
• Using foil tape, put another layer of Reflectix between the ribs and on the belly before installing a vapor barrior (plastic sheating) then the inner skin, the banana peals tucked under the outer wall skin (again slathered with TremPro) and under the belly skin (again TremPro)

Then live with a window and roof vent always cracked open to allow moisture to escape.

Observations from living in climate extremes (Mojave in summer, Colo Mtns in winter) but maybe ridiculous.