Spray Foam Insulation

[BigAl]

In house construction the problem is always humidity inside trying to get out. Any imperfection in the vapour barrier which is installed on the warm(inside) side of the wall allows moisture to migrate towards the outside of the wall. Since it is cold at the outer section of the wall it will condense to water droplets. Therefore it is important that the outer side of the structure is designed to allow water vapour to penetrate the house wrap and get out.
In our trailer the outer skin is hopefully totally waterproof! So where does the condensation go? Seems to me it would run down the inside of the wall and fill up the C channel. Then leak past the hold down bolts and soak into the ply floor.
To minimize this I would think a non porous solid insulation fully adhered to the outer skin would be the ideal solution. Also the inner skin should have vent holes near the floor and in the ceiling so that air could circulate and let the moisture back into the interior of the trailer when temps change.
I'm probably thinking too much!
Al

[J. Morgan]

I used fiberglass insulation, and did not seal any rivets, no vapor barrier, etc. I did calk the top third of all window frames and other openings.... But that is about it.

Sometimes we have a way of making simple things hard.

Originally Posted by vintageracer

After reading 15 pages of discussion on whether "To Foam or Not To Foam", Poly this and Poly that, condensation, fiberglass batting and animals, taping joints, air gaps, never really fixing the leaks in windows and rivets and more it almost makes a guy want to buy double hull fiberglass trailer like the Oliver brand travel trailer made here in Tennessee. It won't leak or have all these insulation issues.

I guess nostalgia has its price!!!

Brevi tempore!

[kidjedi]

Originally Posted by Wabbiteer

Freeze and thaw the 0.05oz almost nothing* sample 8, 12 16 times, resoak and reweigh...

Right, but what are the chances that the double foil faced PIC panels, sealed again at the edges with foil tape, and then sealed in the walls of my Airstream will remain completely submerged for more than a month? If that happens, I've got WAY bigger problems than "moisture."

Not to mention, the test piece has a lot of exposed foam, whereas the foil in the Airstream has minimal exposed foam (it's all sealed in foil).

On top of that, within the hour, the test piece was back down to .05oz. The water weight was likely all at the edges, not penetrated to the center of a very small piece of foam --in contrast to large panels only exposed at the edge; panels where moisture couldn't even get to the center.

The test is FAR from perfect, but I only did it to get a general idea of how the PIC works with water/moisture (and the answer is: pretty darn well).

[kidjedi]

Originally Posted by vintageracer

...almost makes a guy want to buy double hull fiberglass trailer like the Oliver brand travel trailer made here in Tennessee. It won't leak or have all these insulation issues.

I guess nostalgia has its price!!!

Nostalgia certainly has it's price. So does caring about the look and design of the trailer. I don't want a marshmallow on wheels (I'd rather have a metal twinky).

[kidjedi]

Originally Posted by J. Morgan

I used fiberglass insulation, and did not seal any rivets, no vapor barrier, etc. I did calk the top third of all window frames and other openings.... But that is about it.

Sometimes we have a way of making simple things hard.

I completely agree. Sometimes you just need to get on with it with materials readily available. This is why I'm using closed cell poly foam from Lowe's (or maybe the 65 mil EPDM leftover from a roofing job) for rib insulation instead of Aerogel. It's also why I'm using the PIC (available from Home Depot) instead of spray foam (which I'd have to order special equipment for and also have to do all at once).

There's also nothing wrong with testing materials and sharing the results with other to make it easier for those who come after.

[kidjedi]

Originally Posted by BigAl

In house construction the problem is always humidity inside trying to get out. Any imperfection in the vapour barrier which is installed on the warm(inside) side of the wall allows moisture to migrate towards the outside of the wall. Since it is cold at the outer section of the wall it will condense to water droplets. Therefore it is important that the outer side of the structure is designed to allow water vapour to penetrate the house wrap and get out.
In our trailer the outer skin is hopefully totally waterproof! So where does the condensation go? Seems to me it would run down the inside of the wall and fill up the C channel. Then leak past the hold down bolts and soak into the ply floor.
To minimize this I would think a non porous solid insulation fully adhered to the outer skin would be the ideal solution. Also the inner skin should have vent holes near the floor and in the ceiling so that air could circulate and let the moisture back into the interior of the trailer when temps change.
I'm probably thinking too much!
Al

I actually considered using House Wrap at the outside skin.

I think the logic of the above is sound, but I'm actually letting any moisture that might penetrate the (hopefully sealed) outer skin run down that outside wall and into the C channel, which has weep holes (which were pre-existing; not sure if that's from the factory or a "mod" from a previous owner). Interior moisture is vented via the range hood, fantastic fans (or something similar), and exhaust vents in the toilet and shower; hopefully the interior of the walls are warm enough that it doesn't condensate anyway.

The PIC is "non-porous" (foil faced closed cell), but I'm leaving a 1/2" gap on the outer skin side, and a 1/4" gap on the interior skin side. The 1" PIC is R-7 (real R7, not the BS r-rating of Prodex and other foil-bubble wrap) and the air gaps should ad to that R value. Everything is completely sealed with the Nashua 324a foil tape (kind of expensive, but awesome).

These are the decisions I arrived at by informing myself with the information available (forums, product specs, speaking to owners, speaking to people who restore/build RV's for a living, etc.) and that will allow me to finish as quickly/cheaply as possible without worrying down the road (and in the mountains) about if I made the right decisions.

[Wabbiteer]

kidjedi: remember you're building for 40 or 50 years unless you're willing to be that Joe Somewhen that a future owner will be cussing

Just back of the napkin engineering here..

a '72 AS built in '71.. so 45 years old. Even in a milder climate there may be 90 nights below freezing (Jackson Center, Ohio is about 100) so not including day sun warming thaw cycles that is 4,000 freezing events. Denver has the most freezing nights of any large US City with 157 so that'd be 7,000 freeze cycles. That many heave-shrink events loosen seams and rivets, undercuts caulk and could make alien worlds out of dark hidden places come Bayous or Glades...

Sure a little degraded board is not insufferable immediate pain for the occupants or a structural catastrophe in the making, I'm just saying it's too darn easy to rationalize where Airstreams are concerned, they don't fit easily in the human time frame...

Now... piecing in insulation with a friction fit using barrel stave shapes between ribs with the outside faces blind to the installer and achieving near zero gaps is sure to be a manly endeavor I'd like to read about.

I've no complaint over Iso rigid board going into 70's Airstreams, with the 1-1/2" wall cavity we need all we can shoe horn in there, just don't over-simplify the process. Leaving a continuous air gap has a dark side, smokestack air convection from dissimilar temperature materials perpetually trying to equalize, either super-heated or super-cooled air spreading itself to every possible material exposure or air leak trying to get in/out of the living space. I'm of the thought that Vulkem parging over interior seams and rivets then baffling insulation against the exterior shell in small discrete sections would be superior instead of leaving the airspace, 'compartmentalizing' it all. If we're worried about occult water ingress there is always the over-pressure leak check using soapy water and a blower to periodically check for flaws...

Also: Look at Protecto Super Stick Building Tape vs. the Nashua 324a foil tape, a bunch of years down the line I think you'll appreciate you did even if it is 3x the difficulty handling it, consider adult supervision to call the rescue squad when it goes all Charlie Brown kite string trying to trim it in half or doing long runs, it's really that sticky. The Protecto SS tape is made for exterior siding window/door trim weather sealing and made to last the life of the siding in the worst conditions, has a reflective foil face and will never lift and break bond.

With some practice and a narrow/no kerf blade it'd be way smooth to lay the Iso board like bricks and barrel stave mitre the pieces together following the curves of the shell, some of the minimal expansion window/door canned foam gunned inbetween foam joints with the pistol-grip style applicators to provide caulk to seal the horizontal foam board slats with...

Letsee, your 25' has 14' straight wall so including obstructions that would be about 300 linear feet minimum of mitre cuts, then pieced to go between your 6 ribs and various stiffeners and braces less window openings makes 120ish discrete pieces to handle and install with precision. We'll be beside you all the way!

Okay, fine, sorries. I'm doing just that now with my diesel Promaster RV conversion van I'm building. The Promaster van is as tight as an aquarium compared to the AS though, I don't have 1200 rivets and a couple hundred feet of caulked sheet metal overlap seams. What I am fighting is preventing warm moist air from completely infiltrating the structure EDIT: from the RV being '24/7 occupied' in cold weather- 3M 90 spray adhesive, Loctite PL adhesive and Great Stuff foam all as glue then the foam as o-ring gasket meandering the edges of every piece.

Have a look at this insulation, I nabbed a roll to stuff boxed columns with and to stuff in all the gaps between built-ins and van body & chassis...

http://www.dupont.com/products-and-s...mawrap-r5.html

[kidjedi]

Originally Posted by Wabbiteer

kidjedi: remember you're building for 40 or 50 years unless you're willing to be that Joe Somewhen that a future owner will be cussing

Yep! I'm planning on retiring in this thing (my house becomes my "nest egg" and this thing becomes my home!).

Originally Posted by Wabbiteer

...That many heave-shrink events loosen seams and rivets, undercuts caulk and could make alien worlds out of dark hidden places come Bayous or Glades...

Right. That's why I've gone over every rivet (reriveting when necessary) and TremPro 635'd every seam.

Originally Posted by Wabbiteer

Sure a little degraded board is not insufferable immediate pain for the occupants or a structural catastrophe in the making, I'm just saying it's too darn easy to rationalize where Airstreams are concerned, they don't fit easily in the human time frame...

Right, but it doesn't seem like I'm rationalizing. I hope I have done my due diligence and made the right choices.

Originally Posted by Wabbiteer

Now... piecing in insulation with a friction fit using barrel stave shapes between ribs with the outside faces blind to the installer and achieving near zero gaps is sure to be a manly endeavor I'd like to read about.

Pretty close to what I'm doing. I'll have pics up on my blog when I'm finished. I'm not necessarily at near-zero gaps for the staves, because I'm not miter-edging them, but the minimal gap where the panels "curve" is air-tight with the foil tape on the backside scores. All edges on the front side are completely sealed with the foil tape (no air passes from cabin to exterior skin, except a few tiny cracks around windows).

Originally Posted by Wabbiteer

I've no complaint over Iso rigid board going into 70's Airstreams, with the 1-1/2" wall cavity we need all we can shoe horn in there, just don't over-simplify the process. Leaving a continuous air gap has a dark side, smokestack air convection from dissimilar temperature materials perpetually trying to equalize, either super-heated or super-cooled air spreading itself to every possible material exposure or air leak trying to get in/out of the living space. I'm of the thought that Vulkem parging over interior seams and rivets then baffling insulation against the exterior shell in small discrete sections would be superior instead of leaving the airspace, 'compartmentalizing' it all. If we're worried about occult water ingress there is always the over-pressure leak check using soapy water and a blower to periodically check for flaws...

I've actually been wondering how the "bubble test" will work on this thing, since theoretically the insulation layer is air tight at the interior skin level. There could be leaks in the exterior skin that wouldn't show up because the air from the pressurized cabin would not escape through the walls (they are air tight), but instead would escape through windows, doors and hatches. The seal is further completed at the interior skin rivets since I'm laying rubber or foam over each rib, which will form a sort of a "healing seal" at each rivet --I guess the air can pass through the rivet, though, since it's a mandrel through a shaft and perhaps not air tight.

Regarding the "chimney effect..." I went back and forth on the air space on the outside skin. Brett at Timeless Travel Trailers seems to suggest it's the way to go (having an air gap), though Timeless actually fills the wall with the ISO board completely (no gaps). I think this has more to do with time consumption though (creating and adhering all the 1/2" standoffs takes a lot of time/work).

There's also the phrase "all Airstreams leak." Keeping up with sealing from the outside will most likely keep out enough moisture to not need to worry about it, but leaving the gap allows the inevitable small leaks to drain down the wall and out the weep holes. It seems like most people posting about how they are insulating (if not using spray foam or fiberglass batt) are using foam standoffs, either with rigid panels or Prodex/Reflectix, to keep a layer of air between the exterior skin and the first layer of insulation.

Like I said... I'm still not positive which is better (gap/no gap), but I had to do something at some point or I'd never get to use the thing.

Originally Posted by Wabbiteer

Also: Look at Protecto Super Stick Building Tape vs. the Nashua 324a foil tape, a bunch of years down the line I think you'll appreciate you did even if it is 3x the difficulty handling it, consider adult supervision to call the rescue squad when it goes all Charlie Brown kite string trying to trim it in half or doing long runs, it's really that sticky. The Protecto SS tape is made for exterior siding window/door trim weather sealing and made to last the life of the siding in the worst conditions, has a reflective foil face and will never lift and break bond.

Sounds great, but I'm pretty much done with that part. I actually had three 3"x 60ft. rolls of the Nashua 324a that I picked up for $10 at a thrift store. I can't believe how well it sticks, even to freezing cold metal, and how thick it is. It's a billion times better than the stuff they sell along with Prodex at the big box stores. Probably also a LOT easier to use than the stuff you mention, especially with foil faced foam.

Originally Posted by Wabbiteer

With some practice and a narrow/no kerf blade it'd be way smooth to lay the Iso board like bricks and barrel stave mitre the pieces together following the curves of the shell, some of the minimal expansion window/door canned foam gunned inbetween foam joints with the pistol-grip style applicators to provide caulk to seal the horizontal foam board slats with...

At that point, I see no reason why a person wouldn't just go back to the idea of spray foam. It would be way faster, way cheaper, and way more effective (sealing all cracks and crevices by sticking to everything). Plus spray foam has a higher R value than PIC panels, which come second (followed by extruded polystyrene and fiberglass batt).

I have been scoring the backs of the panels to follow the barrel curve and resealing the panels with the foil tape. This leaves a small void in the PIC where the break is, but it's sealed to airflow with the foil tape. Your suggestion might be more "ideal," but it would take forever, and again, I want to get camping.

Originally Posted by Wabbiteer

Letsee, your 25' has 14' straight wall so including obstructions that would be about 300 linear feet minimum of mitre cuts, then pieced to go between your 6 ribs and various stiffeners and braces less window openings makes 120ish discrete pieces to handle and install with precision. We'll be beside you all the way!

Closer to 140 not including all the 1/2" thick stand off pieces (hundreds). Fitting the shapes to all the compound curves in the end cap was the hardest. Having the 1/2" gap on the backside and the 1/4" gap on the front side makes things a little more forgiving.

Originally Posted by Wabbiteer

Okay, fine, sorries. I'm doing just that now with my diesel Promaster RV conversion van I'm building. The Promaster van is as tight as an aquarium compared to the AS though, I don't have 1200 rivets and a couple hundred feet of caulked sheet metal overlap seams. What I am fighting is preventing warm moist air from completely infiltrating the structure EDIT: from the RV being '24/7 occupied' in cold weather- 3M 90 spray adhesive, Loctite PL adhesive and Great Stuff foam all as glue then the foam as o-ring gasket meandering the edges of every piece.

I think the easier way to achieve this on a gutted Airstream is just the spray foam application everywhere (max R value for the 1.5" wall space and completely sealed at every seem and rivet by the foam).

Originally Posted by Wabbiteer

Have a look at this insulation, I nabbed a roll to stuff boxed columns with and to stuff in all the gaps between built-ins and van body & chassis...

http://www.dupont.com/products-and-s...mawrap-r5.html

Seems good, but if it "breathes" and is installed pressed up against the skin, I think condensation would build up in the voids and wrinkles against the exterior skin (causing mold, etc.). In other words, the plastic bag that holds the insulation would contain the moisture where it's pressed up against the exterior skin and cause problems.

Not only that, but it's actually a lower R value than foam or polyisocyanurate (which is R6 at 1").

I'm also not sure what it costs (I'm assuming expensive) and where I'd get it. If those things weren't a concern, I'd just line the entire Airstream with Aerogel and be done with it.

[Wabbiteer]

More bread crumbs for the thousands of readers yet to visit...

Line it with Aerogel? Vacuum panels can make R-30 or better per inch. Since we're dreaming why not titanium double-wall inserts with a strong vacuum? Heh.

My commercial spray foam applicator friend invited me to apply a thin (1/4-3/8") froth coat of DIY foam on the aluminum shell to protect the metal from the high temperature catalyst reaction of commercial foam, he'd be happy to spray it then to avoid the metal warp and strong heave of hot foam in gaps distorting the shell.

Prepping the inside of the shell metal before foaming it would be an acid wash and passivization treatments, Alodine is a chemical treatment of aluminum to prevent corrosion and would be used as a primer for the spray foam to grip to. The unfoamed resins contact with the metal would bond extremely well and there'd be no worry of it tearing off the aluminum oxide layer of aged untreated aluminum and holding water or loosing structural strength.

Plus spray foam has a higher R value than PIC panels

Still air alone has an insulating value of R-5 per inch of thickness. Once spray foams bubble-making 'blow agents' no longer are perfused throughout the bubble matrix and just air (humid air) replaces it the R-value drops to, or close to, R5 no matter the brand. When they allowed heavy Freon molecules as blow agent foams performed better longer since freon molecules were more easily trapped. With the new environmentally safe blow agents escaping easier the foam performance degrades faster.

Even our Iso foam R-value will drop by 20% within five years or sooner depending on environment. Spray foam makers will advertise an 'aged' R-Value but that is usually six months at 72°F, not SoCa and 200°F sun heating or -20°F in places with real winters; expect the advertised values to dive quicker & deeper then.

Prodex is not sold in big-box stores, don't confuse foil/bubble/foil with foil/foam/foil. Prodex is an honest R-0.7 that happens to be real good at herding heat in the direction physics dictates, hot upward and cold downward, when available space allows the air gaps.

Did someone say too darn easy to rationalize? Tyvek Thermowrap is not 'bagged' and is as nearly inert as any insulation can be. Getting into creative uses, there could be standoffs to keep the housewrap side mostly away from touching the exterior shell, as you mentioned you'd considered. Remember it's not a vapor barrier and sun heating & winter dry air desiccation would go a long way to drying it out if/when flooded. Placed with the weave on the vertical it'd also channel live water downwards quicker...

Just more data for lucky future restorers to ponder.

[vintageracer]

Originally Posted by kidjedi

Nostalgia certainly has it's price. So does caring about the look and design of the trailer. I don't want a marshmallow on wheels (I'd rather have a metal twinky).

Marshmallow or Twinky they are both "Tasty"!!!

[J. Morgan]

I will say that the fiberglass insulation was perfect in my Airstream when I removed it after forty plus years of age, I could have reused it if I had purposed to do so when I took it out.

Which is one of the reasons I went back with fiberglass.

Brevi tempore!

[kidjedi]

Originally Posted by J. Morgan

I will say that the fiberglass insulation was perfect in my Airstream when I removed it after forty plus years of age, I could have reused it if I had purposed to do so when I took it out.

You are literally the only person I've ever heard say that. It's always wet and super compressed (like, pretty much gone), or full of mouse droppings and tunnels. Perhaps there is an Airstream museum that would showcase your insulation as "the one that made it?"

Granted, most of these stories come from neglected Airstreams being restored. I guess if someone took care of their Airstream (keeping it sealed, making sure there was no vermin) the fiberglass should last a long, long time.

[Lance M]

Originally Posted by J. Morgan

I used fiberglass insulation, and did not seal any rivets, no vapor barrier, etc. I did calk the top third of all window frames and other openings.... But that is about it.

Sometimes we have a way of making simple things hard.


Brevi tempore!

My simple insulation solution is to throw more BTUs at it in the cold and find shade in the summer.

[J. Morgan]

My trailer was very used, but no mice got in the walls. My insulation was in perfect condition.


Brevi tempore!

[J. Morgan]

There was a time in my build process where I wanted to spray foam, but the do it yourself kits were a lot of money for a little coverage, and none of the contractors I called were interested in calling me back, so I said to myself "well the first insulation lasted over forty years, and I am almost fifty..."

I did money math, age math, and build time math.... I went fiberglass... And in the end without regret. My trailer makes me happy in its thermal efficiency, and also in its sound insulation.

In the end I am certain that using glass made my build a lot easier, and for sure, if I ever need to go back in to do any work in the walls, I will be glad for the glass.


Brevi tempore!

[Lance M]

These pictures show spray foam application in an Airstream. I wonder how it is holding up these days.
https://picasaweb.google.com/1154197...490174/FarmLab

[Aage]

Originally Posted by Top

These pictures show spray foam application in an Airstream. I wonder how it is holding up these days.
https://picasaweb.google.com/1154197...490174/FarmLab

Good lord, what an incredible amount of work! Excellent detail, just excellent.

My question would be what has happened to the TT's weight? Anyone know what this added?

[cameront120]

I think spray foam is less dense than fibreglass. However if open cell foam is used, it'll retain moisture and add weight and reduce R-value. Fibreglass would have the same problem. Mineral wool is hydrophobic and won't retain moisture.

[kidjedi]

Originally Posted by Aage

Good lord, what an incredible amount of work! Excellent detail, just excellent.

My question would be what has happened to the TT's weight? Anyone know what this added?

Yeah... that's some crazy work! Nice.

The spray foam shouldn't add weight (should be same or less than fiberglass). You do need to use closed cell, and a lot of the pro-sprayers use heat that can warp your skins and ribs, so you need to pay special attention to the application process.

[micaso]

Originally Posted by kidjedi

There's also nothing wrong with testing materials and sharing the results with other to make it easier for those who come after.

I'm about a month behind you, using some of the same materials, so I greatly appreciate your posts. I decided to go with reflectix and 0.5" PIC with an air gap between. I'm fairly doubtful of the real R value of the bubbles (but I trust the PIC), but theVAP seemed at least somewhat positive towards the reflectix. The R value of the PIC is 3.2, so that's solid. With the bubbles and air gap I think I'll be in a system R 7-8. So far, with only the reflectix on 2/3 of the interior, if I turn my propane heater on it gets so hot I have to work in a t shirt. And it's around 10 degrees outside. I put some pics of the surface temps inside and out on my blog (AirStream Padawan - Blog). I can't wait to see how the PIC adds to it... I'll probably need to switch to my little electric heater.

I guess I liked the idea of two different materials (and both available locally). Plus the gap between is handy for electrical runs. Oh, and the glass insulation in mine was nasty when it came out and I'd never put it back in. Mice, bees, mold, gross.