Does spray foam cause rust?

[karrlot]

I'm a bit confused. My plan is to pull down the ceiling panels, remove insulation, remove any rust, and put new insulation in. I don't know what kind of insulation yet, but I was planning on "filling gaps" with spray foam.

I came across this post where it appears the spray foam caused the rust. Is spray foam a bad idea? Are there certain types that are okay to use and some that are not?



http://www.skoolie.net/forums/f9/is-...bus-12263.html

[Tippyman]

The guy in that thread never confirmed what type of foam it was.

From my research, closed cell spray foam is actually water proof, dries hard, and to a certain degree becomes structurally beneficial.

Open cell spray foam is more like a sponge. It is porous, absorbs water, and is squishy. Open cell is cheaper, but not good for a bus. I bet that was open cell foam on that bus.

So assuming we disregard open cell foam altogether and focus on closed cell, that does bring up a good topic of discussion: are there certain brands/types of closed cell spray foam to avoid? Most of these foams are probably meant for wooden residential applications and might have a bad reaction to metal?

[nat_ster]

Everything Tippyman said is true.

Then their are one part spray foams like great stuff. The chemicals they are made from are corrosive to metal if not cured perfectly.

Great stuff should not be used in a bus. If I was at the beginning of my build, I would not have sprayed the stuff into everyone of my support ribs.

Two part closed cell spray foam sprayed at the proper temp with full bond to the bus metal should never cause a issue.

Nat

[2kool4skool]

I did my research on this long ago and this is a clip of some advice from a pro.

NOT my words, or my opinion but those of an expert. YMMV.

"Combining foam and metal roofing
The challenge comes when you combine systems, spraying foam onto the metal roofing itself. Metal roofing manufacturers typically extend a 25-year warranty. The concern of manufacturer MBCI is over who is going to verify that the foam will not cause corrosive damage over time to the roofing.
Most foam companies are not willing to provide written guarantees that their product will not cause problems and that they will stand behind any damage that may happen.
Most roofing companies will void or waive their warranty under these circumstances."

[karrlot]

So people have used closed cell foam on buses with no problems causing rust.

What does the "one or two part" refer to? Like its made of two things and as you spray it, it mixes together?

Where do you get spray foam? Are there some made for metal?

I am curious to find out about

[nat_ster]

Yes, one part is a single chemical that needs air to cure.

Two part uses two chemicals and needs no air to cure.

Commercial roofs are sprayed with a closed cell 6 pound two part foam everyday with no long term issues. The video's are all over the net.

https://www.youtube.com/watch?v=TauEOJZaaf4

Nat

[Tippyman]

Just read this on the FAQ page for a company local to me:

FAQs - Spray Foam | Insulation Products | Polyurethane Foam

Is spray Polyurethane foam insulation corrosive to metals?

No, spray Polyurethane foam insulation is non-corrosive.

[m00py]

Originally Posted by 2kool4skool

I did my research on this long ago and this is a clip of some advice from a pro.

NOT my words, or my opinion but those of an expert. YMMV.

"Combining foam and metal roofing
The challenge comes when you combine systems, spraying foam onto the metal roofing itself. Metal roofing manufacturers typically extend a 25-year warranty. The concern of manufacturer MBCI is over who is going to verify that the foam will not cause corrosive damage over time to the roofing.
Most foam companies are not willing to provide written guarantees that their product will not cause problems and that they will stand behind any damage that may happen.
Most roofing companies will void or waive their warranty under these circumstances."

25 years huh? Think it's worth trying to contact the company who insulated my bus and try to get the roof replaced? I bought it from a church who bought it from another person/group who bought it from Champion. I guess I should probably call Champion and see what the deal with that is yeah?

[Jolly Roger]

You can buy poly boards that are cured. A little bit of carving (on the inside of the board ) to make the curve and pushed up tight are cheaper but they are cheaper because you have to form them. Cheaper, a little effort and you get a better product and with a commercial supplier if you tell them the curve then you pay a little more but your pieces fit where you want them. I build commercial tanks for a living. I use poly on everything from chilled water 25-30* to steam 150-200*? The only thing that changes is the thickness. 1-1/2" takes care of most chilled and up to 100* steam and then we change to 2" thick. Go to KNAUF insulation website and research polyiso insulation or BOATWRIGHT.
They are made to order!
If I had to figure my bus roof for this? I would figure a 7' diameter tank at 9' tall. Because I am not wrapping a tank I am only doing the roof so the extra 3/4 should be enough. Sorry I am not a math nerd but I do know how to keep up with my insulation subs and question there quotes?
Sorry didn't mean to put y'all in my world but there are options to the spray foam world? This has started happening in commercial construction in the last 5-years and it is a good green building thing but they are not using it on metal and the off gassing has yet to be determined? The option I suggested is probably cheaper and doable by the owner.
I have demoed steel tanks and steam piping in underground flooded tunnels that were 50-60 years old with the polyiso insulation and the paint was still on the steel. It was a little rusty but the inside of the equipment was past its life and the insulation had not effected the steel?

[nat_ster]

Putting rigid formed foam panels inside your roof will still allow condensation to form on the inside of the outer metal skin.

Properly sprayed foam, onto a clean properly prepped surface will not allow any condensation to form.

It's all about moving, or transferring the due point.

I want the due point on the inside living space surface (finished walls and ceiling), not inside my walls / ceiling.

No cavity or spaces is best.

Nat

[thecrabshomestead]

We purchased the Foam It Green Kit from their website *came with 17 free things, goggles, gloves, booties, Tyvek suit, lots of nozzles and fan tips*
The kit we ordered was for 1200 sqft and was $1500. Included four boxes (2 part A's & 2 part B's) the hose and mixing nozzle..and the above listed. If I didn't have three trash bags of overspray, that would have been enough for the ceiling, walls, and floor. Unfortunately, we were messy so we had to order a 200sqft kit (one small part a tank and one small part b tank)which was $400. So our whole project cost $1900 plus the $20 respirators we bought.

You can apply it between 65 & 78 degrees.there is a temperature strip on the tanks that let's you know if it's good or not. It wasn't super messy to clean up honestly. I'm living with a roommate friend and we are building in his yard, so I'm trying get to keep everything as clean as possible. The small crumbles just find a spot on the floor and will only pack more insulation under there. The medium ones almost the same thing. It did take up three large trash bags, but we're super light! Lol

It is closed cell foam and they sell thermal barrier paint for metal buildings. It cures in 30 seconds to 2 minutes. At least the door and Windows were open when we worked in it afterwards. Had respirators and all while foaming and didn't go in again for a few days. Seems good! Foam it green has lots of videos of how to do it (you have to watch these before you do it per instructions) it was super easy too. The tanks attack to a dual hose with two different color foam ingredients. They go into a mixing nozzle and is combined while you spray. One hose/tank is white the other blue. It comes out green.

They do a good job of showing how to do ceilings and walls. One inch is r value 27 I believe....their website has lots of info.
https://www.sprayfoamkit.com/spra.../spray-foam-stories.html

If you stop for more than 30 seconds you change the nozzle (they give you like 10) and add petroleum jelly to the nozzle (supplied) and trigger so it doesn't crystallize. I only stopped two or 3 times but we were prepped well.

[OMGIBoughtABus]

Originally Posted by thecrabshomestead

We purchased the Foam It Green Kit from their website *came with 17 free things, goggles, gloves, booties, Tyvek suit, lots of nozzles and fan tips*
The kit we ordered was for 1200 sqft and was $1500. Included four boxes (2 part A's & 2 part B's) the hose and mixing nozzle..and the above listed. If I didn't have three trash bags of overspray, that would have been enough for the ceiling, walls, and floor. Unfortunately, we were messy so we had to order a 200sqft kit (one small part a tank and one small part b tank)which was $400. So our whole project cost $1900 plus the $20 respirators we bought.

You can apply it between 65 & 78 degrees.there is a temperature strip on the tanks that let's you know if it's good or not. It wasn't super messy to clean up honestly. I'm living with a roommate friend and we are building in his yard, so I'm trying get to keep everything as clean as possible. The small crumbles just find a spot on the floor and will only pack more insulation under there. The medium ones almost the same thing. It did take up three large trash bags, but we're super light! Lol

It is closed cell foam and they sell thermal barrier paint for metal buildings. It cures in 30 seconds to 2 minutes. At least the door and Windows were open when we worked in it afterwards. Had respirators and all while foaming and didn't go in again for a few days. Seems good! Foam it green has lots of videos of how to do it (you have to watch these before you do it per instructions) it was super easy too. The tanks attack to a dual hose with two different color foam ingredients. They go into a mixing nozzle and is combined while you spray. One hose/tank is white the other blue. It comes out green.

They do a good job of showing how to do ceilings and walls. One inch is r value 27 I believe....their website has lots of info.
https://www.sprayfoamkit.com/spra.../spray-foam-stories.html

If you stop for more than 30 seconds you change the nozzle (they give you like 10) and add petroleum jelly to the nozzle (supplied) and trigger so it doesn't crystallize. I only stopped two or 3 times but we were prepped well.

for the info. How thick did you spray? 1200 board feet seems like a lot of spray.

[thecrabshomestead]

We filled all of the space in the wall cavities and between all the ribs...i guess the ceiling was about an inch or more think, the floor was about 1/2", and the walls were about an inch as well. We had a lot of overspray..so the 1200 sqft wouldve been just enough. they had an 800 sqft kit...so it just made sense to go big or go home bc we usually screw up on stuff..lol. Also the cavities above the driver and above the backdoor is pretty deep too..so a lot went to that area as well.
If you have facebook, here is the link to our skoolie page where yo ucansee pics and all..I just havent put the pics on my computer to upload onhere yet. Also have a blog but i havent written about that yet..
www.facebook.com/chittybangskoolie

[BlueBirdman]

I'd like to echo what Nat and others said.

Two part (heat/high pressure applied) closed cell (CC) foam is the be all/end all of skoolie insulation. Likewise for most any other structure you'd ever want to insulate.

In most of the continental US, two inches of CC foam will give you a complete vapor barrier as well as a total air barrier. (In Alaska or the colder parts of Canuckistan you'd need almost 3" to move dew point to the outside of the body...)

You end up with an aged value of about R6 per inch of foam, so a nominal two inches inside your skoolie means it's better insulated than most homes. (An Oak Ridge National Labs study found that R19 fiberglass batts installed typically yielded < R13 walls, and on top of that the fiberglass allows air infiltration!)

CC foam is not corrosive - to the contrary, the waterproofing aspect prevents rust. Nor is it food for mold, and more and more people with severe allergies/respiratory problems are insulating homes with CC foam to minimize their problems. Once it has cured, there are no issues with off-gassing (if it's properly proportioned and applied foam) and it will be 99+ percent cured in the first hour.

The structural benefits are staggering - both tensile and compressive strength exceed 30 psi. Any resonance in the bus body will be practically eliminated, and concerns about a roof raise weakening the structure are minimized as well. CC foam is fairly good at damping low frequency noises as well, so driving down the road will also be more pleasant.

I'm presently building an off-grid, rough terrain camper. It started life as an 8x14 aluminum box on a one ton truck chassis. I just put 4.5" of CC foam in the roof of the beast, and 3" in the walls and floor. The floor is insulated on the underside in order to keep headroom at 6' 5", and I will put a layer of two-part bedliner material between that underside foam and the road when the build is finished.

This is better insulation than you'll find in any commercially built RV, including the 7 figure Prevost coaches. (The Earth Roamer folks only use 1" foam board. Pathetic!) Regardless of how cold it gets wherever I might go, I'll be able to heat it to short sleeve comfort with a thermostat controlled Webasto Airtop diesel heater, generally running on the lowest setting! I have no plans to carry a generator, but I could summer in Phoenix and air condition it with a small room air unit and a Honda 1000 generator if I wanted to.

In a skoolie, I'd put even more foam in the lid - probably 6 inches. Of course, I'd raise the roof so there'd be plenty of room for insulation. Most likely, I'd drop the ceiling a few inches below the insulation to keep wiring and other systems accessible. I'd certainly insulate a skoolie floor from the underside as well, and would probably put at least 4 inches down there. (Warm floors are soooo nice!)

There is NOTHING else you can do to any structure that will contribute so much to energy efficiency, strength and comfort. No matter how tight my budget, I'd find a way to put at least two inches of foam in anything I built.

[charles_m]

I did 3" in mine all the way around. It's remarkable and definitely the best thing for liveability you can do to a bus