Tubby the 76 GMC Motorhome prepping for foam board insulation
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- เผยแพร่เมื่อ 4 เม.ย. 2020
- Removing the Spray foam IMSU Latino trying to get ready to insulate the inside of the 76 GMC motorhome. First I have to remove the insulation and clean up the huge mess.
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I am doing what most would consider to be a full restore and there is no way I'm doing that! My plan is to cover the old stuff with something about a half inch thick to fill "void". From what I understand that old insulation is pretty good stuff. Good on ya for that adventure but nah ugh for me! Love watching the vids bud. Keep going. You're helping people!
I would say spray it if that’s how you want to go. After trying to remove the froth Pak foam, It really did adhere very well. i just think my application of it stunk lol. I would just cover the spray foam with plastic between the foam and the finish wall to control any kind of squeaking and rubbing.
Interesting to see the difference in the foam application coach to coach. Yours looked pretty evenly applied if a little thin, mine is as thick as it could go in most places, non existent in others and really sloppy. I hadn't planned on removing it but seeing your outcome, I may rethink that. Thanks for the inspiration.
I have three concerns. I have no way of knowing if I'm correct, but here's my logic.
1. The average R-factor for foam insulation boards is about R-4 per inch. Laminate two sheets, for an example total of 2" thick, and you're at R-8. However, you will still spend a lot of money buying 4' x 8' sheets of foam, take a LOT of time molding, gluing, and cutting the sheets to fit all the irregular spaces in the walls and roof panels. With all the ridges and wiring to work around you might have gaps where you couldn't get a piece of foam board to completely fill, which adds up to be major energy loss points. Closed-cell spray foam has an R-factor of ~R-7. The same example total of 2" thick gives you an R-value of R-14. The present generation of spray foam will outperform the old stuff you just removed, and it will very effectively fill in all gaps/voids and all around any wire harnesses. Spray foam acts as a very good vapor barrier. Any overlooked gaps in the foam board installation will not only lose energy, but they will also promote condensation build-up from the hot/warm air of the roof panel and the cool air of the cabin. This could result in the coach taking on a musky smell (stronger than what might be there already after 44 years).
2. What adhesive are you going to use to secure the foam panels to the aluminum and SMC? Will the adhesive stand up to the heat/cool cycles of the metal? Will the foam board stand up to these same expansion/contraction cycles? Or, will the expansion/contraction cycles cause the adhesive to rip away from the more fragile foam? How will all this work in a structure that is expanding/contracting from the heat/cold cycles and at greater rates than the "building" the foam was designed for? All while in a vehicle that is constantly twisting while driving down the road.
3. Spray foam in metal buildings really "tightens" up the structure, and significantly reduces metal "drum" noises from all the metal panels. Our GMC isn't really any different. The polystyrene foam boards will not be able to return this benefit. The coach WILL BE louder than before.
Sometimes the Engineers got it right...and earned their degrees. You've already done a wonderful job of removing all the old spray foam. You've done the hard work. My recommendation would be to save your money from being spent at Lowe's, and instead drive your coach to a professional spray foam installer. Pay him $800 (+/- $200), and drive away with a better product, better end-result, and with a lot less time invested. Just like the Engineers intended.
Shane Brown here is my reasoning for the foam board and what you state is correct. Being the panels are not a single rigid structure like a full spray foam job it would allow the coach to twist like it wants to. I was afraid the rigidity of the spray foam not wanting to give would cause it to break down and fail ( I believe that’s why the factory seemed to purposely skimp on the spray foam) The foam board would be adhered with a styrene glue and a more flexible open cell foam would be used around the edges of the rigid foam board sealing it tight but giving it a slight amount of movement. the wiring in my case isn’t a big issue. The only wires to be run in the wall are the rear signal wires and the tank senders. All the rest of the wiring is going to be accessible from inside the coach via panels for easy access. ( at least that’s the plan) the wells between the shell skeleton are only 1 1/4” deep so I’m going to be running 2 layers of 1/2” rigid and 1/4” of a sound deadening material. Not sure what one yet. Then covered with a 3rd 1/2” layer to cover the aluminum frame and then the finish wall with decoupled thermally isolated mounts protruding through to mount shelving and such. The R value isn’t the best but it will be far above the factory level. Like most works in progress it’s fluid ideas. And subject to change. Thanks for the input it’s always welcome.
lol. better you than me.. lookin good..
Thanks capt.
I KNOW those shoulders were on 🔥 after that ceiling. Great job brother.
Advil and coffee saved me.
That's a big project and well done for doing! Thumbs up from Dublin ! :) ☘
Drone Girl thanks for watching. Be well.
It seems very silly to remove all that insulation that also acts as sound deadening. My plan is to add a one inch plywood strips across the frame and then add more spray foam (filling the cavity as full as possible).
Spray foam removes the posibuility of condensation in your ceiling walls and floor as it seals all surfaces (frame, walls, ceiling, floor).
The removal was more of an issue of mold due to some extreme sensitivities with my wife and that the original foam from what I’ve been told is flammable. Just killing 2 birds. The panels I put up have greatly quieted the walls and I’m less afraid of the foam breaking down with the twisting of the body. Would love to see how the spray foam works out. Thanks for sharing.
I am also removing my sprayed on foam. I used a multi oscillating tool with a scraper blade. I will have to follow up with a wire wheel like you did to get down as far as you did. I had heard that the existing foam was decent but it was so poorly applied that I question the benefits. In addition, the spray foam does not offer much in sound insulation and it makes hard to chase wires. Keep up the good work.
Doug LaVerdiere the application was poor for sure. Insulating for sound is a whole other animal requiring materials with varying densities to block out different frequencies. I’m not sure how far you can go with that with the limited space without adding a ton of extra weight. Would love to hear your plans though.
Get Out Gadabout - I want to share with you what I am doing with my plumbing that you may want to try. Look on Amazon for the Hepvo Sanitary Waste valve. This eliminates the sewer vents from the drains. You still need to vent the waste tank but using this valve can and will make your plumbing simpler. I have eliminated 2 of the drain vents and got ride of the shower drain P-trap that was cut into the floor for the shower. Just sharing....
Neat idea. I’m curious how is the valve held closed. I am assuming they can’t be using too much pressure to keep it closed is there any chances of it opening and closing when you hit bumps on the road? Would like to see how you used it for the shower. I’m guessing you installed it horizontal. Thanks for sharing.
Get Out Gadabout - I am not the first to use these in a GMC or in a motorhome. Justin used it on his www.thegmcrv.com/project/the-bathroom-saga. In addition, this is also used by many in the VanLife community.
Another great episode and lovin the foam angels lol.
Great job as usual brother
Firebird thanks, need to give a heads up for when you go live. If it’s going to be karaoke, I need to tuneup my singing voice lol.
@@getoutgadabout3423 will do just built a green screen and getting sound check tomorrow. Will stay in touch
After reading everyone’s comments and ideas. And thinking it through. We’ve arrived at the conclusion that there’s no simple solution, and either way it’s going to suck. So, we’ve decided to remove all the old foam, apply new spray foam, then use a screed and a sander with heavy grit to bring the new foam down to level. Our concerns, like the rest of you, is for squeaking, condensation, de-lamination, and for achieving the most effective insulation and sound deadening qualities possible. We’ve accomplished a lot of sucky tasks over the years, with a whole lot less return on the investment, this approach will have a satisfying return.
great video! seeing it down to the bones makes me wonder if one could do radiant heating/cooling. also wondered if a poly coat would worth it on the inside. if ever i'm in this stage of build, it will be great to have this foreknowledge, Thank You.
I could see that but seems like a lot of extra weight. I would also worry about loss through the skin being you only have 1 1/2” of insulation but anything is doable. Good luck. Would love to see the outcome.
My opinion would be to have another layer sprayed over it to top it off.
And maybe you could trim the high spots with a nickel chromium hot wire on a bow.
all possibilities are open, still doing research. came across a product claiming to be R13 at only 1/8" thickness I'm kinda calling bulls*#t but will look into it further. I have all the parts to build a hotwire cutter just haven't assembled it yet
Yes, that is the best idea... I will add 1" strips across the framework and then spray the cavity full... I lose one inch on the ceiling and walls, but my rv is quiet, and is warm in winter and cool in summer.
I must have missed something. Why are you removing the original foam insulation?
Squeaking and rubbing is our concern. What do you guys think about non-rigid insulation? Maybe fiberglass, mineral wool, or some other type of synthetic blankets?
Salus Solutions There’s lots of choices, I would just make sure it’s hydrophobic and mold resistant. You also want to make sure it won’t settle overtime leaving big gaps at the top. Mold is my biggest fear.
The major reasons for the use of spray foam are: no condensation forming within the insulated cavity, no squeaking, sound deadening, and very high insulation values... Anything else and you will have condensation in your walls and other issues as well.
SpicyPete In Thailand how does the spray foam stop condensation? If the walls are properly insulated you will still have condensation on your windows and stuff. The condensation is caused by gas appliances and you breathing. My entire aluminum structure will be covered with insulation. Still might get condensation on the windows but spray foam won’t stop that either. Ventilation and air-conditioning are the only ways to control humidity. I happen to do that for a living.
@@getoutgadabout3423 sorry... I was specifically talking about condensation within the wall. I am far far more concerned with condensation that forms in walls as it can very often lead to mold and is extreemly difficult to remove. Condensation on windows is minor in comparison.
Another issue is squeeks from non sprayed foam.
Ahh I see what you meant now. 👍
I hate masks and the more expensive respirators that is used for painting and sanding fiberglass.....but I believe I would have used one of those respirator type for this...other than that, your wire wheel removal was most effective...great work!
I was thinking of just adding new closed cell foam to my remodel, in order to complete the lack of original foam, why do you remove all the existing one? what is your reasoning on that?
I wanted to start off with a clean flat surface. From what I’ve read the original foam is flammable as well. I was afraid being closed cell spray foam being rigid when applied may cause problems with how flexible our coaches are. Unlike modern cargo vans that are very rigid The body’s on the Gmc’s twist and the frame flex. If you try to force the body to be rigid with foam I felt it would cause the foam to fail or worse stress the aluminum seams and joints causing an even worse failure. So I chose the foam board with flexible open cell joints around it to allow the flex. This is all speculation. But that is my thought process. I guess time will tell. Thanks.
@@getoutgadabout3423 Thanks for your reply, your thoughts make perfect sense, I might still add closed cell foam, this is against moisture, I do believe it will still flex unought, however, I did not know the old foam was flammable, so I will do a little research on that..., What about your ladder and rack system, are you selling those?
Why get rid of the old foam?
I removed the old foam for flammability reasons, and the fact I wanted to use Rigid foam board instead of spray foam so the coach could still twist naturally without the foam trying to make the structure more rigid with the old film gone I’m able to adhere the foam board directly to the outer walls and making everything even without fighting with the old form underneath it.