Using foil covered styrofoam on the roof exterior

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I used this to insulate the roof of my slideout and it has made a huge difference.

https://www.lowes.com/pd/Insulfoam-Common-0-5-in-x-4-ft-x-8-ft-Actual-0-5-in-x-4-ft-x-8-ft-R1-9-Faced-Polystyrene-Garage-Door-Foam-Board-Insulation/3033278

So i am considereing using it on my RV roof (foil side up), it would take about 6 sheets to cover the whole roof.  I would cut around the vents and stuff and tape the sheets together, then get 50ft or rope or twine and secure it from the rear bumper over the roof to the front hitch connection.  One tiedown on each side should hold it in place im thinking. Plus adding a brick on each corner would help as well.  The trick would be to just keep the wind from getting under it. 

The Good:

1. It would keep my RV cooler and pay for itself by saving electric cost.
2. It is inexpensive.
3. Its easy to install.
4. It should not impede the flow of water off the roof so no pools will exist.

The Bad:
1. It might break down over time and then i would have that styrofoam stuff all over the place.  I dont know if this stuff will break down with exterior use or not.
2. It would give bugs especially spiders a place to reside under it.
3. In the winter time it would stop needed heat from the sun on the roof.
4. I may have to remove it in the winter and put it up on the summer.
5. It might attract lightning.

Thoughts anyone? 
 

Rene T

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Farmington NH
Another BAD is if the wind should get under it, what's going to happen to the bricks. I wouldn't want to be walking by your rig. Just a thought Dave.
 
G

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Guest
I can always secure the bricks to it.  But i doubt it will come off anyway due to the tiedowns.  The only way would be in a tornado and if that happens everyone is screwed anyway lol    I have had bricks on top of my slide out for a year now and nothing has moved and we have had some very bad winds and storms over the last year.    I have to do something, i cant take it being 90-100 degrees inside the RV and its too expensive to add another AC unit, even a window model is too expensive.

If there was something i could paint the roof with to work the same im all ears.  But anything i put on the roof has to be both self leveling and also safe for the rubber roof and i have found nothing that would do what the styrofoam foil will do.

I could always put a dab of silicone on each corner of the sheet to stick it to the roof and it would just peel up when i remove it.

 

darsben

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May 30, 2018
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Central NY in summer beautiful Casa Grande AZ in w
From experience that foil stuff lasted me less than a year when I used it outside. Foil came unbonded. Probably the glue was not meant to be exposed to the elements.

If you are in an RV park how will they feel about what could possibly be considered an eyesore
 
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Guest

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darsben said:
From experience that foil stuff lasted me less than a year when I used it outside. Foil came unbonded. Probably the glue was not meant to be exposed to the elements.

If you are in an RV park how will they feel about what could possibly be considered an eyesore

Thanks for the info, i will most likely wait until spring to put it on, that will give me time to see how the stuff on my slideout holds up.  If i have to replace it every year, that is still an affordable way to keep it cooler, we are only talking about 50 bucks a year and i can save that in electric im sure, plus the extra comfort is worth it.

I dont think the eyesore deal is an issue, first it would only be seen from the air and from a distance it would just look like a chrome roof.    Also before anyone complains about me there are many other trailers here that are just simply trash and the owner dont care.  I keep my place clean and looking really nice, everyone gives me compliments about it.  But many others here just park trash units here and dont take care of anything.  And the owner here runs this place like a slum lord.  This place could be the talk of the town and soooo popular if he gave a hoot about it, but he dont.    So i dont see a foil roof as an issue. 
 

blw2

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Aug 9, 2012
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Saint Johns, FL
I vaguely remember a video I skimmed through some time ago that might relate, so I went searching for it.  I don't remember any details about it though... except a vaguely think it was a failure.

first
https://youtu.be/zkIvvH1Lkr8

then a follow-up:
https://youtu.be/_xgwWR44w6E
 
G

Guest

Guest
Thanks blw2,

I used to watch her videos alot in the early days, she had some really good info and was motivated by helping people.  But after she got popular the fame got to her head and it was all about the youtube money and gifts from viewers so i just stopped watching her vids.  She has since sold that Class A RV and now has a 5ver and truck.

Anyway i never saw that video before not sure how i missed it, that was a good share thanks again.  Mine will be the firm sheets with styro on it also so it might hold up better, or it might be a huge mess.  All i can do is try and see what happens, it seems its all about securing it properly and keeping the wind from getting under it, if i can do that it should work pertty well.

FYI just a tidbit interesting info here -  everyone calls it velcro but velcro is the brand name of the product.  Its actually called hook and loop and awhile back velcro had some big stink about people calling it all velcro when its not their brand.  :)
 

butchiiii

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Sep 8, 2014
Posts
347
Location
Los Angeles
Anything that increases the r value of your insulation will help keep your interior cooler. I see that the
stuff you are talking about comes in several different thicknesses so you have a choice. Only problems
I would worry about are keeping it secure and the durability. During the winter it should help keep in the
heat from your heater.
 

catblaster

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Jan 11, 2010
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Location
Kissimmee, Floriduh
before you go to all he trouble of installing it I suggest you get a piece and leave it out in the weather. There is one brand (I dont remember which one) that will barely last long enough outside to get it installed while others may even last out the year.  While I know this is not what you are doing, I installed R-Max o the underside of our house trusses when I built it and it knocked the temperature of the attic 15 degrees,people told me the foil would reflect back and cook the shingles but they lased 20 years when Hurricane Charley removed them for me.
 
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Guest

Guest
Thanks All

Yes i have one sheet on my slideout right now, so come spring ill see what it looks like.  The piece is sitting on small pieces of wood for ventilation and has a few bricks on top, 3 at each end, and two in the middle.  Since the sides are protected by the trailer on one side and the slideout flange on the other, this should keep the wind from taking it away.  My intent is to keep the direct sun off the slideout so the ventilation is just fine.  The main roof will be different since the water flows better off the roof (should not be a mold issue) so ill put it directly on the roof and cut out places where i need to.

Anyone know the proper way to cut this stuff, for the slideout piece i used a utility knife.  The foil side cut perfectly but any time i touched the strofoam side it crumbled under the knife.  I have seen some people cut styro with some kind of hot knife gizmo.

Also i know in movie set builds they use something on the styro to seal it before painting it so it does not crumble, ill have to google to see what i can find.
 

signcut

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Jun 12, 2018
Posts
128
This is just a wild guess, but would it help to simply have a tarp of some sort a few inches over the roof to deflect some direct sunlight, and the air beneath to prevent contact heat transfer? I don't know it that would work, but it seems that might be easier to do than to figure out how to attach and detach the Styrofoam...
 
G

Guest

Guest
signcut said:
This is just a wild guess, but would it help to simply have a tarp of some sort a few inches over the roof to deflect some direct sunlight, and the air beneath to prevent contact heat transfer? I don't know it that would work, but it seems that might be easier to do than to figure out how to attach and detach the Styrofoam...

I tested that on my slideout.  Before i got the foilstyro i had my slideout covered with a tarp folded several times to make it really thick to provide some sun block.  Although it did reduce the temperature inside, that reduction was only about 4-5 degrees.  Once i put the foilstyro on the slideout the temperature went down 10+ degrees and was pretty much the same temp as the rest of the rv now instead of being so hot all by itself. 

So a tarp would be easier but unless i can find a tarp that has some kind of insulating factor and some foil on it, it wont do as good as foilstryo.
 
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