[rc12102]

With a lot of the interior apart already (plus the lack of a headliner to begin with), I'm working on insulating as much of the RC as possible.  Looking at the roof, I'm not sure that using the normal dynamat-type insulation is going to work or if it will effect the fit of the headliner.  Plus, there is a decent size space between the actual roof and the drop-down piece where the headliner attaches. 

I was thinking about using some foam insulation (Great Stuff) and spraying it between the roof and where the headliner goes.  Being in Arizona, my main goal is to keep the heat out and the roof is going to be one of the main culprits with the sun beating down on it. 

Any reason this wouldn't be a good idea or what have others used to properly insulate the roof? It seems like the foam insulation would be the best way of covering 99% of the roof with some type of insulation.

 

[u2slow]

My spray foam dealings around the house would shy me away from that. Seems to get messy and overexpand no matter what you do.

I haven't tried anything like this yet, but this is the direction I'd be looking:
https://www.amazon.ca/uxcell®-10-76sqft-Deadener-Dampening-Insulation/dp/B01I4F0D5E/ref=asc_df_B01I4F0D5E/?tag=googleshopc0c-20&linkCode=df0&hvadid=293011345087&hvpos=1o3&hvnetw=g&hvrand=12172746529374320001&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9001591&hvtargid=pla-492923086517&psc=1

 

[rc12102]

I've already got some Noico 80 mil sound deadening material that I'm using pretty much everywhere else like inside the doors, fenders, and potentially the floor.  But my concern is twofold with using it on the roof. 

The first is really how well it can insulate the interior when it is not actually on the innerside of the exterior roof but on a drop down piece with a few inch gap from the actual roof metal.  It also has quite a few holes which I would assume are to ventilate the actual metal roof and if I don't cover those holes, then it doesn't seem like it will really be effective.

The second would be ensuring that it doesn't effect the fit of the headliner, although it is only 80 mil thick so I don't think this should be an issue.

The only way to attach any sort of insulation to the exterior roof would be some sort of spray foam or liquid. But I certainly agree about the messiness and potential for overexpansion, although the holes in the drop down part of the roof should allow the excess to drip out and not cause any structural issues.

 

[dodge82273]

just 1 big reason you haven't fingered out how to disregard yet ,the air space between the 2 "roofs" is the same as the space between your homes insulation and the underside of the roof . If you do not allow air circulation there , condensation forms and everything gets wet , and stays that way . same as a cold glass in the summer .... sweats.

 

[u2slow]

Is the headliner a vapour barrier? or does it breathe? I haven't studied one closely.

Spray foam on metal prevents it from condensating. Bonding a foam mat or board thoroughly (if that's possible) should have the same effect.

IMO, the thin mastic/tar mat product doesn't have the R-value of a thicker foam product.

 

[gremlinmt]

Great stuff is a water cured foam.  Make sure you paint that roof and let it cure fully before you apply.  I'd say it's a bad idea.  The ABS backed headliner from LMC could be a good choice, consider applying a silver metal tape to the back side of it to headline if you are looking for a little radiant protection.  Just don't go completely edge to edge to prevent condensation.

 

[dodge82273]

I was under the impression the foam was to be sprayed between the roof and the metal headliner , an '85 has a 2 layer metal roof / ceiling , then below the ceiling there MAY be a headliner ... a foam backed deal that dries out and fails .

 

[rc12102]

I was under the impression the foam was to be sprayed between the roof and the metal headliner , an '85 has a 2 layer metal roof / ceiling , then below the ceiling there MAY be a headliner ... a foam backed deal that dries out and fails .

Yes this. There's the roof, then a dropdown "ceiling" that has a few holes in it and then the headliner that I will be eventually installing.

The problem is there is not even minimal insulation/sound deadening on the roof like the doors have from the factory and there is really no access to apply an insulation direct to the roof.

If I apply a radiant barrier to the ceiling or the back of the headliner, I'd still have to leave some holes to vent the roof, so all the hot air would still get into the cab.

 

[dodge82273]

back of the headline is how / where the factory -1/4th inch foam was applied , Me I would not spray foam between the steel panels though . 

 

[neil4224]

back of the headline is how / where the factory -1/4th inch foam was applied , Me I would not spray foam between the steel panels though .

I agree with dodge82273, foam on steel or between it seems to draw moisture. Has anyone looked at the new pickups with foam packed in the bedsides, ford, dodge, and Chevy. Rots quicker than old bare stuff ever did. Seems the foam holds moisture like crazy.

Neil

 

[u2slow]

Great stuff is a water cured foam. Make sure you paint that roof and let it cure fully before you apply. I'd say it's a bad idea.

Most of these foams are polyurethane based.... just like windshield adhesive and seam-sealer. They all cure with moisture. It is also common to spray-foam the insides of steel buildings. For rust issues, I think I would rather have it on a ceiling than an area like a fender-well where its exposed to the elements and mechanical damage. Maybe avoid the edge seams, since thats where any leaks would start.

I know my '84 Suburban was a terrible condensation trap (and rattle trap!) after I pulled the badly sagging headliner. I'd probably have sprayed-foamed it, or glued in some 3/4"-1" foam board had I kept it longer.

 

[dodge82273]

ON a ceiling is fine , just not IN between the ceiling and the roof so it traps moisture , these roofs rot out fast enough on their own....

 

[u2slow]

Does an RC have a double-walled tin roof like a crewcab or not? I haven't taken either of my RC headliners down to see.

 

[dodge82273]

he says something about a space ...

 

[rc12102]

Does an RC have a double-walled tin roof like a crewcab or not? I haven't taken either of my RC headliners down to see.

Yes

 

[u2slow]

Hmmm... kind of a tough call. That area up there isn't ventilated in the first place.

Maybe a few 'spots' of spray foam to stabilize the two skins from acting like a drum. Too much and you risk ballooning it.

This guy re-invented the whole roof on his project, and built an insulating layer for it:
https://www.cumminsforum.com/forum/89-93-non-powertrain/2121898-4-door-cummins-powered-ramcharger-2.html#post24800009