insulating cab


I just purchased a brand new cab for my deuce and a half (basically a Jeep tub). Mine is not in any sort of bad shape, but it would take me a couple of days to repair the little bit of rust in the rocker panels, and I got this NOS cab cheap enough that I couldn't say no. The cab was galvanized, and then painted very poorly (no primer), so I've had it sandblasted and before I prime, paint & install it - I wanted to think a little bit about insulation in case there's anything I want to apply to the underside of the floorpan. I think I might end up using some type of dynamat-type product on the firewall and the back of the cab, but is there anything I can apply to the underside of the floorpan to build-up some serious insulation? Is there any type of water/weather-proof spray-foam that I could use, or ____? Just wondering what's out there. I've used Line-X on a Jeep tub in the past, and that was a DISASTER. Don't want to repeat that.


Dynamat --> Fatmat --> ice and water shield for roofs

In order of decreasing price

The surface doesn't have to be completely covered. Just as long as the metal doesn't 'ring' when tapped.

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Thanks for all the input guys, but what about insulation in terms of heating & cooling? I am interested in sound deadening, but I'm equally concerned about controlling temps.


This is a bit of "apples vs. oranges" but may help a bit: A few years ago I needed to reinsulate and recarpet the front cab area of my '85 BlueBird RV (this is basically a school bus chassis set up in this like your truck, you have room to work, weight is not really an issue, drivers area not really designed with "sound control" as a priority, and the engine is right at your feet putting out heat and noise-so you need good stuff).

In the interior, I found marine engine room type insulation (dense closed cell foam with a asphalt layer and foil facing) from JC Witney and West Marine were excellent to work with, apply, and gave good results in both sound and heat insulation. This comes in various thicknesses...I used 1/2" almost everywhere except the interior of the engine compartment/firewall where I used 1" in most areas and 1/2" where access was just not there. Once I got this stuff in, you could really tell the diffrence in noise level and heat transfer. Secured with 3-M heavy duty (99?) spray glue and some mechanical screws/washers. Seams sealed with mylar tape. This type of insulation looks good raw, but could be covered with a fabric layer to finish off if exposed in a driver/crew compartment.

But, prior to this, I had used spray foam to seal up seams and cover the underside of floor panels as insulation....what I found was good heat insulation....but minimal sound deadening. I think due to the light weight nature of the foam when cured...sound deadening needs a range of density to control a range of sounds. Also, upside down, this foam approach is a ***** to work with...and getting this stuff off you is tough. I would use foam to seal up, but rely on a good multi coat application of standard undercoating for exterior exposed areas needing weather protection and sound deadening.

One caution would be to avoid having your insulation "trap" mosisture against your steel, inside or outside...causing unseen rust issues. For your application you might even consider having your floor insulation removable should you need to dry out or inspect area.

Good luck!
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Try ezcool. I read a testimonial from a guy in Australia that did some very intense independent testing but it should be on the inside of the vehicle. I'm thinking about it for a 110 that I am having the interior worked on right now.