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Old 12-17-2012, 06:20 AM   #22
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Default Re: 3M Thinsulate Thermal and Acoustical Insulation

I received my 3M MA6720 Thinsulate. Here is my plan for install. Comments welcome (except for recommending use of spray foam.. hah hah).

(steel vehicle skin)
-- THINSTLATE (additional 2") --

I decided to follow this layering and put the reflectix vapor "retarder" toward the interior for a few reasons:

* Reflectix and other radiant insulation suggests an air gap on the exterior side to provide any R-value benefit. This will also avoid conduction of heat from the metal to the reflectix metallic foil, and also will prevent any galvanic corrosion should the metal be incompatible (although the paint might be enough to protect from corrosion).
* The thinsulate is hydrophobic so it will be less likely to degrade with condensation (this is approved for marine use).
* The voids in the sprinter will not be air-tight, no matter how hard I try. There appear to be drain holes in the wall voids where they meet the floor as well, which may help expel condensed drops.
* It is true, air trapped within the void during installation will have moisture in it, but this is not different than house construction where the air is trapped in the wood wall voids between sheetrock and vapor barrier. Maybe the trapped moisture can diffuse to the exterior in a house, but drywall also allows some moisture diffusion back in. So we assume some amount of moisture by diffusion is tolerable and will not cause damage. I have to assume the auto manufacturers have planned for some moisture to condense at times as well. Most cars fog up at times and they dont tuen to rust buckets.

I plan to adhere the thinsulate to the metal wall with squares of 3M Fastener TB3571/TB3572 Hook/Loop (ie velcro). The glue of the velcro is more important than the velcro itself, and 3M's selector guide indicates this part will hold up to 200 degrees F, which is pretty good (I have white paint by the way)

I plan to adhere the thinsulate layers (as applicable depending on void depth) to each other using 3M 76 Hi-Tack Spray Adhesive. I selected this spray adhesive because its datasheet says it is "an excellent choice for fabric headliners" and is good for 230 degrees F; specifically marketed for "fabric in van conversions" and to "bond insulation in aircraft interiors" here.

I'll use reflectix tape to attach relfectix to the ribs of the vehicle, covering each void.
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