Insulate underneath body?

moosevan

New member
I added 3m microspheres to some paint I used on the inside of an exterior wall. There was a difference of about 3 degrees in the painted area on a hot day using an infrared thermometer.
 

luthj

Engineer In Residence
As mentioned, I am sure the insulation value of paint is improved with microspheres. But they are not in the same class as real insulation products. Thats why no one bothers to show an R value test. If regular undercoating is R1 per inch, then microspheres may increase that to R2 per inch. At 1/8" thick, that's 0.125R to 0.25R. Not even worth considering for the weight/effort/cost.

There is a reason that insulation is quantified with numbers and math. Cause "feels cooler" is not an objective measurement.
 

_hein_

Observer
We have used 3M Thinsulate AU4002-5 1" thick double scrim underneath the vehicle. Thinsulate is hydrophobic so wont absorb moisture. Another trick is to spray the exposed scrim with Rustoleum NeverWet so it repels water. Thinsulate is engineered to absorb noise in addition to providing a thermal benefit. I have installed it under the hood on vehicles and tractors (see attached photos) to reduce engine noise. Works great. Use 3M 90 spray adhesive.

All the best,
Hein
DIYvan
541 490 5098
 

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shade

Well-known member
We have used 3M Thinsulate AU4002-5 1" thick double scrim underneath the vehicle. Thinsulate is hydrophobic so wont absorb moisture. Another trick is to spray the exposed scrim with Rustoleum NeverWet so it repels water. Thinsulate is engineered to absorb noise in addition to providing a thermal benefit. I have installed it under the hood on vehicles and tractors (see attached photos) to reduce engine noise. Works great. Use 3M 90 spray adhesive.

All the best,
Hein
DIYvan
541 490 5098
Are there any long term issues with moisture becoming trapped between the insulation and steel?
 

_hein_

Observer

shade

Well-known member
Thinsulate won't hold water (hydrophobic) and allows for some airflow so moisture will drain and then dry out. The NeverWet trick works amazingly well. You probably would want to spray any exposed steel wih Rustoleum truck bed coating spray or equivalent before installing Thinsulate.

All the best,
Hein

DIYvan
541 490 5098
Air flow is good. I prefer an oil based rust inhibitor to a hard coating, but that wouldn't work well in this instance, since the insulation would have to be removed for re-application.
 

5spd97

Member
I sprayed the underside of my boxtruck with two part closed cell foam last June. I was careful to mask off areas that I didn't want covered and I even sprayed the rear wheel wells over the dual wheels. I then sprayed the foam with a black bedliner paint to protect it from reflected uv. If the foam were to be damaged it would be very noticeable. So far so good.
 

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