Does my wall insulation-sound proofing layering plan sound reasonable? - Ford Transit USA Forum
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post #1 of 3 (permalink) Old 08-17-2019, 01:55:PM Thread Starter
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Does my wall insulation-sound proofing layering plan sound reasonable?

Have read so many threads on insulation-sound proofing that my head is spinning! I'm mainly interested in keeping HEAT OUT. I will have a Maxxair fan and likely one or two vents in the floor to aid in air circulation. Future plans may also include a rooftop air conditioner. Here is what I'm contemplating doing with the walls. Place Frost King (R3) duct insulation on the van walls ( I would use this for insulation and some sound deadening. It is a foil-backed foam, and the foil would be facing the interior of the van. I would then have a 1+" air space followed by 2" foil-faced, R13 polyiso ( with the foil facing the exterior of the van. The foil sides of the foam and polyiso would be facing each other, separated by an air space. Does this plan sound reasonable or would there be a benefit to painting the foil side of the foam black so radiant heat reflected by the polyiso would not "bounce back"?.....or am I totally off base here

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post #2 of 3 (permalink) Old 08-17-2019, 02:22:PM
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Keep in mind that (without Air Conditioning) the best you can hope to achieve is equilibrium with outside air temps. A little insulation will help reduce heat gain, but the vent on the roof and another down low somewhere will take advantage of physics to keep a constant heat exchange going on. As the air becomes hot it will rise and escape through a roof vent. In doing so it will create a lower pressure in the van. If there is a floor vent this will draw cooler air in from below to replace what went out the top. This convection of air will have more of an effect than will going over the top on insulation.

Though you are right to be be blocking the path of radiated heat from the sheet metal into the living space. I didn't want to infer otherwise. Just no need to overdo it, unless it is for a Winter application where you are trying to keep heat in. More R-factor can be better, but you will reach a point of diminishing returns at some point. For a three season van that point may be achieved with a single layer. Adding more insulation won't change the fact that it is hot outside and all you are trying to do is not exceed that inside.

As for the foil, read the manufacturer's instructions. Most will recommend a few inches of air space on the foil side in order to achieve the published result. There usually isn't room in a van build to accommodate this. The foam will be doing the heavy lifting in blocking heat gain from outside. Pick a foam with a high R-factor/in and you'll be good to go.

Sound deadening is best done with a material that is designed for that purpose. I used 0.4" thick CS150 Thinsulate, a garment grade available for reasonable pricing at online fabric vendors. It just happens to have the same properties as the automotive grade Thinsulate for noise control. Other materials might do as well or better, but you should research whether there is data to support acoustic damping as one of their published properties. If so, there should be numbers that can be compared.

Painting anything black will make it absorb radiated heat and will allow the heat to be stored, then released as the temperatures around it go down. That may be counter to your goal of reducing heat gain.
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Last edited by Travlin; 08-17-2019 at 02:35:PM.
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post #3 of 3 (permalink) Old 08-18-2019, 12:15:AM
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Similar to you, I read the various threads on insulation and methods - the ideal solution for keeping heat out is not always obvious (to me)

The metal structure in the vans really makes insulation and fit out - challenging.

What would be really nice is if these van mfg companies would make the body from fiberglass or carbon fiber, like an RV. This would rather dramatically reduce noise and thermal conductivity. I have even considered buying an empty shell of a small class C for this reason. If I could find one that doesn't look like a class C so I could park it in front of my house, I would do it.

As far as your insulation plan, IMHO, the approach needs to be kept as simple as possible, and use an insulation that is at least somewhat flexible / bendable. I have read that the thermax insulation is the highest R value per inch, but I remain concerned that it will squeak. I would expect the same from the menards product.

So far, I haven't seen any approach that looks all that much better than just filling with mineral wool and covering the interior with 1/4 inch of baltic birch ply. "Maybe" a continuous layer of a foam pipe insulation under the ply.

The exception of course is if you are willing to put in insulation that is substantially thicker than the wall cavity. I was in a van that had 4 inches of insulation and it was surprisingly cool on a hot day. I don't like the stuff, but it was the blue jean insulation.

It won't take long for other forum members to make improved suggestions over mine.

IMHO, if you think that you will need air conditioning, you do - so just skip the fan and go straight to A/C.

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Last edited by harryn; 08-18-2019 at 12:19:AM.
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