Insulating Without Insulation For Heat

On the new build I had a bit of a problem ... With such a small budget I really wasn't willing to spend the money on insulation. This was exaggerated by the fact that I live in Arizona and insulation definitely benefits in the cold more than the heat. BUT ... I had an idea and a few things laying around ...

Once I cut the wall panels to fit I flipped them over and laid down a coating of 3M spray adhesive. Already had it but I think it's about $10 a can. One can is enough for this on all panels. Once the adhesive was tacky I applied a layer of mylar. AKA "space blanket" material. Pulled taught, layed down, and smoothed by hand. I already had a bunch of these but one $3 space blanket available from Walmart is only a little smaller than a 4x8 wall panel. You can get a whole roll of the stuff on Amazon for cheap too. The large air gap between the panels and the van walls/windows is plenty of space for a radiant barrier (that's all the mylar is, NOT insulation) to do its job well.

The results ? ...

Well, I temporarily put up a section without the mylar laminated on the back to test side by side. Now, my results may be a little exaggerated since I have a window van and I paneled over most of the windows too but ... WOW ... The unlaminated panels would get hot to the touch on the interior side during the really brutal hours here in Arizona in July. The laminated panels? They got warm but never hot. 

Plus, with the 5% tint on the windows and the very reflective mylar behind it the windows are VERY nicely blacked out. The little bit of light which makes it through the heavy tint just gets bounced back out.

Also, unlike foams or fiberglass this can't move, fall down, come unstuck, or squeak. Plus, it literally only adds a hairs width of thickness. No space sacrifice. 

Is this better than insulation? No. --- It's just a radiant barrier --- Is this a cheap and easy option for warm environments which has a pretty noticeable improvement? Absolutely.

Now ... Do this AND have proper insulation and you'll really have something. Let me know if you give this a shot

That makes perfect sense and is super cheap!! Great idea!

Great idea...NASA does this too!

Hey I would use some type of clips or pins to help secure the mylar, since the heat will probably cause the adhesive to let go...its gonna get pretty hot in that space between the windows and the panels.

It's funny you say that. While my buddy was giving me a hand I was talking about the satellite we were building, haha.
The 3M adhesive is no joke but I will certainly be keeping an eye on it. If it survives Arizona summer we know it's good, lol.

akrvbob said:

That makes perfect sense and is super cheap!! Great idea!

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That was the idea. Maximum improvement for minimum investment/complexity. 
I'll be posting back as time goes on as to how well it holds up and keeps working.
The AZ sun eats plastic but it's on the other side of the tint plus reflective so we'll see.

Awesome, thanks for this information. I've been dealing with the 90 degree heat in my Prius in Iowa with a simple black fabric covering all windows while I've been debating how to build lightweight window covers that take up very little room when put in storage. I even have an emergency space blanket that I can use. You might see a new thread pop up asking for peoples opinions on building a lightweight window cover with the space blanket

Ok, I missed what the actual "wall panels" are that you used. I understand the Mylar, makes good sense, but I need a description of the panels please.

My Prius back window hatch really gets hot, it's tinted, factory (not limo) but needs help.

Thank you for your post.

For the Prius why not just make fabric window covers that attach via magnets and have a layer of reflectix inside? The panels are just interior wall paneling. Thin, flexible, strong. Better for a van where they can be hard mounted to the walls.

Gideon33w said:

For the Prius why not just make fabric window covers that attach via magnets and have a layer of reflectix inside? The panels are just interior wall paneling. Thin, flexible, strong. Better for a van where they can be hard mounted to the walls.

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Thanks, I'll look into that. My sewing skills are limited to button replacement but I'll see what I can do.

There's still stuff called hem stitch which is basically dry strips of glue. Fold over hem, slide strip in then hit w iron. Course not a lot of us carry irons.

Thanks , I will try with my RV

Thank you for the helpful info. Thanks to reading and watching Bob, I actually understand how this works.  I put some Mylar in my Amazon wish list for the day I do my van build - it may be a while so didn't want to forget this great hint.

I tell ya, it makes a heck of a difference. With a window van, you're typically dealing with greenhouse type conditions. Not exactly the greatest thing here in Arizona.
But, with the mylar backed wall panels and my vent fan on low the back stays just over ambient temperature.
Can't yet speak to how much it helps during cooler conditions but given how much body heat can contribute in a small space I'm optimistic.

Bumping for those asking questions on the topic.

Oh, I should offer an update since the van has made it through Arizona summer and into the current high 80's milder temps.

No issues at all with the mylar coming unstuck despite the heat. The 3M adhesive seems to be as great as the rest of their products.

When I've been working in the van it is only ever a few degrees over ambient despite sitting in the sun.
This is also helped by the roof coating I'm sure. Running the vent fan or opening the side door knocks the heat right down to ambient no problem.

Didn't even bother running my 12v evap cooler when I was out there today improving the wiring a bit.

All this despite being a window van.

Thank you for sharing this!

What was the exact 3m spray adhesive called?  Is there a particular number?  Available at big box lumber yards?

Thanks