Neodymium magnets as spacers?

[Anhedonic]

I am (re)starting my insulation shortly.  I understand that reflectix or foil of any kind as a radiant heat barrier needs to have a little bit of space between it and the wall for it to work. I'm thinking about getting some of the foil-backed polyiso board and cutting it to match the spaces between the ribs of the van, and then affixing a number of neodymium magnets to the foil back. I would then use them both to stick the foam sections to the wall and to provide a little bit of space for the radiant barrier to reflect. 

So... Two questions. 

First, what do people think of this as an idea? Good? Bad? 

Second, given the various temperature extremes it will be experiencing, what would be a good glue or tape to use to affix the magnets to the foil? I was considering just using duct tape around the edges, but I'm not sure how that would hold up... 

I'm considering this both for the walls and the ceiling.

 

[Anhedonic]

I should mention that I am also planning to cover this all up with further sheets of polyiso and then plywood. This is just for between the ribs.

 

[MrNoodly]

Just turn the foil side inward. The foam becomes the gap.

But if you still want an actual air gap, you could use something much cheaper than magnets. For example, you could get a sheet of corrugated plastic and cut it into small squares, then duct tape the to the polyiso.

 

[Anhedonic]

You mean put the foil side on the side facing inward rather than outward? I was thinking the foil would go towards the wall, with a 3-4mm air gap between wall and foil. I didn't realize the foam could function *as* the air gap.

I've already got a bunch of magnets so the cost isn't much of an issue.

 

[John61CT]

Reflectix is a waste of time and money in a tiny space.

Two parts, the Mylar and the bubble wrap.

Shiny only works on the outside layer and pointed out, either against glass or with at least a 1-2" air gap.

Plastic works as a vapor barrier if taped, just like dropcloth.

No insulation value at all.

 

[Anhedonic]

So with anything less than a 1-2" air gap, foil as a reflector does nothing significant?

 

[John61CT]

That is correct.

Filling that air gap with polyiso is 100's times more useful.

As is parking in shade.

 

[Canine]

What color is your van? If it is white, it already has a high SRI, Solar Reflectance Index. Instead of trying to reflect what little radiant heat is left to reflect, using that space to put actual insulation in it would be a much better use of resources.

 

[Anhedonic]

It is white. OK. Sounds like polyiso all around, no concerns about any sort of foil.

Thanks guys.