Insulation Question …

[teardroptv]

I am at the point in my build where I am adding foam board insulation to the ceiling. I designed it to allow for 1.5 inch insulation. I am finding that to be difficult particularly in the curved sections. Is there a problem using 1 inch insulation which will leave a gap within the ceiling. Does that end up causing moisture build up within the ceiling due to the air gap? Thanks for sharing your advice.

[Wrecit]

Might want to use 3/4 or half inch and double or triple it up. Play a little with a heat gun to help with flex

[saywhatthat]

https://www.blocklayer.com/kerf-spacingeng.aspx
even gives you a templates

[tony.latham]

Foam board is easy to bend if you cut a bunch of kerfs in it.







Tony

[GPW]

Kerfing is a way to bend foam , but it's messy and I believe it compromises the structural integrity of the foam itself .
I have experimented at bending foam with Heat , and IMHO its a much better /stronger way to do it ...

[tony.latham]

I have experimented at bending foam with Heat , and IMHO its a much better /stronger way to do it ...

Wouldn't you have to build a 6' or so oven to put the pieces in? And perhaps a form for each one to slump onto?

...it compromises the structural integrity of the foam...

With a traditionally-built teardrop (not a foamie), foam board adds significant compressive strength to a part (inside a torsion box). I have not seen a noticeable change in compression with kerfed foam.





Tony

[MickinOz]

My belief is that the insulating properties of foams come from the bubbles in the foam, air and other gases being relatively poor conductors of thermal energy.
are you able to bend foam with heat without collapsing the foam?

[teardroptv]

Tony - Thank you for your reply and the attached photos. I used that as an example and my insulation fit like a glove. I should have paid closer attention when I read your book, which has been a wonderful reference. Thank you and all those who responded to my post. This is a great forum which has been so helpful in my build process.

Mark

[QueticoBill]

I would expect the kerfs in foam are no different than corrugated cardboard or honeycomb panels. From a structural point of view, just dowels or pegs spaced apart would achieve the same strength of the continuous foam.

[tony.latham]

I should have paid closer attention when I read your book, which has been a wonderful reference.

Hey, thanks. I keep hoping to see one of the teardrops that sprang for those pages tooling down the highway.

Tony

[Wrecit]

No one seemed to answer but to heat foam you use a heat gun. A few wood forms to the curve you want will help

[GPW]

Here's how it's done... Bigger foam , more heat guns .. Best to have heat on the top and bottom surfaces, a two person job ...
https://www.youtube.com/watch?v=5WVKttqb6HQ&t=33s

[mountainminded]

...Or thinner foam in multiple layers— no heat, no kerfs, no fuss no muss. This is a 1-1/2” space filled with two layers of rigid foam- a 3/4” thick layer and a 1/2” thick layer. The combination leaves a small gap which I find desirable when installing the sheathing over the top as the foam doesn’t fight me. My local Lowes has every thickness of this product on the shelf.