roof insulation

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roof insulation

Postby tinman52 » Sun Apr 21, 2019 5:11 pm

What are some options for roof insulation? I see sliced foam being used, seems like a pain. Anyone used fiberglass? Foil/bubble? Other ideas?
Would need to be 1.5" thick and light weight.
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Re: roof insulation

Postby halfdome, Danny » Sun Apr 21, 2019 5:40 pm

Just layer 1/2” insulating foam like they carry at Home Depot, easy to do.
On the curved areas I use Tightbond 2 it’ll hold long enough until you skin it. :D Danny
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Re: roof insulation

Postby Shadow Catcher » Sun Apr 21, 2019 7:10 pm

Hard to beat EPS for insulation 3.85 R per inch. We have 1.5 inch roof and sides.

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Re: roof insulation

Postby les45 » Mon Apr 22, 2019 11:46 am

I used 1.5" foam board in the roof of my current build with no problem. I used a box cutter with a couple of passes on each side of the cut line and it broke clean. I've seen people cut it with a power saw but that really makes a mess.

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Re: roof insulation

Postby Esteban » Mon Apr 22, 2019 12:11 pm

Use rigid foam board to insulate your teardrop. Three kinds are readily available.

1) Expanded Polystyrene (EPS) is the least expensive with R values of 3.6 to 4.0 per inch of thickness.
2) Extruded Polystyrene (XPS) has R values of 4.5 to 5.0 per inch of thickness.
3) Polyisocyanurate (polyiso) is the most expensive with R values of 7.0 to 8.0 per inch of thickness (which may degrade to R 6 to 6.5 with aging). It is often foil faced.

links:
https://www.homeconstructionimprovement ... on-values/
https://www.finehomebuilding.com/2009/0 ... d-i-choose

I'm using 1.5" of polyiso for the roof and 1" of polyiso for the cabin walls.
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Re: roof insulation

Postby halfdome, Danny » Mon Apr 22, 2019 7:37 pm

I cut it on the table saw with dust collection, easy and quick.
You do need to be aware it wants to float from the wind created by the spinning blade and could give some kick back :frightened: .

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Re: roof insulation

Postby aggie79 » Tue Apr 23, 2019 12:55 pm

If you have one, a track saw with dust collection makes for an easy no-mess way to cut insulation board.


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Re: roof insulation

Postby tony.latham » Tue Apr 23, 2019 1:02 pm

I see sliced foam being used...


I use my table saw with a dust system and it's clean and fairly quick. I ballpark where the kerfs are.

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The advantage of hard foam is that it adds superb strength to a roof that is sandwiched in two layers of 1/8" Baltic birch. Stiff and strong.

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Re: roof insulation

Postby Esteban » Tue Apr 23, 2019 2:19 pm

A tape measure, a utility knife and a 48" drywall square are handy tools for measuring and cutting rigid foam board to size. A table saw is useful for repeated cuts and kerfing. I often cut the foam board to snugly fit into openings. Then use a drywall spatula or drywall knife to help fit/persuade the cut-to-size piece of foam board into place between the roof spars, wall or floor framework, etc. To create a rigid strong and lightweight torsion box effect the foam boards are glued to the inner and outer plywood skins with construction adhesive.
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Re: roof insulation

Postby Tom&Shelly » Tue Apr 23, 2019 3:22 pm

When I cut the voids in the walls and bulkheads I didn't bother to necessarily make the cuts all that straight--just what I could do quickly with the jig saw. I rough cut the foam with a utility knife snapping it clean, then put the piece behind the wood and traced the void with a Sharpie. Found I had no trouble following the outside of the Sharpie line with my band saw. Gaps between the wood and foam were usually less than 1/16" or so. (Only reason for the rough cutting was for the pieces that didn't clear the 12" clearance of the band saw.)

The foam dust was pulled down into the saw just like saw dust, but the foam dust charged electrically and stuck nicely to the painted metal sides of the saw until I vacuumed it off. Not much in the air, and little on the floor even. This is in New Mexico with single digit humidity. Your atmospheric conditions may vary!

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Re: roof insulation

Postby saywhatthat » Tue Apr 23, 2019 9:32 pm

The fiberglass will sag over time I've try a little foam . Make sure you stop any air getting around it
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Re: roof insulation

Postby Rhinoman64 » Wed Apr 24, 2019 6:20 am

I found that a half-moon blade on an oscillating multi-tool made quick work of cutting the rigid foam insulation. Used a drywall t-square and Sharpie to draw the line and was able to stay very true to the line even moving fairly quickly. The thinness of the blade helped cut down on the amount of dust as well.
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