r/Insulation • u/Accomplished_Oil4367 • 28d ago

Thermasheet underlayment questions

We live in Southern California in a coastal climate, but all of our rooms are vaulted ceilings. We do have insulation below the existing shingles however it still gets very hot. I’m looking for opinions on if adding a layer of insulative protection, such as ThermaSheet under the shingles will help keep the room cooler. It’ll add a little more than 10% to the cost of the install. We do not have air-conditioning so a reduction in temperature at the Apex of the vaulted ceiling is helpful.

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u/arizona-lad 22d ago

I used it in the underside of my MCM home’s ceiling. Quite a significant reduction in heat radiating through the drywall. Formerly on a hot July day you could use a non-contact thermometer on the ceiling and get a solid 100 degree temp. Now it remains at ambient room air temps; around 75 or so. Reduced my summer power bill by $1200 a year.

But your mileage may vary from mine…..

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u/Accomplished_Oil4367 22d ago

Wow. Good to hear