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Community and Q&A

Cathedral Ceiling Insulation between rafter

ListonB | Posted in Energy Efficiency and Durability on


I am looking for ideas/options to provide some sort of heat relief from hot ceiling shared with roof & inside home with no attic.  The roofing material is mix of modified bitumen & shingles in different areas with minimal/zero insulation.

I live in Florida and the ceiling often heats to over 110 degrees on hot days.  I provide some relief now by watering my roof for 5 minutes spurts during hottest times of days which works okay with mini-split systems throughout home.  If I can get roof down to 90-95 degrees then cooling can keep up.

I think the best long-term solution is to add ventilated roof on top of existing room with insulation like spray and then put a metal roof over that but looking for something quicker/cheaper for now.

I’ve looked a couple product in ecofoil bubble foil and prodex 10 that look that they can provide some relief from the heat impact if I provide airgap of 1-2 inches between product and the roof.  The white version of these may be okay to be exposed in areas (mostly bedroom) I am looking to bring down the heat on.  I know these has low/incorrect R value for they are but think the airgap and setup could lower impact 20-25 degrees which can help a lot.

Are there any other options/suggestions for cooling off the ceiling beyond these product and watering roof?

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  1. Jon_R | | #1

    I'd lean towards just adding polyiso foam (on either side).

  2. exeric | | #2

    I've noticed there is a problem on this site when I've mentioned/advised someone to use a certain building technique in a climate similar to my own and then individuals from other climates take the ball and run with it. That's what's happened lately with my advice to: ventilate roofs, don't worry so much about HVAC equipment in unconditioned space, and the use of radiant barriers to solve problems without going to conditioned attics when HVAC equipment is located there.

    To make a long story short. It only works in "some" western climates like I live in. In the tropical climate you live in you need to insulate your home. Since you don't have an attic then you need to insulate the roof of your home. I'm starting to regret offering advice on this site because people so often take it out of context.

    This doesn't just apply to my advice. Individuals that live in mild mediterranean climates, not tropical climates, often get awful advice here from Easterners.

    1. capecodhaus | | #3

      Oh, this is going to be an interesting topic!

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