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Community and Q&A

How to insulate an existing ceiling / roof with no access?

dolfinluvr | Posted in Energy Efficiency and Durability on

Hello Experts and thanks in advance for your help. I live in a 1950’s home in San Diego (zone 3B) and many years ago the flat roof (common to military housing of the day) was converted to vaulted ceilings, which are beautiful and spacious, but not at all insulated. I know those of you in colder climates are gasping and asking yourself if this is even legal. There is no attic or even a crawl space above half the house and we really need to insulate it. Every year when it gets cold (yes, it gets cold in San Diego) and our house is 54F and then again in the summer when it gets hot and our house is 93F (we do not have AC and we don’t use our heater), we promise to look into insulating our ceilings.

Is there any way to do this with green materials (not spray foam, but maybe blow in fiberglass?) without ripping out the entire ceiling of our home?


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  1. GBA Editor
    Martin Holladay | | #1

    There is no agreed-upon definition of the term "green materials."

    The easiest way to insulate a low-slope roof assembly like yours is to install one or more layers of rigid foam insulation (or, alternatively, mineral wool insulation) above your existing roof sheathing, followed by a cover sheet and new roofing (for example, EPDM roofing, TPO membrane roofing, or PVC membrane roofing). If you care about the environmental impact of building materials, and you end up installing rigid foam, either EPS or polyiso is more environmentally friendly than XPS. (XPS is manufactured with a blowing agent that has a high global warming potential.) Many green builders like mineral wool insulation.

    For more information, see Insulating Low-Slope Residential Roofs.

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