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Insulated office inside a larger building

coyote556 | Posted in Green Building Techniques on

I have a large structure that is well insulated (50×80 with 18ft ceiling) and I am building a 14×30 office inside of it, with 8ft ceiling. The main building will be conditioned at 55-60 during winter and 80-85 during summer. The office will be conditioned to 72 degrees year round.

My question is about vapor barrier on the office. I am insulating the office walls to R19 and filling the 2×10 ceiling joists with blown cellulose or fiberglass batts. Should I use a vapor barrier on the office and if so, to the inside or the outside?


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  1. GBA Editor
    Martin Holladay | | #1

    D. Badger,
    Neither your walls nor your ceiling need any kind of vapor barrier. However, your ceiling should include an air barrier on the underside of the insulation (at the ceiling), and your walls should probably include two air barriers -- one on each side of the insulation.

    For more information on air barriers, see:

    Questions and Answers About Air Barriers

    Air Barriers

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