insulating unfinished basement utility room

endlessfixingOctober 27, 2009

A contractor doing some work in my basement today suggested he insulate the ceiling of the utility/furnace room "while he was here". There is no ceiling- just exposed ducts and wiring under the subfloor (shiplap decking). The master bedroom is right above.

He said he would staple faced batt insulation to the joists and cover it with a "vapor barrier" to keep debris/dust from falling into the room. The vapor barrier looks like a thin white plastic with embedded/embossed 1/4 inch mesh. He could not explain exactly what it was or what it's called, but said he uses it all the time.

He would also put the batts and vapor barrier in the exterior wall space above the foundation.

Does this sound like a good idea? I don't want to introduce any moisture/mold, fire hazard, or fiberglass dust problems just for some "possible" heat savings.

I've been trying to read up on basement insulation, here and elsewhere, but I've been finding conflicting info about benefits/drawbacks, use of vapor barriers, etc.

Hope someone can help me decide how to proceed. Thanks.

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I've been finding conflicting info about benefits/drawbacks, use of vapor barriers, etc.

Only from non-building scientists.

See Building Science Corp., link below. They also provide much of the insulation info available from the US Department of Energy: Energy Efficiency and Renewable Energy.

insulate the ceiling of the utility/furnace room

Is the basement heated or not heated? If it's heated, insulate the first four feet of the walls and the space between the joists. If it's not heated, what is the point of insulating the ceiling on one room?

batts and vapor barrier in the exterior wall space above the foundation

Absolutely not! Liquid water or water vapour will render fibrous insulation less than useless and provide a home for mould.

It would help if we knew what climate you were in. I know that everyone puts in their profile they are in the US. It's a big country.

Here is a link that might be useful: Basement Insulation Systems

    Bookmark   October 27, 2009 at 6:23PM
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endlessfixing

Thanks for the reply and the link.

The basement is mostly finished/heated with sheetrock on the ceiling and walls with batt insulation inside. (Determined while tracking down rat problem.)

But the furnace is in a large unfinished room with open "ceiling" and concrete foundation walls except for the top 2 feet of exposed wall/studs. There are rigid metal heat ducts running along the joists, but no heat vents into this room.

The master bedroom is above this unfinished room.

The house is brick, built in 1930. Located in Seattle.

    Bookmark   October 27, 2009 at 6:49PM
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The efficient approach is to insulate the walls below the frost line and the rim joist area with sprayed or board foam as illustrated in this Building Science Corp. publication.

    Bookmark   October 27, 2009 at 8:04PM
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