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ehardman 01-11-2009 12:41 PM

Unvented crawl space insulation
I have an area below a bedroom addition to my house which has a low ceiling of about 5 ft that I use to store lawn equipment. It is an unvented closed space with an insulated access door and a finished concrete floor. The interior walls are insulated. There is clear plastic sheeting nailed across all the studs over the insulation. However, there is a small amount uninsulated wall area which is part of the concrete foundation. The ceiling is uninsulated. There is a single register providing conditioned air to the space. I am not sure if there is a cold air return as I have not seen one.

The room is 15' x 20'. We live in Kansas so winters are cold and summers are hot. With the interior door closed to this bedroom, this winter the temperature in the room in the morning has been as low as 45 degrees. I had a heating/ac tech take a look and he said the floor should be insulated.

If so, what type of insulation should be used between the studs (2 x 10's) in the crawlspace/storage area? Are there moisture concerns? Should the insulation have a vapor barrier? If so, should the vapor barrier be installed against the warm ceiling? Should the uninsulated foundation be insulated with foam sheeting?

Thank you for your input.

Ron6519 01-11-2009 03:36 PM

Kraft faced fiberglass batt insulation with the vapor barrier against the floor. You would get a low cost hygrometer that would measure the humidity level and put it in the room. If the humidity got too high, you would run a dehumidifier.

Winchester 01-12-2009 07:35 PM

If the walls are insulated then the ceiling (bedroom floor) does not need to be insulated. Insulate all the walls. Use 2" foamboard on the uninsulated foundation walls. How much and what type of insulation do the other walls have? IIRC R11 is the suggested amount here in Illinois.

Is this addition connected to another crawl space or basement? I ask because my 4 seasons room has an opening to the basement and a "return" (not heat) to the HVAC. Not sure if this is trying to create some sort of air floor??

Also, if you can inspect the rim joists, they should be sealed and insulated too.

jfishe19 01-13-2009 12:44 PM

I actually had an issue similar to this with my crawl space but in Savannah, GA. As you can imagine, it's quite moist in these areas. I was able to find a very easy do it yourself system at They actually sent me a 20-mil vapor barrier liner instead of a regular 4 or 6. It was a bit more, but it's really worth it. I would check them out if you're in the market...

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