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mitchel 02-17-2011 01:12 PM

Were my rim-joists sealed improperly or did I get ripped off?
I had an Xcel authorized contractor come in and seal the rim-joists in our unfinished basement. They used spray foam from a can to seal the joints and then put new R-30 batt insulation. In some areas they used foam board which they also sealed around with spray foam from a can.

This morning in Denver it's 41 degrees outside.

I am using an infrared thermometer gun to measure the temperature along the base board and right in front of it...the temperature at that spot is averaging 55-57 degrees...two to three feet away from the wall towards the middle of the room the temperature climbs to an average of 64-66 degrees.

The inside thermostat is set to 69 degrees.

Does this sound right or did these guys do a bad job?



oberkc 02-17-2011 02:03 PM

This does not sound obviously wrong to me. Insulation is not perfect. Do you know the air temperature in the basement (not sure where your thermostat is)?

mitchel 02-17-2011 03:32 PM

The temperature in the crawl space which is below the rooms that I did the measurments at is 64.6 degrees with 33% humidity.

The worse part of the house is the large crawl space which sits below the bedrooms in our ranch style house (Denver, CO). The contractors are trying there best...they offered to fully condition the crawl space for free. They are going to install some type of thick vinyl on the floor and up the walls and seal everything and then install a vent in the ducting that goes through there...he said that should help a lot.

ThatDaveGuy 02-17-2011 05:01 PM

I wonder if the issue is not at the rim joists but perhaps in the walls themselves. Gary has posted links and info about convection loops inside of wall insulation.

Wildie 02-17-2011 07:12 PM

In my area we insulate the walls with Roxul insulation.
An earthen floor is covered with 6 mil polyplastic sheeting. This vapor barrier is carried up over the wall insulation.
All outside vents are permanently closed off and a hot and cold air supply is provided to condition the crawl space in the same manner as the rest of the house. :yes:

Gary in WA 02-17-2011 09:59 PM

The rim joist is as cold as the outside temperature, or slightly warmer with the heat from the indoor basement air. Yet it is still cold enough to condense the moisture vapor air going right through the f.g. You need foam board, air sealed at the rim;

Thanks, Dave, copy and paste that link for others, anytime;


mitchel 02-18-2011 07:15 AM

Thanks everyone for the excellent info!


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