# how to insulate second floor rim joist.



## bobinphx (Nov 25, 2011)

Two story home in phoenix. Stick construction with hard board siding on 3/4 of the house and stucco on the other 1/4. Couple of years ago, I was doing a remodel and had a big ole fan running in the closest window. The fan depressurized the house and I noticed that air was coming in from the outside wall outlets. A smoke stick and a walk around the house and I found a lot of air coming in on the second floor at the baseboards. A while latter, I had a need to open up the siding at the second floor rim joists. what I found for insulation was a wad of fiberglass in each bay, half of which had fallen down. I fixed that with cut and cobble foam board and a sealer. A while later, I had the use of an infrared camera. The camera showed a lot of air movement underneath the second story floor (not where I had re-inuslated). so my question.. I dont think I want to rip up the outside hardboard to fix an insulation problem and I dont want to open up the ceiling on the first floor. Given those two idea are out of the question, any suggestions?? we are due for new carpet in a year or two and I guess I would not be totally against cutting the plywood second floor deck in order to open up the area for insulation... again, any thoughts??


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## gregzoll (Dec 25, 2006)

You are going to have to remove a lot of drywall from around all four sides of the ceiling on the first floor, so that you can get up there. I would probably go with Closed Cell Foam sprayed in there. The biggest factor also is that any windows that allow direct sunlight, either have a professional come in and place tint on the windows, to cut down on Heat Gain, and also incorporate shades for those you wish to have sunlight coming in, but can change from room darkening, to 50% light.

The other issue is making sure your attic space is properly vented and insulated. The biggest issue with homes. Especially up North. Is when you drive around and after a night of frost or snow. You can tell which homes have proper attic insulation and venting, and which ones do not. The ones that do not, have nice clean roofs and plenty of Ice Cycles hanging off of the gutters.


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## gregzoll (Dec 25, 2006)

Also keep in mind that every place you see leaking air. Are where outside noises enters the house.


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## BarryP (Jun 14, 2015)

bobinphx said:


> we are due for new carpet in a year or two and I guess I would not be totally against cutting the plywood second floor deck in order to open up the area for insulation... again, any thoughts??


Perfect! Then cut some holes in the second floor and stuff unfaced fiberglass against the joist or blow in Loose-fill fiberglass or cellulose to add about a foot of insulation along the rim.


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## Gary in WA (Mar 11, 2009)

Keep in mind that furnace filters are made of fiberglass because of the low resistance to airflow. And you have air under the baseboards... stop the heat from reaching the fiberglass with rigid insulation board/canned foam on the rim joist, after air sealing the wood joist first. Stop the warm air at the rim from depositing its moisture before it reaches your insulation/framing/cavity to condense against the cold room temps from the AC.

Gary


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