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gt390 · 01-21-13, 01:33 PM

Hope it's alright to bump an old thread, but it's on topic. I wanted to share some of my results.

I'm remodeling my basement which will expose the rim joists. It's common in my area for 70-80's houses to have the joists poured right into the foundation wall so there is only about 1" of space above the concrete to the bottom of the floor above. Leaves not a lot of space for insulating but they did stuff some batting in there. For some background, it's really cold here in winter. Nighttime temperatures have been hitting -30C (-22F). Daytime temperatures in the -20s.

I was able to experiment in my furnace room as it doesn't have a finished ceiling so I have full access to the rim joists. I just got a bottle of large gap spray foam from Home Depot, pulled out the old batting and foamed up in the gap as much as I could. I was able to do about 4 joist spaces. I did not put anything on the face of the concrete wall (yet).

Using my temperature gun, the temperature on the floor in the room above where the rim joists were not foamed was about 3-4C cooler compared to those that were foamed. This is seriously significant. Areas that were foamed was about 18-19C with areas that were not around 14-16C.

I was considering whether to go to the trouble of opening up the ceiling in the rooms I wasn't necessarily going to touch with the reno in the basement, but seeing how significant this is and they are below my kids (on the way) room I will probably go ahead with it.

Next to order the HT-300 gun which was recommended in another thread and open up the ceilings in the other areas and get foaming.

01-21-13, 01:33 PM	#70
gt390 Lurking Renovator Join Date: Dec 2012 Location: Canada Posts: 7 Thanks: 0 Thanked 1 Time in 1 Post	Hope it's alright to bump an old thread, but it's on topic. I wanted to share some of my results. I'm remodeling my basement which will expose the rim joists. It's common in my area for 70-80's houses to have the joists poured right into the foundation wall so there is only about 1" of space above the concrete to the bottom of the floor above. Leaves not a lot of space for insulating but they did stuff some batting in there. For some background, it's really cold here in winter. Nighttime temperatures have been hitting -30C (-22F). Daytime temperatures in the -20s. I was able to experiment in my furnace room as it doesn't have a finished ceiling so I have full access to the rim joists. I just got a bottle of large gap spray foam from Home Depot, pulled out the old batting and foamed up in the gap as much as I could. I was able to do about 4 joist spaces. I did not put anything on the face of the concrete wall (yet). Using my temperature gun, the temperature on the floor in the room above where the rim joists were not foamed was about 3-4C cooler compared to those that were foamed. This is seriously significant. Areas that were foamed was about 18-19C with areas that were not around 14-16C. I was considering whether to go to the trouble of opening up the ceiling in the rooms I wasn't necessarily going to touch with the reno in the basement, but seeing how significant this is and they are below my kids (on the way) room I will probably go ahead with it. Next to order the HT-300 gun which was recommended in another thread and open up the ceilings in the other areas and get foaming.