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I'm exploring options for insulating the rim joists in my finished basement. There is currently bat insulation in some of the rim joists but its needing to be replaced. I've got about 100 sq ft to insulate (1440 linear inches * 10 inch rim joist width). Unfortunately, a majority of the rim joists are covered by a drop ceiling. I can move the tiles to get access but it's still going to be a pain to work around the drop ceiling. I'm considering a few options but have never done this type of project before so was hoping to get some advice before making a decision.

Option 1) Hire a pro and have them install spray foam insulation. I'm concerned that having to work around the drop ceiling will make the job quite a bit more expensive.

Option 2) Buy a combination of spray foam and rigid foam insulation and do the job myself. I'd cut the rigid foam insulation to size and then use something like great stuff pro to add insulation between the rigid foam and the joists to make it air tight. Leaning towards this option at the moment.

Option 3) Buy a DIY closed cell spray foam kit and apply it myself. I'm probably not going to do this but listing as an option. From what I can tell it's pretty easy for DIY spray foam kits to turn into a nightmare and given the price of each kit probably not worth the risk.

Of the 3 options I'm currently leaning towards 2 but wanted to get some advice from people that are more experienced. Does option 2 seem realistic and will it insulate/reduce draftiness as well as just applying spray foam? Any other options I should consider?
 

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I just finised doing mine and I did #2. I took out the builders rim batting and vapour barrier and put in Duro span then applied great stuff to seal around the duro span. and then added the builders R20 batts back into the cavities and re applied vapour barrier with acoustical sealant to seal the vapour barrier.I didn't have any drop ceiling but it was a bit of a pain anyway but it will payoff with no air entering your joist bays! Good luck with your choice.
 

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I did #2 in my laundry room after I fixed the leaky wall. Before I studded the wall I glued 2” Styrofoam SM to the concrete wall and then did the rim joists with the same stuff. Where my outside water tap goes out I put the SM in but did not spray foam it just in case I needed to change out tap and I had to! I wish I did the rest of the basement years before I closed it all in. I wish I knew then what I know now lol.


Retired guy from Southern Manitoba, Canada.
 

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Variation on #2 is rigid foam, with a fair fit, and then latex caulking around the perimeter. In your case, might be harder to get a caulking gun into the drop ceiling than a can, but avoids the mess of the expanding foam.
Not sure how much you have used that expanding foam, but it can be a real mess --- falling off of where you were expecting it to stay, and then cleaning it up from where it fell onto is next to impossible. If you have a finished basement make sure you have drop sheets.
 

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"Option 2) Buy a combination of spray foam and rigid foam insulation and do the job myself. I'd cut the rigid foam insulation to size and then use something like great stuff pro to add insulation between the rigid foam and the joists to make it air tight. Leaning towards this option at the moment. "

This is what I did in my unheated crawl space. Took about three days of work, crawling around on my knees. The results were amazing though. Before, the temps in the crawl space would get in the 30's during winter and I would always worry that the copper water lines would freeze. After the job was done, the crawl space stays around 63 degrees all year long.
 

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2 is great for DIY if you pay attention to how you do it
Option 3... might as well hire a pro as the cost of materials would basically be what they would charge you to do it
Option 1 - if done properly, it can be the best option out there - depending on your location you are looking at 3+" of closed cell foam. With that I have seen plenty of bad jobs so for my own place I would probably DIY it unless there was other work to be done to
 
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