Last winter, we discovered that the cabinets in the north-west corner of the kitchen were noticeably colder than the room. When we opened the turntable corner storage thingie or any of the drawers, a cold draft blew out at us, especially on windy days.

By taking up the kitchen cabinets, I hoped to also take care of the draft once and for all. The drafty spot is impossible to get to from the basement, because the gap between the first joist and the top of the foundation is only about an inch. This leaves an entire joist bay next to the mud sill and above the foundation completely inaccessible and uninsulated.  Instead of breaking chunks out of the top of the foundation, I decided to go in from above, under the cabinets.

Once we ripped out the cabinets, it was relatively simple to cut a hole in the floor. I first drilled some 1/2 inch holes, and then connected them with a reciprocating saw until I had a hole big enough to stick my arm into and a clear view of the top of the foundation.

Once I had a chunk of flooring out, I realized just how big a problem we had. Not only was the floor 2 inches thick (4 layers of flooring), but the hole in the foundation was at least the size of two quarters and I could see sunlight. There were many loose stones laying on top of the foundation, so my first task was to remove anything that came up easily, then vacuum up all the dust, sand, dead bugs, spiderwebs, and bits of wood that were down there. Once the shop vac was full of crap, I sprayed Dap expanding foam into all the nooks and crannies I could find. I prefer the Dap product to Dow's Great Stuff because it washes off with WATER. Even when wearing gloves, I manage to get the Great Stuff all over my hands and clothes. The only way to get it out of clothes is to immediately scrub it with acetone (nail polish remover). I'll stick with the water-based Dap, thanks - It doesn't expand as much as Great Stuff, but it does a plenty good job.

Before the foam had completely set, I cut bits of pink styrofoam insulation and layed them on top, then sealed the pieces all around with more expanding foam. When I figured the job was well enough complete, I wrote my name and the date on the foam, for future generations, and sealed the hole back up.

As we replace the rest of the cabinets and the stove, I'll repeat the process a little further down the line, until we're sufficiently draft-proofed on this coldest end of the house. There's also a similar situation happening, right under the back stairs - the floor will have to come up there as well.  I wish home builders would think more like ocean-going boat builders.  You need to have access from the inside to any exterior walls or bulkheads, in case of a leak.  In the boat's case, that would be water - air in the case of a home.

I need to research a pourable two-part expanding foam, or maybe a sprayable product for these hard to reach spaces that need to be sealed up completely. I would venture a guess that sealing behind the mud sills could prevent up to 15% of the house's heat loss, simply because of drafts.