1927 house in Boston. Removed an old 3-season porch and replaced it w/ a new, full 4 season room (1/2 of it will be a bathroom, 1/2 will be a laundry room). New room was built on the existing footings so the room sits about 3' off the ground. There is a concrete patio surrounding the structure, however, the area directly under the new room is dirt. To seal in this crawlspace, the builders framed it in w/ pressure treated 2x4's and plywood walls (then covered w/ cedar shingles) that come down and meet the concrete patio. They did build a small hatch so we can get in and out as necessary. Because of the cold temperature in the NE (and b/c we will have pipes running to it), were were going to insulate the walls and ceiling of the crawlspace. Also - I was planning on sealing any areas where water / air could get through (in heavy rains, water will run towards the structure - so if the area where the wood meets the concrete isn't sealed tight - water could leak in and get on the dirt floor). QUESTIONS - Do I need to insulate the walls of the crawlspace or is insulating between the joists of the floor sufficient? We do have a basement window that opens below this new structure that I could keep open to let warmer basement air into the crawlspace - should I? What can I use to seal the small gaps where the concrete meets the wood that will keep water out? Is it bad to seal the area entirely? While I am trying to keep it as warm as possible, I also suspect I may need some ventilation (soil gases, musty smells??). Also - Do I need any additional type of vapor barrier to protect the flooring/joists/insulation above?
Help - Please.
The vapor barrier you need is just a 6 mil thick plastic that is applied over the dirt. I would just insulate between the joists and leave the walls bare. Some type of hydraulic cement might work for sealing the exterior gaps. It hardens very fast, so mix small amounts as needed. If your concerned about Radon gas, the only real way to tell if the Radon is high is to have the soil tested. leaving the window opened that you mentioned sounds like a good idea. The crawlspace needs to breathe. Good luck,plumber Tom