Greetings, looking for advice on insulating poured concrete foundation of 1929 school house. 5′ feet below grade, 4′ above grade. Some drainage issues so likely to excavate and install drainage tile at footings and insulate while I’m at it with rigid fibreglass.
What to do on the inside? Insulate the whole wall? From just below grade and up? EPS against the wall, strapped and drywalled? Standoff wall with mineral wool batt insulation? Spray foam? I have read that with draining insulation like the fibreglass moisture barrier is not necessary on exterior wall? Moisture barrier inside up to grade? VDR because of cold wall above grade?
Floor joists are embedded in the concrete, walls are in pretty rough shape from moisture damage, spalling and efflouresence, some cracking
Thanks in advance…located close to Ottawa, Ontario so some pretty cold periods during the winter and warm humid days in the summer
Replies
There are a number of good ways to do it, and I'm sure you'll hear all of them and then some here.
I would highly recommend waterproofing the foundation with that sticky-rubbery-stretchy black stuff on a roll, like the Grace waterproofing material. Run it from the sill all the way down the wall and a few inches down the side of the footing. Then put your stone and drain lines in. You can insulate over the material with a couple of inches of extruded (not expanded) polystyrene. Then finish the above grade part with a finish you like. The waterproofing material will form a moisture break to keep moisture from the ground wicking through the wall.
I think it's especially important to keep your concrete dry and warm because the joists are embedded therein. Effective waterproofing and insulation on the outside is the best way to accomplish this.
Rigid fiberglass is not for direct burial because it will become waterlogged and loose its insulating value.
There was an article recently, I believe in the Journal of Light Construction, that said if you have a vapor barrier on the outside of a foundation, not to have one on the inside also, because any vapor in the wall has to move out to one side or the other. That would preclude an effective moisture barrier from being used inside if you waterproof the outside.
Thanks for reply,
I can't insulate above grade on the exterior as it would alter the existing finish---a parged skirt below brick and 4' high.
I thought that there was a dense fibreglass insulation meant for direct application which also served as a drainage medium.