Can you insulate a cinder block basement/crawl space from the interior?
We are in the North, in a climate that freezes over during winter. Cottage is on a cinder block foundation and is not insulated. It will be very costly and difficult to insulate from the exterior, as it is on a hill and most excavation would have to be done by hand.
I'm getting conflicting answers as to whether I can insulate the basement crawlspace from the interior (spray foam or other). The foundation has a membrane around it. The concern of course is condensation leading to water damage in the foundation.
is there any way to safely insulate from the interior?
Yes you can insulate the interior, but it poses a durability risk by leaving the blocks exposed to the seasonal freeze / thaw cycle, so for cold climates its better to insulate the interior whever possible. Here is our page about crawl space repairs as it may help -
How to insulate a crawl space properly
If you are getting conflicting advice, I would think the person counselling you that you shouldn't do it is more cautious and well-informed if I had to take a guess, as apposed to someone who may be just saying "sure it's fine", because they want the work.
Insulating the outside is way better, it keeps the thermal mass of the blocks inside the thermal envelope and it prevents any damage from freezing. To answer more specifically it would be good to know the following:
I would be most tempted to insulate the outside, and how much excavation are you talking about? If you dug 6 inches down you could put EPS rigid foam insulation boards on the exterior and lay a horizontal skirt on the ground and cover it with a few inches of dirt. You don't need to go very deep at all is my point, insulation extending horizontally is as effective as vertically against the foundation wall for protection against frost damage.
Here is an option for exterior insulation, feel free to dismiss it but at least consider it -
Dig it down slightly - 6 inches or even less, attach rigid foam, put a skim coat of parging on the outside of the EPS, lay a 2-inch thick skirt 2 feet out and cover it with dirt. And if you backfill it even more that would additionally insulate it, just be sure to leave about 8 inches of space from the top of grade to the bottom of siding.
I hope that helps a bit, with more information I'd be happy to help come up with the best solution.