What's the best way to seal a crawl space and insulate?
Hi I was wondering what's the best way to seal a crawl space and insulate? Currently it is a vented space. Should the vents be closed permanently? The floor joists have batt insulation in them now. I have a vapor barrier with stone underneath and the radon pipe runs through the space as wel and out through my roof. I was thinking about putting foam board on the block wall and sealing the rim joists. But does the batt insulation stay or go if I do that? Will that help with humidity throughout the home? Will it help with temp in the finished room next to it (split level home). Thanks!
This seems to be a multi-part question in a way, or at least the answer will be – By insulating the crawl space you can treat it like the above heated space and keep it warm. So the insulation in the floor joists isn’t really necessary, but you don’t really need to remove the insulation in the joists as long as it isn’t moldy. Left in place is actually even better as long as it’s in relatively good condition, since you can then keep the crawlspace a little bit cooler and save a bit more eneragy but still have warm feet. Did you see this page? It should have most of your answers -
Insulating crawlspaces as part of home renovation
If you have a vapor barrier on the floor you should be stopping most of the moisture, how humid is it down there? As for venting – its best not to vent crawl spaces, as drawing in hot humid summer air can lead to condensation as it comes in contact with what is often cooler surfaces down there.
And to the point of putting foam insulation on the blocks, that’s not a bad idea but do proceed with a bit of caution, as block walls are not as strong as poured concrete, and you may then be exposing the wall to different conditions than it is used to. If the walls are in good shape – as in straight and not cracked, it should be fine, but if they are cracked at all I would check with a professional first, as insulating it will mean it will now freeze and thaw and be at greater risk of cracking. Read here about what causes frost heave and how to prevent it.
Last point, on humidity -get a hygrometer (moisture meter) and see what the levels are in the crawlspace. It's best kept below 50% Relative Humiity if you can, and a dehumidifier would likely come in very handy down there.