What is the best way to insulate a crawlspace to keep humidity down and stop mold?
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什么是最好的方法来隔离爬行空间保持湿度和阻止气味?
Dave Bell
Oct. 24, 2019Last updated: Aug. 7, 2020
I have a crawlspace with 4' concrete walls and a cement floor, insulation between the floor joists and has 3 - vents to the outside. I am thinking of 1" foam boards on the walls, sealing the floor. There is no moisture only when I put a piece of plastic down. Just want to warm it up a little and keep away any smell. Can you help me. I live on Vancouver Island
Unfinished crawlspacesreally are asource of moistureandmold, that’s why its so important to keep the damp down tomitigate heat lossbut alsoprotect air quality. They are also a good source of questions for us! This page below is a good place to start for you -
How to Insulate a Crawlspac and Prevent Mold
An inch of foam on crawlspace walls is good, but 2 inches would be better. Think about the returns – you’ll be doing the same amount of labour but you will double your insulation value. A few questions do come up from this side, what do you mean by ‘seal’ the floor? If it is cement, I would be thinking about laying as sheet of 6 mil poly and then laying insulation boards on top. It’s not the worlds most durable surface, but if you rarely need to walk on it, it should last a long time. That would stop the moisture but also stop heat loss. If you like that idea I’d for sure go with 2 inches, not just for heat loss but for durability, if you do need to walk on it on occasion it will be less likely to get damaged.
Here are a couple of other relevant pages you may want to check out:
And about venting crawlspaces, that can be a problem depending on where you live. The foundation walls will be cool in summer, so drawing in warm air can lead to condensation on those cold surfaces, I’d consider closing it up and running a dehumidifier. What climate zone are you in Dave? That may help us help you more.
Thank you for your response. I live on Vancouver Island and i believe are zone (for plants) is 7 or 8. I had also decided to put EPS boards on the walls, and now maybe on the floor, but do I need to put plastic down as well. Once again thank you
Happy to help Dave. You get a reasonably mild winter on Vancouver Island by Canadian and and many northern US standards, and while the 2 inches would certainly not be overkill, I"m glad to hear you aren't In Minnesota or Winnepeg and thinking of 1 inch of EPS.