How do you fix high humidity levels in a basement?
Good morning,
I bought an older house (built 1965) in September 2018 and shortly after moving in (mid October), I was experiencing extreme joint pains. Strangely, I was feeling pain and discomfort only inside my house, everywhere else I was perfectly fine. One year later, the moldy batt insulation in the basement has been removed and replaced with spray foam insulation; the foundation around my house on the outside surface has been waterproofed (4 cracks were found inside the basement walls) and the grading reversed. I’ve had many contractors come to my house and most of their suggestions have been implemented. Unfortunately, $40k later, the humidity inside my home is still high 50-65% .
Furthermore, a contractor recommended installing an air purifying system, adding additional insulation in the attic and refinishing the walls in the basement to reduce humidity and coldness in my home. Frankly, I am not sure whom to trust anymore, therefore, your guidance would be greatly appreciated.
JR Tadinac
You were wise to remove the moldy insulation and re-insulate, as well as taking steps to mitigate water infiltration into the basement. A house that old would not have any vapor barrier below the concrete floor, so even if you did insulate and seal the walls with a spray foam vapor barrier, it will likely continue to absorb moisture from the ground below and release it into the home. And if it is not insulated, it will of course feel cold as well.
I think the next logical step is for you to put a dehumidifier in the basement. 50 – 65 RH is a little bit high, but with a dehumidifier that you could buy for a couple of hundred dollars I think you could bring it down quite a bit and maybe solve your problems. Due to the natural stack effect, humid air from the basement will rise to the living area, so fix the problem down there and you may fix it upstairs. If you do plan to do further work, we can certainly help you choose the best course of action and if so, here are a few questions we would have if you want to work on it further –
Is the basement floor finished?
Is it used as living space?
How much ceiling height do you have?
Is there a sump pump?
Is there any signs of flooding?
Thank you for taking the time to read and reply to my post. The basement floor / area is not finished, nor is it used as a living space. The height from the floor to the bottom of floor joists is 84 inches. There is no sump pump, and I’m not sure if there was flooding before I moved into the house. However, the home inspector indicated the presence of efflorescence marks on the bottom of the walls in certain areas.
At one point, I was thinking of installing roxul insulation in the floor joist in the basement, but my idea was dismissed. I was told that I should add more insulation in the attic and insulate the walls in the basement. More work is required and my goal is to make the house warm in the winter and humidity free in the summer. Your advice is greatly appreciated!
JR Tadinac
Attic insulation is a good idea, but uninsulated basements are a heat sink, so best is to make sure they are both done. The only reason to insulate the joists above your head in the basement is if you plan to keep the basement at a cooler temperature. If so, then it will work, but with pros and cons however - it's cheaper, faster and easier, but it doesn't do anything to prevent moisture infiltration through the pourous concrete floor. And if you heat the basement then it doesn't serve much purpose at all.
Alternatively, you can consider the basement just part of the conditioned space of the home, and insulate both the floor and walls. Here is a page that may be helpful about how to insulate a basement floor properly. That would help a lot with reducing your heating demand, it would also prevent moisture from continually being absorbed from the ground and being added to the humidity of your home. The reason I asked about head room and how you use the basement is to see if insulating the floor is even an option. if it's 7 feet high now, you could raise it up 4-6 inches and only the tallest of your tall friends will bonk their heads.
As for a sump pump, I have never heard anyone say they 'regretted' putting one in. It's easy and relatively cheap considering the nightmare situations that it may prevent. I would do it, especially if you plan to insulate the floor.