Q&A / 

Basement Insulation Tips Video

Hi, I'm Tim Carter and I'm here at a new home construction site in New Hampshire. We are down in the basement to talk a little bit about basement insulation. Look at this.

This is the poured basement foundation wall. It has damp-proofing and even water-proofing on the other side. But concrete can hold water for a long time. And in the Northeast, the ground gets cold and can actually freeze almost four-feet down. This causes the concrete basement wall to almost become an ice-cube. This radiates the cold inside, so you want to stop that.

Two things. First, if you insulation using a solid foam (in this case, 2-inch of rigid closed-cell foam insulation), it acts as a really great water barrier. And it does it from both directions. In case water vapor comes from inside the basement and would touch the bare concrete wall, it would form condensation. That would be the fuel for mold and mildew. If the concrete has water in it, this type of insulation will stop the water vapor getting into the basement.

Secondly, this type of insulation should go all the way from the slab to the top of the concrete. Once the 2x4 wall studs are installed tight against the insulation, fiberglass insulation will be added between the studs. But first, be sure to use a special tape to tape over the joints where two pieces of the rigid foam meet. The tape will be made by the foam insulation manufacturer so that it will stick to their foam.

One last thing, this particular rigid foam insulation sheets comes tongued-and-grooved. This interlocks with the next piece of foam, creating a tighter seal. Insulate your basement this way when you build or remodel.

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6 Responses to Basement Insulation Tips Video

  1. Hi Tim,

    Question on placing insulation panels on basement walls. I painted my walls with latex DRYLOK. Is it okay to put the insulation panels on cynder block that is painted? I wanted to make sure the glue used in securing the insulation panels would stick to he painted walls.

    I live in western PA and am not sure about adding insulation to the walls for may basement remodeling project. I'm reading I should base on moisture alone but need to verify the painted walls won't be a problem.

    Thanks in advance for your advise!
    John

    • John, your question requires lots of typing, plus I have some questions for you so I can give you the correct answer(s). I only do pithy answers here in the comment section. If you want to protect the investment you have in your house and not waste time or money *hoping* you make the right decision, you should talk to me on the phone for just 15 minutes. It'll be the best investment you've ever made in your home!

  2. My basement foundation is the same poured concrete that you show in your video. The only difference is where the wall meets the floor. The basement has French drains, so there’s a ¾ inch gap between the floor and the walls to allow for any seepage to flow down the walls and then run under the concrete floor. The surface of the floor remains dry, while the drain tiles that the water to the sump pump. If I installed ridge foam panels on the walls, could they be glued on with construction adhesive running vertically along the boards to still allow for drainage between the wall and insulation? I would also like to frame in the basement with metal studs, but can’t envision how I would box out 5ft. wide soffits that would cover the I-beans and the air ducts. I live in the Chicago area, to give you an idea of the climate.

  3. Hi Tim

    My house was built in the 1950’s, so it’s time to refinish my basement and insulate it in the process. I live in a northern climate with cold winters. Because of infiltration problems around 5 years ago, I had the entire foundation dug-up in order to waterproof, seal and insulate it from the exterior, and I added a French drain with a sump pump. In order to insulate the inside now, I had planned on using 2 inch closed cell rigid foam as you describe in the video. A local contractor told me that because of the work I’ve had done outside, I should not place rigid insulation on the inside since this would effectively seal all moisture out of the foundation and stop the concrete from breathing. Over time, this would slowly deteriorate the foundation.

    Your thoughts on this would be most appreciated.
    Thanks

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