Insulating A Basement With Cellulose
Written by Todd Fratzel. 
I’ve written several posts about how to insulate basements, How To Insulate Basement Walls and Basement Insulation. One of the best ways I know how to insulate a basement is using a combination of polystyrene foam board insulation and spray-in-place cellulose insulation.
I get so many emails and questions about how to properly insulate a basement. For me there are really two options. Probably the best option out there is to use a closed cell spray foam insulation sprayed directly onto the concrete foundation walls and a framed stud wall. However, spray foam insulation is really expensive and depending on where you live it may be hard to find an installer. That’s why I like the approach I’ve outlined here using a combination of foam board insulation and cellulose.
How To Insulate Basement Walls
- First of all it’s very important to make sure your basement walls are structurally sound and any cracks that are present are properly sealed.
- Install a 1″ layer of polystyrene foam board insulation from the slab up to the top of concrete wall. Use an adhesive that’s rated for use with foam board. It’s also important to seal all the joints with a tape like Tyvek tape or similar.
- Frame a 2×4 wall in front of the foam board insulation. I like to install a piece of composite decking below the wood bottom plate. This ensure that if there ever is some water behind the wall that it won’t wick up into the framing and drywall.
- Hire a qualified NuWool cellulose insulation installer to use spray-in-place cellulose to fill the 2×4 framed wall.
You can see in the photo all the steps involved. The nice thing about the cellulose is it’s fire retardant and mold resistant. The foam board and taped joints help keep moisture from entering the basement from the damp cold concrete walls. Once the cellulose has dried a bit we’ll be installing a layer of gypsum board to ensure that the cellulose doesn’t fall out of the stud bays as it continues to dry.
Related posts:
- Insulating Basement Walls With Spray Foam
- Insulating Basement Walls
- Insulating A Finished Basement
- Insulating Tools
- Basement Insulation | Spray Foam Installation Video
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Detailed and very helpful information. Thanks for sharing.
These info are very helpful!
But how about the ceiling insulation?
We live in 1940 house in Seattle, WA. We are building a bathroom in half-lit basement. Wondering what kind of insulation we should use for ceiling…
Since there will be water pipes, electrical cables, …etc. We prefer not to use spray-in insulation.
Thanks!
How about ceiling insulation?
We live in 1940 house, and building 2nd bathroom in half-lit basement. Wondering what kind of insulation we should install?
Since there are water pipes, electrical cables, …etc. in the area, we prefer not to use spray-form insulation…
Any advise will be appreciated!
@ Jacky – I would say fiberglass or cellulose. You can install a layer of Tyvek, cut small holes in it, blow in loose cellulose, then hang drywall.
[...] insulation in the stud cavities, it’s fine to use fiberglass or cellulose in this step. See Insulating A Basement with Cellulose and Basement Storage Room for more [...]
For Jacky’s basement check out cellulose bats. They do exist, anything not to use fiberglass insulation! Nu-Wool has cellulose bats.
hope this helps,
cheers,
[...] a framed wall that’s insulated with spray-in-place cellulose. you can read more about how we insulated basement walls with cellulose on a new Energy Star Home at [...]
Todd,
I’m stumped on a few things, and I’m glad that I came across your site.
I want to frame the basement walls of my mid-1940s cape cod-style house, and so I’ve been reading books and gathering lots of information so that I can to make sure that I do it correctly. The last thing that I want going wrong is mold!
So far, I’ve painted my concrete block walls with two – three coats of waterproofing paint and a mold/mildew resistant sealer.
I’ve also installed a drycore subfloor, leaving a 1/4″ gap between the wall and the subfloor material.
The next part I’m not so sure about in regards to vapor/water barriers and insulation. In reading your posts, I have a few questions:
1) Can the polystyrene foam board be installed directly to the concrete wall?
2) Should the polystyrene foam board insulation be sealed somehow at the top and bottom?
3) After putting up the polystyrene foam board, should I still install a 6 mil plastic sheet between the foam board and studs or between the studs and drywall?
4) Should there still be a 1/2″ gap between the foam board and studs?
5) Would it be okay use a thermal guard insulation stapled to the studs instead of using a fiberglass insulation between the studs?
Any suggestions that you offer will be of great benefit, and will allow me to proceed with confidence!
(Ignore question #2 – In reading more of your posts, I found out that I should seal the tops and bottoms with “Great Stuff” or similar.)
David – Thanks for visiting the site. I hope you find it useful and bookmark it for future reference.
1. Yes – Great Stuff Pro works very well adhering it to concrete.
2. You figured this one out!
3. No – If you use a minimum of 1-1/2″ (2″ preferred) polystyrene insulation and seal it properly there’s no need for a vapor barrier.
4. Not mandatory – This is more of a concern when using 1-1/2″ foam plus fiberglass. If you go with 2″ of foam and skip the fiberglass then you can frame it tight.
5. Can you be more specific? Not sure what product you’re referring to.
Good luck!