Insulating A Finished Basement

By Todd Fratzel on Basements, Insulation

Insulating Basement Walls

Basement Wall Insulation and FramingInsulating basement walls properly is extremely important if you want to enjoy your finished basement investment. Every year thousands of basements are finished with poor insulation details that lead to mold, mildew and moisture problems that render the newly finished space un-usable.

One of the most popular topics on this site has been how to insulate a basement. Insulating basements walls isn’t that difficult once you understand a few basic concepts.

Moisture Is Present In EVERY Basement

First of all you need to come to grips with the fact that every single basement has excessive moisture. Moisture is present in ALL concrete and block regardless of it’s age. The micro-structure of concrete looks much like a sponge and it holds on to moisture throughout it’s life. The key is to always assume concrete (or block) is fully saturated with water. Even if your basement appears super dry I can guarantee there is a significant amount of water and water vapor in your foundations walls and slab.

Check out my Video On How To Insulate Basement Walls for additional information and tips.

Avoid Fiberglass Insulation In Contact With Foundation Walls

Fiberglass insulation is cheap and readily available and often used in poorly insulated basements. Fiberglass insulation is probably the single biggest cause of moldy basements today. Fiberglass insulation is nothing more than a ready and willing sponge that will soak up every ounce of water in your basement and promote the growth of mold and mildew. There are some exceptions to this rule which I will point out but it’s extremely important that you not use fiberglass insulation in direct contact with your foundation.

Expectations – Be Honest With Yourself

Not every basement is suitable to be finished. Often times I see basements that are finished off and they had zero chance of being successful finished space. If your basement has flooded in the past, or your basement is wet on a regular basis it’s not really a great idea to finish the space. You really need to be honest with yourself and only finish a basement if it has a history of being dry (no standing water, no visible puddles). Of course if you take the steps to correct past flooding issues (better site drainage, sump systems, gutters, etc) then it might be possible to successfully finish your basement. The bottom line is don’t waste your money and time if you have a questionable basement.

Vapor Barriers

There have been tons of questions about whether or not to use a vapor barrier. The discussion is complicated so we wrote another article about the topic. Please check out: Vapor Barriers For Basement Insulation.

Basement Wall Insulation Details

There are several good ways to insulate basement walls. I’m going to list them in order from most expensive/most effective to least expensive/least effective. It should be noted that even the last option works quite well even though I list it as the least effective.

Spray Foam Insulation

The best approach to insulating basement walls today is the use of spray foam. Spray foam is sprayed directly onto the concrete (block, stone or masonry) wall, sill plate and rim joist. The spray foam completely encapsulates the concrete and effectively insulates the wall while locking out moisture and creating a great vapor barrier. Spray foam i s the most expensive running as much as $3 per sq foot installed.

Rigid Foam Board

Using rigid foam board (read more about Foam Board Types and R Values) is an excellent alternative to spray foam. Foam board is cheaper to install and it can easily be done by a DIY’er so this option is more attractive to home owners that want to save on labor costs. Properly installed foam board (joints sealed) can also create an effective vapor barrier while preventing the growth of mold and mildew. Depending on where you live in the Country you’ll want to install at minimum of 2 inches of foam board and be sure to tape or seal all joints. This type of insulation can be installed for just over a dollar a sq foot.

Foam Board and Fiberglass Insulation

As I said previously there is an exception about fiberglass. One of the solutions that I’ve used several times with great success is a hybrid approach that involves using both foam board and fiberglass insulation. In this approach you use a thinner (cheaper) layer of foam board (minimum of 1 inch), properly sealed, then a framed wall in front of it with fiberglass insulation in the stud cavities. This is the cheapest solution and one I’ve used in my own home. However, this should only be used if your basement is reasonably dry throughout the year.

How To Insulate Concrete Floors

If you want to insulate your concrete floor then the following article is a must read:

Basement Wall Insulation References

Building Science – Basement Insulation – This is a great resource. Building Science.com has some great publications and information on basements.

US Department of Energy – Basement Insulation – This is also some pretty good information minus the detail with batt insulation in direct contact with the concrete.

About the author

Todd Fratzel

I'm full time builder for a large construction company in New Hampshire. I run their design-build division that specializes in custom homes, commercial design-build projects and sub-divisions. I'm also a licensed civil and structural engineer with extensive experience in civil and structural design and home construction. My hope is that I can share my experience in the home construction, home improvement and home renovation profession with other builders and home owners. I'm also the Editor-in-Chief and Founder of Tool Box Buzz. Please feel free to contact me if you have any questions, suggestions or you'd like to inquire about advertising on this site.

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66 Comments

  1. Mike L. - St. Louis, MO says:

    This is great information, however I have a question that may be insulation related.

    We had our basement finished earlier this summer. The basement was nice and cool all summer and everything seemed fine. Now that we are starting to change to fall/winter and we have changed over to Heat in the house, the basement is easily 10 degrees above the rest of the house (eg 69 degrees upstairs, 79 downstairs). When I asked my contractor, he too was perplexed. We both have heard about cold basements not too hot. It is around 800 sq ft of space, with 2 large rooms connected by a small hall, 1 small 3/4 bath and 1 small enclosed office. We have 5 vents and 2 cold air returns. All vents are closed. We have some electronics, but not enough to produce this much heat.

    I am wondering though if it is warm due to the fact that I had him insulate the ceiling in a portion (300 sq ft) of the basement. I am wondering if the 8 recessed cans are producing heat that the insulation is holding in the room.

    Any thoughts?

    Thanks,
    Mike L.
    St. Louis, MO

    • Todd says:

      @ Mike L – Where is your furnace located? Many times when A basement is insulated the heat from just the furnace can be enough to heat the space. If you’ve done a great job insulating and the furnace is giving off a significant amount of heat then it’s possible that the temperatures are rising from that. In that case you might want to remove the ceiling/floor insulation which will allow more heat to radiate to the floors above.

  2. Micah says:

    Mike, I put 10 cans in my basement and we noticed the same thing. We also noticed our electric bill jumped.

    If your basement is well insulated, 8 can lights can definately make a differance in your basement temperature… and it will show on your electric bill. You basically have installed an 800W space heater in your basement (8 cans x 100W bulbs).

    We solved our problem by using dimmers with the lights. You could also try CFL’s but if you have dimmers be aware not all CFL’s will work with them. Your basement will be cooler again and your electric bill much lower.

  3. Randy says:

    Hey guy, I’m doing the foam board(Taped and sealed joints) with a 2X4 wall in front filled with fiberglass. Do i still need poly over the 2X4 wall or will it trap moisture in the wall?

    • Todd says:

      @ Randy – It depends on how thick your foam board is. If you read past comments you’ll find quite a bit of info on that subject. It also depends on what part of the country you live in.

  4. Randy says:

    Todd, I used 2inch foam board. Why would you not want to vapour barrier over the fiberglass?

    • Todd says:

      @ Randy – With 2 inches of foam, properly sealed, you’ve already created a vapor barrier and the 2 inches of foam means the foam surface will not be cold. If the surface closest to the warm side is not cold, water vapor will not condensate. Therefore it’s ok if warmer damp air hits the foam. This way you’re not locking in moisture between the foam and drywall.

  5. Rob A. says:

    Hi Todd.

    I was planning on using your procedures you listed in the “vapor barriers for basement insulation” article.

    I would be installing the 1 1/2″ foam then framing directly in front of the foam. You had mentioned leaving a one inch air space around the studs.

    What is the best way to adhere the foam to the wall?? I was going to use an adhesive and then was hoping to use the framing to help hold the foam in position, but if i leave one inch air space i would need another idea.

    Can i also wall anchor the foam in place with screws??

    My township also requires horizontal and vertical fireblocking. How do i incorporate this into framing and insulating article instructions??

    Note: I am not covering the ceiling in my basement as that would make the ceiling too low, so i’ll leave it exposed and paint it instead.

    Thanks for your help.
    Robert.

    • Todd says:

      @ Rob – We typically use an adhesive specifically made for foam board. The key is to put the adhesive on the foam and let it sit for a few mins before you apply to the wall. That allows a skim to form on the glue and it sticks better to the wall. I’m not sure the fire blocking is applicable in your situation. It’s typically applicable with balloon framing which you will not have in this situation. It’s best to check with your building inspector ahead of time and find out what he/she wants. Good luck.

  6. Stephen says:

    Hello
    I have a home with the ground floor is half buried underground.
    I have problems of humidity in the summer when warm air enters the house and hit s the cold walls.
    I have a limited budget and limited space.
    What do you recommend as a solution?
    Can the walls be studded out with 2×2 instead of 2×4 to conserve floor space?
    Can you end a response to my email/
    Thanks
    Stephen

    • Todd says:

      @ Stephen – Part of the answer really depends on where you live. Having said that I’d recommend you install 2 inches of foam insulation board, tape all the seams well, then if you’re really worried about space you can actually use 1×3 strapping, attached over the foam using power actuated fasteners. Then you can drywall over that. The only issue you might have is hanging cabinetry or something from those walls. Good luck.

  7. stephen says:

    Todd
    thanks for the help
    How do you hold the 2 inch insulation to the painted concrete wall?
    Do you glue it?
    Can you recommend a non-toxic glue ?(I live in the basement)
    Do you shoot a fastener through the 1 x 3 and the insulation?
    Will holes from the fastener in the insulation ruin its insulating effect?
    thanks again
    Stephen

    • Todd says:

      @ Stephen – We use foam board adhesive. There are several on the market and they are typically located near the caulking products at most hardware/big box stores. You can shoot the fasteners directly through the strapping, frankly I don’t think it will have that much effect on the insulation value.

  8. stephen says:

    Todd
    Thanks
    Hey I have been able to pick up a roofing type foam board for a steal.
    It is 1 1/2 inch and has a fireproof paper on both sides.
    Do you think this will work well in the basement ?
    Thanks again
    Stephen

  9. stephen says:

    Todd
    Cannot find any name or logo on the foam board
    It goes on flat roofs
    I was told it is about R8.
    It is beat up on corners and we are having trouble making it a seal against the wall
    Can we put a layer of plastic over the foam board to seal it?
    Or will this cause problems later
    Thanks
    Stephen

    • Todd says:

      @ stephen – I honestly don’t think this is a good product for this use. If that paper gets wet (which it will in contact with concrete) you’re going to get mold.

  10. Mike C says:

    Just finished building a new home, and the insulation company told me to NOT insulate the basement walls in a finished area where the poured foundation walls are completely below grade (rooms under a 4 car garage). They would have made more money insulating these walls, but they said since they are 100% below grade it was not nesessary. The walls that are above grade are insulated. Sounded crazy to me, but I took their advice. If it would be necessary to insulate the below grade wall now (studded with drywall – open at the top because of a future suspended ceiling), should I have insulation blown in or just leave it un-insulated since is is below grade.

    • Todd says:

      Mike – First of all some of this depends on where you live. However, I would not have made that recommendation and frankly I think it’s poor information. A below grade foundation wall will be cool (around 50 degrees) and full of moisture (throughout it’s life span). Because of both issues it’s very important to insulate walls properly before framing in front of them. By framing a wall in front of them you are ensuring a cool, damp environment for your framing materials and wall materials.

      At this point you’re limited in options. I wouldn’t recommend blowing in insulation up tight against the foundation wall as it will absorb moisture. Any way to move the walls, insulate and move them back without completely destroying them?

      • Mike C says:

        It is a new home, and I hate to tear off the drywall to insulate the walls. The un-insulated wall is about 48 feet long. I really don’t heat or air condition the space (I do have a separate propane furnace and 5 ton heat pump for the basement – occasionally will turn on the heat when it gets below freezing. I live in South West Ohio, so it does get cold, but it is amazing that the temperature doesn’t get above 70 in the summer even though there is 130 feet of framed wall (fiberglass insulation)facing South for the walkout area. The basement is used year ’round (my son’s bedroom and bath are on the uninsulated wall and he has not complained).

        I thought the inusulation company was wrong (very old, established company) – I worry mostly about the re-sale of the home – I don’t really have a problem with heating and cooling.

        Thanks for the response. I probably will just leave it be, and when I sell it, I will cross that bridge when it comes up…… The other issue I just thought of – the ceiling in these rooms under the garage is concrete – the basement ceiling is the floor of the garage. Of course the garage is not conditioned space – I guess I should place fiberglass insulation on top of the suspended ceiling – or should I attach foam board directly to the concrete ceiling??

        • Todd says:

          Mike – Sorry to give you “bad” news and obviously money is an issue. A very large portion of basements are still today incorrectly insulated. Fiberglass insulation really has no place in that type of environment unless it’s used in conjunction with foam of some sort. What most people don’t realize is how much water is trapped inside concrete and it will dry towards the finished space and it WILL get trapped in fiberglass.

          We deal with lots of insulation companies and quite a few of them are still mis-informed about how to properly insulate basements. For some more detailed explanation along with hardcore science on the subject I suggest you check out: http://www.buildingscience.com/documents/reports/rr-0202-basement-insulation-systems it’s a well known and respected authority on the issue.

          I hope that helps.

          • Mike C says:

            Thanks for your help. The fiberglass insulation that I have in my basement is only on 10′ wood stud walls – walkout basement. They did not use any fiberglass on the foundation walls. I guess I will attach foam boards to the concrete ceiling in the 48′ x 18′ room and then put up the suspended ceiling.

            Thanks! I will read your recommeded document.

  11. Rob says:

    Todd:

    Great information and guidance. Thanks a million.

    I plan to follow your guidance re. using at least 1.5 inches of rigid foam to insulate my damp basement foundation walls in a Washington, DC row house dating from the 1930s. My foundation walls are damp and once every two years or so we get some “minor” flooding in the basement though cracks in the foundation walls — for example when our neighbors pipes broke. I would welcome feedback on the following:

    1. Am, I correct in reading your advice (i.e. your bullet four — ” …Typically we like to leave an inch gap to allow for air flow around the studs …”) that it is advisable to leave an inch gap between the foundation wall and the rigid foam instead of installing the foam directly on (i.e. touching) foundation wall?

    2. Given my situation and my interpretation of your advice, should I leave a 1/2 to 1 inch gap as well as install the foam and the framing material on top of a composite decking plank placed on the floor (3/4 inch x 3 inches). I would also leave 1/2 to 1 inch gap between the wall and the composite plank as well as route out a few “1/4 inch channels” on the bottom of the composite plank that is on the basement floor to allow water to flow out when we get the next “flood.”

    I know the foam is fairly water resistant and that by putting in “channels” the wall will not be “perfectly sealed” and hence I might get some condensation in the gap, but I assume eventually we’ll get some minor flooding and it would be best to allow said water to flow out into the basement than to sit between the foundation and the foam wall. However, by putting in a few of these channels am I dramatically increasing condensation that might accumulate in the gap?

    Thanks in advance
    Rob

    • Todd says:

      Rob – Thanks for the compliment.

      Over the years I’ve been torn on the whole gap thing. While it certainly can’t hurt I’m not convinced it’s necessary. In some regards it makes it more important to be sure the foam is attached properly to the wall with a good quality adhesive. In your situation the gap probably makes quite a bit of sense if you really think that water will be an issue.

      I would HIGHLY recommend trying to patch those cracks before finishing the walls. You can chip them out and use hydraulic cement to try and seal out the water.

      I would also recommend leaving the paneling/sheatrock up off the floor a bit so that if you get water it’s not soaked up.

      I doubt condensation will be drastically impacted by these details.

  12. Nico says:

    Todd-
    I put up 2″ XPS insulation on the wall which will have a 1/2 inch space infront of it and then a wall with 2×4’s, filled with unfaced fiberglass insulation. I attached the XPS to the walls (cinder block) with 3 vertical rows of Great Stuff Foam. The XPS seems like it adhered like crazy to the wall with the Great Stuff Foam. I read that you recommend a foam glue for this. Am I OK having done it with the foam instead?? Like I said, it seems to have glued like concrete to the wall and I already sealed the connections with Tyvek tape. Thanks!

  13. Matt says:

    Todd,

    Followed your advice. 1 1/2″ foamboard, 1″ gap, 2 x 4 studded wall. I still plan on insulating. My question or fear, is that fiberglass insulation may become moist and promote mold. New construction below grade. Would it be worth the extra money to use the Roxul stone wool insulation other than the fiberglass?

  14. Usog says:

    Dear Todd,

    In 2009 we had a heavy rain that lasted for days in Chicago. Lots of houses were deeply flooded. Luckily, I only had less than an inch water in my basement. Not the whole basement were flooded, though. I am allergic to almost everything including molds. So I had 2 handymen cut the wet walls 2 feet from the floor. And we found one long vertical crack on a poured foundation wall. I think that was where the water came in because that was only the area that had water. Last May, our alley was finally fixed. They installed three huge catch basins within the 450 meters long alley. So, I decided to have my basement fixed. The 2 contractors I talked to suggested kraft-faced insulation batts between the 2×4 studs. But I did’nt agree with them. Can I use rigid foam between the studs. I saw Raylite EPS (1 1/2″x 14 1/2″x 48″) at Menards yesterday. What you think about it? By the way, the finished basement walls are uninsulated even the 46 inches above the foundation which is brick-layered. What do you suggest? And I thank you for all the informations I read in your articles.

    uSog

    • Todd says:

      Thanks for the compliments.

      – DO NOT USE fiberglass against/near concrete EVER. You really need to use a closed cell XPS foam board, tapes and sealed.
      – I do not like EPS, it’s an open cell foam and it can absorb water.
      – Keep searching until you find a contractor that understands the situation with foam vs fiberglass.

      Good luck.

  15. Brian says:

    Hello Todd, great website. I’m in the process of finishing off my basement. I live in the midwest. I’m gluing 1-1/2″ Foamular boards to the concrete walls and rim joists. Two questions, I’m going to be closing off the mechanicals (water heater, furnace and ejector pump) with 36″ door access. Do I leave the concrete wall exposed in this small room? If I were to continue the foam board installation against the wall, there would be no room to frame in front of it.

    Also, I have a 6 foot section directly above the basement where the floor extends 2-1/2 feet beyond the foundation. The builder insulated these joists with fiberglass. I removed to find them slightly moldy. Can I simply remove this insulation and install the foam board? I’m considering gluing 6 pieces together to fill the void, thus creating a 14″W x 9″tall x 2-1/2’deep insulation box.

    Thanks in advance.

    • Todd says:

      Thanks for the nice compliment. First off you can leave the mechanical room as is, but I’d insulation the wall between that space and living space, along with the floor above. Remember that foam board does need to be protected from fire according to your local building code.

      Overhangs like that are best done with spray foam. If you’re going to use foam board, then put one layer at a time and seal it to the wood framing with Great Stuff Foam. Good luck.

      • Brian says:

        Todd,

        I just completed the installation of my foam board in the entire basement (including rim joists). As for the framing, it should be straighforward except for one spot. My stairway leads directly to a basement wall where my landing is currently 39″ deep (after insulating it’s 37.5″ and code is 36″ minimum). So I don’t have much room to spare aside from rebuilding the staircase, which I prefer not to do. I heard someone recommend skipping the 2×4 framing in this section and simply installing Greenboard directly to the foam/concrete wall. Is this correct? It seems logical, but now I am wondering how to attach it to the foam/concrete. Do you drill through it along with the foam and anchor to the concrete wall? Sorry for the long post, but I wanted to fully detail my situation. Thanks in advance.

        • Todd says:

          Brian – In that situation, I’d recommend that you buy the foam board that has 3/4″ deep slots on one face. The slots are made so you can run 1×3 strapping on top of it, shoot it through into the concrete, then drywall over that. The strapping gives you something to screw the sheetrock to. Make sense? As an alternative, you can cut that slot in the foam with a router if need be.

          Good luck.

  16. Usog says:

    Dear Todd,

    Thanks a lot.

    This Saturday we’ll start fixing my basement. I have decided to strip the remaining walls and slide-out the wall-framing so we can stick the 1 1/2 inches thick XPS boards against the (concrete) foundation. However, there is a 1 1/2 inches wide sill that ran along where (part of) the brick wall sat. If we stick the foam board horizontally against the 43 inches high foundation that means there is an extra 5 inches XPS board above it…then stick another XPS board against the brick wall behind that extra 5 inches board and tape all the seams, do you think that works? Also, we will insulate the rim joists with XPS boards and GreatStuff spray foam.

    How about if we use ISO foam boards on the upper portion of the wall or the brick wall?

    We will put back the 2 x 4 stud wall next to the XPS boards leaving the cavities empty and cover it with mold and mildew resistant gypsum boards. Then paint it with 2 coats of latex paint.

    The reason for leaving the stud wall cavities empty is because we didn’t get much rain here in Chicago this year and I am not 100 percent sure if having our alley upgraded and the crack on the foundation fixed wouldn’t cause anymore flooding in my basement.

    By the way, the house has 2 floors and built in 1954.

    So, what do you think about this plan, Todd?

    Again, I thank you.

    uSog

  17. Usog says:

    THANKS A LOT, TODD…FOR ALL YOUR ADVICES. YOU’RE A GREAT HELP FOR US HOMEOWNERS WHO HAPPENED TO CONTACT CONTRACTORS THAT DO NOT KNOW WHAT THEY ARE DOING. I WISH CONTRACTORS SHOULD DO SOME RESEARCHES TO UPDATE THEIR KNOWLEDGE (ABOUT THEIR TRADE) THUS AVOIDING DOING THE SAME MISTAKES AGAIN AT THE EXPENSE OF THE UNKNOWING HOMEOWNERS.

    Am hiring one of the contractors I talked to before, though. But he has to do the work my way. I hope he can learn something from this project as I have learned the correct way to insulate a basement through your website, of course, and the http://www.BuildingsScience.com, GreenBuildingAdvisor.com, and the epa.gov.

    But I have to say that your website is great for someone like me (a DIY) because you made it simple thus understandable.

    Thank you very much and more power to your website.

    uSog

  18. Dustin Tabdt says:

    Have a question, the walls in my basement are already finished studded out with 2×4’s with about 1″ gap behind them, and the concrete. Is it ok just to use 2″ of foam in each gap between the studs? Do I need to tape along the edges between the foam and stud if done this way? Most of the basement is walkout with 2×6 framing, no water issues. About 500sq ft of walls that need this type of insulation. Thanks Dustin

    • Todd says:

      Dustin – You’re not alone, many home owners are left with this exact situation. My answer is always the same: Take the time to “move” the walls and install two inches of foam. You can quite easily move them.

      Good luck.

  19. bogdan says:

    I have a finished basement 4 feet of wall is above ground and 4 feet below ground. The walls are bear.I have a drop down ceiling. Is it a good idea to insolate the whole wall or just the 4 feet above ground wall?

    I would have to use blow in insulation. What type of insulation would you recommend?

    If it makes any differenc I live in Chicago

  20. Katie says:

    Hi, Hopefully this thread is not dead..We are in the process of finishing the basement and are trying to figure out how to insulate. Our basement is underground with maybe the top foot above grade. I understand your recommended method of XPS on the foundation wall, however in my area this is pretty costly. We plan on building a 2×4 wall due to plumbing and electrical, so that in front of the 2 inch foam will take up space as well as cost a significant portion of the budget (not to mention not being able to get foam behind exisiting waste pipes). If we build the wall 1 inch from foundation wall, so that no fiberglass insulation touches the foundation wall, will this not prevent the problems of mold/mildew/moisture? We also always run a dehumidifier in the basement. Thanks for you help.

    • Todd says:

      Katie – The method you describe is exactly why there are thousands of basements in our Country that have mold problems. It will not work and isn’t something I’d recommend in any situation. Concrete walls (or block) are filled with water. That water will leave as water vapor and get trapped in your fiberglass. It simply does not work and should never be done. Sorry, but finishing a basement properly can be costly. I recommend you wait until you can afford to do it properly. Good luck.

  21. Tim says:

    Todd,

    We moved into a home with a finished basement with metal studs and drywall over the poured concrete walls. It is cool (and damp, requiring a dehumidifier) in the summer and also uncomfortably cool in the winter. Any practical way to add closed-cell foam behind the walls? Or maybe the cost of that and the work to repair the plaster are impractical? Thanks.

    • Todd Fratzel says:

      Tim – Nearly impossible to fix at this point without removing the drywall. If you remove the drywall, then you can spray foam the stud cavities. Good luck.

  22. Brendan says:

    I have a framed basement and on one side, the wall is about 4-6″ off the foundation wall. What would be the best way to insulate this space with such a large space Inbetween? Should I use foam board on the foundation wall plus unfaced fiber glass in the wall cavitie? What solution would be best here, also the electrical panel is on this wall so would if I went the foam board route would I just snuggly tuck the boards around the panel?- thanks

    • Todd Fratzel says:

      Brendan – That’s exactly what I would do. You may need to add some blocking to help keep the foam tight to the foundation wall. Foam up tight to the electrical panel.

  23. Eric says:

    My electric panel, tankless water heater(had) and water manifold are mounted directly to a piece of plywood that’s mounted to the concrete. Should I put foil backed 1″ foam behind it for insulation, fire barrier, vapor barrier? Are there limitations to how close the unfaced foam can be to a gas heating appliance like the water heater and furnace? I’d like to do the foam board and drywall the whole way around even though I’m only finding half the basement as living space. The other half storage.

    • Todd Fratzel says:

      Eric – In most cases we butt the foam up to panels like that. It’s usually not very feasible to move the panel, install the foam, and put it back. In most jurisdictions….foam must be protected with some type of thermal barrier (foil face doesn’t count). It’s best to check with your local building inspector.

  24. Armand says:

    Easy question that I didn’t see answered in the comments – if we are buying tongue and groove foam boards do we still need to tape them? Also – we have 1.5″ on the exterior of the basement and would like to finish the interior. Is adding 1″ sufficient in your opinion? We live in Wisconsin. Thanks for the detailed article!!

    • Todd Fratzel says:

      Armand – Yes you still need to seal the joints. You need 1.5″ to 2″ on the inside to be a proper insulated vapor barrier. Good luck.

  25. Kathie Penman says:

    I live in a finished basement but the noise from those above me is quite loud. Is there any way to fix that?

  26. Josh Pultz says:

    I am in the process of Framing My basement… I have to Frame out from the walls because I have a Septic line to deal with. I will be approx 9″ off the foundation wall. What is the best way to insulate??

    • Todd Fratzel says:

      I would still insulate the concrete with foam board, use batten boards to hold it in place….fit tight around the pipe.

  27. Eric Coty says:

    Awesome information!

    When sealing the joints of the XPS, is it acceptable to keep slightly larger gaps in between the sheets and then fill with Great stuff? Or do you still need to use tape on top of that? Is it just best to ignore the Great Stuff altogether and try to butt the sheets up together nicely and then tape?

    Also, my plan was to anchor a 2×4 to the floor along a wall, right up against the concrete wall. Foam above that to the top of the foundation with 2” XPS, then lay 2×4’s flat against the foam from floor to ceiling and anchor them to the wall. The 2” XPS plus 1.5” thickness of the flat 2×4 would match the width of the 2×4 anchored to the floor. Would then attach Sheetrock to that framing. Are there any concerns with this approach?

  28. Jennifer says:

    We are finishing a basement in Denver. I see that the insulation discussion is specific to framed walls with drywall. What if we were not planning to put up drywall, but instead leave the concrete walls exposed and paint them? We will be putting up some interior framed walls with drywall, and those walls will terminate at the cement exterior wall – is anything needed between the end stud and the exterior wall? Thanks.

    • Todd Fratzel says:

      I’d be sure the end stud is at least pressure treated, I’d also use some sort of plastic j-bead on the drywall to make sure the drywall isn’t in contact with the concrete.

  29. Jared R says:

    Is this still alive? I live in a 2 year old home with a finished basement in Philly. It’s extremely cold down there right now and it appears the only insulation installed was in the rim joists (poorly done at that). One wall is about 1′ from the foundation due to the plumbing and mechanicals but is framed and used as storage. The other wall is completely framed but I’m unable to tell if/how it was insulated. We have one duct in the basement, with no returns. Am I screwed?

  30. Jeff Sanders says:

    I have an unfinished basement that I am looking to frame in soon. The walls of the basement are currently covered in a “hanging” insulation. I’m not sure what else to call it. Does that need to come down and then new insulation put up in it’s place or do I just frame next to the hanging insulation?

  31. Cherie Collins says:

    My question is about a new build. We just recently had a house built. Since me closed and moved in my husband had to cut a hole in the finished basement wall. He noticed there was no insulation in the wall. Is this normal for a finished basement to not be insulated?

    • Todd Fratzel says:

      Normal? I’d say it’s not a great situation, I’d check what your contract said. Surely it’s a cheap building spec.

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