Foam insulation is a crucial component of a home’s foundation, and it can be effectively covered using materials such as foam boards, insulation panels, or specialized coatings. However, the materials used to protect the foam can eventually get damaged by lawn mowers, baseballs, or other outdoor elements. To minimize the risk of exposing foam board insulation to the outdoors or leaving it uncovered inside a home, proper installation is essential.
There are 11 different materials that can be used to protect the above-grade portion of rigid foam insulation installed on the exterior of a building. Two main ways to reduce thermal bridging through studs are building a double-stud wall or installing a continuous layer of rigid insulation on one side of the wall. For interior foundation insulation, the safest choices include rigid foam board and spray polyurethane foam.
For basement wall insulation, prefinished foam-insulation products and stone or brick veneers are presentable options for a visible foundation. To keep the foundation warm, a layer of rigid foam insulation on the outside of a poured foundation is a smart move. However, choosing a protective covering for exposed insulation above grade can be challenging.
To cover the protective layer with acrylic parging, fasten the Subterra panels properly and use unfaced sheets or remove the film from the rigid foam board before installation. Closed cell spray foam can also help control dampness on basement walls. Rigid plastic board insulation generally has a higher RSI value per unit area.
To strengthen cement parging on foundation foam boards, use metal or plastic reinforcing, such as a stucco-like “parged” finish.
📹 How to Install Rigid Foam Insulation (Owens Corning Foamular Installation On Basement Walls)
Learn How to Install Rigid Foam Insulation (Owens Corning Foamular) on basement walls with this DIY, step-by-step video. In this …
How do you cover rigid insulation on foundation walls?
Dampproof foundation walls as per building code requirements. Apply a dampproofing layer to the concrete face before installing insulation. Protect the above-grade insulation with gypsum or concrete board, then cover it with acrylic parging. Fasten Subterra panels to the exterior of the wall. Apply foam board insulation on the interior side of the concrete foundation wall, applying a rigid layer of insulation to the inside face.
How do you finish exposed foundation insulation?
The panels shown are not termite-resistant and could potentially allow termites to access the house. To prevent this, some companies offer termite-resistant insulation panels that can be installed on the foundation’s exterior and then coated with a stucco-like finish. The insulation should be installed with foam-compatible adhesive, butted tightly together, and cut to size. Some building codes require a gap between the panels and siding for termite inspection.
After installation, apply a stucco-like finish, such as Styro Industries’ TUFF II Pre-Mixed Coating. Etch the insulation with a wire brush to remove sheen, apply Sticky Mesh HD tape over the insulation, and apply two coats of the coating. If desired, paint the coating with an exterior acrylic paint.
What can I use to cover foam board?
Foam board insulation, while not destroyed by UV rays, can create fire hazards when exposed to interior walls. Most North American jurisdictions require a thermal barrier like drywall to qualify a building for occupancy permits. However, in the United States, foam board products that pass the NFPA 286 test can pass this code standard. Three everyday foam board insulation products perform well when left exposed on the exterior and interior of a wall assembly.
Does rigid insulation need to be covered?
Rigid foam insulation, either expanded or extruded polystyrene, must be covered in a building’s interior to protect it from quick combustion during a fire. This type of insulation is combustible and may emit toxic fumes, which can reach occupants even before the fire. Drywall, either Standard or Fireguard, is typically used due to its low cost and fire-resistant qualities. Other wall coverings may be available but may be more costly and difficult to install.
If you don’t want to fully finish the basement, you can install drywall directly over the rigid insulation and air/vapour barrier without taping or painting it. However, it’s important to check with municipal officials to ensure it meets their criteria and if not, drywall taping and painting can be completed later.
Should I cover my insulation with plastic?
Vapor barriers are essential for protecting exposed ceiling insulation, especially in mixed climates or hot, humid climates. They are typically made of polyethylene plastic and start at a minimum of 6 mils thick. Insulation blankets, made of fiberglass, polyester, wool, polyurethane, or cotton batting, are typically thicker than vapor barriers. The best insulation vapor barriers are made of polyethylene plastic and reinforced to stand up against wear and tear.
For extra protection, choose an insulation cover with mold and fire protection. Americover is a one-stop shop for contractors and builders looking for specialty plastic sheeting products like vapor barriers. They can help find the product for your application, whether it’s covering insulation in ceiling, walls, attic, or crawl space. Consult with a building or safety expert to determine where a vapor barrier may be required.
How do you cover interior foundation walls?
To cover unfinished basement walls, consider various methods such as fabric treatments, peg board walls, wood paneling, paint and parging, drylok masonry waterproofer (tinted), and veneers for the walls (stone or brick). Cast concrete or concrete block basements are durable but not attractive. Cement walls may not be suitable for converting the basement into a lounge or man cave. Dry walling partitions can be time-consuming and financially burdensome.
Other options include paint and expertly built solutions. These methods can transform a dreary basement into a welcoming living atmosphere. When considering basement renovation, it is important to consider the cost of the renovation and the additional costs associated with the project. By considering these methods, you can transform your basement into a welcoming living space.
What do you put over rigid foam insulation?
Rigid Foam Board Insulation is a versatile and cost-effective insulation solution that can be installed in various areas of a home, such as basements, foundation walls, roofs, and attics. It is sold as solid sheets, allowing homeowners to self-install the product in strategic areas around the home. For example, in an unfinished basement, rigid foam board can be installed between exposed studs or along the concrete wall, providing a secure base for finishing with drywall or bamboo plywood.
This insulation is more durable than loose fiberglass or cellulose insulation, as concrete tends to seep moisture, preventing molds and mildew from compromising indoor air quality. Standard thicknesses range from ½ inch to 2 inches, with specialty thicknesses up to 6 inches available for extreme climate homes. The thickness of the board increases insulation capacities, with homeowners expecting between 3. 2 and 6. 5 R-Value per inch depending on the type of foam used.
Can you put drywall over foam board?
It is recommended that some foams, which support combustion, be covered with drywall or fire-resistant material. This covering should be secured with 16″ (400mm) strapping and screwed to floor joists or roof rafters for a practical installation.
What do you cover an insulation board with?
In the context of indoor installations, the use of a fire barrier, such as drywall, is essential for the prevention of foam burns. It is unnecessary to install a vapor barrier; furnace tape can be used to seal joints.
What is the cheapest way to cover interior concrete walls?
The article discusses the cost and time-consuming process of installing sheetrock on cement walls. The cheaper option is to paint the walls any color, while the more expensive and time-consuming option involves creating a stud frame to attach the sheetrock. This requires a moisture barrier or paperless sheetrock to prevent mold growth. Additional tools such as mud, seam tape, screws, and paint are required.
The article also mentions the use of wainscot or corrugated roofing, which can be finished using 4’x8′ sheets cut into 4’x4′ pieces and a 3″ trim board for a shelf. The cement blocks are painted a light tan for a visually appealing look.
How do you insulate interior foundation walls?
Basement insulation is a crucial step in insulating basements, as it provides natural insulation and makes the area more livable. It involves applying foam adhesive to rigid foam, attaching boards to the wall, framing the wall, adding fiberglass insulation, installing and finishing the drywall, and priming and painting the drywall. This system differs from the above-grade floor insulation system, which uses wood stud walls enclosing soft fiberglass insulation batts faced with paper.
However, basement insulation faces foundation walls, which absorb moisture and lose some of its R-value. This results in a breeding ground for mold and other allergens. To install basement insulation, apply foam adhesive to rigid foam, attach boards to the wall, frame the wall, add fiberglass insulation, install and finish the drywall, and prime and paint the drywall.
📹 How To Attach Rigid Foam Insulation To Concrete
If you want to help support Shannon to produce more videos like this, visit https://www.house-improvements.com/donate Foam …
I’m about to do my basement. My question is about sealing the top and bottom. Wouldn’t you want the bottom to be open so if there is any water that may appear can drain out towards possible raised subfloor? Same for the top plate. Shouldn’t we keep the top open so that the wall can breathe and allow for drying out etc ? Thanks
Most articles I’ve seen that use foam board on basement walls (e.g. ThisOldHouse) and manufacturer articles, the foam core is actually a vapor barrier (moisture barrier) as well, eliminating the need for the clear plastic sheeting barrier However, when I look up specs on Owens Corning, their best product is 1.1 which is slightly higher than code “American building codes have classified vapor retarders as having a water vapor permeance of 1 perm or less” so not sure what to believe.
IMO, I rather use an adhesive to hold the rigid foam to the wall before I install the stud wall. No need to put holes in the wall plus its simpler and faster. I also agree with use of rock wool insulation for it ability to not mold if it gets wet and its fire rating. Just my $0.02. Good instructional article. Keep up the good work👍
My house sets on a cement block foundation. So I have a crawlspace that averages between 3 to 4 feet. I did what this article shows to the inside walls of the crawlspace, The outside walls are a stucco, So my question is this, can I do the same on the outside of my crawlspace and then spray paint it ??? Also is this type of compressed blue insulation waterproof. I would be grateful for any advice. I just think this coming winter 2019 to 2020 in western Pennsylvania is going to be crazy cold. Thank you for your time.
Is the foamboard not enough of a vapour barrier if I add the studwall in front of it and insulate it with the batts….? I’m in Northern Nova Scotia and it is rather damp most of the time… Appreciate the product name. I have seen some orange spray foam around a window that I removed. It was more dense than the other products I’ve seen used.. Thank you for your suggestions. Humbly yours, Dber
I like your articles overall. But in this case you have 2 vapor barriers installed; the inside surface of the foam board and then the insulation is behind another vapor barrier, the plastic. I have always thought that two vapor barriers like this is bad idea. If moisture gets between those two vapor barriers, in the insulation, it will be a set up for mold.
Hi Shannon, started to work on my basement and I put R7.5 rigid Styrofoam board directly on the inside concrete wall and sealed all the joints with spray foam and tape. I will be adding R12 insulation between the studs has well. My question is in regard to adding a 6 mil plastic vapor barrier over the R12 insulation. Wouldn’t doing so potentially create a double vapor barrier between the foamboard and the 6mm Polyethylene and potentially trapping some moisture? Perhaps I’m overthinking but would love to have your input on this…..Thx. P.S. Love your articles.
Curious to know if there will be any issues down the road doing this? Like between the foam and the concrete wall.Should a seal be put around the foam or leaving it unsealed on top and bottom allow for some air to get behind foam to keep from having any issues down road?Does it matter depending on hot or colder climates?I was curious also if adding foil on the 2″/4″foam board (one side or both)would help in any way
On cinder block walls I would lean toward attaching the foam with adheisive only. the blocks are generally hollow and can break unless you can drill in the grout line areas . The cost of materials is going to vary by region depending on the foam and cost in your area. Labour will vary as well. Around me this would be about $1 sq’ materials and .40 cents /sq’ labour
Great articles Shannon! Really enjoy them. I was recently perusal an episode of Holmes on Homes, where Mike used 2 inch rigid foam on the walls and 1 inch on the floor. Spray foaming and tuck taping all the joints. He did not use bat insulation afterwards like you did which confuses me. Arent you using two vapour barriers? One with the foam and the other with the bat and poly? The studded the walls after the rigid foam board installation was completed. Thanks.
You don’t want to create a moisture trap with the poly vapor barrier #2. I’ve been instructed previously to use just the foam boards (selecting thickness to the appropriate R value) then simply your framing in front + mold resistant drywall. Batts inside the cavities are not necessary with the exception of sound deadening, even then it’s recommended you use mineral wool vs fiberglass. The Blue studs are a good idea for the framing, I usually go for a treated footplate. Here in northern Canada it goes down to -55C occasionally in the winter months. The ONLY way to insulate a basement is with the foam as shown here or with $pray foam. When the concrete gets that cold it doesn’t matter how tight you think your poly is ANY air that gets behind it will immediately condense against the concrete.
I’m attempting to permanently attach 2″ foam board insulation to new concrete slab. (It’s already “stuck” due to wet concrete being poured up against it) Using tapcon screws and large plastic washers, and have broken two screws already. I suspect it’s because I can’t get all of the concrete dust out. Wish I had known about the plastic anchors…They look easier…although I think I may still have dust removal problems either way. Had to take a break from it yesterday I was so annoyed. Plan to “troubleshoot” tomorrow (pipe cleaners and a vacuum???? air compressor, which I’d have to rent?)
Great article. Using a foam gun makes applying spray foam sealant much much easier and neater, and is more economical- if you’re using a lot of foam sealant, it’s well worth investing in a foam gun. You can find a good gun for $50 or less, and the cans are about $8 or less in bulk. These cans hold much more foam and you don’t have to worry about the can or nozzle clogging. Just always keep a can of foam on the gun and run some foam through the gun at least every other week, and the gun will last many months without ever having to clean it. Using acetone foam gun cleaner actually makes the gun clog faster, only use those when you’re going to put the gun away for long term storage.
I found that applying great stuff to the back of the rigid foam and bracing the rigid to the foundation until the great stuff cured worked for me. No added holes in the foundation and it was a quick and cheap process. I needed the great stuff to seal around the foam so I had it handy. I’ve tried to pull it from the foundation wall and it wont budge. I applied the great stuff vertically up and down the back of the board.
Can I stack two foam boards (2″ thick X 2) directly on each other and glue together using foam adhesive glue, tape seals and spray foam around the edges? Would this give an R20? I don’t need to frame and fibreglass, because previous reno built a false wall 1.5 feet out holding the drywall on. I can just pull off drywall and work behind existing framing.
This wall assembly has a double vapor barrier – bad idea. The XPS foam board is a vapor barrier and the poly is too – with a stud space with batts in between them. Moisture from the interior will get between them and there is no drying potential with a vapor barrier on both sides. I’d ditch the poly vapor barrier.
Well I live in Saskatchewan and it definitely gets cold here in winter. I have never ever heard of such a thing! New homes in my area where the basement will not be finished before the sale of the home must have the basement walls from the main floor down to the outside grade level insulated. Usually a” insulation bag” is used for that, but once the basement is finished into a usable living space the exterior walls are completely insulated and inspected buy the local authorities.
Yes I would insulate the wall cavity with batt insulation as well. Most 2″ styrofoams are about R8 or R10 . If you are in the northern States or in Canada that is really not enough so by adding another R12 to the framing you will have a nice warm basement. Don’t forget your vapour barrier before the drywall goes on. I used “Great Stuff” spray foam but really pretty much any type made for filling gaps and cracks will do. The infloor heat is a great way to go, you will be toasty warm .
What do you do with outside corners? Use foam sealant, tuck tape, or what. Also how small a piece can be added. I’m doin some planning and it looks like I might be need2 inches more than a full panel on one wall. So it makes sense to me to insert a 3 foot wide cut-off somewhere in the middle of the wall rather than trying to add a narrow piece at the end.
Can I use liquid nails and put sheet rock up against Thermax sheathing insulating walls without having to start out my basement I have a long wall and I don’t wanna spend the money to start it out but I just want to put up sheet rock so I can hang a couple of things nothing of major weight it’s more just posters and flyers and random toys
Hey Shannon. I built a 2×4 frame in front of the exterior brick wall in my 2nd floor bedroom in Philadelphia, PA. I was going to just fill the cavities with batts and then I was reading you really want an air barrier and at least somewhat of a vapor barrier between the wood framing and the brick wall. I don’t understand why I can’t use Owens Corning 1/4″ Formular the stuff that comes in 2x4x50′ fanfolds. Could I put the 1/4″ Formular between the brick and the wood framing and use scraps of batt insulation to wedge it in there tight against the brick? Would this not be better than no air barrier at all and just batts alone? I see in your posts that 2″ of foam seems to be a better vapor barrier than 1″ or certainly the 1/4″ I’m thinking of putting in there, but this is also not a basement wall, its on the 2nd floor. I’m also confused about if it’s a good idea to have foam on one side and poly on the other, it seems like that could trap moisture in the wall? And, that orange foam, I assume that is specially made to use with the type of foam (Styrofoam) that you used? Sorry, I have a lot of questions! I don’t like the idea now of using only batts in my wall assembly and no air barrier…
Hey Shannon, I joined the forum and posted a few days ago. I was wondering how you would go about installing the foam board on a perimeter drain in the basement. I’m in the process of finishing my basement in Delaware. I wanted to know if I should put the foam board all the way over top of the French drain and then seal with spray foam?
No, no, do not ever use poly as a moisture barrier inside. It will trap water, even water vapor, and create a wonderful environment for mold to grow. You can spray or roller on Ghost Shield, which will keep water vapor from coming through the concrete, and liquid water from penetrating via capillary action. It will not, however, seal up cracks in your concrete. That takes a whole other set of remedies.
I have sheet insulation 1.8″ thick. I want to put it on my basement walls which are 8″ thick poured concrete. My sheet insulation has a fiberglass type backing front and back. Do I need a vapor barrier and if so is 4 mill plastic good to use. Should the vapor barrier be against the concrete wall or overtop of the insulation? thanks your response is appreciated.
Spray both sides, top and bottom of the foam boards with borax or boric acid before installation if the place could have carpenter ants or termites. They would chew through these foam boards like hot cakes and make nests inside if there is no borax to stop them. This is specially important when the foam boards will be covered by stud walls like the article. For places that have carpenter ants or termites, I also won’t use regular spray foam, because they chew through this too. I would use ant proof spray foam or caulk.
If you get a crack and a leak, how would you even know if you use the foam? If you install a subfloor in your basement and have the foam, you could have water flowing through your basement and never know about it. Is there a solution to know you have a leak if you follow this install? I’ve have a basement without foam, just fiberglass insulation and drywall and when cracks developed, I knew about it because water was on the carpet. In my new house, I want to install a subfloor, how would I know if these methods are used?
I think there are a few things that Shannon didn’t explain that has caused a lot of the debate. 1. ) rigid foam insulation needs to be 2″ thick for a complete thermal break unless you live in a climate warm climate and don’t over air condition your basement. The diea is to have a complete break in air temperatures between the warm side and the cold side of the wall. A combo of air temperatures usually means moisture (hence the article of how to make condensation be directed to the floor. Where I live (zone 7A) anything less than 2″ of rigid foam on the cold side requires a vapour barrier (typically 4-6 mil poly) or air tight drywall coded in a high solid/vapor retardant paint.2.) I don’t recall Shannon emphasizing that rigid foam must be covered by a non-material that is considered non-compostable such as drywall. 3.) The 6 mil poly IF being used on the cold side of the wall should never extend above grade. Shannon hit it on the nail when he said that the wall needed to breath from both sides unless there was a thermal break (which as I mentioned would require 2″ rigid foam for an interior thermal break). If I were to try this method I’d be inclined to have the moisture barriers from grade to and inch form the ground.4.) Most concrete homes will absorb moisture from the exterior unless built to the highest standards. Ground water finds it’s way to the base of the foundation slab and wicks up it if it can’t dry out. I’m not an expert and I have no experience but I think that is what allows me to think outside the box.
My basement has a 4 foot concrete wall with a pony wall on top. I’m looking for info on how to frame over the foam boards on the concrete and tie it into the studs on the pony wall. The top pony wall is insulated, with vapor barrier, in the usual method. Based on your article, I have insulated the concrete wall with styrofoam boards. Could you direct me to a link on how to frame over the styrofoam with studs and tie it into the top pony wall??
Hi Shannon, I have a question about a house built in 1967 with brick on the outside wall. I was planning to insulate my wall that is not attached to another house (corner house wall) and was trying to figure out the thickness of the studs by poking a hole in the wall with a drywall blade. To my surprise I was only able to stab 1.5″ inches deep because that is how deep it is and that is including the 1/2″ drywall. I don’t see any insulation at all through wall when I carved a small piece off and see what looks like cement or cinderblocks. Is this configuration normal for my house of that age because I was under the impression that houses are either 2×4 or 2×6 for living rooms and bed rooms. Initially I was going to use fiberglass or rock wool but I guess my only option is 1 ” rigid foam made by Rmax Thermasheath with R value of 6. Do I need a vapor barrier with 3-6 mil plastic with this type of install or does rigid foam already serves as a vapor barrier?
is it ok to put that styrofoam board directly on to cinder block? My basement is cinder block, then probably like 1 ft or 1 1/2 from that is the stud walls. between that is some sewer/drain pipes around the basement. prior we just had insulation with the paper as the vapor, but due to flood had to rip it all out. now it seems like there is such a better method for insulation, mine as well do it a little better this time.
My mom’s house is in Mexico. And in Mexico, most of the houses are built with cinder blocks. However, she has been having issues with a lot of humidity on the walls inside the house. Can I install this type of insulation in direct contact with the cinder block wall with moisture and then put the wood frame for the drywall?
Good day I have a 960 sq. ft. cinder block basement at my cottage that to insulate. I have already purchased 2 ” rigid foam board for half of it from a homeowner who had product left over. 2′ x 8′ x 2″. I also was given Hilti insulation fasteners (full box of 300) and the bullets for attaching it. I think they are far to aggressive. I’ve decided not to use the these fasteners and go with just predrill 5/8 hole into foam/block and attach by hammering in plastic screws shown in your articles. I may also add a bit of adhesive on the back. I was then going to tape seams and spray foam gaps. My question here is …..because I’m using 2″ board do you think I need to use the bat insulation as well? I was not looking at heating the basement but just to use it as my workshop and storage. Any suggestions? Much appreciated Michael
Thanks so much for your article. You mention stud framing the walls and attaching drywall. I assume this project is for living space in a basement. I am looking to seal off and insulate a “cold room” under the front porch. Can i just attach the insulation and tape/seal it and leave it exposed? The thought was to reclaim the damp humid cold room as a dry storage room. Any thoughts?
I know this is years on, but would this solution work without a finished framing over top of it? I have a split level house and the garage brick walled half underground. I wanted to insulate the two exterior facing walls and don’t really have any need of for framing it or going further. Since there’s an HVAC vent going in to the garage already, I’d like to keep it closer to the house temperature. Also, in this case, would silicone caulking work in place of closed cell foam in order to seal the gaps? I figure it would be more aesthetically pleasing since I’d probably paint over or something so it wouldn’t just be foam board.
If your rigid foam insulation is “acting as your moisture barrier” there should be no need to add another moisture barrier in the form of the clear sheet vapor barrier. Installing two vapor/moisture barriers on the same wall can/will create something known as a ‘mold sandwich’. I’d suggest anyone interested in doing as the article suggests should do their own research before moving forward with their project.
Having a tough time finding information on how to frame and insulate when there is septic system piping running across the wall. In the NH town I live we use individual septic systems, no town septic. There are 6″ pipe that go across the walls for sewage discharge. Questions: Is 2″ foam insulation attached to the cement walls enough, or do I need batting in the frame also? Second, the framing will be 6″ away from the cement walls because of the pipes. Any special considerations that I need to worry about?
Great article! I Just gutted my den and found lots of damage to my moisture barrier. it looks to be nothing more than very thick aluminum foil. The house was built in the 70’s so I guess that was code back then. I have a brick house and behind that damaged barrier was brick and mortor . Can I replace that old school aluminum stuff with the rigid foam or should I hunt around for that same type of moisture barrier?
I’m not sure how I feel about this advice. Basement walls are notoriously humid (in most of the northern hemisphere) and adding a vapor barrier on the inside practically guarantees mould growth between the concrete wall and the foam. The concrete wall needs breathing, so some amount of heating is unavoidable, I think. And I am pretty sure there should be a “breathing gap” between the concrete wall and the foam/EPS/XPS.
Shannon, I have been perusal your articles for about 8 years now and have remodeled nearly every room in my house with your help. I have a somewhat unique project that is related to this article. I have a room off of my basement that is underneath my front porch. It has four concrete block walls with a doorway from the basement. The ceiling of that room is the floor of the front porch, which is 4″ concrete slab. The room is not heated but because it is underground, so it never freezes but does get down to about 36F (2C). When the concrete ceiling is colder than that I get frost and condensation on the ceiling and it drips down. I plan on gluing 1″ (R-5 value) foam board to the ceiling. Is this a good solution? Your opinion would mean so much to me.
+houseimprovements you said the foam acts as vapor barrier as well… then you said you’re using the studs with normal insulation I assume fiberglass with a vapor barrier on top. isn’t this counter productive and incite mild grow on the fiber glass since it will be trapped between two vapor barriers where moisture will be trapped?
Ive seen other articles where they used a based moister barrier of some kind of fabric instead of this styrofoam. Do you have any comments on that type of installation? The reason that i am asking is bc my basement is already framed so it would be quite a bit of work to try and slide these styrofoam pieces underneath the framed wall.
Hi, Wondering if I need to insulate a framed wall that I will be putting all around the outside wall of my basement.. Two inches of Ridgid Foam Board… A 2″x4″ studded wall. Should the studded wall be insulated? I intend to drywall the inside studded wall. I installed pex pipe in the concrete floor on top of a two inch thick foamboard with wire mesh for an infloor heating system. Could you let me know the name of that foam crack sealing product you are using in your article. Thank you Dber
I have a kitchen above ground with one wall to outside, I want to insulate it with rigid foam. The drywall was attached to 3/4 inch wood slats. I want to add one more layer of wood slat over the existing one to be able to put 1 to 1.5 inch rigid foams behind drywall. No room to put the rigid foam behind the slats. The wall is brick and block construction. The house is in northern Virginia. Why should the rigid foam be sealed the way you have done? Any reason? Thanks!
I read your using 1″ foam there, what length of plastic anchors are you using? And where can I find some of those anchors at?……I plan on doing our basement in the near future and will use this anchoring method, because using just that “special” foam board glue can get pricey on an entire basement. Thanks for all your great informative articles…..
Great vid .. but question … won’t this create condensation between the wall and insulation overtime leading to weaking the mortar making it fall off ? .. hmm looking foward to insulate my brick basement …but not sure about this… other than that allways see your vids and they r all really helpfull.. thanks Shanon
Hi, I want to install this rigid foam in my basement, but I have a drain stack right against the concrete coming from the kitchen above. There is no hope in getting Rigid behind it, so would you just lay some 6mil plastic behind the rigid on both sides and have it behind the drain stack? And then spray foam around the base of the stack or acosti seal? Thanks!
I find all your articles very informative and learn new and interesting methods every time I view them..Working on a 130 year old house with a new basement under it. What a challange…Another question regarding the best choice of foamboard for the concrete walls inside the basement. Is there a specific insulation used or can one use the white “basement plus” or the pink C-200. I will likely be using something in the two inch range…Thank you for your suggestions..Dave
Hi Shannon, I am planning on installing 1/4 fanfold behind the studs to cover my entire finished basement interior wall. I don’t care for the R value as I will be putting Rockwool on top of the 1/4 foam board before I sheetrock. It will be mainly used as a moisture barrier. Can I use the plastic fasteners to cinder block as it would be easier than foam spraying them in place because of the beams in the way? Also I have French drains installed with a few inches of dimple mat coming out of the ground. Should I install the foam board up to the drain mat or should I go down to the wood plate?
Hey Shannon, First of all your articles are PERFECT! Second Im in the process of finishing my garage. I was just going to frame and add batt insulation but now after seeing this article I’m worried I have to drop another couple of hundreds of dollars to add the foam. Is it necessary to add foam over cinderblock walls?
What I don’t understand after perusal every Foam basement article is that, they are all saying ” Careful!!! use tape and poly sheets to air tight the whole room.” and yet they all perforate the foam, polysheets, tape and any other airtight precaution with screws or nails. what’s the deal yo? the water or vapor will wanna pass through those hole. Another thing is that nobody is building the structure the same way in all articles I’ve seen. it’s like there is no main guide line. I’m an engineer who’s new to renovation and find it a little not well organised. You guys need to get your shit together and use the same method.
When My home was built, I had a room put under the back porch with an insulated door into the basement. This room will be used for a root cellar. There are two vent holes to the outside, one to bring cold air in, and one to vent the warm air out. I plan to use a fan to pull the cold air in and the hot air will naturally vent out. The walls are poured foundation. I plan to insulate the inside with 2 inch thick blue foam insulation to withstand moisture as this will have fairly high humidity. I’m planning on painting the foundation walls with mold and mildew killer primer, install the foam board and tape it with adhesive, tape the joints, then paint the foam board with the same primer. The insulation is needed to insulate the root cellar from the basement foundation walls as they act as a heat sink making it hard to regulate the temperature of the room. Do you think my approach is sound? Are both coats of mold and mildew primer beneficial? Good article!
ANSWER: “For unfaced insulation, the permeability is a function of the material thickness. In general most product manufacturers list the permeance of the material based on a thickness of 1 inch. … 1 inch of XPS has a permeance of 1.1 perms (borderline Class II and Class III vapor retarder); 2 inches decreases the permeance to 0.55 perms (middle of the Class II vapor retarder). Therefore, 1 inch of XPS is … vapor semi-permeable, while 2 inches is considered to be vapor semi-impermeable. “
I just bought my first home which is a full block house. First floor exterior walls have no insulation and studs are on the flat, directly against the block. We are looking for a solution to get some insulation in there. Should we gut the 2×4’s behind the sheet rock and put up the foam board, like in the article? We would really prefer not to use spray foam. Thanks so much. I would be incredibly thankful for a helpful response from you or any of your followers. THANK YOU! – Bryan
Hi. I noticed that you left the notch on the bottom of the sheet. In my project I’m using 2 inch thick indulation so I believe I’d be inclined to cut the lap off of the bottom of the sheet before making my height measurement. I would lose some R value if I left it on the sheet. I’m not in favour of drilling holes into a concrete wall that will be below grade. With my luck I’d end up having a leak… Glad to see that I can use an adheasive and your suggestion regarding the proper one for foambord
I’m surprised you used plastic sheeting for the walls before your drywall. You should have skipped that and also not insulated the 2×4’s at all. Plastic sheeting is almost impossible to install perfectly as just one pinhole will allow air in and trap moisture. (I thought people stopped using that stuff) You use a dehumidifier to control any summer humidity issues. But humidity should be less with rigid foam inside and (hopefully) you poured the concrete floor on top of rigid foam also, or if not, you should do that on top the floor before setting your studs. Of course, you also need to consider that if you insulate against a basement wall inside, you should have an air gap on the outside for drying….so I hope you have the “dimpled’ hard plastic on the outside to prevent ground/water from touching it.
Hey In my basement I have metal studs they are about 1 inch away from the wall at the top but at the bottom of my wall ( old basement concrete block). It comes out a bit and behind the stud I barely have any room maybe for a sheet. Basically can’t fit the rigid board behind it. Can I spray foam behind the studs and just leave spaces between each rigid board? Combine spray foam with rigid board against the wall. Thanks for who can answer this! Brandon.
Hope my question makes it’s way to you. I like your article and had two questions 1) Is 2 inch foam boards better 2) Is the vapor plastic barrier needed? I am concerned mold will grow when it’s foam blocks on one side and plastic on the other. I had a house once that was full of black mold because of the extra plastic sheet barrier. Thank you
Hi I want to install xps foam on the roof and walls from the outside. My house gets really hot in summers and I want to insulate it to lower the temperature inside. How do I do that? If I install it on the wall, how do I protect the foam from damage? Can I cement another layer of thin bricks over the foam? And how should I insulate the roof? I reside in Delhi, India where summers are extremely hot and winters are really cold. I read that xps is waterproof so I guess I won’t have to worry about monsoon season. Please do guide.. Thanks.
Nice article. Quick question. I’m planning on doing this exact same thing in my basement. The question from me is, my walls are bare concrete block right now. I get just a little bit of moisture on the wall in a couple of spots (no standing water or seepage / just visual moisture inside the block). I have a French Drain around and under the house outside and underneath. Will I have to put some sort of “waterproofing paint” on the walls before I attached the rigid foam? Or do you think it’s okay to just foam over it with nothing on the walls? Just curious.
Hi Shannon. Can I using a thicker foam with higher R code? So that I don’t have to do more insulation with batt on top of the foam? Or Can I install stud at the same time with the foam? So that I don’t have to drill more holes and use plastic anchors to hold the foam against the concrete wall? Thanks for your article which is quite helpful.
Thanks for the article Shannon. I’m a bit of a noob, so I may have some silly questions. Am I correct to understand that a moisture barrier and vapour barrier are two different things entirely? Moisture barrier against the foundation to prevent moisture from seeping in from the outside and vapour barrier on the warm side to prevent the flow of warm vapour into the wall? I watched your other article where you had a plastic moisture barrier that went under the base plate and wrapped from the bottom over and on top of the vapour barrier. Which of these two systems do you prefer? How important is the moisture barrier under the base plate (since it’s pressure treated, is it necessary)? If you use rigid foam, do you still add something under the base plate? Thanks again.
My 12 year old house has poured concrete foundation and the basement is unfinished. I don’t have plans to finish the basement but the builder installed insulation has torn away from the anchors and is falling off the walls in some sections. I haven’t been successful in re-anchoring the original insulation and I don’t want to frame out the basement right now. Should I replace bare concrete sections with foam board? If so, should I go ahead and replace all of the original insulation or leave the sections that are not falling down alone? Also, what is the best method to attach (anchors or adhesive) for fairly smooth walls?
All of this is great, but if you do not have the proper barrier over the exterior surface of the concrete, it will always transmit moisture directly from the soil, through the concrete, and into the interior side of the concrete wall. Thus you’ll always get moisture, and mildew/rot if you drywall. That’s why you’ve seen Mike Holmes excavate countless exteriors of basements down to the foundations in order to apply sealants and barriers to the exterior basement walls. Without proper WRB on a building you’ll always have problems.
So your code does in fact approve insulating from the main floor to outside grade which is usually about the top 1/2 of the basement wall but I am astounded that Saskatchewan Code approves insulating the entire wall from top to bottom. I’m in northern Ontario & the destruction I’ve seen caused by this practice tells me that your local authorities have no experience. Mind you, pressure treated basements are the exception in Ontario. But block and poured, never. Thanks for replying.
This idea is based on the principle of beer cooler. You have the foam insulator forming the thermal brake between the cold outside wall and your warm inside wall. I’ve read up on this for my own basement and it seems a difference of opinion between building codes and engineering concepts. Again if you want it “legal and signed by inspector” you have to succumb to the normally “out of date” building codes, i use this as tongue-in-cheek. I’m not a builder, simply a handy DIY’er and maintain/renovate my own properties, I do not know building codes as a rule but I guess the thicker the better. The code is there to create a minimal standard to follow and I generally check with the local authority for guidance when working on such installations.
In a cold climate where frost is a problem, 60 years of observing other people’s mistakes has shown me that if you insulate a basement all the way to the floor, your basement walls and perhaps even the foundation will fail. In Canada most building codes allow insulation only on the upper 1/2 of a basement wall so that heat can move through the concrete and prevent frost from encroaching against the basement walls and breaking them. So I’m presuming frost is not a problem where you live?
The insulation should be on exterior wall, not inside. Even every one do it opposite. New code have smartened up and required insulation outside. Look at it the way of where you want cold to be, under the wall in the corner potentially causing condensation problems at the floor level or cold can stay outside the concrete.
Thanks for the great how to article! I had one question regarding prep for the wall. We have an unfinished wall, and the basement doesn’t flood or appear to leak anywhere. Before it gets covered with foam, then framing, etc do you think it’s worth it to DryLok the wall? I previously owned a home that had water issues, so I’m a bit of a worry-wart with basement moisture!
Another article misleading people into believing that there is such a thing as “cold”; there isn’t. Heat transfers from warm to less warm. No such thing as cold migrating into a warm space. In a basement there is very little air moving through concrete so, considering the FACT that there are only 3 types of heat transfer, conductive, convective and radiant, which ones will all your insulation mitigate? Probably only conductive but then, doesn’t a simple air space accomplish that?
Hey Shannon, was wondering your comments on this “grid system” in a “This Old House” article: How to Frame Out Basement Walls Are the advantages to framing with the way you’ve shown, versus the “grid system”? The grid system seems like it might be less work, but I’ve never seen other do it, so I am a little wary. Love your articles!
Hi Shannon! Nice article as always. I got few questions. I have a partially finished basement which I’d like to renovate. I live in MN so we get really cold winters similar to you guys. I am thinking of using the 2″ rigid foam. The walls are concrete blocks and they are painted. I would like to save space and not use 2x4s. * Would it be ok to use furring strips or 2×2 instead. I guess in case of the furring strips, it needs to be attached to the foam directly rather than the concrete. Does this compromise the seal? * The ceiling is already finished with glued tiles. Would it be ok to attached the foam boards up to the ceiling and fill the gap with spray foam? or do I need to take a part of the ceiling out? I can see that the spaces between the joists were insulated with fiberglass insulation (Basement is partially finished. This is how I think it was done based on the unfinished portion) * I have 3 exterior walls that I’d like to insulate. There is one interior wall with wood paneling. Would it be acceptable to run the foam board up to the wood panel and seal the gap with foam spray? Thanks!
So 2 vapor barriers. Way to go! Not. (You now have a trapped airspace. In a basement no less.) Think bigger picture. Do something that will last. Do something that will be safe. Concrete wall will still absorb moisture from the outside. Moisture will condense. If no heat can get to the moisture, the wall can’t release moisture. Wet wall will eventually crack because wall will freeze even more now that you have insulated the inside. And when it cracks, the moisture will condense at some point and come inside. Ever seen mold in foam? Even if you do this stupid installation; Why waist time drilling whole’s in foundation wall when there is adhesive for this (even 1 year ago). To do a job right and that actually makes best sense is to install rigid foam on the outside of the foundation wall. (Moves dew point outside of the building) Cold climate research says 2/3 of R value insulation should go on the outside but I think that ratio and Thickness of Rigid foam depends on Homes climate zone. Am tired of seeing this BS, wake up, stop eating GMO food and protect your brain from EMRadiation.