On the day of the install, the crew will run a hose into the basement that they will use to spray the foam onto the ceiling, rim joist, and exposed walls. Once the foam is sprayed, if there is any excess in the wall cavity, it will be cut so the drywall or paneling can be placed with no problem.
If the walls are already enclosed, the process is similar except that holes will be drilled into the drywall so the foam can be injected into the cavity. Once the foam is installed, a crew member will put a Styrofoam plug into the drilled holes, tape it, and then place a rough patch of drywall mud over it. For a basement with concrete block walls, holes will be drilled in the middle of the wall into the cavities left open by lining up the cores.
Those cores are then filled with foam preventing air movement. A good insulation contractor should offer several services that start with your call for a free in-home estimate and end with a more comfortable basement.
Heat loss in your home could also be due to little or no insulation in your attic. Cold walls, drafts, and high energy bills are also signs you need new or better insulation in your exterior walls. Insulating your entire home with foam insulation can make a year-round difference in your comfort and energy bills.
However, if you can afford the cost and mess then this is the ultimate insulation product. The next best basement insulating method is using foam board products. There are lots of foam board products on the market so I suggest you read Foam Board Insulation Types and R Values for a quick education on the different products available.
The key to using foam board is choosing the correct thickness and sealing it properly to create an effective vapor barrier. I recommend sealing all the joints with Tyvek or similar house wrap tape. This method should NOT be used if you have a history of water, even small amounts. Again the key here is to come up with the proper R value based on local energy codes.
Most references say that you should NOT use a vapor barrier over the fiberglass insulation in this method. 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. The bottom line is not all basements are acceptable for finished space.
The key is using foam insulation effectively to separate the damp concrete or block from framing and insulation products that promote mold growth. I hope this article will help you decide which basement insulation method is best for your home. 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.
Please feel free to contact me if you have any questions, suggestions or you'd like to inquire about advertising on this site. All posts by Todd ». Search for more articles here. Enter keywords like, 'insulation' or 'kitchens' etc to find your topic. Do you know if insulating the basement walls with foam board cuts the humidity level?
I run my dehumidifier throughout the summer and was wondering if insulation would help cut the humidity in the basement. I have an older basement but do not have an issue with water. Humidity is the only issue, and insulating the walls should fix that. Then would finish the walls afterward with the stud wall and fiberglass. How should I seal around the top and the bottom of the finished walls?? I slo have a small window to deal with. How do insulate and frame around this and ensure airtight??
Rob A. Be sure to seal it all with spray foam Great Stuff in a can works very well. The vapor barrier issue is one that really depends on the moisture levels in my opinion. I also have a small window to deal with. How do I insulate and frame around this and ensure airtight?? You can then create a wood or drywall return back to the window sash. Todd, I was wondering what you opinion was for using spray foam in an attic? Our medium term goal is to finish the space, take advantage of the rebates now and insulate it.
Jeff — There are lots of conflicting reports on this topic because of ventilation. If you spray a sufficient amount of foam directly against the roof, the roof becomes insulated enough that ice dam issues go away. I say if you can afford the spray foam go for it. Your approach seems solid. Just be sure your metal studs are not exposed to cold air that can cause condensation problems. If you install the foam board properly and seal it well then there is no need for a vapor barrier. Good luck.
Todd: After reading your article and the building science article a few questions came to mind. Since it is very apparent that concrete basement walls change in moisture level based on seasonal changes every basement not having an outside membrane older houses will have moisture issues.
If the walls are properly sealed from the interior space then how can a dehumidifer help this issue in-between the concrete and finished wall? Has anyone ever examined using a dehumidifer to maintain low moisture in-between the concrete and finished wall wall out inches, moisture resistant batts, vapor barrier with sealed joints so that mold and odour do not occur?
This is where all moisture issues originate in basements. Would using this method simply cause the concrete on the interior to wick moisture from the outside to maintain an equalibrium in terms of vapor pressures. Using this method of treatment would give the consumer the best of both worlds. The intake and return for the dehumidifer would both be sealed into the wall and the unit itself could be located in a utility room etc out fo site but still accessible to empty the pan etc.
Let me know what your feelings are on a setup of this nature. Jason — Your concept certainly sounds good. It really comes down to finding a solution that is reasonably easy to build. Even with properly sealed walls the slab itself creates a tremendous amount of moisture. I personally am not worried about moisture between the concrete and a vapor barrier such as 2 inch thick foam.
Mold needs a food source in order to grow so it seems like a small problem to me. Definitely an interesting idea though. Todd, another quick question…. Smash — I would insulate the bathroom the same way. Just be sure that you seal the foam really well. I typically put the framing up against the foam. Todd, Great article. No vapor barriers.
I am also skipping any framing on the exterior walls, as I have no need for structural support or utilities electric. Does this sound reasonable? What adhesives would you recommend for both against the existing walls and for the drywall to the foam board? Lastly, any reason for leaving a gap at the floor? Appreciate any input! Thanks, Brian. Brian — Thanks for the compliment. The trick is to put the adhesive on the panel, let it set for a few mins until it tacks up, then adhere it to the wall.
Then you can just screw the drywall to that. The gap is important to keep any moisture that might get on the floor from wicking up into the drywall. Thanks Todd! Bottom line is that I can not go any thicker than 2 inch overall. This in addition to glueing the drywall to the foam insulation would hold the drywall in place. Sound reasonable? SHould I put anything between the 2x and the wall?
Brian — This approach may work ok. What is your plan at the bottom of the wall? One important point I failed to mention, this specific portion of the basement wall is only about 12 feet in width. Other surrounding walls will be framed in front of the foam. As far as the bottom, I plan to run the foam as tight as possible to the floor then fill any voids with spray foam. The drywall will be cut short an inch or so from the floor. Brian — Is this going to be a finished living space?
My luck thus far with shooting anything into the old concrete, floor or wall, ends up making a divit more than anything. They supply the risers throughout the house, one of which is nearby this wall. Pipes are 3 and 2 inch diameter. They are far too costly to relocate for the partially finished basement project. Brian — I only asked because I was curious if you could build in front of them and leave an access hole for inspection.
The return pipe is 2 inches away from the basement wall hence the 2 inch maximum new wall thickness and the supply pipe about a foot or so away. Inconveniently located for creating new insulated walls. First of all i would like to say that this site is filled with great information and will be visiting back every so often to see the new post.
Ok now to the nitty gritty. I have been researching about finishing basements for some tme now and have only seen pictures, posts and comments about drying in solid concrete basement wall construction… What about Concrete Block walls?
Can the same techniques be used? Right now my basement is a square hole dug out of the ground with earth on all sides that has a floating slab floor with a drain channel around the perimeter to a corner point where a drain is. This is a 50 year old house, effloresence is apparant throughout the basement.
In the two years that i have lived their i have never seen the drain channel filled with water. Water is present near the drain but never standing… Is the cinder block wall more porus than the slab wall my fear is that the hollow cors in the block are filled with water and i would need to go abvout drying in my own basement a different way.
Does anyone have any thought on this matter? Michael — Thanks for the kind words. Block walls for are really the same animal when it comes to how they perform as a foundation. They may be slightly more porous but the fact is concrete and block both hold a tremendous amount of water. Todd, is spray-on foam insulation a good idea in a basement with laid-up stone walls and dirt floor? This basement is always damp but has had no pools or moisture buildup excepting when we had a federal disaster-class flood in The house is civil war-era.
Lester — Spray foam is a great application for field stone foundations. The foam helps control moisture and also helps keep stones stabilized and in place. Todd, Awsome site. Full of detail and explanation. My question is this….. I am looking to re-do my finished lower level. Currently, it is paneling. I pulled a section out to see what i might find and as i expected, it is a shotty half — job. No insulation. I want to insulate and drywall. I will use foam panel insulation as you recommend but am not sure on the thickness.
I want to achieve the best R value i can with this project. What do you recommend as far as material and will i need to screw the furring strips to the wall or can i assemble a frame? Are there any alternatives to anchoring at the bottom. Im a little leary of putting any type of hole in the wall below the surface line. Currently no moisture problems. House is in Northwest Indiana. Your input would be greatly appreciated. This will give you less than 4 inches. Hello, I recently moved into a 40 year old ranch style home.
It had a couple leaks, one from around the septic exit pipe and one from a crack below a window. The weaping tile around the house was plugged due a very large willow tree located near the house. Since then i have had no leaks except one little one in the cold cellar probably due to a crack in the step above and there is no vent in their.
I now want to insulate my interior walls to an R24 value. I live in Southern Ontario, please help, should I being doing it this way or is there a better way???? Most people take the easy way and ignore that! Todd thanks for the reply, this site is very helpfull. With THE 2 my wall will be very thick by the time iget it too R ALo I am concerned with all the mixed advice on vapour barriers and moisture build up with this combonation method.
What do you think, thanks. STU — You really need 1. Hope that helps. Wow, so your saying with two inches of foam board directly glued against the concrete wall will keep the moisture whithin the concrete and it wont try and penetrate the foam board.
I heard foam board is capable of retaining water. Also with this methed should their be any air space between the foamboard and the bats of insulation? STU — You need to use a closed cell foam product.
One last thing. I was not planning on drywalling it right away and may even used pannelling later on. Thanks again. Wont that 60mil poly I stuck all around the exterior walls help keep moisture our, reducing the need for 1. Also is it ok to just stuff the 6 inch bats into the header? Todd, I see you mention that you usually frame right up to the foam board. But in my case you siad that leaving an air space would be a good Idea. Do you think if I do not frame up to foam that over time the glue adhearing the foam to the concrete will break down and the the foam board come loose?
It really depends on how well the foam board sticks to the wall. Thanks, Ill do that then, Ill check back later to see if you put the name of that stuff on here. First off I want to let you know what a great website you have. It has a lot of quality information. I do have a few questions for you regarding finishing my basement.
So I was going to install that foam board insulation betweeen the furring strips. I plan on putting up a plastic vapor barrier. Do I need to put up tape between the furring strips and insulation, or can I just staple plastic to the furring strips to block out moisture. What are you recommendations? I do not get water in my basement. It has cylinderblock walls.
One more thing. Do you recommend installing insulation all the way to the ground or should I leave a little space at the bottom. If you place insulation between the furring strips and then screw drywall to the furring strips the strips will still be cold. So, the idea is you need to install sufficient insulation to stop that from happening. Insulation should go all the way to the floor. Yes Todd it definitely makes sense.
Thanks for the great input Todd. It will be very helpful. When I put the insulation between the furring strip do you think I should tape, or caulk it to seal in space between the insulation board and the furring strip?
If tape do you think duct tape would work ok? Do you think it is necessary to take this step if I install a plastic vapor barrier and staple it to the furring strips.
I also want your opinion on if I should leave a space between the insulation board and the drywall. Thanks in advance. Be sure to tape all the seams with Tyvek tape. Which method do you think is better installing the insulation directly to the block walls, or just putting it over the furring strips? Any certain type of insulation foam board you recommend for basement walls? Do these really matter, or should I just base my decision on the R-Value?
Bry — Just be sure to get a closed cell foam, EPS is fine. Well I thought I was done with questions. Guess not. Is it a good idea to get foil backed foam board if it is about the same price as a non foil back foam board? If so I am assuming you face the foil side towards the drywall. Is that the case? I had a contractor come out and give me a quote on the drywall, just to see how much he would charge compared to what I could get the materials for.
He said if I were you I would just put the drywall up over the paneling and not even put insulation? I said really? Do you think that is a good idea? Do you have a general idea if I put up insulation how much warmer it might possibly make it. A few degrees? I am going to install carpet also. The paneling does not really feel cold, but the basement floor is pretty cold.
Currently it is about 10 degrees colder in the basement now compared to the first floor. Then I started thinking by the time I cut all this insulation and piece it together between the furring strip is it really going to insulate that well and make a noticable difference? Is it really worth the extra money to insulate?
Bry — These are questions you need to evaluate yourself. Insulated basements are healthier, warmer, more valuable and frankly better for the environment. Paneling is one thing, paper faced drywall in that environment is another….
I had also thought about just putting up insulation over the paneling I currently have down there. Then drywalling. Which way do you thing would be the better way to insulate. Insulate right over the paneling or take down the paneling and install between the furring strips? The furring strips are ran horizontal, so I will have to make a lot of cuts.
Will the insulation lose a lot of its R-Value if I cut the insulation to put it between the furring strips. Putting the foam board over the paneling would be the easiest, but is it as well insulated that way?
Which method do you think would insulate better between the 2 options I listed? Thanks again for all your advise. It is greatly appreciated. Bry — Either method will insulate just as well as the other. You may create a situation where the water vapor is trapped between the paneling and concrete wall. Why is this the case? Can you elaborate? I live in Toronto Area. JeffB — I made the statement because some people finish their basements without fixing the water problem sounds like you have.
Then they are upset when the basement floods a bit and all that fiberglass insulation starts to mold. Todd — thanks for the clarification. I say go for it. Excellent website.
The feet of the foundation that is above ground does not have anything on the exterior walls. Otherwise the floor is poured concrete and runs right up to the plastic at the base of the wall.
Would I install the foam over the plastic and seal it against the floor? Not exactly sure of the floor drain detail…maybe you could email me a photo? Very interesting site, thank you for all the info.
Is this a bad idea? Also, has anyone used or have any knowledge on magnesium board or MgO board instead of sheetrock. There are 2 places that advertise their use one has an all in one system with insulation between 2 pieces of magboard and the other site sells just straight sheet of magboard that can be installed like sheetrock.
Oh yes, there is another question I forgot to ask. Why is this, were there 2 different size blocks used? If I were to use the foam board from the floor up, would I need to fill in the gap of 4 inches wide and approximately 2 feet high, or can I just go straight up from the floor with the insulation board and leave an air gap behind the insulation board? George — No issues with the space, just run the foam up over it. The installation of the product is simple.
I think the market is still tight with few suppliers and that price will come down in the future as more start to offer the product. I plan to finish the basement and I am concerned with the concrete walls that I have had some water leaking problems in the past due to cracks on the walls. I repaired the cracks from the interior using a product called Sanitred which seems to have done the job.
The contractor plans to first put a French drain in, then I plan to have him use the foam board insulation on the walls, then frame and insulate using R11 fiberglass insulation. My question is, if the walls have a leak sometime in the future, is the foam insulation that is glued to the wall going to be a problem?
Do we need to put something on the wall like plastic sheeting first so any potential water will run down and into drain without touching the foam? There are also small amounts of efflorescence present throughout the basement on the bottom of the walls. I live in NJ. What if the upper wall is studded, insulated fg with vapor barrier.
Can I still run the foam board up to the joist or will be vapor barrier be an issue. Should I pull the barrier off? Matt — If you do the sub-floor first…your bottom plate will be high enough to attach base trim, otherwise you need to add blocking. Also, unless the walls are load bearing.. I have a question slightly off topic. What method s should I use in insulating an above ground space built with concrete block? It is located in Lewisburg, PA. Some authorities have expressed concern about the possibility of frost action and structural damage when foundations are insulated from the inside.
The concern is that frost will penetrate deeper down the outside of the foundation wall. Research has found that this is not a problem. Under some circumstances, such as in soils that are particularly frost-susceptible in extreme climates, there could be a problem caused by some construction techniques. Check with your local building authorities or find out if your neighbours have experienced any difficulties with frost action on their foundation.
This involves excavating around the foundation, waterproofing and installing insulation, as per Figure Flashing must be attached to keep water from getting behind the insulation and a protective covering installed on exposed Parts of insulation.
Refer to Part 1. For every underground service that enters your home e. Utilities provide this service at no cost. The work may require several weeks of effort.
Plan for extra time if you need to excavate, repair cracks, waterproof the exterior foundation walls and install a drainage system. The excavation should ideally go down to the footings but never below. The trench should be wide enough to work in. It is a big job, so do not make it even bigger with an oversize trench.
Digging may be done by hand or using appropriate machinery. The excavated dirt can be stored on a tarp or sheet of polyethylene at least mm 24 in. In some cases it may only be practical to install insulation to a minimum of mm 24 in. This will reduce the excavating required while still offering substantial thermal protection, and can be coupled with further interior insulating.
An optional horizontal rigid insulation skirt can also be added to reduce heat loss to the surface, which can mitigate frost-related problems see Figure In particular, follow safe trenching practices to avoid accidental burial and trench collapse. Protect the trench from running water and the elements, and ensure that people and animals cannot fall in.
Some soils are not stable and may require bracing to prevent collapse. If you are doing this yourself, consult local building authorities for advice on proper shoring and trenching practices. First clean the surface of the foundation with a wire brush and scraper or use a pressure-washer if you can easily remove the water.
Inspect and repair any major holes, cracks or damage and then seal all penetrations. Smooth or replace deteriorated surfaces and old parging with an appropriate type of new parging. Allow repairs to dry. Figure Draining-type insulations must be installed vertically all the way down to the footings. Check the condition of the drainage tiles and repair as needed. Install a drainage system if one does not exist but only if it can be done properly i.
It is best to do this task after completing work on the foundation wall. Consult a drainage systems expert before proceeding.
Have a contractor apply waterproofing material from grade level down to and over the top of the footings, and then seal all penetrations and overlaps. Sheet materials, sprays and roll-on compounds are available. Some experts suggest using two layers of insulation with overlapping joints. The insulation is held in place at the top edge by the flashing and by using corrosion-resistant fasteners and washers.
The below-grade portion of the insulation will be held in place by the backfill, but may require some fasteners to hold it in place during the process. See Part 4. Type IV polystyrene board is the material most commonly used in exterior below-grade applications see Figure and Figure Insulation with drainage capability see Figure , such as mineral wool board, must be used only if:.
Measure and cut the insulation to the desired height generally from the top of the footings to the exterior wall flashing.
Start installing the insulation at one corner, overlapping at the corners and keep the insulation sheets as tight to the wall as possible see Figure It may be convenient although more expensive to purchase a special interlocking system of grooved polystyrene boards with steel channels. These should be used in the above-grade portion only to a depth of mm 12 in. There are also special clips and fasteners for applying the rigid board to the wall; check building-supply stores.
Apply parging to rubble and brick foundations to smooth the wall after all repairs have been completed. The type and flexibility of the insulation will determine the smoothness of the parging required. The correct parging material will also act as a sacrificial surface material to help protect the mortar in the foundation wall. Waterproof the parging, insulate and then proceed as noted above. Flashing helps keep the insulation in place, prevents water from getting behind it and provides a clean, neat junction.
There are two major considerations: the location of the flashing, which defines how far up the wall the insulation extends, and the type of flashing used. If the siding can be partially removed or pried up, use standard Z-flashing inserted at least 50 mm 2 in. If you cannot insert flashing behind the siding such as with brick , then either a metal J-channel must be installed prior to the insulation or a wood flashing installed after the insulation.
Flashing should accommodate the width of the insulation and protective coat. For wood flashing or a J-channel, seal the joint between the flashing and the house with a suitable caulking. Ideally, carry the insulation up past the header area by at least mm 6 in. This often cannot be done because of practical or aesthetic reasons.
If the insulation is carried up only to the header area or lower, then air seal and insulate the header area from the interior. This is described later in this Section. Protect the insulation from sunlight and physical damage with a covering applied from the top of the insulation to a point about mm 12 in. First, cover the drain tiles i.
If drainage insulation is used, the gravel should extend at least mm 4 in. Backfill the excavated area in stages by removing large objects from the backfill and then compacting or tamping the ground.
In poor draining soils such as expansive clay, it would be better to bring in free-draining backfill. When the excavation is filled, make sure the ground slopes away from the house.
Usually a slope of 10 percent i. This will encourage drainage away from the insulation, as will the addition of eavestroughs and downspouts that direct excess surface water away from the foundation by at least 2 m 6 ft. Cover the filled excavation with any type of surface — patio stones, grass or a garden.
Some additional settling may take place, so it is better to wait before undertaking any expensive treatments such as paving. Windows can usually be finished by wrapping the insulation around the foundation to meet the window frame.
Apply lath and parging on top of the insulation to the edge of the window frame. Caulk the joint between the frame and parging, and inspect it periodically to make sure it is still sealed. Doors should be outlined with a J-channel or equivalent flashing.
You may have to extend the doorsill to protect the flashing beneath the door. Seal penetrations through the insulation and covering to prevent wind, water and vermin entry. Some penetrations gas lines, electrical conduits should be sealed with a compatible and flexible sealant. If the exterior insulation does not extend above the header area by at least mm 6 in.
See Part 6. Where part of the basement wall encloses a cold cellar or unheated garage, apply the insulation inside the basement, against the cold cellar or garage walls, treating them like exterior basement walls. Weatherstrip and insulate the doorway from the basement.
Finally, insulate the ceiling of the cold cellar or garage. Extend the outside insulation around the rest of the basement by at least mm 24 in. For information about insulating a cold cellar, see Part 6. If a concrete porch is butted against a basement wall, a paved driveway or some other obstruction, the insulation should switch to the inside around these obstacles.
Allow at least mm 24 in. Insulation can be added to the outside, but the excavation required should be done by a professional and that is usually expensive and complicated. Over the years, many homeowners and home building professionals have discovered that using combinations of fiberglass batts or blankets are poorly suited to handling the problems of basement moisture. This is due partly to the fact that paper faced insulation is a vapor retarder , not a barrier.
In the winter, water vapor would pass through the insulation and condense against the cold concrete wall, wetting the insulation. In the summer, water vapor would move from the wall inwards and condense on the room-side of the insulation. The result in both cases was the same - a big wet and expensive mess. Extruded polystyrene foam insulation panels not only provide excellent insulation R-values in a compressed space R-5 per inch but they also have low moisture vapor permeability.
That is, XPS can prevent most but not all water vapor from passing through. These panels can be glued onto concrete walls with an inexpensive foam adhesive. In most cases, just cut the panels to size and cover the wall from the floor to the top of the foundation wall. NOTE: As with the joist bay, foam insulation panels are required by code to be fire-protected by drywall. For moisture penetration problems, polyisocyanurate PISO foam panels are faced with a vapor barrier already applied.
Panels can be taped together to form a continuous barrier. If you decide to go with XPS insulation panels but have a moisture penetration problem, try this method:. After sealing all drafts and all the joist bays, seal the concrete walls with basement waterproofing paint to reduce the amount of vapor infiltration. Next, cut XPS panels to fit and glue these in place with the proper foam adhesive. When completely dry, tape all seams with foam joint tape.
This adds another layer that reduces vapor infiltration further. Next, staple 6 mil plastic sheeting to the mudsill or sillplate and let it hang down over the entire wall to the floor. The sheeting acts as a vapor barrier vapor diffusion barrier to prevent any more water vapor and moisture from entering the living space.
Edges should overlap and be completely taped to make the barrier seamless and sealed. The bottom edge can be fastened to the very bottom of the wall with battens. To finish, furring strips can then be attached through the plastic sheeting and foam to hold the drywall. Another option is to tape the bottom edge of the plastic sheeting to the floor. By framing a covering wall, additional insulation can be placed before the drywall is installed over it.
It will be less humid overall and your basement will feel drier and warmer. Best of all, your energy bills will reflect the improved efficiency. When you sign up with an energy plan from Direct Energy, you'll get tips and tools to stay informed about your energy usage and save on your bill. Use these preventative measures to help maintain a healthy water system in winter. When it comes to plumbing, there are certain preventive measures that can help you avoid unnecessary water and money loss.
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