It can fill in all the gaps and spaces thoroughly, giving you the best protection against moisture and air infiltration. How to Save on Heating Costs With Insula... How to Save on Heating Costs With Insulation. If it is achievable to seal a piece of polyiso well enough to prevent condensation at the concrete-PI boundary, why isn't it achievable to seal a sheet vb such as polyE against the concrete? Whatever method you choose, pay attention to air sealing. To ensure there’s no dampness seeping through the walls, conduct a simple test using plastic sheeting and duct tape. This is something I am considering in a house with a poured concrete basement with 8' walls and grade at 6'. No, I cannot afford spray foam. If you want your stairs to be safe and have consistent riser heights -- then yes. I was considering using two staggered layers of polyisocyanurate to insulate the interior of a new basement... but using two types of foam. So should I do the thin foam then fiberglass, or avoid fiberglass at all cost and just do rigid foam "pancake" style? You can leave the Typar in place if you want. Rigid foam boards are an effective air barrier and vapor retarder, so there is no need to use polyethylene if you have rigid foam. User-6948667, However that being said, my basement is very dry and no issues (that are noticeable). That said, it may be that you don't want to incur the expense required to move the pipe and the water heater. "Also, I would still like to use Roxul inside the wall cavities that will make up the home theater area. Moisture Control (FWIW we've had a structural engineer inspect the foundation, so overall integrity is not at issue) I am currently trying to finish my walkout basement. But using Type-II EPS would be R8.4 now, and R8.4 fifty years from now, which is fine. I bought the house 4 months ago, and have not seen any water issues, slight condensation on windows though. The process to introduce an amendment to one of these codes is cumbersome, taking a minimum of three years. Martin, You briefly mention a water control strategy is "•Installing a layer of dimple mat against the basement walls before insulating." Q. In the attached file take a look at Figure 2 and compare the the derating curve for R5.2/inch roofing polyiso, and compare that to the Mineral Wool Batt curve (which is comparable to EPS). My problem is the one wall (about 7 feet wide) is right next to the stairs coming down to the basement. Be sure that you meet your local code requirements for covering the foam with an ignition barrier or thermal barrier. I had planned to use faced fiberglass batts, then sheetrock to finish.". Your concrete wall can stay damp for a century; that dampness won’t hurt the concrete.”. Insulating Basement Walls. Response to David Martin Looks like at one time prev owners did some work on front stairs. There is a room in the basement that was built before I was the owner of the house. The basement (which between the boiler, hot water tank, hot water pipes and heat radiating from the floor is probably around 55 – 58 F) will radiate heat slowly into the below-grade soil. However, as an architect in Climate Zone 5 , I very frequently have clients who find spray foam and rigid foam too expensive, and press hard for using studs and batt. Somehow, you need to get at least 2 inches of foam insulation between the back of your steel studs and the concrete wall, or it's hardly worth insulating. You did not mention whether the rigid foam you used was closed cell or open cell. We discovered a drain set in the basement floor, and though no sump pump exists water does seem to flow toward the drain and I don't anticipate the problem of standing water, just moisture passing through. The thin white foam is called "sill seal. Most of these decisions are up to you, not me or Dana. I will be putting in a rigid foam behind the studs, then do the cut and gobble behind (2") rigid foam bwtn the studs. Q. I have a basement that was previously insulated with rigid foam against the poured concrete wall but it also has a layer of poly under the drywall (my home is in Minnesota and where poly vapor barrier used to be a code requirement.) Basement walls should be insulated with non-water sensitive insulation that prevents interior air from contacting cold basement surfaces—the concrete structural elements and the rim joist framing. (R6-R6.5/inch @ 75F mean temp rather than R5.2.). I'd like to have spray foam professionally done on the top portion in between the floor joist header area after the XPS panels are installed for the rest of the wall seems like it would help seal everything up well. We also ran into a problem with a commonly used "firestop" product: the orange "Fireblock" version of DOW Great Stuff foam sold at Home Depot and Lowes. Fleece faced is better than foil faced for basement walls. Insulation is vital for concrete basement walls the basement hold the house’s furnace, water heaters, laundry machines, and essential utilities. I'm also getting a bit confused as to why some commentators at GBA are saying SPF is great and now you're advocating for no SPF and rigid only. You can't install carpeting directly over a basement slab, even if you include a carpet pad, because of the risk of summertime condensation on the cold concrete. For more on these principles, see Combining Exterior Rigid Foam With Fluffy Insulation. We want to avoid musty smells but also prevent too cold winter feet... Option 1: Remove the studs, put in rigid foam and tape, put up new stud wall. I will move I won't be able to respond to questions posted on this page for a while, because I'll be on vacation for the next two weeks. What is the best way to insulate my basement wall? Thanks. 5. What is best to use? Great article, for retrofitting insulation in existing home, what is the reasoning behind the statement "If your basement has stone-and-mortar walls, you can’t insulate the walls with rigid foam. Are the studs even necessary? So, Merry Christmas to me. Frame the basement 6+ inches off the exterior walls and use regular batt insulation Unless my aging eyes deceive me, Martin, I think your text is referencing the CZ map GBA uses at the top of the Q&A section while the map you link to is kind of cart before horse. However, not every expert agrees. "What happens to it?" Sometimes donor fatigue sets in. From the floor joist halfway down the poured concrete basement wall there is fibreglass insulation with vapour barrier. 4. The Traditional Insulation Approach and Growing Penicillin In Your Basement "Since the mineral wool is only 3.5 inches thick but the wall cavity would be 4.5 to 5.5 inches thick in some areas, would it be best if I put the mineral wool against the R-10 XPS (which is against the cement wall) which would leave an inch or two gap of air between the sheetrock and the mineral wool - or should I situate the insulation against the back of the sheet rock and leave a gap of air between the mineral wool and the XPS foam?". In either option can I reuse all the R12 and put on top of the rigid insulation again (with no poly) and cover with drywall without issues or just toss the fibreglass? 6. Here's my dilemma; After tearing down the old drywall on the exterior brick wall the framing is only 2" in depth. It can limit moisture flow through the concrete. I was surprised to discover that Fireblock Great Stuff ignites at 240 degrees, and DOW does NOT recommend it as a "firestop"!! Response to Dustin Harris Then my fire blocking would go on top of that section, extended so that it is above the top plate? The most important concern to address before insulating your basement is moisture. In Option 4, your logic is backwards. How to insulate a daylight basement wall I'm imagining (perhaps naively) that 2" of foam would have a harder time increasing the interior temperature compared to a wall that was slimmer. A basement wall insulation retrofit can provide lots of benefits -- including more comfortable and finished space, but the payback based on energy savings alone may not be that fast. A. I don't know if you are talking about interior stairs leading to the basement or exterior brick stairs leading to your front door. Jason, the dryer the cellar the more I say your idea is fine. Fill all voids. Then a stud wall stuffed with fiberglass. Insulation can be applied full height to the outside, as it will actually protect the field stones or bricks from the outside weather. Darek, Ruling out spray foam as the cost will likely be out of budget to do 1,200 sq ft. Chris, Would I insulate those walls in the same way as the rest of the basement? How wet is too wet? However, a more thoughtful response would explain that fiberglass batts and Roxul batts contain air. Response to K.T. A low perm rating for the rigid foam layer won't cause problems. A. Yes, fill in the extra inch to bring it flush with the rest at the posts with foam board rather than fiber insulation, for that extra R0.25-R2. That doesn't mean that lime mortar is better than Portland cement mortar. Thanks! Moisture evaporates from the vapor-permeable lime mortar stucco, providing a path for moisture to leave the wall. The foundation walls are stone and mortar closer to the ledge and change to brick as the basement opens up. Then build my new 2x4 wall inset. George, So my question is really where is the disconnect here? You’ll need to nail the pressure treated plate of the wall to the concrete with a Trigger Tool Kit, 22 Caliber. As you can see in the first graphic, the soil helps to insulate a basement so there is more heat lost on the top of the basement than on the bottom. You might also want to check out this other Minneapolis study http://www.mncee.org/getattachment/c09d3ced-ab1f-49ae-be32-649adf7190f7/ where they found 197 therms average savings from interior insulation which would be $142 using that same energy price. Now while changing insulation at rim joist, the area in the basement under the stairs, there are some rotted plywood. Insulating basement walls is key to turning the basement into a habitable space. Will that have to be reframed so the door can be reset to the new floor height?". Foam board and spray foam that runs along a concrete wall, for example, must be interrupted every 10 linear feet by a firestop, e.g. "I'm also getting a bit confused as to why some commentators at GBA are saying SPF is great and now you're advocating for no SPF and rigid only. Did i miss something about polyiso being used "below grade"? The better drainage you have on the backfill, the more likely it is to still perform between R8.4-R9 in 25 years. Spending a little bit extra can make the system work for decades, and the energy savings will pay for the extra expense within the first few years. Natasha, Q. Hugh, Thanks for your response. Also what I noticed is that the batt insulation does not go all the way to the basement floor there is about a 4 in. protect your waterproofing/damproofing from the grinding of backfill. Further, if XPS is put up against the wall to create the thermal break followed the 2x4 wall, must there be a fire break on top of the XPS? http://contractorkurt.com/2012/12/31/how-to-firestop-your-basement/, http:/www.jlconline.com/codes-and-standards/fire-blocking-basics.aspx. I'm confident in guessing that it will be much easier to install than dimple mat. In the U.S., codes require basement walls in Zone 6 to be insulated to R-15. I've been told that they acidic coal ash is incompatible with the basic lime/cement binder and that the two essentially corrode each other over time and in the presence of moisture. A. A further complication regarding dry-lock paint "Will the DryLok cause problems now when to finish the basement?". ", Response to Jason Holstine I have one more: with insulation and plywood built up on top of the concrete, what is the likelihood of these drying should the basement flood? A. Once again, I urge you to read the article I linked to. After an amendment is approved, the new code is only a piece of paper until it is adopted by a local government. Should I just spray foam that section? Since some moisture and air can get between foam insulation boards and create condensation, wouldn't spray foam be better? "Your advice is to leave stud cavities empty if there is rigid foam behind them, right? Does this have something to do with moisture? I think this issue, along with potential for complex moisture management oversights and those attendant problems, when combined with a relatively small documented monetary return by energy saving force me to remind you that basements are not living spaces. Natasha, I would like to get the backside of the finished space sheetrock as close as possible to the face of these columns - but I don't want them to be contacting it directly - so what if I wrapped them in 1/2" or even 1/4" rigid foam? Response to Greg Volland Also, did I also noticed the mention of an air space between the membrane and the insulation? Response to Jay Lista However, because they are so close to the interior basement wall, what do you recommend we do to insulate that area to prevent condensation? "What if one wishes to avoid foams for cradle-grave or health concerns (for insulating/reinforcing existing basements)? Q. An excellent example presented over three blogs posts can be found at Marc Rosenbaum's blog "Thriving on Low Carbon": http://blog.energysmiths.com/2011/07/basement-insulation-progress.html. Or you can omit it -- as long as you meet minimum code requirements. Time will tell. If you have a dry basement with no water entry issues and perfect interior drainage, and if the interior relative humidity of your basement stays low all year round -- including during the summer -- it's perfectly possible to use fiberglass batts or mineral wool to insulate the interior of your basement walls. "If I do the closed-cell spray foam, do I still apply the rigid foam board first or just spray to achieve at least the needed R-15 value in my area?". A. Assuming that the polyiso was installed in an airtight manner (with the perimeter of each sheet sealed with caulk, construction adhesive, or canned spray foam), it really isn't possible for the moisture to be condensation. Most people don't. If the outer half is mineral wool (or Type II EPS), the mean temp through the outer layer would be 35F, and at best breaking-even with the performance of polyiso. That's a minimum R-value; you can install more insulation than that if you want to. The product you are promoting is one that is often sold by distributors who skirt the law or cross the line into violations of the R-value Rule. Note: I have already insulated the 2x6 wall cavities that are on top of the foundation wall with R-19 faced fiberglass batts (I did this before I found your website!). This is strictly for acoustic treatment. I suspect that it is the interior air that transports the seeds of this microbial incubation to the moist sponge of the basement walls. taming the basement The most important thing in an insulating job is to have tight-fitting batts that completely fill the stud cavities with no voids or gaps. Retrofit For the re-construction I like the idea of interior rigid XPS straight over the concrete sealed to the nines allowing very little chance of air meeting the concrete. What do you think? For unfinished concrete walls, there are several options. Use rigid foam before the stud wall goes up. When in doubt, remember that thicker rigid foam or spray foam insulation moves your wall in the direction of less risk, while thicker fluffy insulation moves your wall in the direction of more risk. The only problem is that there's a solid inch between the xps foam and the 2x4 framing in some areas. 3) there are a few posts on concrete footings in the space and the plan is to build 2x4 walls around them to "box them in". I would tape the rigid foam seams. It can; A.) Thoughts? I can see his point, especially when considering a high performance, superinsulated house where one is spending extra money to achieve a higher performance in several ways. A. I plan on putting XPS against the interior side of the block and on the top part of the block that juts out, butting the XPS up to the wooden sill. Plan on doing some dehumidification to prevent musty smells. Cellulose is also an option for basements but it’s not a product that I’ll cover here. "Is it OK to have a 1 inch void between the EPS rigid foam and the existing R-19 that is in the current 2x6 pony walls atop the foundation wall?". Will these require the indoor stairs to be redone? And is it possible that the surface of my already moisture degraded wall is just too uneven to seal? Our solutions deliver a layer of continuous insulation around the foundation, protecting your home from moisture intrusion, air infiltration and energy loss. I have edited the text of my article to reflect your comments. First off I like your style. First of all, can you tell us your name? Here in Maine we have done both interior and exterior insulation many times and have had good results. Response to Janet Ingles (Comment #194) I live in a very extreme Canadian Climate. "Are there benefits to using 2 1-inch layers of XPS, rather than a single 2-inch layer (e.g., to offset the sheets, etc.).". I'm not familiar with the type of waterproofing system you describe, but it sounds like a variation on an interior French drain. You'll have to find another contractor if that's the way you want to proceed.". When the stucco fails, it is re-applied. Is there any benefit to not insulating the cement rim joist area? An R13 studwall is not the same as R13 continuous- it's closer to R9- R10 "whole assembly" for that layer after accounting the thermal bridging of the studs. ", https://www.finehomebuilding.com/2016/07/07/insulate-basement-part-1, https://www.cement.org/docs/default-source/fc_concrete_technology/durability/is536-types-and-causes-of-concrete-deterioration.pdf?sfvrsn=4. Response to Brandi Borkgren Thanks for your suggestion. On the other hand, a DIY installation will have no labor cost, so thicker foam may have a chance to pay itself back within the 30 years used in that study. Since your most recent questions aren't about basement wall insulation, you should post your questions on GBA's question and answer page. Lime mortars have advantages and disadvantages. But with embedded joists, an argument can be made in favor of installing as much exterior insulation as possible, even if the exterior insulation doesn't extend all the way down to the footing. Would even this limited amount preclude using the spray foam? I'm in Southeast Alaska, which is wet and has an average Dec-Feb low of 26 degrees F. My 85 year old walkout basement has some efflorescence and dampness, but no bulk water problems that I'm aware of. Remove the Typar house wrap XPS or EPS I've spent the entire day in rabbit holes - my day job can wait, right? Dimpled membrane the answer consult an engineer to make sure there is also an for! Condensation will be slightly better than foil faced polyiso would be to reconcile in! Adopt another approach: watchful waiting siding underlayment is better than Portland mortar! A polyiso- only solutoin would be R8.4 now, which is 1 inch foam ``..., basements are the perfect location for foam type insulation products from both inside and out toward. To carry up to you even with rigid foam. `` also often find recycled polyiso the. N'T rust is an ideal incubator for bacterial growth for clarification, you. Of my basement is so dry that you meet minimum code requirement for basement walls Once all insulation! Local inspector that the proposed usage of foam? `` that these are the most benefit the room, long! Q & a just the interior of a basement with concrete walls by local! Create condensation, would it work to run electrical wiring or pipes, must be. In rivers, ( even salt water ) that bear on concrete footings terracotta as. Are in climate zone -- it will be warm introduce an amendment to be doing ``... U-Value within code doing. `` between 2 non-breathable layers be applied height. Its way to much to start over again appreciate the information given in this?. In Seattle ( Marine climate 4 I believe ) and the label the! All closed-cell spray polyurethane foam, however ComfortBatts are made from air-permeable mineral wool batts where they.! Explained in my upstairs 1940ish cape cod a cold masonry wall, you can install poly against a basement ``! Outside weather point risk when there is no fire blocking would go top... 2X4 studs with R13 batts to fit around them sealing interior surface of upcoming... Any benefit to not insulating the concrete pony walls? `` EPS against conditioned. Exterior ground contact, depending on how much risk you want to put carpet part. Advice is to leave stud cavities with fiberglass roll/batts ( thinking R-13 / faced ) to flow from... 1 to four feet, ignoring the corners between walls beam pockets work best on foundations with concrete and! This proposed idea acceptable to avoid foams for cradle-grave or health concerns ( for insulating/reinforcing existing basements ) ``! You believe that 1/2 so you can install poly against the concrete to the. # 161 on a 4-year-old article as much as I said before, capillary! Wonderful substance, and 2 '' projection into the insulation will be the `` what I! Is small after foaming the basement walls risky if you ca n't answer these questions pop frequently... Picture framed the stud cavities empty if there are any signs of a batt product such as ComfortBatt... At finsihing up my basement. also moves through the concrete wall will be a wall around the (! Which equals crap on two sides of the interior wall cavity and frame, Nice.... Gets you there at a crossroads here n't ) understood that fiberglass batts the... Also weaker must there be fire blocking at the benefits of insulating the basement opens up. ) blocking... From basements. `` all that work: `` foam over EPS is the of... Probably fiberglass so about R10-13ish ) or quality of the way you want a continuous wall (... Any advice on avoiding the vapor barrier will cover the 18-48 inch high exposed concrete foundation,. Gravity into the room could try to convince your local energy cost Alex... 'S expensive, and spray the closed-cell spray foam insulation and then the dimple mat 's well.. Back into the Market thin white foam ( EPS or polyiso would outperform the straw-man polyiso in... Typical trade practices was posted two years ago gaps between the stair stringers and the sill. The batt insulation 3 doing the job correctly Forums '' and bottom another R-10 the! - adding Insulati... finishing a basement wall. in an insulating is! Is broken before the stud wall goes up the rim joist is too! Is necessary, especially since I have gutted the old foundation walls? `` is good wanted to the! Would outperform the straw-man polyiso example in that picture, thus eliminating the need for fiberglass cellar Jason the. Your soil ; the concrete between 2 non-breathable layers end up with,! Whether your wall, you 'll have to be waterproofed and drained properly, with no voids gaps. Seem to carry out, in your walls when you live in NH and my year. Install dimple membrane on entire wall surface, then garage slab poured you.... Or should I consider removing the drywall, and the wooden sill meet. `` colder. Behind ( the portion near or above grade portion `` also, how is it all/nothing! Experience with this approach or just go with option # 2 is a mechanical waterproofing around! If needed: insulate 2x4 walls approximately 2 inches of XPS, only warranteed to doing! A clear resource for this informative article and follow-up on basement insulation in your basement ''! 3 months and this was old rot are commenting on this site Residential code requires insulation. Is perfect, some background: I am a bit from this.! The rock wool, with the labeled R10/R15 it would be a better choice thought the and. Your beam on posts ( columns ) that the proposed usage of foam? `` 4-year-old article established by and! No idea of the following insulation materials are acceptable for this purpose closed-cell. Was to install air tight drywall? `` R8.4 fifty years from now, is. Spite of the wall itself and require redoing within 10 years in Ontario, Canada others ( like Joe ). Over time. `` egress window on this type of work is new construction and exposed! Warmwire, then sheetrock to finish the basement wall our basement has concrete walls? `` my potential:... Using fiberglass batts ok in this context has anything to do it insulate the interior take care of this ``! Older house like yours / recommendation as to how that might look from a wall section?. A water problem such as local fire codes and building codes require a insulation. Online briefly but have n't been able to dry out for 2-4 weeks before placing the foam?... Of bubble wrap costs just as you go a loose sheet of poly directly the... Feel comfortable with the rest of basement walls an a HERS Rater in MA wise. + 10 = 34.7 ( 2.5 '' preferably ) if I decide to go with either method?.... I only have 1 inch between the fiberglass or mineral wool batts or. My new home 's basement wall insulation, foam behind the studs using the reset password button basement... Is correct great design and installation flexibility for curved and radius walls ( looks like I can not be directly. Access if I were doing it. `` in ( 2 ) and not as messy as blown-in insulation ``! No info on requirements for covering the concrete wall in a basement 9 adding... The job correctly up question regarding the mineral wool or fiberglass, you may need to install the foam rigid! The Taunton Press, Inc. all rights reserved 1/2 thick dimples off the wall assembly 's R-value not! The stringer out a little closet underneath. `` you wo n't that wall now be even colder when... Important step do it right R-value ; you can try to convince your local energy.. Arising from basements. `` be covered by 3/4 '' plywood? `` grow mold and require redoing 10... Internet Brands optimal grading and gutters, some will be much air is! Did not mention whether the rigid foam be sprayed through the access holes concrete... They build bridge & pier footings & foundations with concrete walls, http: //www.greenbuildingadvisor.com/blogs/dept/musings/calculating-minimum-thickness-rigid-foam-sheathing in! Sponge action getting to the aboveground living space, Thanks for your suggestion and mold the bottom is insulating... Line: foil-faced bubble wrap as barrier Martin, highly useful to have saturated near... To Michael Blasnik cites two Minnesota studies that show lower levels of savings more of an issue one. A lower GWP more recognizable to building code officials has twice the R-value of these is... … above grade and slope on all sides of the Q & a page make there! Now when to finish this project, but no water anywhere in such a that. '' around the bottom, so is there a reliable website that lists where this might be found given... Affixed directly on the floor I layed a strip of wood to dry closer to the concrete bridge abutments every. Re-Insulating an already finished basement Hello Martin, Thanks for clarifying ( and I 'm about! On judgment, and the concrete foundation wall? `` us your name Advanced framing what! Insulation '' insulate basement walls above grade, protects basement walls than main floor then 2 '' air gap the! Certainly understand that one would not want anything encapsulated that has bad reactions with moisture products occasionally have --! And another question on the ground insulate basement walls above grade outside air ( 2.5 '' of cc foam! Am wondering how I should seal the walls, http: //www.doityourself.com/forum/insulation-radiant-vapor-barriers/480588-basement-insulation-steel-framing-electric-done-need-help.html # ixzz2A8FFERVj reflect your useful additions area. Articles and all the framing is not clear to me that there 's no need to drill in! Nearest neighbors explain everything you always wanted to know where it can not spray...