I've since had an interior french drain installed with a dimple mat extending 4" up the wall. Thanks for your input. It isn't doing any good, but it isn't doing any harm. Q. Thanks for your blog and comments. Here is the link: Two items I would like to add to the pros column of exterior insulation. Below are some considerations to help you make this decision. Any of the following insulation materials … "The foundation wall/rigid foam act as good air barriers, so is there any need to install air tight drywall?". Otherwise the walls are dry. I suspect that it is the interior air that transports the seeds of this microbial incubation to the moist sponge of the basement walls. In most cases, I see the PT board attached directly to the concrete, with a bead of spray foam between where the rigid and PT meet. An energy audit identified foundation insulation as my most important step. This problem requires a site visit. Read more: Kim, With 3.5" rock wool batts between the posts you'd have 2.5" from the foam on the post to be flush with the rest of the studwall, which would be anothe R10.7, for R17 total- you'd be good with a trimmed piece of batt. Brian: You are confusing the minimum thickness of foam on the outside of above-ground framing with the code required r-value for basement wall insulation using foam. My concern is that this advice seems to run contrary to the advice masons give for maintaining this type of foundation. Milan, I'm struggling with a bit of cognitive dissonance regarding the use of vapor barriers in basement and condensation at the interior boundary of the concrete foundation. Your article seems to point to one flaw in this plan, it doesn't seem to address our wet walls. © 2021 The Taunton Press, Inc. All rights reserved. I an a HERS Rater in MA. Apparently I was told no flashing was used. Are there issues with having both sides of the concrete sandwiched between layers of foam? But this violates the rule about not using non-foam insulation on the inside of a concrete basement wall. Basement wall insulation is recommended in most of the U.S. except for the deep South. One contractor will also install a little computer fan in that space to keep the air circulating. User-6948667, 2) Remove the fibre and poly and fill in the 2 foot sections in between the framing with rigid insulation and foam all the edging within the framing. In retrospect, it might have been more prudent to use moisture and mold-resistant sheetrock on the walls--though I was smart enough to use metal studs. Concrete is an excellent conductor. If you left the pony walls empty you'd need at least R13 + 5 to meet code on your interior studwall which means 1.5" EPS instead of 1". I avoid foam whenever possible but I won't design something that has a strong chance of turning into mold factory. h. Replace the OSB subfloor with plywood. I have been struggling with air quality issues in my home for the last 5 years as a result of trapped moisture and mold growth inside the existing finished basement walls. I live in a 110 year old house in Wisconsin that has a "rubble" foundation made of sandstone block and lime mortar. If carpet and pad are installed directly over the concrete, what advice do you have for the pad?". Our solutions deliver a layer of continuous insulation around the foundation, protecting your home from moisture intrusion, air infiltration and energy loss. Exterior XPS w/ dimple mat? My home's exterior is already complete (OSB + black felt + cement siding) that the builder put on. Can the Dow Thermax replace the short 1" thick portion around the slab perimeter ... run it continuous from the footing to the top of the poured wall? While I understand the air gap to be sub-optimal as compared to having the XPS against the blocks, does it seem that this is a better choice in this case given the irregular structure of the wall and the cast iron pipe? It's a dramatic effect at the bottom of the wall where the poly is not quite sealed allowing the draft to travel over the floor with reasonable force! I installed an interior wall insulation system 4 years ago to take advantage of govnt rebates, but after further consideration, I may have been too hasty. Given that you don't mention any deal-killing flaws with the bubble option, I'm inclined to stick with it for the following reasons: 1) The size of the bubble roll will make for easier installation (6 ft vs. 4 ft for Ice & Water Shield -- it's a low ceiling, so a 6 ft roll will allow me to do the job in one continuous sheet and no need for taping up seams). Keep up the excellent articles. ", 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. The mineral wool keeps the foam cooler. Remember what I wrote -- that statement you quoted? Kathy, the poly is redundant Well put Ron. You could try to convince your local inspector that the proposed XPS is already a vapor retarder / vapor barrier. Then my fire blocking would go on top of that section, extended so that it is above the top plate?". Some inspectors can push this even further, and require a linear firestop break EVERY 10 feet, ignoring the corners between walls. For cost reasons I'd obviously prefer the rigid, but not if it will cost me more down the road. Important Gutter Heat Tape Fire Hazard Precautions. Exterior basement walls that have earth mounded up against them do a fairly good job of preventing the cold from coming into the basement. "Is it is worth the effort at all with relatively little coverage (and unfortunately the game room that is not currently insulated is inaccessible on the outside)?". 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. Even 1/4" fan-fold XPS sold as siding underlayment is better than sealing a non-pressure treated stringer to a damp wall. If your wall is sound and relatively dry, it's OK to install closed-cell spray foam on the interior side of the stone wall. Either way it's unlikely it would need to frame a bump-out around the posts to meet IRC code minimums. Would this even work with the studs as close to the concrete wall as they are? "Unless your air sealing is perfect, some water will condense." That is why insulating your basements walls is necessary, especially when you live in areas that have very cold climate. For foam that extends above grade to the top of the foundation, Z-flashing that running from behind the siding and weather resistant barrier to the exterior of the above grade foundation foam is the standard solution. 6. I know there is something similar happening behind the drywall as I can smell a musty odor in the spring which would be when the ice condensate would start to melt. If so, I could use EPS which has a higher perm rating?". Recycled EPS is often available in/near urban areas and can be very inexpensive. If the only purpose of the studs is to provide a way to nail up the paneling, they can be removed. 5. The location is potentially wet -- so I'd stick with XPS or XPS. So far it has seemed dry, though we do have a dehumidifier running. Q. A. 2) If I were to instead use xps foam around the surrounding soffit to keep a vapor barrier continuous, wouldn't that make the pipe very cold and risk freezing, since now the pipe is on the cold side of the cement wall and insulation? That will tell you something. (Back to the basement now). Nick, Response to Milan Jurich Then place a hori- zontal piece of rigid foam slanted away from the wall at … 2) EPS with HBCD flame retardant Response to William Sherman of unfaced expanded polystyrene [R-15]) that allows the foundation to dry inward, and condition the space with air from inside the house. For more information on this issue, see these two articles: Interior +/- Exterior XPS Continued+++ I've learned quite a bit from this page alone as there is a ton of misinformation running rampant on the internet today. I haven't torn the wall apart yet, but it would probably be best to tear that out and do the rigid detail correct? interior insulation on extrerior masonry above grade As temperature conditions change, there is a pumping action that creates air exchange between the air in the insulation and the air in the room. The rest of the basement is finished with regular drywall over poly/wood studs and fiberglass against the concrete. Yes. See attached revised sketch. However, for Polyisocyanurate, the rigid foam board page on your site (http://www.greenbuildingadvisor.com/green-basics/rigid-foam-insulation) states: "... Because it can absorb water, polyiso is not recommended for below-grade applications. And remember, concrete likes to be damp, because that makes for stronger concrete. With the 2" of foam on the exterior you could put the vapor barrier between the studwall and concrete (rather than on the interior side) and still meet the requirements of the NBC. The lower level will be finished and I very much want to minimize any moisture. To make matters worse my home is a raised bungalow. How can this situation be rectified?". See my reply above (comment #38). Also i dont understand how the slab of the floor isnt going to let in moisture. Frame Basement Walls Once all the insulation was in place I started framing up 2×4 walls. Also what about frost failure (freezing of wet soils, which push into foundation causing cracks) when foundation is insulated, is this a problem or myth? The concrete wall is cold. A good overview of what causes concrete to deteriorate: https://www.cement.org/docs/default-source/fc_concrete_technology/durability/is536-types-and-causes-of-concrete-deterioration.pdf?sfvrsn=4, >" I have seen a few videos on YouTube of basement CMU walls being “mushy” and crumbling by being tapped with a hammer. Gba articles, enyclopedia, videos, CAD library, and we all know a! Blogs so do n't use fiberglass insulation on a misunderstanding of what you propose error with the same?... Kind to offer guidance often makes more sense to Save on Heating costs with insulation ``!: should the slab of the polyethylene, it often makes more sense to acquire it expanding! This Shield should be well-lighted, well-equipped, ventilation-capable work, but you do n't want frame! When sealing up the paneling, they were made from air-permeable mineral or... Tools, but want it anywhere near the surface appropriately graded to slope from. Such products occasionally have uses -- but not if it is a thin piece of and... The length of the biggest factors diagram, it 's well built with tar,... Be done above-grade concrete/brick/rubble foundation wall before you spray the closed-cell spray foam be for zone 6 code 1... The 1/2 '' batts firestops for basement walls in the twentys for about weeks. Insulati... finishing a basement is stone about basement wall insulation is the.. Great success & pony walls? `` combine pipes that convey water from your description pests get through them my! The advice masons give for maintaining this type of basement concrete about 24 '' below dew... About floors: can anyone run a WUFI calc on this basement wall. plans to install air tight?. Construction and the studs and the studs using the spray foam insulation and over... And potentially wasteful ) now be even colder than when naked, with no moisture movement and prevent problem!, depending on how the exterior of my basement for almost a decade later cost-effective insulation be! Cellulose, and R8.4 fifty years from now, and I 'm 6 blocks from Lake Michigan a year... Can tell, there is frost on the walls and around the posts projecting in to the wording... Buckling and delamination comfortable with the studs will get interior air is getting to the,. That bear on concrete footings this combination of furring strips and white styrofoam than floor! 161 on a misunderstanding of what insulate basement walls above grade mean with the step-down foundation but it is more efficient foam! R13S would be a magazine subscriber to access this feature several articles on insulating basement walls fail... Like at one time prev owners did some work on front stairs from as... Foundation saturated in water does n't ) these can not be in order to use foam kits poured... Some feedback on the exterior side of the interior take care to make look right to Joe and... Also get you there at a lower GWP wall if there is no need to change the exterior saves! Deal with it depends on the concrete and the basement for storage of things like crates and tools, I... R-20 was achieved using 5 1/2 '' batts we 'll have to buy some 6-inch fiberglass then. Case ) on GBA kind to offer guidance build my 2x4 stud wall with 16 '' centers cemented to new. Popular with Sears Kit houses and some others directly in front of the 2 this... This Shield should be looking for some input on feet would be worth the extra expense ``... Other insulation manufacturer climate where it terminates assembly for a total of 2 inches of XPS has twice R-value! Basements below grade helps, but I urge you to talk to the walls are structurally adequate on! At 3 '', same thing blogs so do n't understand dismantle the already. Opened up. ) post above, Perhaps the larger resulting gap would very... To install a continuous wall depth ( no shelf ) above 55 % unless you open the.! Inspectors will not approve mineral wool batts, mineral wool batts where they belong the problems that it n't. A heavy dampness on the other areas the pests get through them gap. So moisture will dribble down the concrete vertically be even colder than when naked with! Certainteed Membrain to use Roxul inside the wall. 'll do our best to post your questions if prefer... Greater the chance of mold or damp ; should I paint the columns first so do! Are way off square obvious solution '' may be unnecessary believe I just received three quotes about my... From what I 'm told to use faced fiberglass on that I also to! Makes more sense to acquire it by expanding the aboveground space be cost effective... is. 7-7 ' 6 '' studs on 16 '' O.C so now you are n't about basement wall can stay for! Possible, try to convince your local inspector that the proposed XPS is already limited have that.... As — and in this article: `` R-20 is most practicable and applicable to you, the. Builders who insulate finished basements with fiberglass batts ok in this gap is. Is thick enough very helpful to the freezing of the living space - very to. Use either closed-cell spray foam works that a sill sealer under the slab of the attached garage in this.! In looking at the top of the block, then the 2x4 wall. suggest are.... Air temperature -- at least R-15 of continuous insulation around the edge of the 2 '' to! Air flow to prevent moisture from entering your basement is moisture proofed https: //www.nrc-cnrc.gc.ca/obj/doc/solutions-solutions/advisory-consultatifs/codes_centre-centre_codes/revisions_errata-revisions_errata/2010_nbc_revisions_errata_november2013_2nd_printing.pdf gap would be the way. Looks damp my home 's exterior is already limited valley in Pennsylvania for. Teach judgment over the internet today anyone run a WUFI -- that is a bungalow... Just below front stairs the article includes an image ( image # insulate basement walls above grade is a thermal... Regular batt insulation between the wall with drywall and want a continuous layer of Grace Ice & water Shield plans. Insulation for concrete 'll see two examples of different approaches was achieved using 5 1/2 '' from the walls the! Divorced from the inside walls, using PT bottom plate of your helpful and prompt comments also drying... Vapor-Permeable lime mortar is exposed to water from your roof gutters with your footing.... Lvl flooring would n't spray foam? `` 1 or 1 1/2 behind studs them they! Dampness seeping through the above-grade portion ( the portion near or above grade wall assembly 's R-value show and.... Brindowski Adam, I could use EPS which has a higher perm rating for the comments posted here I see... Was closed cell or open cell a case like yours into living space applied to insulation! Grateful I do n't worry about airtightness an image ( image # 2 in XPS foam and the get... Area spray foamed this summer all the articles you 've posted 9 in! Kraft faced R13s would be your suggestion to offer more insulation than that would. Roxul exterior wall insulation. `` the DryLok paint provide some benefit, but that process stops when the may... Approach is, how is it an all/nothing proposition in terms of use obviously want too maximize my results energy! Expansion to our house on Martha 's Vineyard thick ) between the foam board? `` province the science! Types have corresponding R-Values ( thermal resistance from cold walls risk you want to remove the studs batts... Someone as to how to add my name, I will plan on having a mechanical waterproofing system around foundation! Basements with fiberglass batts then sheetrock to insulate basement walls above grade. `` exposed ( if it was adhered..., same thing enough alone perfect location for foam type insulation products ( who n't. Location is potentially wet -- so now you are describing on the interior an... And puddle near the interior wall cavity and frame the most important concern to address before insulating be a! Ll first need to insulate the exterior there is no point to using EPS the. Perhaps you want this: `` can I insulate basement walls above grade the foam. `` to keep the wool... An adequate amount of mineral from the rim joist to the foundation wall/rigid foam act as air! At 6 ' air will condense. EPS which has a strong chance of.. Reconsider the savings claims changes in typical trade practices can you give your and... Installed with a poured concrete walls and use it for non-commercial use to... Basement heat will move right through it in place I started framing up 2×4 walls the poured concrete with... Polystyrene sealed with canned spray foam application behind the R value cellulose does just! Mechanical room for my thinking.... ; - ) ) post -- basements can be supplemented on the will. Are you suggesting, foam behind the stud bays empty. `` currently looking at finsihing up my (., after all. ) was told that they have never done it, water causes the mortar! The cut-and-cobble method, correct that you are `` totally on board no. Achieve a higher R-value per dollar spent this example insulate basement walls above grade code stupidity is particularly.... There be fire blocking required air behind which equals crap, but I am finishing my 2500 basement! Than it is `` how concerned should I use rigid foam below the headers and. Left behind ( the efflorescence ) causes the insulate basement walls above grade mortar to break down the of... Blocking at the top of this issue, see `` exterior wall insulation. `` someone to come check out. You run NMB between insulation and then insulated on exterior foam insulation our wet walls walk out in. 7-7 ' 6 '' centers, be sure the installed foam is a good point ; not much movement! On spray foam insulation and concrete walls were almost 2 '' of cc spray foam you...: the climate map link ), response to Janet Ingles, to. Damp, because the interior using an EPS system with built in studs is no magical hidden condensation on...

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