The installation of above-grade rigid foam insulation on the exterior of foundation walls is a crucial step in reducing energy loss and protecting against moisture problems. While metal flashing is a good solution, there are other materials that can be used to protect the foam. Prefinished foam-insulation products and stone or brick veneers are also options for visible foundations.
Insulating foundation walls on the exterior side can minimize the impact of the freeze-thaw cycle by providing a cushion that allows expansion and contraction as the Earth’s temperatures change. Stucco, fully adhered membrane strips, aluminum sheets, fiber-cement, and cement board sheets can be used to protect the above-grade portion of the exterior rigid foam used to insulate a foundation wall.
One solution is to put a copper termite barrier sealed to the top of the foundation wall, extending horizontally to the exterior. Metal or plastic reinforcing can be used to strengthen cement parging on foundation foam boards, with a stucco-like “parged” finish being the most common approach. Borate-treated expanded polystyrene is a great choice for exterior foam on foundations.
Rmax Thermasheath is a premium foil-faced polyiso insulation used in new construction and renovation projects for exterior foundation insulation panels. Other generic products include pressure-treated plywood, fiber-cement panel siding, stucco, and surface-bonding cement. A layer of styrofoam insulation outside a poured foundation is a smart move as it keeps the wall warm, reduces condensation potential, and protects the insulation.
📹 UMN NorthernSTAR: Exterior Foundation Insulation
“Excavationless” – Process for retrofitting exterior insulation & water management on the outside of a foundation with minimal …
What is the best insulation for the exterior of a foundation?
The ranking of exterior foundation insulation panels is based on their effectiveness in preventing common problems such as mold, mildew, water intrusion, and structural element shifting. The best option is Polyisocyanurate (Polyiso), which can minimize or eliminate these issues. Condensation problems can be eliminated by installing exterior foundation insulation panels, which keep walls warm to match the interior space’s temperature.
Additionally, exterior foundation insulation panels protect the structure from extreme temperature fluctuations, such as the freeze-thaw cycle, which can cause expansion and contraction of building components. By shielding the structure from direct contact with these extreme changes in temperature, foundation insulation panels help to maintain a stable and comfortable environment for building owners.
How do you protect exterior insulation?
Insulation placed on the exterior surface of a concrete or masonry basement wall offers several advantages over interior placement. It provides continuous insulation without thermal bridges, protects and maintains the waterproofing and structural wall at moderate temperatures, minimizes moisture condensation problems, and does not reduce interior basement floor area. If the insulation extends up to cover the rim, it can be left open for inspection from the interior for termites and decay.
However, if not treated adequately, it can provide a path for termites and prevent inspection from the exterior. Insulation exposed above grade must be protected with a coating to prevent physical damage and degradation.
Exterior wall insulation must be approved for below-grade use, typically using extruded polystyrene, expanded polystyrene, and rigid mineral fiber panels. Extruded polystyrene is a common choice, while expanded polystyrene is less expensive but has a lower insulating value. Below-grade foams can be at risk for moisture accumulation, which can reduce the effective R-value as much as 35-44. Research conducted at Oak Ridge National Laboratories showed that moisture may continue to accumulate and degrade thermal performance beyond the fifteen-year time frame of the study. This potential reduction should be considered when selecting the amount and type of insulation to be used.
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.
Can you insulate a foundation from the outside?
Insulation is a crucial component of building systems, but it is often overlooked. It is essential to protect insulation from bugs and critters, as it works well on the outside of slab, basement, and crawl space foundations. However, insulation should not become an insect “interstate” and a home for critters. There are various insulation systems available, including extruded polystyrene, expanded polystyrene, mineral wool, rigid fiberglass, spray polyurethane foam, polyisocyanurate, and wood fiber.
To protect insulation, it is essential to drain water away from the building perimeter, gutters, downspouts, and other sources of water. Avoid making surface water into groundwater beside your building and send the water to your neighbor’s property. This will help prevent the insulation from becoming an insect “interstate” and a home for critters.
What do you put on the outside of a foundation?
To prevent moisture damage to your foundation walls, apply a waterproof membrane to the outside of your home’s foundation after repairing and prepping the surface. This membrane can be a liquid-applied coating, a sheet membrane, dimple board, or a combination of the three. Concrete is porous, and when wet soil is pressed against the foundation walls, it absorbs moisture, causing moisture issues on the inside of the basement. A liquid-applied waterproofing membrane creates a barrier between the soil and concrete, preventing moisture-related damage.
How do you cover exterior foundation?
This article explores various ways to cover exposed house foundations, including bricks, cement blocks, conceal and paint, flower beds, gravel, high bush and hedges, river rocks, and steel sheets. House foundations are crucial for maintaining a home’s strength and durability, as they serve as protection during harsh weather conditions. However, not everyone is fond of having exposed foundations as they can be an eyesore.
Some ideas include creating a lattice with bricks, using cement blocks, concealing and painting, flower beds, gravel, high bush and hedges, river rocks, and steel sheets. By considering these options, homeowners can protect their homes from deterioration and moisture intrusion, ensuring their structural integrity.
What is one disadvantage to installing insulation on the exterior of a building?
External wall insulation boards have two main disadvantages: impermeability and size. Impermeability can cause issues if existing walls allow moisture to pass through, leading to dampness in the walls or insulation material. To address this, a vapor barrier or additional ventilation may be needed. Size is another disadvantage, as external insulation boards can add around 50mm to the exterior of walls, creating problems when installed around windows, doors, or roof eaves. Addressing these issues can require costly adjustments and increase the overall cost of the insulation project.
What can I use to cover exposed insulation?
Fabric panels are a cost-effective and easy-to-install alternative to traditional wall materials for covering exposed insulation and improving room acoustics. They can be stretched over a wooden frame or directly on the wall surface, and can be customized to suit the home’s aesthetic. Foam board insulation is a rigid material that improves thermal efficiency, energy efficiency, and moisture resistance. It is lightweight, durable, and easy to install, making it suitable for various areas needing insulation or covers.
How do you protect an exposed foundation?
This article discusses various ways to cover exposed house foundations, including using bricks, cement blocks, conceal and paint, flower beds, gravel, high bush and hedges, river rocks, and steel sheets. House foundations are crucial for maintaining the home’s strength and durability, but they can deteriorate over time due to moisture intrusion and deterioration. To cover an exposed foundation, consider using various materials such as bricks, cement blocks, conceal and paint, flower beds, gravel, high bush and hedges, river rocks, and steel sheets. Despite their importance, not everyone is fond of having exposed foundations due to their potential visual appeal.
What can I cover insulation with?
Fabric panels are a cost-effective and easy-to-install alternative to traditional wall materials for covering exposed insulation and improving room acoustics. They can be stretched over a wooden frame or directly on the wall surface, and can be customized to suit the home’s aesthetic. Foam board insulation is a rigid material that improves thermal efficiency, energy efficiency, and moisture resistance. It is lightweight, durable, and easy to install, making it suitable for various areas needing insulation or covers.
How to externally insulate a house?
To install external wall insulation, follow these steps:
- Render test the building.
- Remove and adjust pipework.
- Protect windows.
- Fit a starter track.
- Install insulation boards.
- Add mechanical fixings.
- Add beading.
- Add reinforcing mesh and render.
External wall insulation is a great alternative for improving building insulation, reducing heat loss, and improving the building envelope. Buildings built before the 1930s typically have solid walls, making it essential to install insulation on the exterior of the walls. Installing insulation on the interior would decrease usable space and room sizes.
📹 Foundation Insulation Effectiveness: Basement building science
Pat Huelman, Cold Climate Housing Coordinator with the Univeristy of Minnesota Extension discusses the issuses associated …
Wish I would have found this 3 years ago BEFORE I built a new cabin in Northern Wisconsin. This article is at least 10 years old, why isn’t this more common info by now and hasn’t been adopted / required by the building practices. I insulated inside with 1″ foil faced placed tight to the foundation wall, foil side facing in. Taped all seams. Then built my 2×4 framed wall and added 2″ foam sheets to the wall cavity. Hindsight, I would have placed both 1″ and 2″ behind the wall framing to make running electric easier. I would have only lost a total of 4″ in overall length and width of the basement, been able to attach full sheets of insulation. Great information… maybe next build… if I ever do.
Excellent information! I am just beginning to plan my future home build here in Ohio and after reading 100s of articles and perusal 100s of articles on building science strategies, I’ve learned that the most important thing to get right, by far, are the 4 envelope control layers (water, vapor, air, thermal). If you spend an appropriate amount of the budget on getting the envelope right, you will absolutely prevent problems down the road AND get a more comfortable house, overall. I’ve decided to go all out with my envelope and try to save some money on aesthetics, which can always be upgraded later. It’s the structural details that should never be overlooked during initial construction because they’re not easy to fix later.
When one thinks about it, when you’re in the frozen North, you don’t eat your winter parka. The parka works best on the OUTSIDE. And I think I read where Mt Everest climbers learned to put vapor barriers on the INSIDE of their sleeping bags to prevent their moisture from freezing halfway out. Always place the vapor barrier on the side with the greatest vapor pressure. This article is great at explaining the best way to insulate a home in the Northern states. Best done on new construction though…
Thank you for this article. My house was built about 17 years ago; I have owned it just 2 years. I was going to finish the basement but ran out of money since I totally renovated the upper floors. Instead I applied DryLok Extreme – 2 coats covered by SW reflective white paint. The walls were reinforced poured concrete with a brick pattern on both sides. If anybody is thinking of this – use Thro Seal and save your shoulder. Both are “pulled into the concrete” and virtually impossible to roll due to the brick pattern. The floors were painted with two coats of SW concrete paint. NO dampness, not cold? I dug around the foundation and found the builder had tarred the foundation, covered it with a mesh, a second coat of tar and then applied 4″ of rigid foam insulation. A Swiffer is all you need to maintain the basement. After this article I understand why the contractor put that insulation on the OUTSIDE. I don’t have to think twice about off-gassing.
Thank you for that article. I’m assuming that on existing homes where the outside has not been insulated, that you are left with no other choice than to insulate, and vapor barrier the inside foundation wall ? …or would you still leave it alone and take the heat loss in exchange for risk aversion to moisture buildup ?
Great article. Pat touched on so many issues but was superficial on some critical parts of the waterproofing system. From over 20 years of experience I can add that the most important part of the waterproofing system is the exterior drain tile. 99% of all drain tile installation on new construction are done pretty quickly with almost no effort to paying attention to making sure the tile is completely clean of any foreign matter. You can waterproof using the Ferrari of systems but if you have a clogged or obstructed tile system water can and will go through; it’s not a boat. Also I think the worst method of waterproofing a basement from the interior is to use spray foam (closed or open cell). The reason for that is that moisture is standing on the outer side of the foam waiting to infiltrate and has no way of trickling in any direction because it’s essentially glued to the concrete. Concrete can and will crack in turn cracking the insulation with it since it’s glued to it. Now you have a huge problem because you have a website of water infiltrating all the water from all sides. I’ve seen it it’s not theory it’s experience. NEVER use foam. Basically the best system is the driest system. Follow gravity and concentrate on the bottom part. Drain tile, sump system, a good pump kit will give you a comfortable basement even with minimal bells and whistles. Again it’s a great article thank you for posting it.
Great article. I’d like to suggest that a basement wall with insulating batts should employ rock wool instead of fiberglass. Rock wool is hydrophobic. It will not absorb or hold water even if exposed to liquid water. So, in the event of a flood or plumbing disaster, it would not have to be dried out. Perhaps the wood wall construction would need a little drying. Your drywall will be cashed and need to be removed anyway. Rock wool will also inhibit mold growth due to its inability to hold water. What opinions do you have about products that supposedly “seal” concrete such as RadonSeal?
I’m not trying to be a dick, but as a home owner, when the fuck are they going to start building houses properly the first time around?? I have been hearing about “problems” for the last 40 years that involve HUGE projects with HUGE cost, with a million little specialty companies out there, just waiting to take your money to fix your specific problem, that SHOULD have been done right when it was built. Builders, contractors and developers in this country, really should be ashamed of themselves.
This is an interesting article that made me believe the “main culprit” in managing the issues of water, vapor, air, and heat is the use of concrete! With all the “space age technologies” available, what would be a better solution for foundations as opposed to using 100+ year-old technology of concrete blocks and mortar? (cost aside)
One thing to keep in mind is that if you insulate a concrete basement or even slab on grade from the outside. You are giving the house a huge thermal mass. An other way say thermal mass is a thermal reservoir because it is a mass that stores hot or cold. This thermal reservoir will make a huge difference in emergence situation where the house looses heating. The warm “indoor” concrete in the basement will keep the home warm probably for several days if not a week even with extreme conditions outside if the house is properly insulated.
Excellent! Just wish you showed exterior insulation using other products like mineral wool, or graphite polystyrene. Keep in mind that foam products make great nesting material for insects, even below grade. I’ve seen insects in foam in northern Michigan, it is not just a hot/warm climate issue. Thanks for the excellent articles on the subject of below-grade insulation.
Good article, I have a daylight basement with no vapor barrier in the floor. The walls in main room are covered with 3/4 tongue and groove attached horizontally directly attached to foundation wall (3 foot hip wall) on top, 2×6 wall framing bat insulation r19, plastic barrier. cover T 1-ll. The wood stove takes care of all moisture. In another room foundation has a thin layer of joint compound and paint. No molding unless something blocks air to it. This room I have two layers of pile carpet, the ground is very cold. Your presentation is Correct. However the other room has thin industrial carpet and is very warm to my feet. I am going to do an addition, brainstorming the best design. I really like to go geothermal with Rocket stove. Search and brainstorm until the light goes on and you got it. Thanks
I have efflorescense on my basement floor. It has a thin concrete slab with an air gap underneath, where the soil has settled. We put a roll-on moisture barrier and vinyl tiles. Almost immediately the problem became obvious, as it looks like ant hills under the tiles. Its a house in Toronto, On. built in 1928. One room has a ceramic tile floor and has no issues.
The real moral of the story here is that you basically cannot safely insulate a basement from the inside in any manner using any materials if your sill plate is not separated from your foundation by a capillary break. All methods(fiberglass + plastic, XPS taped and caulked, or a full spray foam job), WILL drive the moisture into your sill and rim joist because they prevent inward drying. Either you seal off that sill from your concrete foundation or it is no deal of any kind.
I am built on a gravel hill. Thank gox because my house is exactly how he says not to build it. However my walls are gapped 1 inch from the outside wall. Also my floor has delta floor under it. this allows any moisture that builds on the concrete wall to run down to the floor and remain under the dekta flloor. before I finished my walls my basement humidity never rose above 35%. So I think I am good.
Well ! Thank you sir for this very clear and scientific explanation of insulation performance, including thermal and moisture control in a building envelope. I see this on this day March 25/2020, eight years after the production of this information and this is still new information it seems to me as I have been for many months inquiring of “professionals” how to properly insulate my older home. Those I have queried have not understood what you have so clearly, eloquently and correctly described and explained. The explanations i had been offered left me thinking something was not quite right. I now know how to correctly proceed. See Lok Tom’s comment from 2 months prior. Kidding. Great information and thank you Mr. Huelman.
I’m concerned about how flammable foam is and other insulation products demonstrated. has this system been tested for what happens when there is a fire. Just look at the London fire. Why can’t something like Rock wool products be used instead of foam & plastic sheeting? I would love to see alternatives that also are tested systems for reduced flammability for residential and commercial apt. buildings. there is drywall on inside walls and ceilings to slow fire coming in, but you are still trapped in house inhaling smoke/ carbon monoxide. What if you have a 3 floor residential house and all that outside foam goes up in flames (like London fire) and people just can’t get out because entire outside of the house is on fire. they would be forced to jump out of high windows. These are simply questions I’m interested in adding to the discussion to see if there are other methods that could be considered.
Hello Pat and thank you for one of the most informative articles on this subject. Question: Though I have no water issues in my below-grade block walls, I still applied UGL’s Drylock Waterproofer to the walls as an added measure. Next, I built a stud wall, keeping the studs about 1/2″ from the block wall, and insulated with unfaced fiberglass insulation. Then I applied Certainteed’s “Membrain” to the inside of the stud wall. The Membrain repels vapor from the inside of the basement (keeping vapor from getting into the insulation) and allows vapor in the insulation (if any) to permeate inward to the inside of the basement. 1/2″ Water/Mold Resistant drywall was used as the inside finished wall. Aside from your concerns about a water event that could soak the drywall or fiberglass insulation (though possible, is not likely in my case as I have pretty good drainage in the basement), do you feel that what I’ve done is adequate? I should also add the I have added two intake vents to the basement that draw air to the heating and cooling system. There were no intake vents there before and the basement only had a very small area of mold growth behind a large cabinet placed next to the wall. Thanks, Steve
Great article. I hope you get comments on here because I have a question. I have a 1956 split foyer home. Lower 3 ‘ of conderblock walls. We’ve gutted and remodeled downstairs so don’t have time to rip walls out to insulate with under fitting strips with rigid insulation, we did it between furring strips. What are your thoughts on having spray foam objected through holes on exterior of home? So the foam fills the cinderblock cavities. We have no weep holes or interior French drain. Just exterior tile drain.
All this stuff sounds so great but NOBODY is building homes doing any of this stuff so with all the stuff you mentioned although nice…its like a zillion dollars to do after the fact on the outside of the home and also impossible to do almost before the fact unless you are the actual builder or on site everyday perusal the half assers build yr ish …..so its like thanks but uhhh what am i going to do about it now??????……….but thanks for the ideas and info
“In the summer “heat loss” is in.” Hmm. Heat moves from “hot” to “cold”. Below the “frost line” soil temps are pretty much consistent and constant around 50 degrees year-round. Your “heat loss” to that relatively “warm” soil (relative to say…air temps outside in the winter months” is more dependent on interior insulation than exterior “foundation insulation”. Simple studded/framed interior walls, fiberglass insulation and quality sheetrock is good enough to be called “excellent” and if you use a radiant non-forced air heat source such as electric baseboard heating and have a good quality indoor/outdoor carpet over a quality thin foam backing, once the basement is “warm” it will stay that way. The various “air-gaps” between the warm basement air and the “cold” and dry soil outside the walls are the real “insulation”. Warm walls and slabs also expand to “seal” well and moisture is much less of an issue with a “tight” finished and well-insulated basement because what heat loss does occur tends to “carry” moisture with it. Warmer air is less dense but contains more “energy” than cold, dry dirt. Eventually walls dry out, the soil outside the walls dries out and you don’t have a saturated soil profile right next to the wall. And GUTTERS and DOWNSPOUTS that take water at least 2-3 feet from the foundation work WONDERS. After a few years with a warm in the winter, cool in the summer (heat is “lost” OUTWARD in the summer from the relatively warm inside air to that “cold” dirt – heat always moves toward cold.
All this bullshit called building science. As a professional remodel contractor in the Northeast USA i laugh every time I see these youtube Building Science (=BS Session.) We have demo’d basements from 60 years plus..finished. 2 x3 Walls 1/2 drywall on bare concrete/poured foundation. No mold or moisture in walls or studs or drywall…top to bottom. Out side foundation down to bottom..back then no drainage tiles. NO WATER PROOFING ON EXTERIOR. Drain system put in the 1960’s interior. Floor ontop of tile on cement..2 x 4 -5/8 ply and wall to wall. Room size of finished 24×26. Carpet area moisture due to no vapor barrier/plastic under 2×4 sub. New interior Perimeter Drain system to sump. Delta MS Mat on wall/foundation down to below foundation wall. Poured concrete over new drain system. 4″ Drain Solid PVD holes on bottom sides. Any moisture on concrete is trapped by mat down to drain tiles. IF at all. 2×4 Framing insulation vapor barrier out. R-15. Plastic 12Mill on floor 2 x 3 Floor joists (like a framed wall laid down) 5/8 Ply…and Finish laminate flooring. I forgot to mention on the demo we reused all the ply that was down from 1987 to 2012 that was down for 25 years no mold or smell. Keep a fan running..dehumidifier and you are good to go. Building Science I think not.
I’m currently in the process of applying an interior insulation strategy in my basement (located in the Northeast). Applying the insulation to the exterior would have been too costly, so I’m going with the next best thing. The strategy I’ve taken so far is to use Rigid XPS on the interior foundation block walls (taped at all seams) and have applied spray foam insulation to the rim joist cavities. The basement also has an interior drain system, with a gap between the foundation wall and slab to allow any moisture to drop down into the drain and ultimately get pumped out. After perusal your article, I have a few questions that I hope you can help me out with: 1) The interior drain has a plastic, ribbed sheet that comes about 3″ up out of the gap between the slab and foundation wall. I’ve been tucking the rigid board into this sheet and gluing the boards with vertical strips of adhesive so that any water potentially making its way between the foundation wall and XPS can drip downward into the drain, and ultimately get pumped out. However, I have not been sealing the bottom of the rigid board where it gets tucked into this plastic sheet. Should I put a bead of spray foam along this joint to air seal that area? and; 2) I have not yet applied any insulation to the top of the foundation wall – the XPS ends at the height of the wall and the spray foam was applied at about 2″ thick to the rim joist cavity. So, there is exposed concrete block still at the top of the foundation, and part of the mudsill is also exposed.
One thing I am not too sure about, but favor over any of these FINAL solutions is. Why not just space the interior wall away from the concrete, say 3 inches and leave an air gap. Have a vapor barrier on the dry wall side only. When we dress with clothing, air is the best insulator….does this not work well enough on a house? At least any kind of moisture present can circulate behind the insulation and dry up eventually.
Facts can be hard to accept. You can’t ignore physics. Summary of this article: if you live in the north/Midwest and you’re building a new house, insulate and manage water infiltration on the exterior of the foundation. If you have an older house, you’re screwed, not much you can do (without inviting risk). Maybe just insulate minimally with rigid. You’ll just end up turning your basement into a soggy mess. Discouraging. Viewers, keep in mind that these details vary considerably based on what climate zone you’re in. Maybe just best not to have a basement at all!
I️ like the detail of the discussion here but if I️ am not mistaken there is NO WAY to insulate a basement from within which is not risky….am I️ right? The reality for us contractors is that we almost never know what the exterior foundation really looks like so I️ would always assume it’s been done poorly. Given that as a starting point….what is the solution for a client that wants a insulated basement with finished walls??
Excellent tutorial and model! I have 3.5 questions for the speaker. First, What product or type of insulator is best suited for the exterior of the foundation wall below grade? Also, is a secondary protective layer recommended to the outboard side of that insulation layer? Secondly, in regard to the V-groove style footing shown- is the rebar grid within the foundation wall to be isolated from the footing (due to the waterproofing applied to the top of the footing)? Third, If ICF systems are being utilized below-grade, what precautions might the builder use to prevent the exterior polystyrene layer from being compromised from a puncture/moisture infiltration perspective? Thanks again!
Great article even if I intuitively assumed most of what u said was the case. It’s good to have confirmation my assumptions were correct. And the importance of a vapor barrier between foundation or basement wall and the rim joist was not even a consideration, So that was very enlightening. But I hope u have or will have articles on Aircrete or ACC (Autoclaved Aerated Concrete) or any related building material since it seems to have so many advantages vs its disadvantages. For a building material developed in the 1920s its a shame its taking so long to be used on wide scale. And the fact its still not used that widely used in the US is real shame
Hi Pat, I’ve dug out some area outside. I found the sale fiber insulation as you have on the below ground. We have lots water circulating around our foundation. My question is this: this fiberglass insulation is soak and wet, so cold weather the water must freeze against the wall cause of cold transfer. Wondering why the heck is this used below ground outside? If wet fiberglass insulation does not work in doing it’s job, why put it on the outside walls below ground, rigid or not fiber? I’m totally perplexed on this knowledge… please answer
At around 6:39 you speak of moving the rim joist assembly inboard and continuing the exterior insulation / vapor barrier up over the rim joist? 1. Isn’t rim joist above grade? 2. Are you saying to bring the exterior insulation up higher and then sheath underneath the above grade exterior sheathing? 3. If so … how do you protect the foundation’s exterior insulation/vapor barrier from grade to where the sheathing would typically go. You don’t want your sheathing touching the ground. I’m just not seeing how you can bring that exterior stuff above grade and keep it protected from bumps, folding, and mutilation that exterior surfaces experience. Do like the vid tho …. Will be subscribing.
From perusal this is sounds like I have no chance at making my basement actually dry… so… i’m down there right now trying to figure out how i want to give it a finish look….. we have a sub pump.. its never gotten water down there… overall the dehumidifier keeps it nice and dry…. i guess just drywall right against the concrete? and if the mold resistant dry wall starts gettin water dmg, i’ll just take it down easily 12$ replace..
What is the rule of thumb when it comes to partially framing your basement? I have split my basement into two parts: one, making a living space that is finished and second a tool space, along with the furnace room that will not be finished? I am planning on using fiberglass insulation between studs. My problem is, that I was told to leave an inch gap between the cinder block wall and the framing, in which I did. My question is will there be an issue with mold having that gap between the wall and the actual framing, since there will be airflow behind the wall. Second question, how much distance the cinder block wall to the stud framing is needed not to need insulation. I have a wall going to be a foot away from the wall due to plumbing. Thank you matthew
Great article. But, what if you have a granite rock house with a crawl space? I also have cinder block on the inside of crawlspace perimeter. The cinder block walls have condensation on the walls but I can’t figure out if it’s from the HVAC duct work that’s uninsulated and sweating. I have a dirt floor, no vapor barrier. I closed off the outside vents, hoping it would dry out but after perusal your article, believe the heat build up is hitting cold walls and sweating. I thought encapsulating and adding foam board on the inside exterior walls of crawlspace, a vapor barrier and wrapping duct work with insulation would help. I’m not so sure now. Any advice would be appreciated.
Fantastic, well thought out article. Thank you. Q: We’ve just poured our basement walls. Footer rests on natural undisturbed ground (mostly though there are slight gaps here n there under the footer form, they were filled with concrete that spread out a bit. Footer was a very tight, stony mix) The walls were a looser mix and our contractor has never used a capillary barrier and even after asking for it, it was “forgotten” and so the walls are up and in forms over the long weekend. Our footer drain is in its own ditch alongside the footer and about 1/2 of it’s diameter below the footer bottom and out from the footer about 4″, completely filled with clean stone to the top of the footer. The plan is for 2″ xps and a dimple board outside of that with native fill against that. A plastic barrier up the wall a foot above the footer, behind foam board, down and across the top of footer and onto the clean stone above the drain. There will be a ditch drain at the surface with clean stone and a 4″ perf pipe, tied by vertical “downspouts” into the footer drain. Because of siding overhang issues with builder we’ve agreed to not take the insulation up over the rim joist. Rather, the foam and dimple board will end at top of fndn wall and we will spray-foam that rim-joist void from the inside. My understanding is the spray foam will not allow for vapor trapping and so will not be a major source of heat or vapor transfer. And, no mold. So the only place we’re not good here (I think) is that vapor up through the footer.
Just bought a 1960 house with an unfinished basement. Cement block foundation, no french drains and no subpump and dirt floor.. Trying to figure out what are my priorities in the basement with a limited budget. My main concerns are humidity, mold, heat cost and radon. I have to say, perusal hours and hours of youtube articles has done nothing to help me. Actually confused me even more. The internet is nothing more then a bunch of conflicting information.
So I’d say build a wall about 2-4 inches away from the concrete wall on the inside, insulate, put up sheet rock. And put the intake to a dehumidifier into the gap. Kind of a frakenstien design bit I’d bet it would work. That adds insulation, deals with humidity and moisture. And you don’t have to touch the outside of the foundation if it’s not something you want to do
Really good article. ICF should really solve all the basement & rim issues in one shot, you should still waterproof with a peel & stick to prevent both termites and moisture (if in termite zone) or spray waterproofing should be fine if not in one.. The aggregate base, insulation & vapor membrane in the slab are spot on, although I would overlap 1″ insulation boards then put your vapor membrane overlapped 6″-12″ and taped.
Thank you great article, our new home has 4.5 inch foam board on the outside of the basement wall along with 15 mill vapor barrier and a tar under it all it goes from the footings to the top of the rim joist along with 2 inch spray foam on the island of the rim joist grade outside is to the top of the rim joist, the walls seem very dry I was thinking of just framing the walls inside without any insulation or possibly 3 inch of fiberglass,any thoughts from an experienced people please help thanks
Am glad to see someone finally talking so much about Moisture. I basically deal with retrofit so there is usually no water proofing in the homes I come across. The only solution I could add for folks is to spray on Penetrating Concrete Sealer onto inside concrete block foundation walls and cement slabs. This doesn’t quite get the footing sealed, spraying from the inside so I often dig up outside perimeter and spray the footing then exterior foam. Just wanted to offer penetrating sealer option
21:40 he is saying that we can frame as we normally do, use an (inside) paperless drywall, make sure that the framed walls are 3/4″ off the floor and use semiflat latex paint. All other systems he mentioned can potentially fail unless you have a perfect exterior wall prep which I doubt with old properties, guess I will stick to the framing insulateless system. As far as the interior rim joist goes, I will use foam panels and seal them with spray foam.
Interesting. I wonder if having vertical aggregate along side the outside basement wall might help keep moisture away from the wall, along with the exterior water sealing and insulation of course. It all looks like something we are still trying to figure out. Most of it though seems to say we need to seal and insulate the outside. There seems to need to be an escape route for moisture at the top of the cement wall so it does not get into the base of the framing. Probably best to use treated lumber at the base, if not plastic lumber. I will have to watch this again and take notes.
My neighbor added to the front of her house. It’s a couple feet off the ground in south Florida. It’s just wood studs and wood flooring. The house smells of mold and has mold issues. Can I just paint under there, foam insulation, and staple plastic barrier? What should I do to help? I can smell the house from my house. Thank you anyone for advice.
This guy really knows what he’s talking about, but it’s a pity he’s demonstrating with such feeble levels of insulation both below slab and outside the wall. If you are putting some batts on, it really should normally be a lot more than 30mm/1″, especially that image with the battens in so it’s 15% thermal bridge. You can’t fix it later (or at least it’s extremely difficult/expensive). Depends where you are in the world of course. I guess 30mm of XPS may be adequate in some places.
I wonder how this compares to leaving a 50mm air gap behind your stud frame and running a dehumidifier for that space? An extra solar panel or two would cover the running cost, and you wouldn’t have all that synthetic foam sitting there offgassing and being a fire hazard inside your home. You would have to make sure the insulation couldn’t fall out the back of the stud frame and block up the air gap, but that wouldn’t be difficult to design in.
1) To prevent wicking from the soil through the footing, could you not pour the footings on a “runner” of poly sheeting? The excess width could be brought back up and taped into the basement floor vapor barrier. Outside, it would be wrapped up to the bottom foundation wall and fixed somehow. Then sealed over with the outside foundation ration waterproofing. 2) To prevent moisture wicking through the interior face of the foundation wall- Dry Lock?
So I’m assuming a thin lzyer of closed cell spray foam applied to the interior of the rim joists is preferred to open cell spray foam due to its decreased permeability ?? Please advise as my rim joists are not insulated, and i am planning to insulate them. Home built in 1989 on hill side. Cement block basement foundation. 2/3 of basement block wall is below grade. Home located in Knoxville, Tennessee area. I have no knowledge of exterior barriers or insulation.
Amazing presentation. I’m still just a somewhat beginner to moderate DIYer and so I was hoping someone may still be monitoring this article’s comments. I was hoping you might be able to give me the big picture view of what can we do to be the safest in an existing building that is an old house? For sure probably not a dry foundation although no evidence of leaks through the block foundation wall in the basement. I’d really like to do what I can. I obviously can’t dig outside of the foundation to add anything exteriorly and don’t want something ugly on the exterior. It sounds like maybe my best bet is rigid board insulation on the block walls and a small amount of spray foam in the rim joists?
Fantastic article! So basically don’t try to insulate your basement for a renovation, is that right? I have a house built in the 1940s and I doesn’t look like that the foundation has any water proofing on the outside. If I understand this correctly trying to do insulation on the inside would cause a lot of moisture and mold issues. So that sucks… Sounds like I should just focus a more efficient heating system for my particular case.
Nice presentation. Thank-you. What about crawl spaces, crawl space wall insulation, rim joist insulation, encapsulation, etc? We are in South Carolina, and homes appear to have much more trouble with basement or crawl space moisture and mold than in northern states. Any guidance would be appreciated.
2 years of listening to so many article’s without answering the problem i am experiencing. At 6 minutes, approx 20 seconds, you are the 1st to give me the answer. Plus, at 28:24. Right now the corner of my house has been dug by tractor shovel to the drain. I removed the 1 inch fiber insulation that was soak & wet, why do they use this stuff? Gets wet and freezes. We get minus 45 Celsius/Fahrenheit temps. That made the inside wall sweat so much behind the pink insulation, that i had a ice buildup of up to 1/2 inch inside. Though i had water coming in from roof… thank you for this amazing article. I will share it at large. Cheers. PS: any other suggestions, feel free to let me know please. Going in to do the work in couple/few days after rain stops. The water table is very high here.
Instead of placing the moisture barrier on top of the footer, why not make a moisture barrier ‘bathtub’ by excavating uniformly in depth to undisturbed earth, placing down a moisture barrier that encapsulates the footing and the exterior wall until above grade, then install polystyrene insulation with an additional polyethylene barrier on top of the polystyrene insulation to prevent “Iceberging” of the polystyrene foam sheets?
Pat Huelman : very informative to the non skilled builders out there. An additional approach based on that you don’t build where a natural swimming hole exists is if possible build higher out of the ground and back slope to move water away naturally from the foundation while still implimenting all the details that you have shown. In addition if the backslope is not too extreme a piece of poly plastic can be placed 4 to 6 inches under the soil slope to move surface water dramatically away from the building and possibly the outer edge of the plastic drainage slope intersecting a french drain there by keeping a large dry mass of soil surrounding the building.
Interesting that he says placing a capillary break at the bottom of the wall should be required but complains that putting one at the top is just adding an extra step. Also noted that the large grain size of gravel under the basement floor will defeat capillary action, but that water is going to come up through there anyway. Not a big fan of exterior insulation. I can see its merits, but there are a few significant drawbacks.
I implemented a few of the techniques some 23 years ago when I had my 3 story sog home built. I asked for a 6 mil vb under the slab for radon which was over the head of the cement man. The only thing that was done to ur standard was the exterior rim joist foam. The trusses were inset 1 1/2″ for this. I need to have u clarify something. I just have a 6″ wide block under 2×6 studs n with the 10’ f f ceiling height I’m considering redoing the bottom. Would u remove the slab n sand 4″ n redo with i f heat or just go over the slab n do i f heat n finish to ur standard for the sog construction. Also there’s no external anything over the block foundation for water. They put foam on the inside but not up to the sill plate. It’s about 1 ‘ short n the slab sits on the perimeter of the larger block. Another thing I did was to put 1/2″ foam on the inside under the drywall which I never saw before as well as the upper ceiling. The actual living quarters is the center of the building with the bottom being a huge garage n the upper is a high n dry basement. Ur info is spot on !!
Getting ready to build a slab on grade with 5 foot walls…what do u recommend for the 5 foot walls on top of the footing…I see some contractors are putting styrofoam on the inside of the wall only then backfilling up to the top, and then I see some putting the styrofoam on the outside of the 5 foot wall up to a foot below the top with a tar coating on the inside of the styrofoam…Its a solid styrofoam not the pink batten that u are using in your article..Thks for any info..from the top of the footing to the under side of the 5 foot wall its just concrete on concrete…
According to a lot of systems here in Sweden you sould remove the vapor barrier towards the outside and then let the condensation point be in the insulation on the outside. That should pump moisture from the wall and offload it outside the wall. Normally you use a product called isodrän, but I think Rockwool would work the same. To offload moisture from the soil one could use a plastic sheet called Platon mat. But most just removes the membrane on the wall and put up isodrän.
My house already has a brick exterior so there’s no chance of putting foam on the outside. You stated to not go too thick on the rim joists if using spray foam. In that thought, I want to use polysio but how thick is too thick? I want great insulation value so I would like to use a 2″. Will that be too thick?
Im perusal this with someone elses phone so i don’t go by the name this comment has but I’ve residential and commercial insulated for nearly 20 yrs let me tell u guys this is way over thought i have found a much better way it would only add $60 to $150 to price and guarantee humidity stay well below the 60 percent threshold ive been thinking about it a long time it will increase r factor and decrease the need for more r factor don’t mean to be rude but if they would listen us little guys a chance sometimes that don’t have money to start small business and get a patton on ideas we wouldn’t have this maybe some of us working people they might find we its possible we have i.q.’s over 160 to we could get some finances instead of robbed of them this is not a bad article or idea just to much of a switch from the norm for an all in one switch. I want to help people save money Im starting up in east tn soon and you will im not f.o.s. l know a few things just not everything. Im not a crawlspace ninja either. Sorry about grammer dont really care to fix it.
I need help!!! We had some flooding and I’m remodeling our basement portion of our tri-level home. The basement portion is partially under grade thus there is a “knee wall” of about 2 feet along the bottom of the outer walls. My plan is to paint DryLock on the inside of the knee wall to provide a barrier on the vertical wall. then EpoxySeal on the floor to provide a barrier on the floor. We’re looking to put commercial grade carpet with padding on top of the EpoxySeal. Will this system work or am I missing something or am I totally off base??
lol- never put fiberglass insulation on the outside. It would not do anything unless you plan to not backfill and build an extra wall of foam around it. Now people build with ICF (insulated concrete forms) that are waterproof, have greater strength, and greater insulation values. (below grade you may want to put a water barrier on the outside of these also though. Just in case)
One of the best explanations on foundation insulation and moisture mitigation I have seen. I now better understand how and why my 32 year old concrete block foundation does what it does. I have efflorescence on the walls, mostly at the bottom course and the top few, exposed to outside air. The foundation was waterproofed with a product called Theroseal. It adhered and held up quite well on the outside foundation walls but unfortunately does not have good waterproofing properties. It probably would have been better to just use an asphalt coating. If I were to build a home today I would certainly use the techniques described in this article. Now if I could just find a way to stop the efflorescence on the inside walls. The last product I tried on some of the virgin walls was a product called Hydro-seal 75, an epoxy paint product. Now after about a year the efflorescence is pushing the paint off the walls. It works great on the areas where there was no efflorescence.
Hello, I love this article. I have foam on the outside of my basement wall below grade. I have a block wall. I would like to finish a small room in one corner. Could I just build my wall an inch or two away from the concrete to allow air from completely around the room. And we always have a dehumidifier running
I have a 80-year old home with a basement that I’m currently renovating. It was renovated before and had moisture and mold problems that I’m trying to avoid this time around. The basement is a walk-out–only subgrade on one wall. Unfortunately, I can’t really dig down and add an exterior barrier on that wall because there’s a large covered porch that I’m afraid would be compromised structurally. So that leaves the interior approach. Thankfully, I pretty confident I’ve solved any standing/table water issues due to extensive french drain and downspout drain installations and reworking. Still, I’d love to get anyone thoughts on my interior wall plan: 1″ layer of XPS R5 foamboard installed seamlessly and sealed with foam spray for both a vapor barrier and insulation. Then, on top of that, metal 2×4″ studs with unfaced R13 fiberglass insulation for a combined r-value of R18. On top of the studs, but before the sheetrock, I plan to put CertainTeed’s Membrain vapor barrier, which blocks vapor from passing from the heated space into the wall, but allows vapor to pass the other direction (to keep vapor from being trapped inside the wall). MemBrain is not very expensive and my understanding its much better than using a traditional vapor barrier, which can actually make the situation worse because it can trap vapor in the wall. On top of all that, I’d put a mold-resistant sheetrock. Any thoughts or comments?
For interior insulation you might use following strategy, it looks like it reconciles with physics described in this article: put dimpled membrane on the floor, plywood or OSB on top and screw it to concrete floor. This will take care of moisture coming from below. put 6 mil poly or better still dimpled membrane too on the wall all the way down to basement floor, and seal it to dimpled membrane on the floor: this will take care of incident water and water vapour through the wall. Because it is dimpled membrane, the air underneath it gets to Rh 100% and equalizes vapour pressure. Put regular frame on top with fibreglass insulation, but instead of using poly as vapour barrier on the inside, use variable permeability membrane like Certainteed MemBrain. It changes it’s permeability with change in RH: once RH goes above 60% it opens up, let’s water vapour through. So if you get some condensation inside the wall, variable permeability membrane will let it dry to the inside.
What I have found in my time in construction is that removing SM foam boards from below grade, I have seen first-hand that this product absorbs moisture. What is normally less than a pound in weight brand new, ends up being thirty pounds when it absorbs water. The only recommendation I have if placing it on the exterior foundation and below grade is, tar the entire concrete wall, place your blue SM rigid board and then tar the outside facing once again. I know this sounds like a lot, but if your SM board is absorbing water, then what good is it in a thermal capacity? This was a great and informative article. Thanks for posting it. Cheers!
Bill on studs no basement all the airflow can go beneath in between earth and house. Use a wood structure with straw for the floor and on top of that you can use water heating system in the floor walls also I would add straw make sure to and one and the outside can be rendered with lime it is effective against bacteria and moist and works really good together with the wood and straw. Inside a 3 cm or 1 inch plus carb layer with special finish carb will give a breathing and very pleasant atmospheric enrichment to your life. The carb works also really great with the straw and wood structure and breeze all in and out but the straw is so highly dense and insulating that no other construction can resist it Plus the wood straw cob and lime constructions are in general extremely more cost efficient than all modern strategies and tactics you need so in the end all the strategies for example the bathroom to get water insulated with all kinds of layers of plastic in special blues and tiles are diminished when you change your mindset because even the most great idiots can repair the clay and the initial rendering of all the walls will last at least 10 years.
Excellent article! Water and condensation are finished basement enemies, especially in Northern parts. There are so many insulation products available and the same amount of opinions out there, many of them contradicting each other. Seems the best way is to insulate with rigid foam board on the outside, however very few builders will/have put in the expense and do the bare minimum to meet building code. So that means most of us homewoners need to find the best practices for our already built homes and insulate properly on the inside; from the rim joist all the way to the floor. The one thing I learned today that a carpet would effectively make the slab cold 17:52 “a warm slab is a drier slab”..and a cold slab is not a good thing. I originally was going to build my subfloor with Delta FL (dimple membrane), then 1″ XPS foam board, then 5/8″ plywood on top, and then my vinyl plank flooring. Now I think I will scrap the foam and plywood portion so the subfloor will not get too cold…allowing my heated space to also heat the slab and breathe a little more. I can just have a few area rug to keep the toes more comfortable. Vinyl plank is pretty warm to the touch. Several other bonuses with the using only Delta FL and Vinyl Plank only floor. 1) Increased ceiling height (in my case 1-5/8″) 2) Much less cost (plywood and foam board and Tapcon screws are expensive) 3) Much less labour of cutting plywood especially around corners and fastening wood down with Tapcon screws (I never liked the idea of drilling holes through the concrete since through capillary action, would draw water up from the slab.
I mean, sure, its great with a basement, but we in sweden kinda gave up on basements. They suck, need a lot of maintenance, or super expensive to keep fresh. So most if not the majority of homes in sweden are built entirely above ground, the slab never tutches the ground. Dont even know what a basement is good for in this day and age anyway.