The RIGHT WAY to Insulate Your Concrete Floor
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- Опубликовано: 18 янв 2021
- If you are building a new home, do not forget to insulate your concrete floor. Whether you have a slab-on-grade home, or a home with a basement, you need to insulate the slab. As much as 1/3rd of your homes heat loss can come from an uninsulated basement. I suggest building an ICF house from the footings to the roof and insulating the slab with rigid foam board to provide a whole house insulation envelope. There is a proper order to place your under slab insulation products, so make sure to watch the video all the way through.
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This is the best video I've seen for teaching people how to insulate basement concrete correctly, even the details of sealing the gaps with tape, and why we should put vapor barrier above the foam were well explained. Thank you!
Thank you so much for sharing these informative videos as we are planning our build next year and these provide us questions to ask!
Glad it was helpful!
We just did our basement slab with 2" and seems to go in well. And the lip of the footers with 1" foam on the plate to create a thermal break. The infloor heating loves this type of system the most to create that thermal mass for heating. Keep up the good work on the videos.. 👍
Did you use 2 x 4 or 2 x 6 wall studs? Did they hang over the 1 inch thermal break? Thank you!
This is a good start. I specialize in homeowners building their own performance homes and guide them through the process. We use a minimum of 3” under the footings and slab. I typically run 1.5” one way and lap joints running the other direction, so I don’t tape anything except the vapor barrier, which we use 10-15mil. We also use in floor heating to heat those spaces. The only issue to be aware of in that scenario is the electrical grounding. When you thermally break your house you also eliminate the ability to do a Ufer ground (concrete encased grounding electrode). My remedy to this is to pour a small 6”x6”x20’ trench and fill it with concrete and a rebar piece in it just outside the foundation and have it tie into the basement wall like standard. This makes it so there is no break in the vapor barrier or such. You can also just use grounding rods depending on your jurisdiction. Just bury them before you backfill so you don’t have to pound them in. I have details for all these if anyone wants them.
Josh, can you send me some pics or drawings of that ? ? Appreciate it .....Bob
bobjmariano@msn.com
Josh, can you send me also the details of your walk out basements too ! ? Thx Bob
bobjmariano@msn.com
@@bobmariano1695 just sent it. Let me know if you didn’t get it.
Good info thanks!
Hi Joshua, would mind sending me the details? (Not sure how i contact you though)
Great info here, thanks for taking the time to put this together!!!
I appreciate the comment
For some interesting perspective, here in the cold of Sweden a typical slab nowadays has around a foot of foam insulation underneath it, except for under the footings and any interior load bearing walls
Damn man, what’s the low average in winter over there?
I'm surprised such a thick layer of foam doesn't compress and cause problems
@@richfortin08 These last few years it has actually been relatively mild here in Stockholm, with around -5C/~20F as some low average, but we can often get periods of around -25C/~-15F. And that's in a fairly southern part of Sweden
@@tryscience I meant styrofoam, "foam" was a bit fuzzy perhaps. Styro of various ratings is used, but the range of allowed weight per square meter (or roughly10 sq.ft) for a 50 year maximum 3% total deformation is around 3-7 tons depending on the rating (if you trust the manufacturers word). The thick slab also helps with load distribution
@@caboom1057
Om inte man satsar hårt på Finnfoam XPS-skivor 😉. Men håller med om att minst 200mm isolering och golvvärme är grejer 💪🏼. Energianvändningen är nog jätteolika, värmepumpar verkar vara ganska okända men att elda ved i alla olika former tycks vara vanligare. Hälsningar från södra Finland 🇫🇮🤗.
I love insulation, one of my favorite topics in home building, I would think using closed cell spray foam on gravel under the slab would work great as well. Not 100% sure its rated to do that but I would think it would work perfectly.
Yes, closed cell would work great under a slab. It's just very expensive.
Another interesting perspective, in Upstate NY I have switched to spray foam under the concrete in all my basements. I usually spray 1.5 to 2" thick, and there are 3 major objectives accomplished: continuous vapor barrier with no breaks, proven radon barrier, thermal insulation. The spray foam sticks very well to a gravel base.
Makes perfect sense. I assume you are using closed-cell foam.
This is the right time to install a in ground safe. Pvc pipe with a threaded cap works great. When finished it looks just like part of the plumbing. 😉
@@assassinlexx1993 Great Idea
Is that cheaper than buying foam board?
@@clayjones553 3-4x more expensive, but better r-value and seal at the end of it.
I built 9 ICF homes. They are great, but often built wrong. Yours sounds perfect. Type 250 and moisture barrier and stucco tape is great
Thanks for the comment
Anything is better than nothing in terms of floor comfort, but a little more is better IMO… In fact code minimum where we are at is R10 if you heat the slab. The only real problem with the barrier under the foam is if you are on gravel. It is OK if you are on clear sand which is how ours is as we are built on clear sand. So we planned out the stack and for the most part only excavated to that height leaving the naturally compacted sand as our base.
Having the insulation on top of the barrier also protects it from the rebar/mesh and from the yahoos pouring the slab as they reach for the mesh with hoes and rakes to lift it so it is in the middle of the slab. In doing this as they work, they will regularly punch holes in it if it is exposed on top. In fact is is pretty much a requirement to put the VB under the insulation if you are putting in radiant tubes in the slab as they are often attached to the insulation sheets to hold them in place so they don’t want to float during the pour. If you are stacking sheets, you could also put the VB between layers of insulation. We used a henrys product on the outside of our ICF basement wall and footing, and then added a 1” 25psi layer on top of that to protect the barrier from the gravel and also provide a second drain path/drain-board between the insulation and waterproofing for water to drain down to reach the perimeter drain. This was about the same cost as using a product designed as a drainboard/protective layer, was available locally and added another R5 to the basement walls…
As for stuff getting under the insulation sheets, if they are on top of the VB: If they are taped, about the only thing that can get there is water, and the concrete will displace the water and force the sheets back down as soon as it is poured onto the sheeting. We had heavy rain before our pour and all the excess water went out the garage bay and walkout doorway(daylight basement). As we added the concrete to the back end and worked our way forward…
Don't know if this is still the case but there's an insulation method called the "Alaska" slab on grade. It was a result of federal
research done in Alaska decades ago. Basically it involves insulating the exterior foundation down to and around the outer
footing. And then installing 2' wide horizontal panels at the footing level before backfilling. Did a dairy mono-poured slab with
stem wall using this method and worked like a charm. The main discovery was that the cold cannot travel very far horizontally
at freeze level depths. There used to be a gov site about this but I was told it had been removed. Never checked to see.
Some people say that because "heat rises" so underslab insulation is not necessary, but heat in a solid goes all directions equally. Insulating under the concrete makes it dryer inside, as well as so much more pleasant. We now also insulate (and vapor barrier) under the footings, with an insulating mix.
Good point. Heat does not rise. It is hot AIR that rises. Heat will flow in the direction of the most dense material. Concrete, being very dense, conducts heat better than air.
Exactly! Heat goes in the direction of less heat, plain and simple.
Heat transfer is by conduction (touch the pot of boiling water - not really - OUCH!), convection (feel the heat rising over the pot) and radiation (hold your hand off to the side and feel the heat).
Convection rises. Conduction and radiation operate in all directions.
Cold raises from the concern if not insulated
Heat doesn’t rise, it goes from hot to cold. Warm air rises because of the difference in density between hot air and denser cold air. Conduction is what cause heat to be lost through a floor slab , hence the insulation under the slab.
Would highly recommend against the vapor barrier going over the foam. It should go between drain rock and insulation. Especially if it is extruded foam instead of expanded. Extruded foam will become water logged or calcify over time and lose its r value when exposed to water. No insulation should be getting wet.
I belive the issue with that approach is that the rocks can penetrate and rip the vapor barrier.
The Vapour barrier should always go on the warm side of the insulation to prevent condensation. That is why the poly goes on top of the insulation….. the house is warm the ground is cold…… look it up
Also the foam will float unless the poly holding it down
@@jessemathews7470 The ground is warm and slab is cold actually during night thats principle behind ground source heat pump.. Condensation occur when you have warm air touches cold surface similar to opening cold soda thats why they put vapor retarder under slab, in this case i would agree to put it above vapor retarder below insulation to avoid calcifying the insulation
Slightly different terminology here but on the floor we put the dpm (damp proof membrane) against the sub base (compacted stone) to stop moisture coming up through the ground but on walls and structure above ground level the vapour barrier goes between the insulation and interior otherwise it becomes waterlogged with vapour from inside the house which would otherwise travel through the insulation and condense on the cold wall.
Like you say, eps is open cell so it's hardly ever used anymore, far superior alternatives.
And yes I have used XPS under my slab and use at least TWO layers of the 2" for total of 4" and if it is a "walk-out" basement, the outer wall is set with THREE layers of 2" of total of 6" and I also am able to typically set another 4' x 8' sheet on the OUTSIDE of the wall, which is usually about 10" to 12" below the basement floor elevation, to cover with topsoil and sod. If no sod, then aggregate for some type of patio. BUT it has an added effect of insulating the slab even with greater affect!! I learned that from a builder in the extreme cold of northern Canada.
it does not freeze UNDER ground, just isolate the walls from basement.....
@@dolmarf411you will find there's different freezing depths in different places. Anyways, you should definitely insulate the entire building envelope to eliminate thermal bridging. Doesn't matter if it freezes, if there's a temperature differential you need to insulate.
Actually living in a slab on grade no under slab insulation, or even perimeter insulation, half the amount of energy costs for same size house next door that has crawl space floors are insulated. I find that heating cooling with wide temp swings where I level night/day the slab next to hearth acts like a heat sink, but at a slow rate so makes indoor temp a lot more stable at least for my house
I have pressed gravel undernwith blocks eall , should I apply it same way ? Foam connect to the block and it up ??
We now know the XPS foam will eventually take water into it. This will lower the R value of the product. We now use GPS, a graphite infused XPS foam. I always put a vapor barrier under and above the foam. If your area has issues with termites use a termite-proof, woven vapor barrier first. In my area I put down a generous layer of Diatamaceous Earth on the bare ground first. This is cheap insurance for anything that might attempt to chomp on your under-slab sandwich.
Do you have any recommendations on retrofitting a home that has an uninsulated slab floor?
On an existing slab home, if you seal the concrete do you need to install vapor vents in a wet environment?
we always used reflective bubble wrap or paper on top of or in place of the insulation
Thanks for the video 👍from Davenport Iowa
Thanks for video on how you did it.
FYI - I'm doing similar but a bit DIY since I'm in E. Texas and we aren't as concerned with heating but instead cooling and moisture... But you still insulate.
Yes on the Form-a- drain then I am putting down crushed limestone (what's available value priced around here) then a vapor barrier but I've set up to pour aircrete instead of buying expensive foam (and don't have to worry about anything floating). The vapor barrier mainly keeps the aircrete from draining down into the crushed rock until it hardens.
I don't have to be concerned with having batches of pours for the 'insulation' fill as there's no concern over cold joints under the slab, just like sheets of foam. I'll put another layer of polyethylene on top of that.
Then I'm capping the aircrete with the regular concrete.
Neat concept. What kind of insulation values do you get with the aircrete? Limestone is what we have around here too. While not the hardest rock, it does great in these applications.
@@Challenged1 because the aircrete is home-made I can't say for sure but it varies from R3 to R6 per inch depending on how much air is entrained. I just guesstimated R4 and poured 6" on top the gravel which brought me to the top of the footer.
Note that I painted Rub-R-Wall on top of my footer to create a capillary break before going up with the wall. Sheesh, $9000 of ICF blocks, and I still haven't poured the walls yet.
And I wish I was a 'rich' as you to afford to buy equipment, rental is killing me.
On the aircrete, I made 50 gallons and poured it, made a batch and poured it and kept doing that all day long for a couple of days until inside the footer was filled.
This is a small house, just 2040 ft2
First course of ICF is down but the top slab above aircrete not poured yet... Soon.
Great content!!!
How do you use the pex clips that screw into the foam? You would put holes in the vapor barrier.
Great informative video, sharing knowledge to others is so important !
There must be a vapor barrier under the ICF too. Otherwise diffusion will bring some moisture form the ground up into the walls.
Usual solution in Europe: reinforced slab (optionally XPS below) goes on top of the footing. Then a continuous layer of vapor barrier is put on the slab. Then the walls are built. Then comes heat insulation inside and a thin foil to protect this insulation from the concrete while liquid. Optional floor heating is installed and finally a think concrete slab is made.
Do they make ICF pieces for flooring?
Going to miss that free 10 deg drop in the summer though. Moving into the basement in the dog days was always a nice option to have.
Ok iso on a new slab, you have the vapor barrier over the insulation, I assume the insulation lies over the compacted gravel base. So concrete slab over vapor barrier over 1" inaulaulion over compacted gravel base.
I installed blue board under my slabs and on the outside of the foundation in 1984 .
Recently I was installing piping to a well for a heat pump, when I cut the blue board out it was very heavy because it had become saturated with water. This was very disappointing! The soil around my house is very well drained and I live on the top of a hill . So I would not count on extruded polystyrene to not absorb water in ground contact applications. Now I don’t know what to use!
thank-you
Hello Garrett, firstly: nice job in the videos!!
Regarding the basement and foundation mechanics, can you explain your approach to the need for a capillary break?
My local code requires it.
@@Challenged1 sorry, let me rephrase: how are you working the capillary break?
@@scottlurken9667 I have foundation drains on the inside and outside of my home. I used form-a-drain
@@Challenged1 don’t think that s what he talking about- how CEO you prevent moisture from rising up the footer into the foundation wall/slab ?
I built 1100 Sq ft slab on grade double wall construction super insulated home I bluit on edge of bank for river view. Dug out 1 foot of top soil and pile 2 ft high around slab area than back feild with 3 ft of compacted sand .than 6 mil plastic vapor barrier than 2 inches blue foam one way and another 2 inch foam running the other way to eliminate seams than 6inch wire mess to tie radiant floor tubing too than 4 inch concrete floor lt been several years and no problems and I know vapor b barrier
Part 2. : vapor barrier works well as when I relocate toliet line I could the plastic did it job.
NOTE! Disclaimer. Know your local climate first! In many parts of the American South and Southwest we have termites and ants that love foam insulation and ICF. Insulation should not be within 8 inches of ground contact minimum per IBC and I always built higher to offset people planting flower beds and soil accruing over the years. There were many lawsuits with ICF manufacturers and installers from ground contact with ICF or foam and termites and ants used it to build nests and tunnels into 2nd stories at times. And poison doesn't always work like it should. So, check your codes. Know where to use and not to use. Sometimes you have to build a hybrid system or use AAC block. But in the right area's insulating slabs right is a key to comfort.
You can buy foam with pesticide in it, or go with rigid fiberglass panels. Also treating the ground annually with a pesticide can reduce or avoid ants making foam insulation into swiss cheese.
We do radiant floors.... compacted base, vapour barrier, foam , clear stone on top of foam and then mesh (which you attach the pipe to).... nothing moves or floats and the radiant tube heats your stone and slab for better heat retention.
How do you drain the stone?
@@Challenged1 sorry i guess my post made it sound like the base was just dirt....Theres still a weeper on the perimeter ... and the base is a compact "A" gravel (less dust) which is firmer than clear (drain) stone but still permeable, the stone on top holds the foam from teetering shifting and lifting and makes it way easier to pour . Costs a few hundred bucks extra but worth it in my opinion. It could all just be in my head, but I think the density of the extra stone on top of the foam aides in heat retention of the slab as well...sorta like a stone fireplace.
@@macleanclassics Stone/rock has great thermal transmissibility numbers. Do you place a weeper on the inside of the footing as well as the outside? Anytime I talk to someone building a new home, I recommend they place weepers on the inside and outside. Cheap insurance.
@@Challenged1 yes 100%, thats the weeper I mentioned, under the slab... some go to sumps some don't, depends on native soil and topography. The exterior one is a hydrolic pressure relief.... using ICF for all of our foundations....( thats a no brainer).
@@macleanclassics Awesome!!!
We used 8cm expanded polyurethane, damn expensive though. It's lovely to have a warm floor (tiled)
I was told this is the best way for hydronic heating
Garrett, I have a question. How would you suggest that I insulate the concrete floor in my garage? I plan on building a house inside the structure and framing in the walls, raising the floor about a foot to enable me to lay the plumbing, ect. What I had considered is laying insulating foam board, much like what you have shown. Then laying down foam pads (kinda like the green one on the floor under you) but I will use black, like they use on the floors for exercise rooms in garages or basements, then laying the floor framing down on that. But I also considered laying the foam insulation boards down first on the concrete, then laying the wood floor framing, then cutting the black foam pieces to fit inside those frames. I know that's a lot of work, but I want the floor to be well insulated and do what I can to keep out the cold. I'm a single older Woman and have lived in an old mobil home that is very cold in the winter and I want to do what I can to not have to deal with living as I have been. Also, do you suggest any kind of vapor barrier directly on the concrete before I lay the initial foam insulation board? I appreciate your time and thoughts on this matter and look forward to hearing your response. Thank you!
I'm not sure code compliance officials will allow you to build your interior walls on top of foam. You may want to check with them first.
Great may be doing that
Thanks for the practical tips! Just curious, would there be any bennifit using spray foam under the pad instead of foam board?
It would have to be closed cell foam to meet the psi standard, which has a greater r-value per inch than the board. If you can afford it, it's the way to go.
@@Challenged1 im building a small home so i can make it higher quality. Thanks for the tips!
Closed Cell only. If you can afford then yes
Nice presentation thanks
Thank you
Thanks for the good content bro. I have a question: I want to use a basement as a cold room. Would you still insulate it? Or should I only waterproof it to keep the cold inside? Thanks
Uninsulate
What exactly are the advantages of the ICF technique compared to a cavity wall made from CMU >> open cell foam (air + acoustic barrier) >> brick, from the inside to the outside, on a reinforced concrete column-beam-slab system?
Much cheaper and faster
Very interesting, thanks
Heat rises how do you loose 1/3 of the heat throught a basement? Walls i understand but are there any numbers on slab or under slab heat loss. Really trying to figure out if the expense is worth it. Hoping to build next year thanks!
The heat loss of the slab is going to be dependent upon the temperature of the ground it sits on. If the ground temps are pretty cold, the payback will be much sooner. If not, it may not be worth it.
yess, old house built close to sea with cellar- at least 10degrees temp drop or even more. and if you have 30-35 degrees outside it starts to condensate A LOT of water. nightmare.
Where outside weeper system comes into the home through holes in footing you should trench a 3-4 inch groove to place and hookup your weeping tile (with holes) to your sump, storm hookup (which should be BELOW your lowest grade in basement, ie pads/footings etc.
That way youcreate a burried trench river for outside water to come into the basement and not pool/spread all under the pad.
If you have a sump pale or below water table or close to it, your service trench can and will bring water under the pad like a Trojan horse.
Sump pales should have holes 3-4 inches from BOTTOM of the pale, not the hole at the top, if water is coming into that hole, your basement is already waterlogged.
I have form-a-drain weeping tile on the inside and outside of my house connected to two sump pumps.
Once I saw how great lower holes in sump pits worked, I made sure to expose them in any pits I installed. I worked on hundreds of new homes , mainly semi custom to million dollar homes. It's amazing how something so small can lessen water problems almost immediately. Nothing like a dry basement.
The vaper barrier is a good thing, but it is redundant. The closed cell foam you showed us and taped up tight is a vapor barrier in itself. Also, I agree with the commentors that say the 6 mil plastic belongs under the slab. It is the same principle you use on your above ground walls. The vapor barrier goes on the cold (& humid) side.
You mentioned rebar. Concrete has great compressive strength. Rebar adds tensile strength. The tensile strength helps if the base under the slab settles or heaves. Think of a bridge or your foundation walls. They resist forces just not present with a well compacted base under a slab. I could argue that it is unnecessary in a footing, but at least there, they have considerably more weight than a basement floor will have.
In a home, vapor barrier goes on the warm side to prevent condensation. Under a slab, that requirement is to keep the high moisture content soil from transferring moisture into the dry basement. Believe it or not, EPS insulation can get water logged and lose r-value. Local codes always require the moisture barrier regardless of the presence of insulation.
I would never be onboard with footings without rebar. Never to do we have a spread footing with a uniform load evenly distributed over it. It's almost always a point load. Even a typical basement foundation has an 8" wall sitting on top of a 21" wide by 8" deep footing. I would argue, more rebar should be placed within the footing as well as transverse bars placed every 24". Almost every home I've been in has had some sort of settlement issue.
Another factor most folks don't think of is the differing moisture content under the footing at different points of a home. A home with a view out or walkout basement will have footings at different depths. Footings at shallower depths are much more susceptible to the conditions near the surface. During a drought, the soil under the footings in the shallower areas will dry up and shrink at a drastically different rate than the soil under the footings in the deeper areas. Without proper rebar, significant home settling occurs. I've seen this firsthand. Minimum code is inadequate. I'm a licensed professional civil engineer by the way.
I understand what he is doing here. However, it is the opinion of many experts that the plastic sheeting belongs under the ridged insulation.
Over time rigid insulation that is exposed to long periods of moisture degrades and the R values go down. Protecting it from ground moisture but exposing the insulation to cement with heat pipes will actually help to keep it dry.
Do you compact the stone?
Yes, with a plate compactor
Hi great info. I was wondering what is the the reason to use 3/4 crushed stone instead of 0-3/4 crushed stone. I always though 0-3/4 was better for support and traps less water in case if freezes but everyone keeps telling me to use 3/4 net crushed stone. Is it because it’s easier and doesn’t need compaction? Thanks
The 3/4 crushed stone drains well. Make sure you run an interior and exterior weeping tile as well.
in the UK they put 3 or 4 inches of insulation under the slab or screed as they call it i think more is better
If you can afford it, put as much as you can.
Garrett, not sure if you mention this in any of your other videos, but I'm about 10 videos in and still didn't see it. Did you do ICF between the floors or just the outer walls?
Just outer walls
You mentioned to overlap 6mm poly a couple of feet. Does it need to be that much? Do you also tape the seams of the poly?
6" is the minimum with the seams taped.
Hi, I appreciate you technique, but I think you will do yourself a better service if you put the vapor barrier (plastic) beneath the insulation. Especially if you have ground water in close proximity to your basement floor. I like the I C F construction design you are able to control the heat / cold transfer. What I have found is that water will wick up through the insulation if the plastic vapor barrier is above the insulation. Undermining the concrete floor. The vapor barrier should be placed beneath the insulation to avoid the migration of moisture, in fact I’ll take that one step further, after the gravel is tamped in the base, if finances permit, pouring a 1.5” to 2” rat slab provides a good base for a vapor barrier. Myself I’ll use a 90lb felt paper and have some roofers “hot mop” it and then put down my plastic vapor barrier, 2-4” of the engineered polystyrene you mention is rated for 40 or 60 psi ( 40 is fine it’s designed for forklifts when the insulation is under concrete) foam fill any cracks or voids between the sheets of insulation. This insulation comes 1”, 2”, and 3” thick, it’s made by DOW Corning. Place your “dobies” and rebar or mesh and pour your concrete.
I think 1” is too thin. Just my 2 cents
Stan, can guy send me any pics or drawings on what your describing ? Really appreciate it ! Thx Bob
bobjmariano@msn.com
@@bobmariano1695 actually the vapor barrier goes on the warm side of your insulation… just like in your walls
The ground water should never reach the underside of the foam. Place at least 6" of good drain rock, linked to a drainage pipe, like the Form-a-Drain that he used. Make sure that drain pipe has a way to carry the water entirely away from the house, either to "daylight", or if necessary into a sump with a pump. Then if water rises under the slab it will never reach the top of the drain rock.
A little bit of water won't harm the insulation. It will be blocked from ever reaching the slab by the vapor barrier.
Just spray 2” of closed cell 2lbs foam it’s a seamless meaning minimal thermal bridging and also a vapour barrier so no need for the plastic. You can also spray the outside foundation (slab on grade) and connect to the floor to make it one continuous seamless barrier plus there’s more r value per inch (6.5)
The cost is 3-4 times higher than rigid foam board
Not in our area $2/sqft for 2”
@@Challenged1
Which is comparable to 4” of the rigid foam when you factor in higher r value per inch and thermal bridging
Rigid XPS foam is about R-5 per inch and sprayed polyurethane foam is rated at R-7 per inch but loses some R value to become R-6, so people use the 6.5 number - it’s close enough. Generally, there is not a big enough difference to bother with closed cell spray PU foam cost unless you are using it in cavities that are small and too hard to fill with XPS foam board
Best system with spray foam under the slab do it once regardless of cost then it’s done wright you spend the money on ice but cheap out on one of the largest thermal mass just doesn’t make any sense.
if you have a basment it should 100 percent be cooler down there in the summer and a little warmer in the winter.
Similar to Cabooms note, here in the UK we have to build with a much higher R value floor insulation (over 200mm EPS!). re: vapour barrier placement, this is always on top of the insulation otherwise, yes, it will have a tendency to float. I thought expanded polystyrene, as I believe all rigid construction insulating foam,was a closed cell foam consequently it couldn't get waterlogged?
I saw a study where expanded and extruded foam performed about the same when water logged. In the States, we typically only get extruded foam, as it is perceived as being higher quality. Stores will sell some expanded foam, but it is low density and sold as a cheaper option. People complain about the little beads of foam that break off when cutting expanded foam...
"vapour barrier placement, this is always on top"
Yes, there should be a foil on top of the insulation, but that is not the vapor barrier. That is a thin technological foil, which has a role only while the concrete is liquid. The real vapor barrier should be under the insulation if that is EPS. (In theory XPS should not be protected form moisture, but still I would put the vapor barrier below.)
My builder did 2" FOAMULAR NGX F-250. They didn't put any plastic down. They said with the seems taped it was a good enough vapor barrier. What are your thoughts?
It was such a cheap addition I'm not sure why they wouldn't do it... This is Clinton Missouri
I would do it, but that may just be me. Like you said, it's cheap insurance
Thanks for the video,
From my experience vb should be underneath the insulation.
If using closed cell (XPS) insulation, then it can be on any side.
Pretty good advice, however, I recommend strongly that you install an expansion joint between the wall and the slab all the way around. The coefficient of expansion on a concrete slab is significant, especially on the long axis. I've seen the basement wall crack or bulge from the expanding slab.
Concrete contracts and does not expand- contraction joints are mistakenly commonly referred to as expansion joints.
Wonderful videos. What are your thoughts on insulation under footings? Im planning my build with a full icf envelope, foundation + walls + roof. Im in Canada.
From what I've read, insulating under the footings shouldn't be a problem as long as the insulation psi rating is equal to or greater than the psi rating of your soil.
Do it! There is no reason why you can’t thermally break the entire house. I am in a similar climate in Idaho and I do full insulation under everything. (I specialize in these high performance homes built by owners for a living.) My minimum is 3 inches of EPS. If you have a walkout basement or are wanting to do a simple slab there’s a convenient form called Monoslab EZ form that is pretty slick. I have some details I have made I can send to you to show you I how do them.
I'm in Newbrunswick Canada the footing is the most over looked
Insulation stops the wicking of moisture also
Im in Ontario, bought some land near Barrie. I have been doing some research on some products. Theres Legalett and IntegraSpec here that look promising. I am trying to go the full passive home route or as close to it within budget. Waiting for the weather to get a bit better and I will make some videos myself.
@@infinityexpressesitself9278 " thermo bridging " is the biggest detail to look at look it up if not familiar matte rinsler in USA on you tube
He's got detail vids of his house insulation insulation insulation
Mike Holmes said it best r20 insulation in walls is the minimum
THERMO BRIDGING
How do you run the vapor barrier on a slab on grade application?thanks Stone
Exact same method
Poly under foam is code in most states , why over can be big moisture problem for deteriorating insulation is what inspectors told me ,,,,,,, hmmmm confused , I think I’ll go with inspector advice, any thoughts?
I've been hearing about that too. I've never experience waterlogged foam, but I've heard of it.
Why not use foam seal instead of tape on the foam?
RADON is Radioactive
Concern
It comes from the earth the Soil Itself
Low lying area's like Basements are of particular concerns
Ventilation seems to be the best way of managing it.
Hi Garrett. Great video. Could you explain your slab insulation detail at a door opening in the walk out basement? Did you use the ICF below grade for frost footing on the walkout side of the basement?
My basement is view-out, so no door opening. I don't know that there would be a great way to insulate at the door opening. As you mentioned, you could definitely insulate the footing and run the floor insulation straight to it.
@@Challenged1 thanks for the reply. I thought I had seen your project as a walkout. My bad. Yea it is a tricky detail to get. I haven’t seen a great way in practice honestly. I am thinking about running a vertical piece of insulation in the slab underneath the threshold of each door. It would provide a thermal break and still allow for strong concrete threshold support.
@@franklinmade396 Makes sense since that part of the footing wouldn't be very structural. I like it
There are some ICF walkout videos on the "Bondo Built" channel:
ruclips.net/channel/UC2bdWYzIRMq_r6Rnidr4tdQvideos
In particular this video:
ruclips.net/video/cf5MAhQkYx0/видео.html
The footer wasn't insulated IIRC, but if the slab above it is insulated that'll get you most of the way. Might be a good place to put some skirt insulation inside the form (a poor approximation of ICF but good enough for a footer). I've seen that in some videos but can't recall where.
I have done a walkout basement on the house I am working on. I can send you my details and some pictures if you would like. Jlrubybusiness@gmail.com
can we pour the walls and footing at same time and make it monolithic on traditional concrete walls (NOT ICF)?
Probably, but I haven't seen it done
@@Challenged1 in florida under the slab do we need insulation or just the moisture barrier
Hey Garrett, you said your basement temp is consistent with the main floor. Do you have heat/ac going into the basement?
Yes, it is a fully conditioned space with air returns as well. So many folks forget about the return air in the basement
would you say it is redundant to put a heated slab in this situation? in my situation i will have vented heating as well
I dunno. Ambient ground temp in my region is only about 5 deg F off from preferred indoor temperature. So I would tend to think that you wouldn't want to thermally insulate your interior space as separate from the ground, since ground temp is closer to desired indoor temp (than exterior air temperatures) about 95% of the time.
Obviously, this is latitude dependent though.
Exactly. There are certain places where it doesn't really make sense, or the gain is too minimal vs. the cost.
@@Challenged1 Been thinking about this since I last posted. There are winter storms which invade the area... about how deep would you go with insulation on a basement, if local cave temperature is pretty comfy, but there is maybe a week or two of snow on the ground at some point each winter? Just do the whole walls, but not the bottom? Or maybe just a foot or two down?
@@kathrynck The top 4 feet of the basement walls are where the majority of the loss is located.
@@Challenged1 good to know, thank you :)
Half inch foam installation already has a vapor barrier on it so two layers of that would do the same as one layer one in the vapor barrier on top.
That method costs more
Always have your membrane on the warm side of the insulation.
Is there anything you should do different or possible to even do if your garage is your basement? I'm thinking of building a ICF house with the majority of my basement as my garage.
I know ICF makes slab deck forms. I have no idea if they would be up to the task of being a garage floor though. It might be something you'll want to look in to. If it works, you would have the thermal break you need.
I believe that polyiso insulation can stand the load of a slab and vehicles in a garage.
You'd do it just like Garrett said but you might want to put down some geofabric on top of the crushed rock then s THIN layer of sand (like 3/4") in top of that to fill in / bridge the irregularities of the crushed rock (so the edges of the rock don't cut up into the insulation) then put down the polyiso, the polyethylene vapor barrier and cap with concrete.
I'd sure recommend for a garage to use AT LEAST 1/2" rebar in 12" centers grid.
I think I read your post wrong. I was assuming the garage on top of the basement, not the basement as the garage. The real question is, do you want the garage insulated? It would be easy to insulate the walls and ceilings, but for a garage, I would forego the insulation in the garage part of the slab. If the garage is more of a workshop and is heated/cooled year-round, then maybe insulate the slab. I know you can get higher rated 60-75 psi XPS panels if crush is a concern. As Bob said, I would use rebar in the slab and probably thicken it up to 5-6"
@@Challenged1 just curious, why would you forgo the insulation in the slab of a garage? Just to save costs?
I'm getting starting on a shop/garage and plan on properly insulation it so I can install a mini split in the future if desired.
Will also make working in it much more tolerable in the winter.
You put out a lot of solid, nerdy engineering content which I why I watch and also why I'm asking 😃
@@gabelumby149 Mostly cost and the fact that it probably isn't constantly heated or cooled. If it's heated and cooled every-so-often, I'm not sure the cost-benefit would line up. Regardless, the 1" foam board isn't that expensive and can make a pretty dramatic difference. I sure wouldn't steer someone away from it though, I just look at things a little differently than most. Return-on-investment drives many of my decisions.
Nice video Garrett Glaser! Helped me a lot but I have a question.
My 100 year old house and currently my basement is only full of soil. There was concrete but it was removed a few months ago.
If I run the vapor barrier up 1 foot on the wall and tape it like you said on 4 minutes 50 seconds of this video. When I pour concrete, do I pour over a foot of concrete to cover the vapor barrier along the wall? OR just pour the minimum of 4 inches of concrete and leave the vapor barrier with taped seam expose so I can see it?
Second question I see that some people said there's concrete curling because of temperature and vapor barrier. How do I avoid it? Do I need to nail the vapor barrier to the ground on top of the gravel?
I'm also trying to run drain pipes with a sump pump along the walls inside my basement but I don't know if it's a great idea. The only time water comes into my basement is when it rains very hard outside other than that, it is always dry.
Do I need the insulation foam over the gravel floor?
If I use insulation foam over gravel, next vapor barrier over the insulation foam, then pour 5000 psi concrete on top of the well taped vapor barrier. We are planning to put tiles and can I place it directly on the concrete?
What's your advice?
Thank you, Zeke.
To anyone reading this... If you own a house that's 100 years + old, don't just pour concrete in it! Ask yourself what were the building methods used when the house was built.
A house like that already withstood the test of time, if it needs improvement, at least use materials that are compatible with the existing substance.
My house for example is also around that age and the cellar is always wet. But it's meant to be like that! The most important thing to do in such a case is to give the moisture a way to go! Do not trap moisture !!
Concrete is a very rigid material, wood is not. Concrete traps moisture, wood hates that!
I've seen too many old houses torn down because modern materials were used without any consideration.
My neighbors house is around 300 years old and was built the same way as mine, no major repairs are visible and its still standing strong.
Old houses need to move and breathe, don't work against your house, work with it!
Great information, I am wondering what the process is for insulating a slab that will also have radiant heat, is there a minimum thickness or concerns for getting the vapor barrier too hot !
In my area, 2" would be the minimum. You'd have to check with you local government.
No need to insulate below the slab with radiant. Insulate the perimeter down below the frost line. Insulating below the slab with radiant will not decrease your heat loss. Any load calc will show this
yes to insulation because you don't want to heat the dirt. The water temp will generally be no more than 100 degrees because the aim is to make the floor only 5 - 10 degrees above room temp. In order to do this the pipes must be in the top 2" of the concrete.
@@rupe53 the top 2 inches will cause striping, and put the tubing at risk of damage when cutting control joints. Heating the stone/base will not take away from the overall efficiency of the system. You will lose 0 btu's, and you get the advantage of increased mass. Nothing wrong with insulation under a slab, it just simply not needed. The perimeter is by far the most important
@@danray104 ... if you know there are pipes in the floor then you don't cut the joints with a saw. You can trowel joints if needed. BTW, do some reading on floor heating. They all say to keep the pipes closer to the surface. Matter of fact, most say to zip-tie the heating pipes on top of the rebar. Pipes that are too deep DO reduce the BTUs on the surface and also slow the room temp rise. If you are getting stripes on the surface, then your water temp is probably too high, and your pump cycles are too short.
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If you live in a climate where you need cooling way more than heating I guess it would be a bad idea to insulate ?
My utility bill in the winter is less than 1/3 my utility bill in the summer, I would think I would want all the free cooling I could get.
It would depend on your ground temperature. If the ground temp is higher than the temp of the home, it would work against you.
Doesn't seem like you're inside slab is going to be tied to your ICF walls. Won't this be a problem with reactive soils?
Only if the perimeter drain fails
I used 3/8" roll out foam insulation as per a northwest radiant heat supply company 10 years ago. Now everyone say it's insufficient. But I never hooked the radiant heat up and garage stays above freezing even in 5° weather. Anyhow..now I'm worried it may be a waste of money to heat with radiant and thinking of abandoning it.
We have under slab radiant heat and love it
if you are going to heat the space then radiant is the way to go. Since the floor is warm it will always be dry, and the bonus will be it feels 5 - 10 degrees warmer because your feet are not cold. BTW, you did the expensive part already. You could actually heat the area with an electric water heater instead of a ceiling hung electric forced air unit. The same goes for a small gas unit of either style.
@@rupe53 I'm going to try hooking it up. I agree the warm floor would really help in the winter
@@johnw4590 ... insider tip: If you go the route of using an electric water heater you can set the t-stats to the lowest point, but sometimes they only go down to around 120 degrees from the factory. If you have the older style (read: cheap) t-stats you can pry the pointer off and turn the dial further / lower, then put the pointer back on. I used this trick to make a single feed for a pool shower. Had to do some experimenting but found my sweet spot around 104 degrees and put it back together. If yours is newer then you may have to use a mixing valve to get the desired temp.
@@rupe53 Thank you for the tip! I'll keep it in mind before purchasing.
I assume ICF is insulated construction floor? I don’t know. Would have been nice to explain that.
Insulated concrete forms
ICF stands for Insulated Concrete Forms. That is what he use for the walls.
What’s the roofing system that you recommend
I went with a traditional wood frame/composite shingle roof.
@@Challenged1 any concerns about losing heat with a conventional vented roof
@@drchamp1902 As long as you spend some time air sealing and install the correct amount of insulation, no.
Is there any way to insulate old basements?
There is, but I don't know a ton about it. I do know there are some videos on RUclips showing different methods.
Insulated slab also prevents sweating on humid days.
Very true
Yes and no, it really depends on the temperature and humidity swing as well as the thermal mass of the concrete. But generally yes it will be better.
Generally it is better to insulate outside also in the slab if the building is used continously, because you will profit from the thermal inertia of the concrete slab, with a very interesting effect once it is heated or refrigerated.
I know this is a popular belief, but it just doesn't work. Modern humans want their houses at roughly the same temp year around, day and night. And high thermal mass is significant liability in this scenario. What you want is good insulation, low thermal mass, and an efficient heating and cooling system. This will keep your home comfortable year round!
If you want to use thermal mass in a passive solar design, (that's where the thermal mass idea comes from), you will get massive temp fluctuations inside your house. The house will get hot in the day when "charging" the solar mass, and the temp will drop below the temp of the thermal mass at night when you are expecting thermal mass to "heat" your house. On average your house will be warm, but it will rarely be at the ideal temperature.
@@fredygump5578 Other than statement contradictory to entire Europe building system I want to ask you - when you go to sleep is it better to have lower temperature or as high as during the day?
@@Bart-dg6qv Are you really claiming that there is a homogenous building system used across all of Europe, from Spain to Germany to Norway? Because it sure sounds like that is what you are saying!
@@fredygump5578 Stick to the sleep questions.
@@Bart-dg6qv I will take that as an admission that you know your initial statement is false.
This man only showed when you use an ICF foundation - and only a basement one. Not the other scenarios, such as slab on grade with shallow footers, or a crawl space foundation. - Only showed what he decided to build.
Architects require the plastic to go down first! Then the insulation on top! Every school state job I've ever done! I dont know if it's because of radon gas we have I dont know. But they will make you take it out if plastics on top I do not know why!
I’ve always understood it as plastic on bottom as well. I thought it was to keep the concrete from wicking up moisture from the ground
Here in Minnesota it’s plastic, 2” foam, tape on seams then concrete
Yeah, I'm wondering about this too. Even Risinger says foam and then VB as a 'last line of defense' and to avoid the foam floating. However, I've read about this a lot, and foam does absorb moisture which vastly reduces its R value. The VB first stops that R value degradation in theory. Add to that I've seen some other guys saying as long as your foam seams are taped good, it's impossible to float.
Thanks for sharing your experience here, because I am/was leaning towards VB first for my build next year, but wasn't sure. You've helped confirm this is a better way to go without any other risk.
All the houses I lived in in Maryland had 'uninsulated' basements. This was before the days of ubiquitous air conditioning. We lived upstairs in the Winter and in the 'finished' basement in the Summer. Cool and Comfortable. I love the mid-atlantic area for living, just not for their screwed up politics. Too close to DC I guess.
your technique with the vapour barrier on top of the foam does not work in case of radiant floor, or you will have to poor another layer of concrete later on.
I had the gravel, then the vapour barrier, then 4 inch of foam that includes space for 1/2 inch pex tubing, then your poor the concrete on top...
Dont you need moisture wicking insulation
Why put a vapour barrier over the rigid? Isn’t that an effective vapour barrier?
Required by code
@@Challenged1 didn’t realize that, I’m in Canada, I’ll check to see if that’s code here as well.
The Inside of the drain should be housed for raiden! And not for water?
It is capable of dual purpose assuming your sump pit it capped and vented to the roof.
What about Radon exposure ????
You have a low lying non vented Basement
A sealed Basement home
It needs ventilation
Mine has form-a-drain on the inside and outside of the footing, with 2 sealed sump pumps vented to the outside
The main reason for putting the vapor barrier (plastic) on the top of the insulation is for condensation reasons. If you put it on the 'cold side', meaning at the bottom, you're creating an area of cold (from the outside) and moist (from the inside) air. Which will result in condensation and finally mould. So flapping by the wind is pretty irrelevant. :) BTW. same is true for wall and roof insulation.
How is the bottom side the cold side under a basement or footing?
Do not use that big box 6” crap poly barrier. Only use a cross laminate ASTM 1745 barrier.
And don't forget this detail in your garage and even your exterior porch slabs. Is the peace of mind knowing your slabs subgrade will never freeze worth $0.50 /foot???
I hear for the 3rd time in American video "6 mil" plastic (first actually said 60 mil). What do you mean by that? Obviously, it's not 6 mm thick. First I thought they mean 0.6 mm, which would make sense,except that canvas is rated with g/m2 (i.e. 300 g/m2).
6 thousandths of an inch
@@Challenged1 Thank you, that explains where it comes from. I thought I!m reasonably familiar with imperial MUs :-). But I'm still a bit confused, I wouldn't think it's possible to make a canvas/foil so thin. In reality, the most thin plastic foils used as vapour barrier I know have thickness in tens of milimeter, much thicker.
@@oakld It's just plastic sheeting. It sounds thin, but it's actually fairly thick (many times thicker than a plastic sack received at a store).
icf are not approved by codes because termite inspection cannot be performed
Where are they not allowed by code?
Picture or drawing would help. Thank you.
We put vapor barriers under foam
That’s what I was just doing and I was a little worried. Is it important one way or the other?
It achieves the same thing. Some guys put it on top to keep the concrete from going under the foam. Tape the foam and you will be fine
@@justanbaker8937
You need the concrete to stick to the form,you don’t need air pockets between the concrete and the foam that’s will result in heat lost
@@hanghad7645 I understand the science thanks. I've installed 100s of slabs