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Old 12-28-2016, 08:36 PM   #16
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Re: How is vapour barrier of basement wall typically tied in with rim joists?


Well that's new to me, so are you saying that vapour barrier plastic is actually not air tight? I know about using foam too, but that's easier to do for a wall that is not already framed, and I feel the R value is too low, and by adding batts on top after you end up with a vapour barrier not being on the hot side, which can be problematic. Typically people here frame first, then use batts then vapour barrier on top as it keeps it on the warm side which will prevent condensation. Most of the time they use fibreglass though, but I'll be using Roxul. Don't like the idea of fibreglass touching the bare wall.

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Old 12-29-2016, 11:09 AM   #17
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Re: How is vapour barrier of basement wall typically tied in with rim joists?


Rigid foam is not a vapor barrier, it is a vapor retarder. Generally speaking, vapor barrier is not advised on below ground walls as moisture will move through the soil into the concrete wall and into the living space so you want the wall to be able to dry to the inside. Additionally, the foam creates a thermal break to prevent condensation.
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Old 01-01-2017, 08:18 PM   #18
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Re: How is vapour barrier of basement wall typically tied in with rim joists?


So foam is not air tight? I always thought it was, and made a proper replacement for plastic in situations where you just want to insulate at same time or where plastic would just be harder to install.

But I'm still confused with the whole vapour barrier/retarder thing, I always figured vapour barrier was just a word for something that will make the space air tight as to not let air in/out so that you can retain heat better.

As far as moisture, if there is any then you have to fix that problem first. Moisture is something you fix on the outside, but vapour barrier is something that is on the inside. Idealy you want a continuous evelope for the entire building but that is often not achieved due to imperfections in the building process etc.
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Old 01-02-2017, 01:53 AM   #19
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Re: How is vapour barrier of basement wall typically tied in with rim joists?


If continuous and the seams taped, the foam could be your air barrier. That said, it is still going to let some moisture through - it is a vapor retarder but not a vapor barrier. If the foam is thick enough, it creates a thermal break so you do not get condensation forming on the inside of the foam.

One more thing to define - moisture is not solved on the outside, water is. There are ways to move water away from the foundation but a below ground concrete wall is going to let moisture (vapor) pass through from the soil into the house. This is why you don't want a vapor barrier below ground, as you want to let the wall dry to the inside instead of trapping that vapor and allowing it to condense into water inside the wall.
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Old 01-02-2017, 06:41 AM   #20
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Re: How is vapour barrier of basement wall typically tied in with rim joists?


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So foam is not air tight? I always thought it was, and made a proper replacement for plastic in situations where you just want to insulate at same time or where plastic would just be harder to install.
Inspector in my area would not accept foam board as a VB. He insisted on a sheet of poly in front of the Roxul which would have been in front of 2" Styrofoam.
I told him no way I would do that as I've seen so much moldy insulation every time I've opened a basement wall.

Spray foamed the whole works, no VB, sweet.

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Old 01-02-2017, 04:25 PM   #21
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Re: How is vapour barrier of basement wall typically tied in with rim joists?


Yeah spray foam would be the ideal thing, but at ~4k (got an estimate many years ago, would need to get another) I'm just trying to see what is the best method to insulate myself. Most people here just put fibreglass insulation and vapour barrier. I think most don't even bother with vapour barrier for the rim joists and just shove batts in there. But I want to do better than that. Suppose my best option might be to get the rim joists professionally spray foamed and have the foam extend to the top plate of the wall. Then I'll just do batts/VB for the wall itself.

As a side note some people say you should not insulate all the way to the bottom, but that seems a bit counter productive to me, is there any reason for that? I would want to insulate right to the bottom unless there is actually a reason not to. I suppose once you get to a certain depth the wall won't be as cold but if I don't insulate to the bottom it's basically a break in the thermal envelope. Given the subfloor is not insulated (just drycore) there will be a thermal break no matter what but may as well make it right at the bottom.

I do have some money coming in soon though. Tax return, company shares etc... so maybe I will just splurge and do full spray foam. But I was kinda thinking of putting that money towards a wood stove. With the carbon tax I really need to start thinking about cheaper ways to heat. Solar is another thing I have on the back of my mind but more expensive to do. Wood stove would see immediate results. Costs of everything keep going up so money is getting tighter every year.
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Old 01-02-2017, 06:23 PM   #22
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Re: How is vapour barrier of basement wall typically tied in with rim joists?


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Originally Posted by Red Squirrel View Post
Yeah spray foam would be the ideal thing, but at ~4k (got an estimate many years ago, would need to get another) I'm just trying to see what is the best method to insulate myself. Most people here just put fibreglass insulation and vapour barrier. I think most don't even bother with vapour barrier for the rim joists and just shove batts in there. But I want to do better than that. Suppose my best option might be to get the rim joists professionally spray foamed and have the foam extend to the top plate of the wall. Then I'll just do batts/VB for the wall itself.

As a side note some people say you should not insulate all the way to the bottom, but that seems a bit counter productive to me, is there any reason for that? I would want to insulate right to the bottom unless there is actually a reason not to. I suppose once you get to a certain depth the wall won't be as cold but if I don't insulate to the bottom it's basically a break in the thermal envelope. Given the subfloor is not insulated (just drycore) there will be a thermal break no matter what but may as well make it right at the bottom.

I do have some money coming in soon though. Tax return, company shares etc... so maybe I will just splurge and do full spray foam. But I was kinda thinking of putting that money towards a wood stove. With the carbon tax I really need to start thinking about cheaper ways to heat. Solar is another thing I have on the back of my mind but more expensive to do. Wood stove would see immediate results. Costs of everything keep going up so money is getting tighter every year.
I hope you have a source of free wood.
That sure wouldn't be cheap to buy I imagine.

Insulating halfway down, nonsense!
They may have been referring to the minimum requirements of a new home build.

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Old 01-02-2017, 06:25 PM   #23
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Re: How is vapour barrier of basement wall typically tied in with rim joists?


Remember when you're comparing costs to include the foam boards, the Roxul, the VB , the tuck tape, the acoustic sealant and any cans of great stuff.

As a whole, all those things really add up.
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Old 01-02-2017, 11:15 PM   #24
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Re: How is vapour barrier of basement wall typically tied in with rim joists?


Wood is pretty cheap if you get it yourself. Just need a license and to pay a small fee per cubic meter that you take. Lots of free source too, like sometimes people just want a tree taken away and will let you take the wood. But if I got lazy I'd probably just buy it, still fairly cheap. Natural gas is only going to go up, especially now that the government seems to have a war on it's usage and wants to tax it from every direction and even talks about banning it.

And yeah kinda figured it was odd to only insulate half way. I'll do all the way to the bottom.
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Old 01-04-2017, 11:01 PM   #25
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Re: How is vapour barrier of basement wall typically tied in with rim joists?


I haven't talked to you for awhile... hope you have been well. They leave the bottom with no insulation when they use a plastic vapor barrier- that completely stops the incoming moisture- then it dries and it gets to the bottom. Your code requires a vapor barrier on the concrete- but not necessarily a plastic (Type1) sheet;

"It is also required where wood members are applied in direct contact with below-grade concrete or unit masonry for the installation of insulation and/or finish."------------------------- AND; In the case of walls, the dampproofing must extend from the basement floor up to ground level. Permissible dampproofing materials include polyethylene film that is 0.05 mm, or thicker; type S roll roofing; or any membrane or coating with similar properties. This implies that a variety of plastic foam and specially faced insulation materials also satisfy requirements for interior dampproofing. However, in general such materials with a permeability of less than 170 ng/(Pa.s.m2) should meet the requirements for low-permeability materials in Section 9.25 of the NBC 2005, if they are applied to the interior surface of the above-grade portions of the foundation wall. from; http://www.nrc-cnrc.gc.ca/ctu-sc/ctu_sc_n70

So, that 170 ng is about 3 perms in US, far from plastic at 0.6 perms- Type S roll roofing- (mineral faced asphalt saturated felt at 3+ perms) would work but not let it condense to pool at the bottom if not wanting to leave a bottom strip off. There are other ways than using plastic on the wall- housewrap also comes to mind; https://www.google.com/url?sa=t&rct=...kMDFpA&cad=rja

Plastic vapor barrier problems; http://users.encs.concordia.ca/~raoj...nce001343.html

A very good read by BSC member- check out the Frame/FG/Latex paint wall and results, as well as the history leading up to code requirements; https://www.google.com/url?sa=t&rct=...RZ6Sbg&cad=rja

Gary
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Old 01-05-2017, 05:52 AM   #26
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Re: How is vapour barrier of basement wall typically tied in with rim joists?


Hmm yeah too late to add anything to the walls now, since the studs are already in place. Well it could be done but very tedious and there would be lot of seams. Studs don't touch wall, I made sure of that. But that explains why there was tar paper on there before, I thought that was odd since I had never seen that before. There is a rubber spray on membrane on the foundation outside though. But I guess some moisture can still come in from bottom as mentioned.
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Old 01-05-2017, 08:07 PM   #27
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Re: How is vapour barrier of basement wall typically tied in with rim joists?


Summer will drive the outside moisture through the concrete above grade to your insulation. Code requires something on the inside above grade... or the gap-- which give convective loops around the fibrous insulation, degrading the R-value and depositing moisture at the top of wall. Tar paper was a good fix back in '95 and even extruded foamboard as mentioned on pp 2; https://www.cmhc-schl.gc.ca/publicat...ech/95-207.pdf But tar paper of old is not the same today- so it has to be roll roofing- underlayment- without the granules works as it is much stronger than thin papers of today; http://www.fortifiber.com/pdf/fortif...sk_vs_felt.pdf

Someone else; http://www.askthebuilder.com/vapor-b...ndation-walls/


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Old 02-14-2017, 03:18 AM   #28
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Re: How is vapour barrier of basement wall typically tied in with rim joists?


Been pondering this and since rigid foam is actually not a vapour barrier I think I will go with a spray foam kit and do the rim joists myself with that. Can do a "L" shape where I spray the very end, then the bottom all the way to the top of the top plate of my wall, covering the gap between that top plate and the foundation top plate, as well as any holes that were done for electrical, and trying to get as close as I can to the edge of the top plate to meet up with the vapour barrier. Doing the plastic would be too tedius, trying to tape it all right in those oddball corners etc. Then I will do batts and plastic for the main wall cavities. I will probably stick some batts in the rim joists too as foam should not be exposed due to fire risk.

Considering how badly done my upstairs is, I think anything I do in the basement is going to be better than the upstairs, so no sense in trying to go with 100% seal.

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