Finishing Basement - Insulation Question

JoeRider

JoeRider

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From the various sites I've read it appears the days of framing + batt insulation + vapor barrier in the basement for poured concrete walls is no longer enough on its own. Although builders still do it because of the cost - it meets the minimum code of R12 for gas heating.

I'm looking into adding additional R value without the high cost of spray foam and the following seems like the next best thing:

1) Install the extruded polystyrene foam board (1.5"-2"); seal all the joints with tuck tape; use spray foam around the top and bottom.

2) Install the standard framing (2x4)

3) Use the batt insulation in the frame (R12 in my case)


My question -- Is the foam board considered a vapor barrier or should a 6mm poly sheet be installed over the batts?


Various sites mention the foam board is the VB if it's thicker than 1.5" and to not install the poly after the batts. Other sites mention because of it's permeability rating it is considered a Vapor Retarder and NOT a VB, therefore requiring the poly.



If you've used foam boards (Foamular C-200 or C-300 or the equivalent) in your basement did you install the poly after the batts or not?


Thanks,
JoeRider
 
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A buddy is going through the insulation Q & A with a renovation and it's all over the place. Foam is no good, FG is no good, blah blah blah. In the good old days there was one choice and it worked. Now there are multiple choices and every manufacturer has "Reports" of problems with the other manufacturer's products. Short of starting your own test lab you take a stab at whatever sounds good. If it doesn't work you move.

I would use a vapour barrier over anything. It's cheap and can't hurt unless there was some condition that required the wall to breathe.

Keep in mind that adding R value has a diminishing return.
 
nobbie48 said:
I would use a vapour barrier over anything. It's cheap and can't hurt unless there was some condition that required the wall to breathe.

Keep in mind that adding R value has a diminishing return.
Click to expand...


Double vapor barrier can definitely hurt. Sealing humidity between two impermeable membranes is a recipe for disaster. I guess it might work if you sealed the second layer while your basement was at some really low temperature to push the humidity down, but who wants to freeze their basement?

Does OBC have anything on this? It seems like something that should have been tried in the past (successfully or otherwise).
 
nobbie48 said:
A buddy is going through the insulation Q & A with a renovation and it's all over the place. Foam is no good, FG is no good, blah blah blah. In the good old days there was one choice and it worked. Now there are multiple choices and every manufacturer has "Reports" of problems with the other manufacturer's products. Short of starting your own test lab you take a stab at whatever sounds good. If it doesn't work you move.

I would use a vapour barrier over anything. It's cheap and can't hurt unless there was some condition that required the wall to breathe.

Keep in mind that adding R value has a diminishing return.
Click to expand...


I will probably play it safe and install a 1" foam and poly.

I found the "Best Practice Guide - Full Height Basement Insulation - Ontario - Ministry of Municipal Affairs and Housing" for anyone wanting more info.


Also for anyone thinking of going with the spray foam, you may want to check this CBC doc out - http://www.cbc.ca/news/spray-foam-insulation-can-make-some-homes-unlivable-1.2224287
 
GreyGhost said:
Double vapor barrier can definitely hurt. Sealing humidity between two impermeable membranes is a recipe for disaster. I guess it might work if you sealed the second layer while your basement was at some really low temperature to push the humidity down, but who wants to freeze their basement?

Does OBC have anything on this? It seems like something that should have been tried in the past (successfully or otherwise).
Click to expand...

If i don't seal the top and bottom with foam it won't be a VB and I'll poly it......... then it defeats the purpose of installing the foam board....

Otherwise I can start the project now and determine whether the poly is needed around early December when it's below 0.
 
Do the job properly. Don't take shortcuts and if you already have a leak or crack, have that fixed first. Covering it up with a coat of paint or whatever doesn't make the problem go away, it needs to be fixed where it is entering through the foundation. Yes, it is more work and costs more money. It is cheaper than waiting for a worst case.
 
Previous idiots who lived here did not fix problems right. Water would enter through the wall if it was very wet. They had started the process of hiding (or renovating) it badly. Can't remember if they put plastic sheet on both sides or what, but the outcome is that they used pink Fiberglass batts against porous concrete which turned them into soaking wet sponges. Between the Fiberglass and the space they put up plastic sheeting which they attached to the metal using tar. Yup. That was their attachment method.

I would have made a fuss except I bought from an estate so the person who did it in all likelihood was dead.

Lots of little problems around here like that, learning experience to be sure.
 
Sunspark said:
Do the job properly. Don't take shortcuts and if you already have a leak or crack, have that fixed first. Covering it up with a coat of paint or whatever doesn't make the problem go away, it needs to be fixed where it is entering through the foundation. Yes, it is more work and costs more money. It is cheaper than waiting for a worst case.
Click to expand...


That is exactly what started this reno.... :p

Last fall/winter saw some moisture on the floor below the insulation. Decided to wait until the spring to do the repair.

I ended up removing all the insulation in the basement and found two cracks 6 feet apart. Of course, my luck the warranty on the house for the foundation is only covered for the first 2 years! I trenched 12' x 4' x 8' down and used the Bakor Blue skin which I highly recommend....
 
JoeRider said:
That is exactly what started this reno.... :p

Last fall/winter saw some moisture on the floor below the insulation. Decided to wait until the spring to do the repair.

I ended up removing all the insulation in the basement and found two cracks 6 feet apart. Of course, my luck the warranty on the house for the foundation is only covered for the first 2 years! I trenched 12' x 4' x 8' down and used the Bakor Blue skin which I highly recommend....
Click to expand...

I was going to dirty up this thread by pointing out finished basements are just trouble waiting to happen but decided not to. Then you post this. ;)
 
inreb said:
I was going to dirty up this thread by pointing out finished basements are just trouble waiting to happen but decided not to. Then you post this. ;)
Click to expand...

You're absolutely right! They say every house gets water in the basement sooner or later. It's just a matter of doing the proper repair and not temporary patch work...... That's part of the reason i didn't want to do the foundation crack injection from the inside in the two cracks which started from the forming rods.
 
It's hard for me to repair stuff where I live on the foundation. The reason is because on 2 sides of the house (it's an old house, built 1947 I think) a driveway comes right up to it. I guess in a way that is water shielding. But in the back, there is a craptastic ghetto deck. To fix that means removing or partially removing the deck which unfortunately also has a rear door porch roof whatever it's called. The deck side definitely has pinholes that let in water.

Front side has multiple bushes and a humongous concrete front step. Can't see right now because it has Fiberglas in front of it. I'm probably going to remove all the crap inside and figure it out sometime.

Here is a photo of one of my basement mysteries.
su5ybesu.jpg
It is a floor drain of some sort. If you look at it directly or poke at it there seems to be soil at the bottom and we were told there is no drain and it drains into the soil.

Well I don't completely buy that. While it might not be directly connected to the sewer, at the very bottom partially obscured by dirt are visible terracotta ceramic curves. Those are ceramic pipes that go.. somewhere. Maybe to a catchbasin.
 
Ok no disrespect , who the heck gives a 2 year foundation ? that's a shame they should stand behind there work, wonder how many other things are half assed :(
 
Typically, a vapor barrier always needs to be installed on the warm side of the insulation. We always used to strap a 15 felt roofing paper to the concrete then frame, insulate, vapor barrier and drywall
 
carboncat said:
Ok no disrespect , who the heck gives a 2 year foundation ? that's a shame they should stand behind there work, wonder how many other things are half assed :(
Click to expand...

The builder would of probably insisted on the injection repair from the inside which I did not want.

On the positive side, when I trenched I added an additional yard of clear gravel over the weeping tile as there was barely anything there; replaced about 10' of the black membrane as it was completely damaged when they back filled; and added several rows of the Bakor blue skin...
 
Man my house is built in 59 , it's never had the foundation touched, sucks they don't make em like that anymore, luckily my house was one owner and he was the homebuilder :)
 
vapour barrier always goes on the warm side of the room. I'd use roxul rock wool insulation over glass batts, it doesn't retain or absorb moisture like glass batt, a few cents more per sq ft but worth it.
 
No comparison.... Old is much more structurally sound unless your building a custom home $$$ (as long there is no asbestos and knob & tube).
 
JoeRider said:
No comparison.... Old is much more structurally sound unless your building a custom home $$$ (as long there is no asbestos and knob & tube).
Click to expand...

Most custom homes these days are the same garbage underneath with tall baseboards and crown molding to identify them as custom.
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