[darren]

I got all excited back in the spring and completely demoed my basement down to concrete foundation walls. Summer came and I had no time to work on it, it did give me a chance to see the basement did remain dry.

Now that winter is here I have more time and have started framing the exterior walls. With the cold weather here, the concrete walls(mostly the north wall) is getting condensation on it where the concrete is above grade.

I don't plan to insulate or vapour barrier until spring when it has all dried up. I am keeping my framing 1.5 to 2" of the concrete, would I be alright to frame it all up(want to get electrical done) but leave the insulation out until the warmer weather returns.

 

[SeniorSitizen]

If you put the framing up every spring and take it down each fall it'll be just fine. Otherwise it will follow the trend of " repeating the same mistake and expecting different results ".

I fear there will be a hellof a bunch of folks tearing basement walls out in the future and calling mold remediation X-Perts.

 

[darren]

So if I would have vapoured barrier the walls in the summer, my walls would have still have condensation.

When I demoed the walls there was no sign of waster damage so I was hoping once I had the vapour back up I would not have the issue again.

 

[gregzoll]

Dew effect. Take a look at a soda can after sitting out from being Ice Cold. That is what is going on without your Basement.

If you keep the furnace vented down there. You should not be seeing any condensation.

Condensation long term is what destroys Foundation walls.

 

[darren]

Once I have a proper vapour back on the wall, the chance of the condensation happening should be nil since the hot moist air can't get to the wall.

 

[Bud9051]

The previous walls were keeping the majority of the basement air away from those cold walls. Your condensation on the above grade portion (because it is colder) will continue behind your new walls even after being insulated. it is that space you are proposing that will allow moisture from below to circulate with the air up to where it can condense.

Applying the appropriate thickness of rigid insulation against the concrete and then building your wall directly against the rigid ensures that any inside surface that remains exposed to basement air will be above the dew point.

I'm not familiar with the minimum basement insulation levels for Winnipeg, but you are cold. I would guess a minimum of 1.5" of rigid and then more insulation in the stud bays. Check local code officials for vapor barrier requirements.

Bud

 

[darren]

I am learning quite a bit during this reno.

Winnipeg requires R20 in the basement walls. I looked at doing 2" of foam and than 2x4 walls but the price was quite high.

I decided to go with 2x6 walls and R20 batts.

Now I am understanding the other function of rigid foam. Would 1/2" or 3/4" foam be enough to give that break that is needed.

I have a few walls framed up and may be able to get 1/2" or 3/4" foam behind them.

 

[Millertyme]

The foam is key. Thicker the better. You need tape the seams and keep it all tight for it to be most effective. Never place your wood studs against the concrete. They should be on top of the foam. The foam does more than just insulate. I

 

[gregzoll]

Once I have a proper vapour back on the wall, the chance of the condensation happening should be nil since the hot moist air can't get to the wall.

Again the air inside the house is not moist. It is warm dry air during the Winter, unless you are venting bathrooms down there, to allow the steam to get into that space.

You are seeing what I stated before, which is Dew Effect. The walls are colder than the inside air, so they sweat. You need to find out what the Relative Humidity is down there and get it lowered and also at the same time, have the furnace vented and returns to help circulate the air.

 

[gregzoll]

Bud9051, the amount of insulation needed for Basements have been discussed in prior threads. The Building Science .com website is the best resource out there for how to make a structure not only healthy while insulated, but also how to insulate to keep the air quality from being contaminated by mold & fungi.

It has been argued whether 2" or up to 4", or Hybrid with foam & batt insulation, or even foam and needing to stop sound if the space will be used for watching movies or sports in a Home Theater setup.

 

[Bud9051]

You can use a combination of rigid and batt insulation to meet your r-20. The guideline is to prevent the inside surface of the rigid foam from cooling to that dew point, since the batt insulation may allow inside air to reach that point. In your cold climate I would guess 50% should be rigid and NO MORE THAN 50% should be batt. Too much batt will make the foam colder. I can dig out the article on that ratio if needed.

So, 1" of rigid would only allow r-5 of batt, not enough. 2" of rigid (R-10) gets closer. Then 2x4 studs and batt insulation. R-13 batts would probably be acceptable, but local code authority is your source.

Note. only the exposed exterior foundation and one or two feet below grade are a concern, although code requires full height. The rim joist is in that exposed group so air seal and insulate it well. Also, air seal your 2x4 wall assembly, but leave it vapor open if code will allow. Easier to manage a trickle of moisture vapor passing through than to deal with an accumulation behind a vapor barrier. But some are still required.

Bud

 

[Beepster]

I was in the same boat as you, 2" XPS seemed like a bit much and was pricey. I did 1" XPS and 2x4 framed tight against the XPS and used enough unfaced bat insulation to get me to the proper R value. In you follow Gary's links, 2" may be required to be 100% sure there is no condensation, I monitored beforehand and determined that I do not have a very humid space and went the route I did.

B

 

[darren]

Thanks for the all answers it has been a great help. I think I am going to get someone into spray foam the walls to give me that break and finish with batts(spray foam to R20 may not be in the budget but will make room to get a little done to have a mould free basement).

I also started framing already and don't want to take down what I have put up to install rigid foam.

Will putting the framing up(keeping 1.5" to 2" off the concrete) cause any issue.

 

[gregzoll]

The Sprayfoam will pay off for itself in the long run. Especially for keeping the sound down. If you plan on having a Home Theater setup down there, you will need to install clips to de-couple the drywall and use Green Glue between two layers.

Even if you do not plan on a Home Theater, but plan on placing an office or Bedroom down there, even a utility room. The two layers of Drywall, Green Glue and decoupling clips help a lot in keeping things quiet. Just remember to make sure that you have a way to still bring in fresh air for the utility room area and laundry if down there. Same for the living area, so that the air does not get stale down there.

 

[Gary in WA]

I agree the foam needs to be thick enough to prevent condensation and too much fibrous insulation on the warm side in front of it is detrimental;

If your average temps for 3 coldest months is 10*F, and using only 1" of closed-cell foam, with temps above grade and lower, as your frost depth is around 6-8'; 68*F in room, R-5 (XPS), R-15 (Roxul) in frame cavity- total R-20= foam inside surface at 21*F, relative humidity more than 16% will condense there.

You could try a "perfect" air seal of the drywall,http://www.buildingscience.com/documents/information-sheets/air-barriers-airtight-drywall-approach/ but you already forgot foamboard/sill sealer under the frame wall plate on concrete (unless you know for certain there is plastic under the slab). Then you would still need it for the air seal and thermal break unless the slab is foam board at perimeter. If so, you could caulk the slab/wood joint against air and run a dehumidifier a lot...

Read the above/below grade insulation strategies with/without a vapor barrier for your location, here; ftp://ftp.cmhc-schl.gc.ca/chic-ccdh...ngual/Vapour_Permeance_Volume_1_Web_sept5.pdf

Gary