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Discussion Starter #1
I recently bought a house and started renovating the basement. By removing a divisionw all, that ran across the exterior walls, I was able to see how it is insulated. 2x4 framing, Fibreglass insulation (not insulated to the floor....only the top six feet of a eight foot ceiling height) with the white wrap on one side and vapor barrier on on other side before the drywall. Half the exterior wall is framed about 1/2" gap from foundation to framing and other half has 4" (could of been less than 2") gap because of plumbing. So far I have only been able to see the foundation wall with the 4" gap and I do see condensation/ice....it's -20 here in Quebec this's week. I also noticed black stains....which at first thought was mould but not convinced yet. Ok now to the point ;)

1. How can I test if the stains are mould and not tar paper or sheeting stains? I can pretty much wipe it off just by touching it. Would mould smell? I have no smell of mould in the basement, humidity is at 38%which is the same as the rest of the house.

2. As for the condensation....I think the issue is that since there is a 4" gap, the heat from the joists of the top floor actually goes behind the framed exterior wall and onto the foundation wall. Does this make sense or it is not the cause?

Now obviously for me, the easiest to do is leave basement as is, as I expected to do andjust finish the rest like floor, paint, etc. but I have children and want to make it as comfy as possible.

Would you guys rip off everything to see what is going on and fix the joist issue? Will I get much benefit to insulating the bottom 2' of the wall? I have 170' of exterior wall....so it won't be cheap to gut, install 2" eps, reframe and then fibreglass insulation, drywall, etc. need some help and opinions here

Thanks
 

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Discussion Starter #3
No clue if we will stay here for long. We overdid it on the last house then sold it because we got a good offer ;)

Any comments or suggestions on my other questions? Is the air in the joist going behind the wall the issue with condensation or is condensation really normal in -20 winters?
 

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You can contact a local lab and have the black staining tested for mold and type. Likely answer is that it is mold when you have -20 temps and 38% RH.

It is unlikely that moist air from the living space above is coming down, through the finished flooring, sup-floor, etc. to get into the the wall.

The conditioned air, shared by the entire home, is certainly getting around that wall assembly in the basement and getting to the condensing and cold wall.
 

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Discussion Starter #5
I have a humidification/dehumidification system with my central heat and maintain it at 35-40% for my hardwood floors through out the house. It is 38% at this minute with +1C outside temp and 20c inside temp.

Is there any DIY test you guys know of to test if mold or not? If it was mould wouldn't I have a musty smell or some types don't smell?
 

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Just lost a long post on this, so I'll make it short. Plan on trenching the top and bottom of the wall, pulling out the fiberglass insulation through the trench, inspecting the wall for water intrusion, fixing any intrusion problems, and then having it blown with rock wool.

The black streaks are most likely from air circulating across moist areas - particles in the air stick to moist surfaces, causing black streaks. I think that's what you're seeing.

There is no DIY mold test I'm aware of.

Find an insulating contractor that blows in rock wool, show him what you're dealing with, explain what you plan to do with trenching the walls and pulling out the fiberglass and get a quote. Practices vary by climate / location, so he may say that would be a no-go. You may have to gut it.
 

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Discussion Starter #10
Opened up the wall to clean up mold/stains. Still debating weather to redo everything and re insulate. Currently r-13 and if I redo with 2" xps and then the batt, I will be up to r-23. The difference between the two in energy loss annually is 8 Mmbtu. I have no idea how to calculate how much that would save me per year. I figure it will cost between 5-6k in material to redo the entire basement. Trying to see if worth it and when I will be back into my money.

Any ideas?
 

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There are calculators out there that attempt to project fuel savings based on fuel types and R-Values.

Search around for one and see if you can get some cursory calculations on it.

You won't make your money back in 1 year but you might be surprised by the projections.
 

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I am using electricity. I found one for oil but they did not include electricity. Will keep looking, but it won't be something like 10-15 years?
 

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Opened up the wall to clean up mold/stains. Still debating weather to redo everything and re insulate. Currently r-13 and if I redo with 2" xps and then the batt, I will be up to r-23. The difference between the two in energy loss annually is 8 Mmbtu. I have no idea how to calculate how much that would save me per year. I figure it will cost between 5-6k in material to redo the entire basement. Trying to see if worth it and when I will be back into my money.

Any ideas?
Compare Fig. 2 and Table 5, and Fig. 5; http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=11&ved=0CCgQFjAAOAo&url=http://www.dow.com/webapps/lit/litorder.asp?filepath=styrofoam/pdfs/noreg/179-70015.pdf&pdf=true&ei=jzymUoHcF4XnoATI7oCADQ&usg=AFQjCNH9s9_jodzP8lUxY1F96PEW7c2C4A&cad=rja

And; http://www.quadlock.com/technical_library/bulletins/R-ETRO_Value_of_Basement_Insulation.pdf

Your basement air is getting to the cold concrete wall past/around the insulation; starting on pp. 25;http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&cad=rja&ved=0CDoQFjAD&url=http://apps1.eere.energy.gov/buildings/publications/pdfs/building_america/measure_guide_basement_insul.pdf&ei=1k6eUu7KDqeViQLBnYDABg&usg=AFQjCNFx-LlLjPvnQgyUNBXd7F4za_-LyQ

Gary
 
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