[jbillups]

Should I insulate the basement walls before putting drywall up without vapor barrier or do I need vapor barrier ? I'm in the Cleveland area and the basement is block with exterior waterproofing

 

[Bud9051]

Hi jb, a very common question with many answers. One of the reasons for thevariety of advice is, all homes are different. Now, I can't see yours so my reply will be generic to start.
1. The tar covering on the outside has proven to NOT be a waterproof solution. And, liquid water is only half of the problem, moisture vapor is the other.
2. The most common approach is to install a layer of rigid, minimum of 1" in your climate (a guess) and then fill the stud cavities with batt insulation, I like Roxul.
3. Then, omit the vapor barrier. A small amount of moisture vapor will pass through the rigid insulation (no foil or plastic coating) and allow drying to the inside. Obviously it would have trouble drying to the outside.

I'll add a link on basements for a broader explanation. http://buildingscience.com/documents/digests/bsd-103-understanding-basements?full_view=1

Bud

 

[GottaFixIt]

I'll respectfully contradict Bud and say that sometimes it does make sense to use a vapor barrier under the right circumstances.

Assuming there is no vapor barrier on the exterior and no liquid infiltration, an alternative approach is to forego the batt insulation and install a 2" layer of foil faced polyiso insulation directly to the block. This stops drying to the interior, which can have benefits and potential consequences.

This satisfies the commonly required R13 and may reduce indoor humidity.

 

[Bud9051]

Nick, this is a topic that has far too many contradictions and I'm far from happy with the advice I have to give. The with or without a vapor barrier starts with, does local code require one. That trumps all advice. If not required, then is this new or old construction. if new then there will be less accumulation of dust and other food sources for any mold. If an existing foundation then one need to wonder whether mold spores and food will decide to start growing in a moist environment. With a vapor barrier the inside surface of the foundation will slowly accumulate moisture until it matches the outside. I've seen what can grow behind a vapor barrier so my best advice is to omit it when you are allowed to and control the small amount of moisture that does dry to the inside.

The use of rigid against the foundation has the added advantage of keeping the inside surface that any air can reach above the dew point and it slows any moisture movement as it is a vapor retarder. If you were to use just a vapor barrier against the foundation and then fiberglass insulation, then humid basement air that leaks into the wall assembly will be able to find a surface cold enough to form condensation.

Open for suggestions.

Bud

 

[Gary in WA]

Not for Cleveland; "Exceptions:
1. Basement walls." from; https://www.google.com/url?sa=t&rct...sg=AFQjCNGTavH8-ccBDQZg5I2rgwEjH6tDdw&cad=rja

As you are under;https://www.google.com/url?sa=t&rct...sg=AFQjCNGTavH8-ccBDQZg5I2rgwEjH6tDdw&cad=rja

Gary