Hi,
I am in the process of framing my basement and I see a lot of articles stating that you should put 2 inch rigid XPS foam board over all concrete in the basement.
I am wondering if this is really needed if the basement has R5 on the outside of the foundation.
Currently the basement has never been colder than 59 degrees even when it was -17 during the "polar" vortex ( I am in southeast wisc).
From what I understand for condensation to form on the concrete, the temp of the concrete would have to be lower than the humidity of the air in the basement which during the
very cold months is between 34 and 36 percent. I also have a radon sub slab suction system which really cuts down on the humidity.
I also should add that I don't heat the basement and it stays around 68 in the summer and 63 during the day during the winter and the walls are not that cold.
So I just don't see why I should put 2 inches of XPS over my basement foundatation walls when the exterior already has 1 inch XPS and my sill boxes are spray foamed.
Also the framing will be at least 1/2 inch from the concrete so any insulation I put in the cavity wont actually be touching the concrete and I can always have it spray foamed after framing and mechanicals are done.
The house is a 2200 sq ft ranch so I would need a lot of the XPS and at 25 bucks a sheet would add up as well as making all the rooms smaller.
I am just not convinced that in this case it's needed.
Oh, I should add that the cove joint all around the permiter is sealed as well as all expansion joints in the floor and the slab has a vapor barrier, so there is no moist air coming up from the cove joint.
Comments?
I am in the process of framing my basement and I see a lot of articles stating that you should put 2 inch rigid XPS foam board over all concrete in the basement.
I am wondering if this is really needed if the basement has R5 on the outside of the foundation.
Currently the basement has never been colder than 59 degrees even when it was -17 during the "polar" vortex ( I am in southeast wisc).
From what I understand for condensation to form on the concrete, the temp of the concrete would have to be lower than the humidity of the air in the basement which during the
very cold months is between 34 and 36 percent. I also have a radon sub slab suction system which really cuts down on the humidity.
I also should add that I don't heat the basement and it stays around 68 in the summer and 63 during the day during the winter and the walls are not that cold.
So I just don't see why I should put 2 inches of XPS over my basement foundatation walls when the exterior already has 1 inch XPS and my sill boxes are spray foamed.
Also the framing will be at least 1/2 inch from the concrete so any insulation I put in the cavity wont actually be touching the concrete and I can always have it spray foamed after framing and mechanicals are done.
The house is a 2200 sq ft ranch so I would need a lot of the XPS and at 25 bucks a sheet would add up as well as making all the rooms smaller.
I am just not convinced that in this case it's needed.
Oh, I should add that the cove joint all around the permiter is sealed as well as all expansion joints in the floor and the slab has a vapor barrier, so there is no moist air coming up from the cove joint.
Comments?
Last edited: