So, normally we have a lot of older homes with unfinished basement. Usually there isn't any insulation on these foundation walls. But from time to time we have a newer home with 2" rigid on the exterior. They are sold and a couple years later the homeowner wants to finish out the basement. I guess my question becomes, do we insulate the interior walls against the already insulated foundation walls? Most times the homeowner and contractor provide details that show more insulation being added as R-13 batt in the stud spaces. But if they don't do this, wont that change the location where the freezing point is located in the overall wall system? The inside foundation wall will actually be colder due to closing up the space, right?
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Finished basements from unfinished
- Thread starter rktect 1
- Start date
steveray
SAWHORSE
Does the existing wall assembly meet code on a U value or ResCheck or something else that might not be quite prescriptive? I so, nothing required, if not add....And don't forget to upgrade the windows if they don't meet todays code. If they frame those walls out the insulation needs to continue to the deck above and any walls that separate non-conditioned space as well with weatherstripped doors and all of that stuff....
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tmurray
SAWHORSE
Are you referring to convection currents? It may depending on the geometry of the house, HVAC equipment and sealing practices, etc. But, it likely wouldn't be enough to matter. The way we've been dealing with this is we require the amount of insulation specified in the code unless they do modeling to show it is not required. In this case, the folks with 2" of rigid have a leg up on everyone else.rktect 1 said:
JBI
Registered User
Insulation on the exterior of the mass wall reduces the minimum R-value required.
What is the R-value of the rigid on the exterior?
What climate Zone?
Which Code and year edition?
What is the R-value of the rigid on the exterior?
What climate Zone?
Which Code and year edition?
We use the 2006 IRC. Climate zone 5
The home was built with an R-10 rigid insulation prescriptively on the exterior side from top of foundation to the footing.
The home was built to code at the time even though todays 2012 IECC requires R-15. But if the R-10 is in compliance and all they are doing is framing interior walls in the already conditioned space around the existing foundation wall, I have a hard time telling them to add any insulation. At the same time I am worried about the building science aspect of the unconditioned space between the foundation wall and the stud wall.
The home was built with an R-10 rigid insulation prescriptively on the exterior side from top of foundation to the footing.
The home was built to code at the time even though todays 2012 IECC requires R-15. But if the R-10 is in compliance and all they are doing is framing interior walls in the already conditioned space around the existing foundation wall, I have a hard time telling them to add any insulation. At the same time I am worried about the building science aspect of the unconditioned space between the foundation wall and the stud wall.
steveray
SAWHORSE
If the basement is already conditioned space, nothing is required in the new wall. as far as a concern for condensation in the "dead space".....Steel studs and mold resistant drywall...Or don't finish the wet basement...
JBI
Registered User
This is why I used ICF for my house...