Unfinished Basement Insulation Requirements – IECC 2009
Hello All,
I recently just purchased a new home. When I signed the contract, the local residential building code was to use the IECC 2009 requirements. I built in zone 5.
As far as I can tell, it explicitly says that basement walls should be insulated.
The builder insulated one wall cavity (approximately 12′ x 4′) and thats it. The entire basement has concrete walls. Additionally, they did not insulate the ceiling, or the walls against the staircase which I think they are required to do if they did not insulate the basement?
I am using 2x more natural gas then average in my area for a brand new home. Something does not seem right. I am very obviously a layman so I don’t want to try and fight the builder to do more insulation without some ammo. I would appreciate any advice. Thanks!
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
2009 IECC Table 402.1.1 Insulation requirements for basement walls in CZ5 are R10 continuous insulation or R13 cavity insulation. I would make sure your sill plate, rim joist and any opening thru the walls are well sealed and insulated as well. Insulating the ceiling will work if there is a door between floors.