Where to insulate with 3.5" Foam Board

JRMichler · 10-04-12, 08:29 PM

Put it on the walls. Pull the siding, put the foam over the existing sheathing, seal the joints with "foam in a can", tape the joints, then side over that. You will need to either replace the windows, or move them out by the thickness of the foam.

The inside of the foam is your new vapor barrier. As long as that surface is above the inside dew point, you will not have any condensation.

I know of three houses built this way. They all need mechanical ventilation. One of those houses is heated with propane. The owner fills the 500 gallon propane once per year, in the summer when he can fill it cheap.

10-04-12, 08:29 PM	#10
JRMichler Apprentice EcoRenovator Join Date: Apr 2012 Location: Phillips, WI Posts: 109 Thanks: 10 Thanked 30 Times in 25 Posts	Put it on the walls. Pull the siding, put the foam over the existing sheathing, seal the joints with "foam in a can", tape the joints, then side over that. You will need to either replace the windows, or move them out by the thickness of the foam. The inside of the foam is your new vapor barrier. As long as that surface is above the inside dew point, you will not have any condensation. I know of three houses built this way. They all need mechanical ventilation. One of those houses is heated with propane. The owner fills the 500 gallon propane once per year, in the summer when he can fill it cheap. Last edited by JRMichler; 10-04-12 at 08:31 PM..