Insulation Upgrades for the Walls - January 7th 2004
Q. My question is regarding inner wall insulation. The room location is on the west wall of a bedroom which dimensions are 10' x 13', there is a door and one window. The outside wall has the window and is 4' wide and 3' high located on the west side of the room. The only other side that needs insulation help is the south wall that joins the west wall. It needs insulation because part of the outside wall is set back because of the front entry. There is approximately 12' of outside wall that I would like to improve the insulation on, the walls are 4" thick and have brown paper backed fiber glass insulation (R7). I would like to add a form of rigid insulation on the inside walls. The walls are of lathe and plaster and in good condition as of 1958 when the house was built.
A. To upgrade your insulation, I would suggest a rigid polyurethane insulation applied to the inside of the outside walls, minimum 1.5" thick, overtop apply .5" drywall. This project will require you to build out the window/door frames and add box extenders to your electric duplex and switches.
Note: With this type of improvement, you should understand what affect the changes you make will have on ventilation.