Insulation, Radiant and Vapor Barriers - Basic but Necessary Insulation Question

Hi, All -

I am getting ready to insulate a basement room with faced R-13 insulation, 2X4 wall construction. There are a few places in the framing where, due to obstructions, etc., the studs are not 16" on center (the distances range from approximately 8 to 12 inches). I would like to know what is the proper way to cut (should I cut?), install, and if necessary replace the vapor barrier now compromised by the lengthwise cutting (if cut) of the insulation.

Thanks,

Dave

First measure the width of the wall cavity. To cut the insulation, you will need the following.

1. At least a 20 inch by 20 inch piece of plywood to protect the floor.

2. A 2 x 4 at least 20 inches long.

3. Tape measure and utility knife with extra blades.

Lay the plywood on the floor and roll the insulation over the plywood. Measure the width of the insulation you want and move either the plywood or insulation over the plywood to that measurement, with the vapor barrier facing down.

Lay the 2 x 4 over the insulation with the plywood underneath with one edge of the 2 x 4 on the measurement you made. Kneel on the 2 x 4 to compress the insulation and take your utility knife and cut along the edge of the 2 x 4 to cut the insulation. Before you get up from the 2 x 4 make sure the insulation separates. If not, make another pass with your utility knife. Keep moving the insulation over the plywood and cut similarily until the entire length is cut. If this is done right, the vapor barrier on the insulation will be intact.

If for some reason the vapor barrier is torn, cut or has gaps in it, you could use a vapor barrier tape to seal it. You can buy this at any home improvement store.

Thank you very much for the advice.

One question - I realize I will be stapling the "un-cut" side of the insulation to one of the studs, using the kraft-paper edge. I am assuming the "cut" side will not be stapled to the stud on the other side of the cavity, but stays in place with kind of a press fit. Is this a correct assumption?

Dave

If cut correctly the insulation should stay up without any stapling. If for some reason it does not, then you can tape that side and that should hold it up for you.

Thanks again for the help.

Dave