Insulating Attic Roof Joists

They have floor joists or the bottom chords of roof trusses with drywall below.

Insulating attic roof joists.

Then blow another layer on top of the roof rafters. This construction approach was first used in the 1970s and it has been implemented much more widely since it was first included in the international code council s icc model building code in 2007 irc section 806 4. The advantage of this approach is that the heat that is generated and circulated in the floors below is not lost through the attic floor into the rooms above. Typically you will fill the insulation blower with the insulation and blow it between the attic floor joists.

Closed cell spf is an effective thermal air moisture and vapor barrier. Most unvented attics incorporate spray polyurethane foam spf on the underside of the roof deck and attic walls. Insulating the floor and the roof this is certainly the most interesting solution when the attic is also going to be used. You ll be installing insulation on top of this drywall ceiling.

Look for water stains on the roof sheathing or damp or moldy spots on attic joists and existing insulation as a clue to where leaks might be. When you are in the attic you re usually stepping carefully on top of the floor joists looking down at the back side of the drywall ceiling. Unless you re using mineral wool insulation or your fixtures are rated safe for contact with any type of insulation don t allow the material to touch or cover recessed cans or lights from the floor below it s a fire hazard. If you have a solid floor covering the roof rafters use the claw end of a hammer to pull the floor up in several locations and blow the insulation under the boards.