Attic Insulation In 2x4 Ceiling Joist Space

There are some unfinished crawl space areas in the corners on the upper floor.

Attic insulation in 2x4 ceiling joist space. Install one r 19 batt or roll in every joist space with the paper side facing down and add a second layer of r 19 on top perpendicular to the first layer. In an older home a typical roof rafter can range between 2 4 s to 2 8 s. Work from the perimeter of the attic toward the door or hatch so that you don t trample all over the insulation you just put in. Some amount of thermal transfer will still occur through the joists themselves.

The standard width for joists is 24 inches. Find your zone on the map and then use the chart to determine the level of insulation you need to properly insulate your attic walls floors and crawlspaces. Achieving greater r values in attics the higher the r value the better the thermal performance of the insulation. Current insulation code requires r 49 insulation in the ceiling.

Put insulation meant for 2x4 framed walls between the joists which will be the same height as the joists then lay a perpendicular layer of attic insulation maybe r 30 on top of them. Put standard fiberglass insulation that s appropriate for the climate probably r 38 between the joists. The second layer which should be. Since this insulation will be 12 inches thick the top will sit above the joists but will not cover them.

Ceiling joists are typically 2 8 lumber floor joists are usually 2 10 or 2x 12 lumber. Always cover the tops of the ceiling joists to make sure the insulation is deep enough to reach your target r value and to prevent thermal bridging the heat loss that occurs through the wood framing. Set up a stepladder tall enough to work comfortably from. If the attic were designed as living space those ceiling joists would become floor joists and be much bigger.

That s a big size and strength difference between the two types of attic joists even if the joist spacing is the same. They are directly below the roof sheathing and are were insulated with fiberglass batts stapled between the 2x4 rafters. If your attic joists won t bear the weight necessary to finish out a living space but the engineer cleared them to support floor decking for light storage you can install inch plywood or.