How to Install Insulation Between Floor Joists

Joist bays — the open spaces between floor joists — are prime hosts for insulating material under particular conditions. When the basement or crawl space has vents installed, insulating material joist bays prevents cold temperatures from entering to the house’s interior. Building codes frequently call for these vents as a means of circulating air in crawl spaces, and at times in basements. Insulating joist bays also prevents warm air from escaping the heated space.

Don a dust mask, safety goggles and gloves. Wear a long-sleeved shirt when handling fiberglass insulation. The fibers are a skin and respiratory system irritant.

Trim pieces of fiberglass insulation using a utility knife, so the pieces fit into joist bays along the rim joist. The floor joists are all secured to the rim joist, which runs along the perimeter of the house and on top of the house’s foundation. Utilize a 2-by-4 as a straightedge where you want to trim the insulation. Make the cut together with the utility knife running together the 2-by-4.

Push the insulating material pieces into place along the rim joists. Do not compress the insulation as you push it in to place. Insulation is contingent upon its attic so as to understand its entire R-value.

Trim lengths of paper-backed insulating material so they follow a joist bay in 1 rim joist into the 1 opposite. Based on the size of your house, you may need more than 1 piece of insulation to complete the run.

Fit the insulating material to the joist bay with the paper facing up toward the living room. Paper facing provides a moisture barrier and is always positioned facing the space that is warmer in winter. The newspaper should maintain contact with the subflooring but prevent squeezing the insulation.

Work with the insulation around wires, pipes and heat ducts. Whenever possible, run the insulating material between the struggles and the subfloor. Cut slits in the insulating material so that you can run it on either side of a pipe or electric wire that runs through the joist bay. Run insulation under the pipe so that it has some protection against the cold where winter temperatures are cold enough to cause unprotected pipes to freeze.

Hammer nails to the joists 6 ins in a rim joist and hammer extra nails 24 inches apart down the length of each joist pair. Loop a piece of wire about a nail and stretch it across to the contrary nail and then twist it about that nail. The cable helps maintain the insulation in place. The wire should only have enough pressure to hold the insulation without undermining it.

Repeat the process for each joist bay you would like to insulate.

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