Loft Insulation Between Floor Joists

A basic floor system is installed in about 10 stages from preparation to boarding the floor.

Loft insulation between floor joists.

The insulation should press right up against the floor between joists. A new floor system is installed using a frame trimmer joists to support the floor joists that span the width of the loft. Gaps between the insulation and the floor can lead to inefficiency and heat loss. You need insulation between and over the floor joists when you are dealing with an unfinished attic space.

With some structures floor joists are required to be 12 or 24 inches apart on center. Joists are the horizontal beams which make up the floor. Given that 2x8s are actually 1 inches wide it works out to be 14 inches between each joist. Encapsulating the floor system including duct work with thermo cloth and closed cell spray foam insulation creates a perfect wood framed floor system.

Typically the gap between the joists is either 380mm or 570mm so you will need a width of insulation similar to this so it can fit snugly between the joists. To find the actual distance between the inside edges of each adjacent floor joist. This will seal off living space below if the room is cantilevered beyond the exterior wall bellow you need floor insulation slab floors build directly on the ground need insulation. The first layer of wool is placed between the joists and then a second layer is placed at right angles which covers the joists and also makes the insulation up to the correct depth of 270mm.

The inside of the rim joist is sprayed from the sub floor to the bottom of the rim joist to drop the building envelope to the bottom of the joists. Trimmer joists form. You also reduce the space in which joists and floorboards can vibrate which reduces vibration noise. Clearing the loft area of all debris insulation struts and temporary boards to expose the ceiling boards.

Rolls of mineral wool can be used if the joists in your loft are regular. The fiberglass will also need to be secured in place using wire mesh twine wood laths or other securing methods which can be an intensive project that adds to the overall cost. This means from the center of one upright joist to the center of the next. Pir insulation is thermally efficient and can be used as part of a complete refurbishment of the loft floor or in conjunction with existing insulation laid between the joists to help improve heat loss from the property and where necessary meet the requirements of national building regulations.