Best Insulation For Floor Joists

According to the 2012 irc the minimum r value for floor assemblies is r 13 in zones 1 and 2 r 19 in zones 3 and 4 r 30 in zones 5 and 6 and r 38 in zones 7 and 9.

Best insulation for floor joists.

Fiberglass insulation batts or rolls are the most economical and easiest diy choice for insulating between the floor joist in a crawl space. Floor joists on new construction. 4c as an alternative to floor insulation foundation walls of unvented crawl spaces. In attics aluminum sheeting is often used for insulation and this same method can be used for insulation for floor joists but this will not be the most efficient method for retaining heat within the home.

Fiberglass insulation works as an insulator because it traps air in the fibers of the insulation and slows the collision of warm and cold air. 4b slab floors built directly on the ground. In some cases if the floor is accessible from below it may also be possible to partially insulate the joists from underneath which offsets thermal bridging through timber members but this is not often the case. Clarification for march 23rd e mail.

Department of energy recommends r 11 3 insulation under floors in warm climates and an r 25 6 to 8 in cold climates. If you want to insulate a floor assembly by leaving the joist bays empty and installing rigid foam on the underside of the joists here are a few things to keep in mind. The best insulation material for crawl spaces is rigid foam insulation board. 4d extend insulation into joist space to reduce air flows.

We chose 2 in thick r 10 extruded polystyrene don t use expanded polystyrene which is a less effective air and moisture barrier. The floor joists are all fastened to the rim joist which runs along the. Rigid foam is the best insulation for rim joists. If the fiberglass insulation gets wet or very damp it will begin to collapse get heavy and fall from the floor joists rendering it useless to trap air and be an insulator.

Less than the height of the rim joist. Any compromised floorboards or joists can also be replaced as part of the retrofit project. Also insulate 4a any portion of the floor in a room that is cantilevered beyond the exterior wall below. Instead of installing the foam insulation between floor joists in the crawl space the foam board is installed against the crawl space foundation walls.

First insulation will be going between the floor joist i only filled gaps with foam.