Best Insulation Between Floor Joists

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.

Best insulation between floor joists.

First insulation will be going between the floor joist i only filled gaps with foam. Clarification for march 23rd e mail. Joist bays the open spaces between floor joists are prime hosts for insulation under specific circumstances. Installing this type of insulation is an inexpensive and diy friendly project since the materials are designed to fit into the standard width between wall studs attic rafters and floor joists.

Department of energy recommends r 11 3 insulation under floors in warm climates and an r 25 6 to 8 in cold climates. Owens corning has a 23 x39 roll of pink unfaced insulation that fits between trusses joists or studs adds 6 1 4 thick of insulation with an r 19 value and an nrc rating of 1 05. Fiberglass rolls can be placed between joists but the fiberglass itself will need to be cut to fit properly between joists. 4b slab floors built directly on the ground.

It is moisture and mold susceptible though. Gaps between the insulation and the floor can. When the basement or crawl space has vents installed insulating joist bays. Second i have foundation vent all around the house should the remain unblock or do the need to be covered.

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. We chose 2 in thick r 10 extruded polystyrene don t use expanded polystyrene which is a less effective air and moisture barrier. Fill the ends of joist bays with rectangles cut from rigid board insulation. Rigid foam is the best insulation for rim joists.

Fiberglass insulation batts or rolls are the most economical and easiest diy choice for insulating between the floor joist in a crawl space. 4c as an alternative to floor insulation foundation walls of unvented crawl spaces. 4d extend insulation into joist space to reduce air flows. Use caulk or foam sealant to seal the joint between the top.

You can insulate second floor rim joists following the same steps shown here if you happen to tear out a ceiling during remodeling. Fiberglass insulation is usually the best option though handling fiberglass can be dangerous and it is not the most eco friendly option in some cases. Use foam sealant such as great stuff to seal the joints.