A crawl space is an unfinished, accessible area below the first floor of a building. Remember, the main purpose of insulation is to enclose the living space in a thermal envelope. Therefore, if the space below a floor is unconditioned, either the floor or the walls below it must be insulated.
There are two types of crawl spaces: vented and unvented. Vented crawl spaces open to the outside, while unvented crawl spaces are part of the basement. How and what is insulated depends on whether the space is vented or unvented.
In a vented crawl space, the underfloor should be insulated, much as it is installed in ceilings. This may be done either before or after the sub-floor has been applied. JM ComfortTherm®, Kraft-faced and unfaced insulation are all possible products to use for this application. With Kraft-faced insulation, the facing is generally against the sub-floor.
In an unvented crawl space, you should insulate the perimeter walls.
If the sub-floor is already in place, the insulation is installed from below, much as it is installed in ceilings.
When installing Kraft-faced insulation, use wire lacing, screen or stiff wire fasteners to hold the insulation firmly in place. The fasteners are bowed upwards into the insulation, pressing it gently
against the sub-floor without overly compressing it. Place the fasteners at least six inches from the end of each batt, and no more than 24 inches apart.
You may want to consider using JM's special ComfortTherm® for Underfloor, specifically designed for floors, with the stapling flanges on the bottom side, and the vapor retarder on the top side. It is stapled to floor
joists in the same way as ordinary faced insulation is installed in ceilings and ensures insulation is up against the floor. The vapor retarder side is installed up against the subfloor, and the non-vapor retarder has flanges for stapling to the sides or bottom of the joists.
Where heating ducts between joists are exposed to cold air, insulation should be installed below the ducts to prevent heat loss.
In cold climates, if water pipes are running through the joists in the crawl space insulation should be installed below the pipes to protect them from freezing.
In an unvented crawl space, the general rule is to insulate the perimeter walls. This eliminates the need to separately insulate the water pipes and heating ducts.
ComfortTherm® insulation is a lightweight, thermal and acoustical insulation made of long, resilient glass fibers bonded with an acrylic thermosetting Formaldehyde-free™ binder.
JM's EasyFit® Formaldehyde-free™ insulation is available unfaced or with kraft facing, and has vertical perforations for fitting non-standard wall cavities.
JM's Unfaced Insulation is a lightweight thermal and acoustical fiber glass insulation made of long, resilient glass fibers bonded with an acrylic thermosetting resin made without formaldehyde.