Wood floors look attractive and are comfortable underfoot, unless they are cold. Insulating the wood floor is a bit of a misnomer. The space between the floor joists under the wood floor will be insulated. The project is not difficult but can be a challenge if you're working in a cramped crawl space. However, the utility savings and the improved comfort usually make the task worthwhile.
Fit R-19 insulation with paper facing between the floor joists. Staple the insulation in place, using 1/2-inch staples and a staple gun. Fit the insulation as closely as possible to the sills and other framework around the joists.
Stretch 18-gauge wire across the insulated space, stringing the wire perpendicular to the floor joists. Stretch the wire tight enough so it will not sag with wires spaced about every 18 to 24 inches. Other options for securing the insulation include rope or strips of wood nailed in place.
Cover the bottom of the floor joists with 6mm polythene sheeting. This serves as a vapour barrier, preventing moisture from entering the joists and floor area. Overlap any seams in the sheeting by at least 1 foot. The sheeting can be stapled in place, but wood strips hold the polythene sheeting more securely.
Wear appropriate safety equipment, including a respirator and safety glasses, while working with insulation. Insulating the foundation walls with foam board also improves the warmth of the wood floor. Insulating a floor over a crawl space is easier to accomplish during the construction process rather than as a remodelling project after the building is complete.
Make sure the area under the crawl space drains and does not accumulate any standing water. Use caution when working in the crawl space. These areas can be the home to potentially dangerous vermin.