To improve comfort, safety and system balancing, seal all plenums and supply and return ducts with aluminum foil duct tape, approved flexible plastic tape or water-based mastic. Heating ducts running through unheated or cool basements and crawl spaces should be insulated. Cut RSI 2.1 (R-12) or more of batt or blanket insulation to size or use specially designed foil-faced fibreglass blanket insulation designed for this purpose. Wrap the insulation around the ducts and secure with string, wire or approved tape - do not use vinyl type duct tape.

Do not wrap the ducts within 1.8 m (6 ft.) of a wood-fired furnace unless you use a special, approved non-combustible insulation.

For houses with hydronic systems, place foil-covered insulation board between radiators and exterior walls to reflect heat back into the room. Metallic supply and return lines can be insulated with minimum RSI 0.7 (R-4) approved insulation. Insulated jackets are available for some types of boilers and may offer some efficiency gains for equipment installed in cold parts of the house.