Furnace Duct Insulation — Stop Heat Loss in Unheated Spaces
Published: July 23, 2026 — BC Wide Home Services Ltd, doing business as BC Wide Heating & Air Conditioning — Greater Vancouver, BC
Why Insulate Ducts
Uninsulated ducts in unheated spaces (crawlspaces, attics, garages) lose 20-30% of heated or cooled air through the duct walls. Insulating ducts reduces this loss significantly. In winter, heat is lost from supply ducts. In summer, heat is gained by cool air passing through hot attics. Insulation helps both seasons.
Insulation Types and Cost
Fiberglass duct wrap: $2-5 per linear foot installed — most common, effective R-4 to R-8. Rigid foam board: $3-6 per linear foot — higher R-value, better for tight spaces. Pre-insulated flexible duct: $3-8 per linear foot — best for new installations. Professional duct insulation for a typical home: $500-2,000 depending on accessibility.
DIY Insulation Tips
For DIY: use fiberglass duct wrap with foil facing (reflective surface facing out). Wear gloves, long sleeves, and a dust mask — fiberglass is irritating. Wrap the duct completely with no gaps, overlapping the insulation at seams by 2 inches. Use foil tape to secure the insulation and seal all joints. Insulate both supply and return ducts in unheated spaces.