Surrey Doors Ltd.
Garage Door R-Value Guide
What R-value means, how it's measured, and which insulation level is right for your garage.
R-value measures a material's resistance to heat flow — the higher the R-value, the better the insulation. For garage doors, R-value is one factor in thermal performance, but the whole-door U-factor is a more complete measure. Here's what Surrey homeowners need to know.
What R-Value Means
R-value measures thermal resistance. A door with R-18 resists heat flow better than one with R-6 — but the door's construction and seals also affect real-world performance.
Attached vs Detached Garage
Insulation matters most in attached garages, where the garage wall is shared with living space. Detached garages benefit less from high R-value doors.
Polyurethane vs Polystyrene
Polyurethane (injected foam) achieves higher R-values in thinner sections and bonds to both skins. Polystyrene (rigid board) is less expensive but lower R-value per inch.
R-Value Examples
Clopay Bridgeport Steel: R-18.4. Amarr Olympus: R-19.40. Garaga Standard+: R-16. Hörmann Clima Tech 4400: R-15.7.
U-Factor vs R-Value
U-factor measures whole-door heat transfer — a lower U-factor means better insulation. Compare U-factors when available for a more accurate performance comparison.
Which Level Do You Need?
For attached garages in Surrey's climate, R-12 to R-18 is a reasonable target. Higher R-values offer diminishing returns beyond R-18 for most residential applications.
Choosing an Insulated Door in Surrey?
Call for a free consultation — we'll help you choose the right insulation level for your garage.