Insulated garage doors, explained

Panel values and whole-door values, 40 or 60 mm panels, and the seals between them: what makes a garage door warm, and when it matters.

Garage doors
4 min read
October 2026

A dark garage door glowing softly at night in falling snow — Concept visualisation · a winter night

An insulated garage door keeps the garage closer to the temperature of the house. Whether that matters depends on what the garage is for, and on two numbers that are easy to confuse.

What insulation does

A garage door is the largest moving surface of a home¹. Insulation slows the heat passing through it; seals stop the draughts around it. In a garage that is part of the house, under a bedroom or used as a workshop, you feel the difference in the rooms beside it.

Insulated sectional doors use two steel skins, folded at the edges, around a polyurethane foam core¹.

Two numbers, not one

Thermal performance is given as a u-value, in W/m²K: the lower the number, the warmer the door¹. Manufacturers publish two kinds. A panel value describes the panel alone. A whole-door value also counts the joints, seals and frame, so it is always higher. The two are not directly comparable¹.

Manufacturer’s published values. Whole-door values vary with size, and with glazing, wickets or grilles.
Door	Panel	Panel value	Whole door
UniPro	40 mm	0.48 W/m²K	1.1 to 1.3 W/m²K
UniTherm	60 mm	0.33 W/m²K	0.90 to 1.1 W/m²K
PRIME	60 mm	0.33 W/m²K	0.90 to 1.1 W/m²K

Those figures come from the manufacturer’s tables^{2, 3, 4}. When you compare doors, compare a panel value with a panel value, and a whole door with a whole door.

40 or 60 millimetres

Forty millimetres is the market standard¹, and UniPro’s 40 mm panel is our everyday warm door¹. The 60 mm panel in UniTherm and PRIME is the reason those doors are rated for energy-efficient and passive houses: the manufacturer’s words¹.

The thicker panel comes with deeper seals and concealed hinges, and on PRIME every moving part is covered^{3, 4}.

Seals matter as much as foam

Heat and draughts find the gaps. Rubber seals between the panels and around the perimeter close the gap between garage and weather¹. PRIME uses five types of seal, including a double bottom seal and double-lip side seals⁴; UniTherm has a full perimeter seal set³.

Seals keep out wind and rain too. Weather performance is declared under EN 13241, and in the manufacturer’s data the 60 mm doors reach air permeability class 5 and wind load class 4^{3, 4}.

Other kinds of door

Roller garage doors use foam-filled aluminium profiles⁵. Up-and-over doors can take an optional polystyrene lining on some models⁶, and side-hinged doors can be insulated with 20 to 40 mm of polystyrene⁷. Our catalogue publishes no whole-door value for these types, so ask us before relying on one for a heated space.

For a warm side entrance, aluminium side doors pair a thermally broken frame with the same 60 mm insulated panel as UniTherm⁸.

When it matters most

The garage is part of the house, especially under a bedroom. The 60 mm systems are designed for energy-efficient and passive buildings¹.
The garage is heated, or used as a workshop, gym or utility room.
A detached garage for a car and tools. A 40 mm panel is the everyday choice¹.
Condensation. Insulation helps, and so does air: some drives can stop the door a hand’s width open to air the garage⁹.

Confirmed at survey

The performance of an installed door depends on its size, glazing and fitting, and is confirmed at survey¹. Ask for the whole-door value for your size and configuration, and keep it with your written quotation.

If the door also needs to resist a break-in, ask about the RC2 anti-burglary package, which is offered across the sectional range^{2, 3, 4}.

From the catalogue