Can Garage Doors Save Energy?
An often-overlooked option for saving energy, certain types of garage door have over years of development by manufacturers evolved into an effective insulator for homes with integral garages. This article explores this notion.
Heat Loss Measurement
Garage Door manufacturers offer guidance using U-values. The U-value is a measure of the heat transfer through a 1m2 surface area for every degree of temperature difference between the inside and outside. A lower U-value indicates greater energy efficiency in the material.
Building Regulations
While there isn’t specific legislation that directly addresses U-values for insulated garage doors, Part L of the Building Regulations does cover garage conversions. For example, when previously exempt unheated spaces become part of a heated dwelling, a garage door used to access the space, if being retained or upgraded, may need to comply with the energy efficiency regulations.
Multi-Layers
Garage door manufacturers employ multi-layered designs to enhance energy efficiency, much like individuals wearing several layers of clothing during winter to keep warm. To achieve this, they utilise a combination of materials to create a double-skin structure, using steel, aluminium, or vinyl on the outer skin and a CFC free polyurethane rigid foam filling. This provides exceptional insulation whilst enhancing strength and durability. Naturally the thicker the panels are the better they will perform.
As an indicator of optimal performance, the best ‘sectional’ garage door designs are sub 1.0 W/m² K insulators and have the lowest U-values. Furthermore, to improve on this ‘layered’ model, some manufacturers construct the design as a broken sandwich to create thermal separation of the outer and inner shells. This can produce heat insulation values below 0.5 W/m2K.
Additionally, to brighten a dim garage area using glazing that won’t compromise the energy efficiency, triple-glazed windows are used.
Weather-proofing
Double seals are very effective at addressing air leaks around the frame. Additionally, seals can be installed on the floor to close the bottom edge of the door, allowing for unobstructed access while preventing water from entering. For sloping thresholds, potential gaps can be avoided using a bottom rail to even out an unlevel driveway. This close-fit between the bottom of the door and the uneven floor ensures that insulation properties are maintained. Furthermore, the highest quality garage doors can have plastic profiles fitted to the frame to create a thermal break where it connects with the brickwork.
Wood as an insulator
It’s no surprise that timber garage doors are airtight. Cedar wood’s cellular structure creates natural air spaces that give it an insulation value higher than most woods, as well as having excellent sound suppression and absorption qualities.
What are the best insulators?
Whilst capitalising on the multi layered ‘thermal’ design principle, sectional garage doors also use space filling seals at every panel interconnect. They are intentionally made and tested for the purpose of insulation. A sectional garage door installed fully behind the garage opening usually offers the highest levels of insulation as the door and frame will be sealed fully against any brickwork. Where sizing issues create gaps at the top of the garage opening, the best manufacturers provide options for fascia panels, which are made to size, to fill the space to the lintel.
Roller Doors are good insulators! Aren’t they?
Roller garage doors, on the other hand, are made up of up to 24 individual foam-filled slats. Whilst offering some protection, they are untested on a fitted door. Because the interlock between the laths/slats are not sealed they are unable to carry a meaningful U-value. The gaps simply don’t prevent air and moisture from escaping. Other features however do play a role in determining the amount of heat that can be saved. These include weather seals placed in the guides, a full surround hood cover for the roll, and the extent to which the door slats overlap the sides.
Energy efficient Side Hinged Garage Doors
Side hinged garage doors are available in single or double skin options. Single skin doors are a cost-effective option best suited to spaces where there’s no need for insulation or draught sealing. Double skin doors are a thicker, insulated alternative. The actual door leaves are constructed in a similar layered design to their sectional garage door counterparts using a rigid Polyurethane (PUR) foam core inside steel. Furthermore, side hinged doors made of natural wood around a tight-fitting frame are also inherently a good insulator.
Non-insulating up and overs
Generally, up and over doors do not offer very good insulation but some effort can be made by adding off the shelf insulation packs. That said there is still the problem of having a gap all around the edge – A failing affected by the whole door having to move through the sub frame when opening and closing.
Conclusion
Garage door manufacturers are making progress as the significance of energy efficiency grows. The development of new materials, construction with multiple layers, advancements in seal design, and the use of weather stripping are all contributing to the production of increasingly efficient garage doors.