Thermal breaks significantly improve the energy efficiency of commercial building components, resulting in a lower, better U-factor rating. Their use in rolling steel doors is a key design strategy for minimizing thermal transfer. While many manufacturers offer rolling steel doors for commercial applications like warehouses and educational facilities, not all use thermal breaks to their full advantage. For architects, designers, and specifiers who select rolling steel doors for new commercial construction, renovations, and retrofits, it is important to understand the basic science behind thermal breaks and how they can be applied to doors for maximum benefit.
Thermal breaks defined
A thermal break is the strategic placement of material with low thermal conductivity to reduce the flow of thermal energy between parts of building components or materials. In the context of rolling steel doors, a thermal break can be applied to curtain construction and other structural features like guides to prevent
the direct transfer of heat or cold through the naturally conductive steel material. By disconnecting the conductive pathways or thermal bridges created by steel-on-steel contact, thermal breaks improve the door’s thermal performance and increase energy efficiency.
How thermal breaks are achieved in rolling steel doors
Engineers introduce thermal breaks into rolling steel doors using construction techniques in combination with insulating and low thermal conductivity materials to minimize thermal transfer. Examples of how and where these techniques and materials are applied include:
Double-wall construction with an insulated core: Insulated rolling steeldoors engineered for climate control
typically feature double-wall construction where the steel slats of the door curtain are configured in two layers. The double layer adds structural strength to the door, creating a hollow space or core between the layers for insulating material. The insulation may be polyurethane, polystyrene, or, in some cases, mineral wool for additional fire safety benefits. Double-wall construction with core insulation is a proven strategy for making
rolling steel doors more energy-efficient. However, in some designs, the interior and exterior steel walls may still be touching, meaning thermal bridging still exists.
To create a thermal break between the two walls, some manufacturers use low-conductivity chlorinated polyvinyl
chloride (CPVC) to construct the interior curtain wall layer and interrupt the connection points of the steel slats. This alternative material removes the thermal bridging occurring when steel is used for both sides of the double wall while strengthening the door’s curtain structure.
Thermally broken guides: One area of a rolling steel door that is overlooked as a source of thermal bridging and energy loss is the door’s steel guides. Guides are the vertical tracks installed on either side of the door’s opening that control the curtain’s movement when opening and closing. Guides keep the door curtain properly aligned as it moves and provide structural support. Manufacturers generally offer weather seals for door guides to prevent air infiltration along the sides of the door. However, weather seals do not address the thermal bridging that can happen in steel-on-steel contact in the guides. To solve this, some manufacturers have developed their own unique solutions to strategically place low-conductive materials in the guides to create thermal breaks and improve the thermal performance in this area.
Thermal breaks improve energy efficiency and more
Strategically integrating thermal breaks into insulated rolling steel doors offers multiple benefits, particularly for commercial applications such as warehouses and educational facilities where a rolling door is all that stands between a climate-controlled indoor space and the outdoor elements.
Particularly in four-season climates and extreme climate zones, insulated rolling steel doors with optimal thermal
breaks do a measurably better job of preventing heat loss in cold conditions and minimizing heat gain during hot outside temperatures. For example, one rolling steel door model with a CPVC interior wall (double-wall construction) and thermally broken guides was third-party tested per DASMA-105, which demonstrated the door
has a U-factor of 0.532, the lowest in the rolling door industry. A low U-factor door can translate into measurable energy cost savings for end users.
Rolling steel doors contribute to maintaining more consistent indoor conditions and help control humidity
and condensation, which are often problematic in climate zones where interior and exterior temperatures widely
differ. Better indoor climate control also contributes positively to the work environment by improving personnel
comfort and operational efficiency.
Commercial applications that enjoy the greatest benefits from a high-performance, low U-factor rolling steel door include:
● Warehouses and manufacturing facilities with loading docks.
● Cold storage facilities for food and beverage and pharmaceuticals.
● Commercial storefronts with customer-facing areas.
● Educational facilities where large openings are required in the building envelope.
Specifying rolling steel doors with thermal break technology can not only enhance energy efficiency in these environments but also provide long-term utility cost savings, comfortable indoor conditions, and greater operational effectiveness.
Choosing an energy-efficient door
To select the most energy-efficient insulated rolling steel door, consider these performance indicators before making the choice.
● R-value is not a reliable measure of thermal performance in rolling steel doors. R-value measures the thermal
performance of a single point on a rolling door, typically a slat. A higher R-value indicates better insulating
properties. U-value is also used and expressed as the inverse of the R-value. R/U-value can be used more reliably
for static building materials, such as drywall or insulation.
● U-factor measures the thermal transmittance of the entire rolling door assembly, factoring in all points in the
assembly. A lower U-factor indicates better thermal performance. U-factor is not U-value.
● Testing, standards, and certifications, including Doors & Access Systems Manufacturers Association (DASMA),
ASTM, International Energy Conservation Code 2021, ASHRAE, and California Title 24, can independently verify the doorʼs performance.
● Doors with double-wall construction, an insulated core, and thermally broken curtain walls and guides generally offer superior performance. Ask for product cutaways or samples to verify construction details.
Understanding thermal breaks and identifying the construction options and materials that make rolling steel
doors more efficient helps specifiers and building professionals make informed choices that lower energy use and cut costs for commercial building owners. Now, instead of being an architectural afterthought, rolling steel doors are at the top of the mind in commercial construction, breaking new ground in thermal performance.
Parts of a rolling steel door
Hood: The protective cover at the top of the door encloses the coiled curtain when the door is open and shields the rolling mechanism, including the barrel and spring assembly, from dirt, debris, and weather. The hood helps protect the interior space from exterior weather elements by sealing off the top of the door when it is closed. In
thermally efficient doors, the hood may be insulated or have additional weather stripping to prevent heat loss or gain.
Curtain: The main body of the rolling door comprises interconnected steel slats that move up and down to open or close the door. The slats are the visible and functional part of the door. The curtain’s construction plays a crucial role in thermal insulation. Double-wall slats with insulating materials and thermal breaks significantly enhance the door’s thermal performance.
Guides: The vertical tracks installed on either side of the opening guide the curtain during operation. Guides keep the curtain aligned as it moves and provide structural support. Guides can be designed with thermal breaks and weather seals to minimize air infiltration along the sides of the door. Thermally broken guides contribute to the door’s overall energy efficiency.
Bottom bar: The horizontal bar at the base of the curtain reinforces the door’s bottom edge and ensures a secure seal when the door is closed. A well-designed bottom bar with effective weather stripping can prevent drafts and air leakage at the bottom of the door. In some thermally efficient models, the bottom bar includes a rubber or foam seal that compresses against the floor to create a tighter closure, reducing the potential for
heat transfer.
Ian Hudock is the associate product manager for the Clopay Corporation strategic marketing team. He specializes in both high-performance and new product lines. He uses competitive research and market analysis to provide customers with informed, innovative commercial closure solutions. Hudock can be contacted at ihudock@clopay.com
