Raising the Standard for Thermal Performance

In addition to making it easier to moderate indoor conditions for workers, insulated rolling doors also decrease energy consumption, which reduces the building’s carbon footprint. Selecting an uninsulated or unsuitable product, on the other hand, can result in excessive heat loss or gain, putting stress on heating, ventilation, and air conditioning (HVAC) systems, which have to work harder to moderate the climate in the building. And when HVAC systems are running more frequently to compensate for inefficient sealing, they cost more to operate and maintain.

There is clear value in choosing wisely, but with so many variables, the decision can be overwhelming. Confusion about how components and doors are rated is a big part of the problem.

R-value versus U-factor

Understanding the difference between U-factor and R-value is a conundrum for many, but a simple memory aid could change that. A good way to remember the difference is that U-factor “factors in” the whole door assembly in a third-party testing process, while R-value is a calculation of an individual insulated component of a door.

In simple terms, R-value measures the thermal resistance of a single point on a door. This is a calculated value that ranges from 4 to 12, with a higher rating indicating better thermal performance of the point. Understanding that the R-value is calculated on a single point is critical because it’s possible for a door with inadequate seals to have a high R-value if the door includes slats constructed of highly insulating material. Although the slat has a high R-value, the entire door assembly can be missing key features that can affect thermal performance.

U-factor is the inverse of R-value. While R-value calculates the insulation of a point on the door, U-factor calculates the rate of transfer of that single point.  

U-factor measures the rate of heat transfer through an entire door assembly. Doors are tested by a third party to determine U-factor, which ranges from 0.8 to 1.1, with a lower rating indicating better performance. The U-factor tells a more complete story because it reflects a third-party verification of the thermal transmittance of the fully installed door assembly.

Designing for Low U-factor

Cornell has a long history of designing secure, durable, and customizable rolling doors for exterior openings, setting performance standards with the Thermiser Max^® Door, which was introduced in 2013. As the rolling industry’s most energy-efficient product of its type at the time, it features a full perimeter door sealing system that combines thermally broken guide construction and an insulated curtain to minimize air infiltration and thermal transference. This insulated roll-up door delivers a 94% decrease in air infiltration compared to standard products and has a U-factor of 0.82 for top-tier energy efficiency.

The Thermiser Max Door design was the result of growing demand from the commercial building industry for a product that improves air infiltration performance. The new Thermiser Max^® - Low U Door builds on this solution-focused design, integrating thermal breaks between the wall and the outer angle of the guide assembly, an insulated curtain, a patented perimeter seal, and a CPVC backer on the interior curtain to resolve thermal bridging. The insulated slat with plastic backer carries an ASTM E84 Class B fire rating, compared to a regular steel insulated slat, which has a Class A rating.

The result is an industry-leading roll-up door with a U-factor of 0.532 that sets a new standard for thermal performance.

The value of superior design

The door’s impressive U-factor rating translates into energy cost savings ranging from $300 in Climate Zone 1 (hot) to $920 per year for Climate Zone 6 (cold) when compared to a standard insulated door. Calculations are based on installing the Thermiser Max - Low U Roll-Up Door in a building that is heated or cooled 24 hours per day, an HVAC system operating at 90% efficiency, and an electricity cost of $0.16 per kWH.

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