In an auto dealership, customer comfort is crucial, even in the service center where there has been a move away from relying on ambient temperature to heated or cooled environments. (This consideration makes visiting the service counter pleasant and the employees more productive.) However, with large doors opening and closing every few minutes, massive amounts of heating and cooling energy escape the building. That loss amounts to thousands of dollars in utility costs, in addition to making the systems conditioning the air work harder.
The rapid door speed minimizes energy loss by exposing the doorway for just seconds. For a typical service center, each door cycles well over 60 times a day. According to recently released research from the Door and Access Systems Manufacturers Association (DASMA), the ability of high-speed doors to minimize air infiltration when cycled at least this amount can exceed the energy savings of a slower, insulated door.
The DASMA research alters the perspective in evaluating door energy efficiency. It took into consideration common U-factor, air leakage, and motor horsepower values in a comparison of high-speed doors to conventionally operating insulated doors. Rather than strictly relying on door thickness or insulation to prevent energy loss, the study showed high-speed doors become more efficient when cycled 55 or more times per day.
High-speed doors are excellent at controlling ‘air exchange’—that is, the air flowing through a door opening that is not fully closed. In fact, when taking thermal transmittance (U-factor), air leakage, and door power usage into consideration, the air exchange can be the most significant part of the total energy loss for a door, depending on the application.
The DASMA study brought about code changes related to high-speed doors. Given the significantly reduced air-infiltration window, Addendum da of American Society of Heating, Refrigeration, and Air-conditioning Engineers (ASHRAE) 90.1-2010, Energy Standard for Buildings Except Low-rise Residential Buildings, relaxes air leakage requirements for high-speed doors by factoring in this trade-off. (To read the January 2014 Consulting-Specifying Engineer article, “What’s new in ASHRAE 90.1-2013,” by Jeff Boldt, PE, LEED AP, HBDP, FPE, visit www.csemag.com/single-article/what-s-new-in-ashrae-901-2013/85cefb05bf5d6ceacbdf804fe32d2945.html.) This is also reflected in ASHRAE 189.1-2014, Standard for the Design of High-Performance Green Buildings. In fact, last year, the International Energy Conservation Code (IECC) recognized the energy-saving benefits of high-speed doors for the first time. (For more information, read the October 2015 Building Design+ Construction article, “2015 IECC recognizes benefits of high-speed doors,” by Peter Fabris. To check it out online, visit www.bdcnetwork.com/ 2015-iecc-code-recognizes-benefits-high-speed-doors.)
Beginning with the 2015 edition, IECC includes a maximum allowable air infiltration rate of 1.3 cfm/sf of door area for high-speed doors. This requirement is consistent with the 2013 version of ASHRAE 90.1. In the current edition of IECC, ANSI/DASMA 105, Test Method for Thermal Transmittance and Air Infiltration of Garage Doors, is listed as the acceptable approach to obtain air infiltration values for high-speed doors. Although IECC requires a restrictive R-value (minimum 4.75) for the door component, a design professional is permitted to employ the U-factor trade-off method across the entire building envelope to compensate in the form of increased wall and/or roof R-values.
When they are closed, high-speed roll-up doors have gaskets on all four perimeters to effectively bottle up conditioned air in the building. The tight seal on any door can be threatened if it is hit, but the speed of these assemblies means this is unlikely to happen at a dealership, despite the very short distance a car travels to enter or exit the building. By the time the driver shifts the car into drive, the door is very likely rolled up and tucked away under the door header.
This same tight seal of high-speed doors to keep energy in the building, also keeps intruders out. Although many of thefts involve taking vehicles off the lot, break-ins at the dealership can be common as well. Along with the cars, thieves will take tools and spare parts from the service area. This is greatly discouraged by the closed doors’ rigid aluminum slat construction and integrated locking system.
Some dealerships are using fabric high-speed roll-up doors during operating hours with a backup garage-style door to lock up at night. While this may be a lower up-front cost investment, two doors double the facility’s maintenance costs. As for the issue of aesthetics, the surface of a fabric door also will show signs of wear and tear over time, while a rigid panel door will not.