Before specifying efficient heating and cooling equipment, it’s important to do what we can to reduce heating and cooling loads. Insulation is one of the key products to consider here, but because there are so many insulation products on the market, we look for additional benefits. Examples include cellulose insulation with recycled content, mineral wool insulation with no flame retardants, and fiberglass insulation with no formaldehyde binders. Other products in this area are high-performance windows and glazings, products that contribute to building airtight envelopes, products that reduce thermal bridging, and window-retrofit products.
With products in this area under constant development, we are always refining our approach. For example, as we have learned about insulation products with hazardous flame retardants and blowing agents that have high global warming potential, we have removed those products from GreenSpec, pending manufacturing changes. We encourage building professionals to pressure manufacturers for those changes through specification language and purchasing decisions.
C.J. Rush Revolving Doors
C.J. Rush Industries, a division of Stanley Security Solutions, offers manual and automatic revolving doors for commercial applications. The 1500, 2500, and 3500 series are available in three- and four-wing models: the 1500 uses a frame, while the 2500 and 3500 are all-glass. The standard size is seven feet in diameter, but custom sizes and designs are also available. A quarter-point-closing option helps minimize air loss and improves energy efficiency. The company’s 5500 is a four-wing automatic model for 12- to 16-foot-diameter entrances. Among the features are motion detector activation, quarter-point closing, and an open position that allows the wings to collapse for clear passage. Safety features include emergency stop and handicap buttons and sensors in the ceiling, near the floor, and in front of the wings that stop the door if people enter “safety zones.” The company also offer security doors that help control access to buildings.
Loss of conditioned air through entryways is a major source of energy loss in commercial buildings. The stack effect—where cold air from air conditioned upper floors flows down to lower levels (and out the front door) in summer, and heat rises in winter, pulling cold in through entrances—can result in so much air infiltration/exfiltration through swinging doors that they become difficult to open or close in taller buildings such as skyscrapers.
Revolving doors solve this problem by maintaining a reasonably good, constant seal against the outdoors, minimizing the loss of conditioned air while allowing traffic flow in a limited amount of space. They also reduce the amount of dirt entering the building, which can help reduce maintenance costs. As the energy saving benefits of revolving doors becomes more recognized, we look forward to greater attention to reductions in air leakage through these doors while maintaining ease of operation.
Revolving doors have two to four wings, and are available in both manual and automatic models. Smaller four-wing models and large automatic two-wing models, which have two smaller wings on either end (like a “Y”), provide better seals to the vestibule than do three-wing models. All of these wings collapse outward in case of fire, allowing an unrestricted exit.
Manual three- and four-wing models are six to ten feet (1.8–3 m) in diameter and can typically handle 20 to 50 people per minute. They use speed reducers that keep the rotations below 8 to 12 per minute (the maximum speed allowable by the National Fire Protection Association), depending on diameter. Automatic revolving doors come in a variety of sizes, from four-wing models eight to ten feet (2.4–3 m) in diameter to two- and three-wing models over 20 feet in diameter. As with manual doors, maximum rpm is based on door size, with large models spinning at about 3 rpm. Some of these doors can handle 60 people per minute, and are used in hospitals, grocery stores, hotels, and other high-traffic settings because of their large compartment sizes.
Important considerations for selecting a revolving door include size of the building opening, number of people using the entrance per minute, handicapped accessibility, luggage usage, and security or control of access.
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