GAS TECHNOLOGY: Air Curtains Can Make a Difference
One of the most frustrating problems for industrial building energy managers is large openings between conditioned and non-conditioned spaces. Often dock doors, warehouse access doors and other openings need to be kept open to facilitate movement of personnel, equipment and goods. Unfortunately, these openings also represents a major building energy leak and source of indoor contamination. A solution to this challenge that is increasingly being used is air curtains, sometimes called air barriers. These can not only help reduce energy loss, but can prevent entry by other environmental contaminants such as fumes, dust and insects.
Challenges Where Environments Meet
Most industrial buildings have several openings to the outdoor environment, or openings between a non-conditioned warehouse environment and conditioned storage or manufacturing spaces. These are problem areas because forklift, conveyor and foot traffic require that doors be kept open much of the time. Yet open doors allow the escape of conditioned air and entry of outdoor air contaminants. Various solutions have been tried.
One approach has been to use suspended vinyl strip doors. While these can be effective in separating environments, they have several drawbacks. According to one industry spokesperson, “Vinyl strip doors are unsightly and do not provide effective environmental separation.”
Potential Visibility Hazard
Though quite transparent when new, vinyl strips quickly become scratched, stained and dusty, particularly if they are used for
motorized traffic, creating a potential hazard for traffic through or near the doors. When there is a breeze on one side of the door, they are of limited usefulness in preventing intrusion of outdoor conditions. They can require frequent maintenance because the strips are often damaged by forklift operations.
In addition to doors to the outside and between conditioned and non-conditioned spaces, another area where environmental separation is needed is entrances to refrigerated spaces and freezers, particularly where forklift transport is being used. Where these are high-traffic entrances, physical barriers like motorized doors or vinyl strips are impractical and inevitably slow down production. Here also, a better solution is needed.
A Better Solution for Reducing Infiltration
The approach that is gaining in popularity is the use of air curtains. These use an overhead air pressurizer that directs a narrow laminar flow of recirculated air down or across the door opening. This high-speed stream prevents entry of outdoor environmental elements and escape of conditioned indoor air. This is achieved without any visual or physical barrier to foot or motorized traffic.
Enershield Industries, headquartered in Edmonton, Alberta, is a manufacturer of air barriers for the U.S. and Canadian markets. Dan Hallihan is the Regional Manager for the firm and was a recent presenter at a Tecnology & Market Assessment Forum sponsored by the Energy Solutions Center. Hallihan indicates, “One of the greatest energy inefficiencies in any building is an open door. Enershield Air Barriers can create up to a 90% seal on open doors against a 15 mph wind. We supply our clients with an energy loss calculation using an ASHRAE formula to show what the client is losing in energy as well as what we can save them based on the amount of time the door is opened. “
Hallihan feels there are numerous locations in the industrial building where it is important to prevent the infiltration of outside air into facilities. “This not only affects indoor temperatures but in some cases also affects manufacturing processes. When outside air infiltrates into a facility, it puts an instant demand on either the heating or cooling system. The installation of an air barrier helps to reduce the cycle time of those systems and thus reduces wear and tear on those units and saves facility energy.”
Air curtains are often designed to start automatically when the physical door is opened and stop when it is closed. Often, conditioned warehouse facilities have rows of multiple bay doors. Where each of these is equipped with an air barrier, the indoor environment remains stable and comfortable, and temperature sensitive products and equipment are protected. Air curtains are available for doors in a wide range of sizes. Systems are available for openings as small as retail food takeout windows, or as large as aircraft hangar doors.
Air Barriers Withstand Tough Environments
Standard models are typically constructed of a welded, powder-coated frame with a galvanized metal jacket. Manufacturers also produce models for harsh, damp climates or areas that require a frequent washdown and need to be able to tolerate a wet environment. Other considerations in specifying an air barrier are building orientation to prevailing winds and the local climate.
Another provider of air curtains is Mars Air Systems of Gardena, California. Mars offers a broad line of air curtains for door and window openings of virtually all sizes. Betiel Abraham from Mars emphasizes that their air curtains help maintain comfortable indoor temperatures, so employee productivity increases and energy costs decrease. Abraham also points out that through the use of air barriers, an industrial or commercial facility can garner points toward a LEED certification.
Air Curtain Heating Available
For users of air curtains in cold climates, Mars offers doors that use heated air to increase comfort for workers near the opening. Several heating options are available, including electric, gas-fired hot air and steam heat. The Mars website includes a calculator to help owners determine potential energy savings through the use of an air door. According to Abraham, the doors can be installed over any door opening and are available in a variety of colors. “These can be customized to conceal into any opening and are available with a standard five year warranty on all unheated systems and and 18 month warranty on heated units.”
As energy costs become increasingly critical with tight manufacturing margins, the savings and improved environment realized from an air curtain can be important. Engineers have designed air curtains to solve the challenges of traffic safety, energy conservation, facility comfort and control of the indoor environments. Now is the time for owners to take a look at this valuable technology.
Biddle Air Systems
Mars Air Systems
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