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Ventilation & air handling

Maintaining Air-Handling Equipment

Proper maintenance of air-handling equipment can prevent energy waste and help to ensure the comfort of building occupants. Fans alone—the main energy-user of air-handling equipment—use about 7 percent of the energy consumed by buildings that use conditioned air. They can be either in self-contained equipment—for example, with air handlers used in chilled-water systems—or integrated into packaged equipment like rooftop air conditioners. Other air-handling components include filters and dampers, which can also waste energy if not maintained. In this topic, we cover mai…

Underfloor Air Systems

Underfloor air systems, in which raised-access floors serve as plenums for distributing cooled air throughout buildings, are growing in popularity in North America. The potential benefits of underfloor air distribution include improved thermal comfort, improved indoor air quality, reduced energy use, and improved flexibility for office moves. Although slow to catch on in North America at first, the burgeoning underfloor air distribution industry is feeding itself in an upward spiral today. As more systems are installed, manufacturers have more examples to point to when trying to sell builders …

Fans

According to a recent study, more than 25 percent of the energy consumed in commercial buildings is used for heating and air-conditioning. Of that, a good portion (anywhere from 20 to 60 percent) is consumed by the fans and pumps that transfer heated or cooled air or water from central heating and cooling plants to conditioned spaces. Supply and exhaust fans are the major players, primarily because most fans operate continuously while the building is occupied. There is a wide variation in efficiency between different fan designs (from as low as 40 to as high as 80 percent). In light of their l…

Economizers

If you are responsible for a cooling system that has a capacity of 7.5 tons or more, you probably have an air-side economizer—and chances are it could use some attention. When the outdoor temperature and humidity are mild, economizers save energy by cooling buildings with outside air rather than using refrigeration equipment to cool recirculated air (Figure 1). A properly operating economizer can cut energy costs by as much as 10 percent of a building’s total energy consumption (up to 20 percent in mild coastal climates), depending mostly on local climate and internal cooling…

Duct Sealing

Properly sealing ductwork results in several benefits. It improves comfort by increasing the rate at which air is delivered to a space; it can prevent safety problems caused by carbon monoxide gas leaking from water and space-heating equipment; and it improves indoor air quality by reducing the infiltration of dust, humidity, and outdoor fumes and odors. It also saves energy. The most cost-effective time to seal ducts is when an HVAC system is first installed in new construction, because the ducts are easily accessed. However, ductwork can also be sealed in existing buildings. Duct sealing may…

Demand-Controlled Ventilation

Across the U.S., many stores keep long hours every day, and although they may be full of browsing shoppers during some hours of the week, relatively few customers will be milling about the floor space at other times. Occupancy fluctuations like these offer retail stores and other commercial facilities an opportunity for annual energy savings that can amount to as much as $1.00 per square foot (ft2). Instead of continuously ventilating the space at a constant rate designed to accommodate the maximum number of customers, building operators can implement demand-controlled ventilation (DCV) so tha…

Dedicated Outdoor Air Systems

In most buildings, HVAC systems combine fresh outdoor air with recirculated air in the main air handler for conditioning and distribution into the interior space. Some new buildings are using a different configuration called a dedicated outdoor air system (DOAS). In this design, the outdoor air is conditioned separately from the return air before it enters the building (see Figure 1). Dedicated outdoor air systems are a useful tool for improving humidity control and delivering precise amounts of ventilation air. Also, compared with conventional HVAC systems, they eliminate restrictions on the …

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