Page 26 - OHS, October 2020

IH: INDOOR AIR QUALITY
There are many types of ductwork systems. They may use oval, round or rectangular shapes and can be made from a wide range of materials including flexible plastics, fiberglass or—most commonly—metal. Recently, fabric ductwork has been gaining widespread acceptance, and for good reason.
The Benefits of Fabric Ductwork
Fabric ductwork/diffuser systems have a number of benefits over traditional metal systems, most of which stem from the fabric itself. Since these fabrics have continuous linear dispersion, they diffuse air evenly across the entire length of the ductwork system. This full-length diffusion eliminates the hot and cold spots created by localized diffusers in traditional systems, which may be placed many feet apart. Conventional metal systems with high-volume diffusers also suffer significant performance differences from heating to cooling and fresh air dispersion, due to buoyancy and
volume of changes.
Fabric duct systems are particularly useful in industries that
require strict temperature and humidity control, such as growing facilities, other food and beverage facilities and data centers. Minimizing harmful turbulent air, which can spread illness, is possible with fabric systems that produce soft moving air by way of more exchanges.
Fabric options are also becoming popular in gymnasiums and pools, where moisture may cause metal ductwork to degrade. In a worst-case scenario, this degradation creates “rust rain.”
The light weight of their fabric also makes fabric duct systems less expensive and easier to ship than metal ductwork, as well as significantly less time-intensive to install.
Unlike metal, fabric ductwork systems are immune to scratches and dents, and since they do not have resonating properties like metal, they are quieter than their traditional counterparts. They are also easier to clean; while they may have fittings similar to traditional ductwork, they are designed with zippered sections for easy removal. These sections can then be vacuumed or laundered and are sized to fit into most industrial washing machines. Optional fabrics are available with anti-microbial agents to inhibit bacteria growth.
Fabric Diffusers
Fabric diffusers are an ideal fit for spaces where air distribution is necessary, but fabric ductwork is not feasible. In applications that require low velocity airflow, a directional displacement diffuser is an option. Engineered to create optimal airflow patterns, the 360 degrees of even air dispersion is designed to not disturb particulates that may reside on surfaces, such as allergens or chemicals that cannot mix with other inventory or spaces.
Kitchen and restaurant spaces commonly implement fabric diffusers. Industrial kitchens are filled with essential equipment, which limits the space for ceiling mounted fabric ducts. Instead, the fabric diffuser is designed for applications with fume hoods or other airflow-sensitive environments. Air passes through specialized fabric panels, resulting in uniform, low-velocity, radially diverging air patterns with little—if any—turbulence. Complete with a snap frame attachment for easy removal and cleaning, kitchen applications are able to stay compliant and efficient with their airflow.
Food processing facilities are also switching to ceiling mounted
diffusers with 360 degrees of air-porous openings. Compared to metal, the round fabric diffuser brings the occupied space to temperature 22 percent faster while offering a lower ceiling load. A diffuser like this presents facility managers who are struggling with budget or space limitations the same level of food-grade sanitation and airflow benefits of fabric ductwork. They also eliminate drip pans that are often used with metal diffusers to prevent condensation leaking into production areas.
HVLS Fans Help Even Out Temperatures
While traditional HVAC systems can heat and cool air, they do not optimize airflow. Since air temperature rises one-half to one degree Fahrenheit for every foot in height, there can be a difference of 20 degrees between the floor and ceiling in tall facilities during the heating season. An HVAC system must work hard for extended periods to maintain the floor-level temperature, wasting precious energy and dollars.
By gently mixing the layers of conditioned air, HVLS fans can help HVAC systems work more efficiently and economically. In air- conditioned facilities, the breeze from an HVLS fan typically allows up to a five degrees Fahrenheit increase in the HVAC system’s thermostat setting with no change in comfort. Since electric costs are reduced approximately four percent with each degree the setting is raised, this can mean an annual savings of 20 percent can be achieved in warm-weather climates.
HVLS fans are also beneficial to facilities without HVAC systems, helping to guard against heat stroke, heat exhaustion and other related maladies by providing workers with an evaporative cooling sensation. Just a two to three mph breeze can reduce the effective temperature by seven to 11 degrees Fahrenheit, making employees safer, more productive and less prone to quality- compromising errors.
HVLS fans’ benefits are equally pronounced during the winter months. By gently circulating warm air from the ceiling back toward employees at the floor level, they de-stratify the layers of heated air that would otherwise accumulate and mitigate the rising heat effect. Thus, facilities equipped with HVLS fans reduce the burden on their heating system and are able to reduce energy consumption and save money. As an additional benefit, air movement created by HVLS fans helps eliminate moisture on floors and walls.
Fan Networking and BMS Integration
Facilities such as big-box stores, warehouses and convention centers may sprawl over tens (or even hundreds) of thousands of square feet, with different areas of the building facing different
22 Occupational Health & Safety | OCTOBER 2020
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