By Rachel Tsvetanov
Canadian green construction is booming, with research indicating the trend is not slowing—by 2017, the amount of green construction projects will double, motivated by the desire for high-quality, environmentally responsible buildings.
At its core, green building is a focus on making smart and sustainable decisions about building site, water use, energy and atmosphere, materials, size, and indoor environmental quality, both during construction and over the life of the building. Efficient HVAC systems are critical to these goals, but full air-conditioning upgrades are often costly and cumbersome. An increasingly popular solution is the incorporation of high-volume, low-speed (HVLS) fans and ultra-efficient residential fans into the design and renovation of commercial and industrial spaces.
With the rise in green building comes an increased focus on the problems of traditional HVAC design. In the 1990s, research linking freon to ozone depletion pushed innovation of more environmentally responsible refrigerants and more efficient HVAC equipment. This research highlighted the shortcomings of traditional overhead HVAC designs that feature a single distribution system and regulate temperature based on the conditions surrounding a thermostat.
In the winter, this setup created heat stratification when warm air, which is approximately five to seven per cent lighter than cool air, rises to the ceiling. This increases the temperature at the ceiling, effectively wasting energy by distributing heat to areas without occupants.
The recent versions of the American Society of Heating, Refrigerating, and Air-conditioning Engineers’ ASHRAE Handbook recommend including measures to avoid heat stratification. A 2007 ASHRAE Journal article points to the fact “in spite of this, engineers continue to design systems delivering low-velocity, high-temperature air at the ceiling” and therefore do not meet the minimum standards for thermal comfort and ventilation.
Ceiling fan innovation
HVLS and ultra-efficient residential fans solve traditional HVAC problems through air movement, shifting the system focus from the thermostat to the occupants. HVLS fans are traditionally defined as fans more than 2.13 m (7 ft) in diameter that include airfoils and are ceiling-mounted. They improve heating capacity by moving large volumes of air slowly and gently, simulating natural air movement without creating drafts.
In warmer months, HVLS fans make building occupants feel cooler. While air movement does not lower the actual temperature in a space, the perceived effect can make an occupant feel up to 5.6 C (10 F) cooler.
Pairing a HVLS or ultra-efficient smaller fan with a traditional HVAC system allows thermostat setpoints to be raised in air-conditioned spaces. The thermostat setpoint can be raised by approximately 2.7 to 3.9 C (5 to 7 F), saving energy without sacrificing comfort. Increased thermostat setpoints due to fan use can result in an up to 25 per cent reduction in energy costs from decreased air-conditioning usage. For less-severe climates, the cooling effect provided by fans can minimize, or even eliminate, use of refrigerant-based air conditioning systems.