Indoor environmental quality
The frequently quoted estimate that people spend 90 per cent of their time indoors comes from a study two decades old. (For more, visit cfpub.epa.gov/roe/chapter/air/indoorair.cfm or check out
www.buildinggreen.com/blog/we-spend-90-our-time-indoors-says-who.) Yet, it is safe to say the rise of the Internet and video games in the intervening years has not led to a significant decrease in that figure—quite possibly the opposite. That means indoor environmental quality is more important than ever, especially in regions where cold weather hangs around many months of the year. Research has linked poor indoor air quality (IAQ) to numerous illnesses, and experience shows it is linked to increased absenteeism or reduced productivity. (To read more, visit ohsonline.com/Articles/2016/10/01/Sick-Building-Syndrome.aspx.) The American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) provides a number of standards and guidelines addressing the issue, and all homes and other buildings must adhere to the National Building Code of Canada (NBC) as applied in their province.
As more changes are made to building design and operation in response to climate change, making buildings tighter and more efficient, it is critical to maintain good indoor environmental quality. For projects looking to earn points under the Leadership in Energy and Environmental Design (LEED) program, HVLS and other high-efficiency ceiling fans help meet Environmental Quality (EQ) Credit, Enhanced Indoor Air Quality Strategies, by efficiently distributing the heated outside air into the ‘breathing zone.’ HVLS fans can also help earn Energy and Atmosphere (EA) credits such as Optimizing Energy Performance and Thermal Comfort.
Thermal comfort and productivity
The most obvious benefit of HVLS fans is the thermal comfort they provide. Thermal comfort is defined by ANSI/ASHRAE 55, Thermal Environmental Conditions for Human Occupancy, as “that condition of mind which expresses satisfaction with the thermal environment and is assessed by subjective evaluation.”
When it is absent, achieving thermal comfort becomes the first thing on people’s minds. Many factors contribute to this consideration—the most obvious are air temperature, air speed, and humidity, but clothing and activity level also play a role. Complying with ANSI/ASHRAE 55 means 80 per cent of occupants should be satisfied with a space’s conditions.
How do HVLS fans fit in? Increased air movement from the fans makes occupants feel cooler in warm months and comfortably warm from destratification or air-mixing when the furnace is on. Just like the cows for which HVLS fans were developed, people are more productive when they are comfortable and the air is circulating, whether working on an assembly line or doing crunches at the gym.
In workplaces, HVLS fans make it possible to eliminate floor fans and other personal cooling devices, which create clutter and tripping hazards. They improve safety by quickly drying spills and condensation, and they can even prevent condensation from forming. For instance, one metals service centre in Missouri tested drying capabilities by installing an HVLS fan over one of two neighbouring service bays. The one with the fan dried in four hours, while the other, with the same amount of water, took a day and a half. Further, thanks to the fan, less rust formed on nearby tubing.
In industrial settings without air-conditioning, the presence of HVLS fans means workers take fewer breaks because of the fans’ cooling effect. Where there is air-conditioning, the increased air movement allows thermostat setpoints to be raised without sacrificing comfort, leading to perhaps the greatest benefit of HVLS fans—energy savings.
The energy savings from HVLS fans can be significant. According to ANSI/ASHRAE 55, during cooling seasons, the fan speed can be increased to create a cooling effect of up to 5.6 C (10 F). The air movement allows facility managers to increase their air-conditioning setpoints by several degrees while keeping occupants comfortable. One study found energy savings of three to five per cent per degree are typical. (The study, “Extending Air Temperature Setpoints: Simulated Energy Savings and Design Considerations for New and Retrofit Buildings,” by Tyler Hoyt, Edward Arens, and Hui Zhang, can be viewed online at escholarship.org/uc/item/28x9d7xj.) Conversely, during heating seasons, the fan can be slowed so the air continues to mix, moving hotter air at the ceiling gently down to occupant level without causing a draft. This keeps occupants comfortable and can reduce heating costs by up to 30 per cent, as Richard Aynsley first noted in a December 2005 article in the ASHRAE Journal.
Generally speaking, the higher the ceiling, the greater the savings. There is also now technology available on some HVLS fans that automatically responds to the conditions and ensures that the temperature within a space is always comfortable and consistent from floor to ceiling. This simultaneously guarantees the greatest energy savings for the consumer.