High-Volume, Low-Speed Fans
A high-volume, low-speed (HVLS) fan up to 24 feet in diameter, capable of displacing many smaller constant speed fans.
Item ID: 620
Residential, Commercial, Industrial, Agricultural
HVAC--Air & Fluid Distribution
Technical Advisory Group: 2015-1 Commercial HVAC TAG (#11)
Average TAG Rating: 3.2 out of 5
TAG Ranking Date: 03/10/2015
TAG Rating Commentary:
- This can be a great addition to a DOAS system design to allow for the main air handler fans to be eliminated while still providing a comfortable amount of air movement. Reduces distribution ductwork and fan energy, also reduces stratification.
- While this technology is more suitable for new construction, it would be helpful to identify good retrofit applications and guidelines for estimating and verifying energy savings.
- It is likely to be most useful in high-bay environments for destratification. Could be a great retrofit where old-fashioned gravity unit heaters draw and use the hottest air in the building for combustion.
- I support this technology because there is market acceptance. I think it can be deployed in light commercial spaces for air cooling. I think it may have even greater potential for savings if we can demonstrate that air quality is maintained.
- Particularly good using DC motors and adjustable speed drives. I think more data is needed on the air flow and damper controls. Area fans like the Big Ass fans are different and I strongly support them.
- Need more robust third-party testing for this destratification technology.
A High-Volume, Low-Speed (HVLS) fan is a large fan with sizes in diameters that range between 6 and 24 feet. A single HVLS fan is capable of displacing several smaller conventional propeller, box or panel fans to improve the de-stratification of warm air. Benefits include improved comfort, quieter operation, and energy savings, especially since HVLS fans are equipped with variable speed motors and temperature controls which can adjust fan speed in response to changes in air temperature. Energy savings are obtained by: displacing multiple fans with a fewer number of HVLS fans; increasing air movement in occupied spaces; increasing temperature setpoints of HVAC equipment in the cooling season, and; through a reduction in heat energy needed due to de-stratification.
A single HVLS fan can displace several conventional high-speed fans, while still providing the same airflow, thus saving energy. The metric used for comparing HVLS fans to conventional fans is the airflow per Watt of fan power, in cubic feet per minute per watt (CFM/W). A conventional high-speed 48” fan could produce 29,000 CFM with a 1-hp motor (40 CFM/W), whereas a HVLS fan could produce 140,000 CFM with the same 1-hp motor (194 CFM/W). This comparison demonstrates how a single HVLS fan can replace several fans of similar total horsepower. Energy consumption also depends on the operating time and fan speed. Manufacturers of HVLS fans estimate that their cooling systems can save up to 30% to 70% of the energy used by conventional fans.
During the cooling season, HVLS fans provide comfort through the convective cooling effect when airflow comes into direct contact with human skin. This cooling effect allows occupants to perceive an ambient temperature reduction of 4-8°F, which can allow building operators to increase the temperature setpoint. For many of the HVLS manufacturers, this is the default mode of operation, sometimes called 'forward mode' or 'cooling mode.' During the heating season, HVLS fans “de-stratify” or mix warm air that is trapped near the ceiling, and circulate it down to occupant level. Heating savings occur due to reduction of the temperature gradient from floor to ceiling, allowing thermostats to sense higher temperatures and thus reduce heating unit runtime.
Baseline Description: 82 single-speed ventilation fans in a commercial warehouse.
Baseline Energy Use: 2.6 kWh per year per square foot
The baseline fans provide cooling effect in a 40,000 square-foot warehouse. These fans are driven by single-phase,1 hp motors. The motor efficiency is assumed at 82.5%, with an annual operating time of 1,400 hours per year.
Annual Energy Use: 82x 1 x 0.746 x 1,400 / 0.825 = 103,807 kWh
Annual Use per sqft: 103,807 kWh/ 40,000 sqft = 2.6kWh/sqft
Manufacturer's Energy Savings Claims:
Savings Range: From 30% to 80%
The Big Ass Fan Company performed a case study of the Bullitt Center in Seattle, Washington. The study cites an 80% improvement in energy efficiency over conventional ceiling fans. [http://www.bigassfans.com/case-studies/bullitt-center/]
Best Estimate of Energy Savings:
"Typical" Savings: 96%
Energy Savings Reliability: 3 - Limited Assessment
The energy savings for the warehouse described above, compares the baseline energy use of 82 conventional 1-hp constant speed fans driven by single-phase, 1-hp motors. The baseline rated airflow performance is 18.2 CFM/W with an airflow of 24,590 CFM - totaling to a baseline airflow of 2,016,380 CFM.
The HVLS fan application matches the airflow requirements with 10, 20-foot diameter, high-volume, low-speed fans driven by three-phase, 1-hp motors with helical gearboxes and variable frequency drives. The rated airflow performance for this fan is 368 CFM/W. With the VFD capability taken into account, the annual energy use is: 3,601 kWh/year
The energy use reduction is (103,807-3,601)/103,807 = 96.5%.
Energy Use of Emerging Technology:
.1 kWh per square foot per year
Energy Use of an Emerging Technology is based upon the following algorithm.
Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))
Potential number of units replaced by this technology:
In the Northwest there are 275.5 million sq.ft. of floor area in commercial warehouses, of which 64.3% is conditioned. (Table C-GB4, 2009 CBSA)
The total conditioned commercial warehouse floor area in the Northwest is 177 million sqft. Assume that 5% of the warehouses are currently equipped with ventilation fans and will be upgraded with HVLS fans. Note that warehouses are just one of a number of potential commercial sector applications for HVLS fans, so the total technical potential would be greater than the conservative estimate above.
Regional Technical Potential:
0.02 TWh per year
Regional Technical Potential of an Emerging Technology is calculated as follows:
Baseline Energy Use * Estimate of Energy Savings (either Typical savings OR the high range of savings) * Technical Potential (potential number of units replaced by the Emerging Technology)
Installed first cost per: square foot
Emerging Technology Unit Cost (Equipment Only): $1.63
Emerging Technology Installation Cost (Labor, Disposal, Etc.): $0.00
The first cost of HVLS technology will vary depending on the size of fan and the features (if any) that are added to the package.
The first cost of installing a 20-foot diameter, 1-hp fan was $6,500, which included the cost of the equipment, retrofit of the existing metal building, electrical service upgrades and installation. The actual fan cost was $5,600, with the remaining amount being for electrical, structural and installation. Compared to a conventional fan installation, the incremental cost of this project was $1,500. The Efficiency Maine TRM manual states that the HVLS fan technology has an incremental cost of $1,165 per fan, which was based on interviews with suppliers.
Equipment Cost: $6,500/4,000 sqft/fan = $1.625/sqft
Installation Cost (Incremental): $0/sqft
Conventional Equipment Cost: $5,000/4,000 sqft/fan = $1.25 sqft
Simple payback, new construction (years): N/A
Simple payback, retrofit (years): 7.3
Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.
A high-volume, low-speed (HVLS) fan is a large fan with sizes in diameters that range between 6 and 24 feet in diameter. A single HVLS fan is capable of displacing several smaller conventional constant speed fans (sometimes called propeller, box or panel fans) and can improve the de-stratification of warm air. Benefits include improved comfort, quieter operation, and energy savings, especially since HVLS fans are equipped with variable speed motors and temperature controls which can adjust fan speed in response to changes in air temperature.
Energy savings are achievable three ways: the first tier is saving fan energy by displacing multiple fans with a fewer number of HVLS fans, the second is by increasing air movement in occupied spaces and increasing temperature setpoints of HVAC equipment in the cooling season and third is through a reduction in heat energy needed due to de-stratification.
This technology can be adopted as a retrofit or new construction application in many types of commercial buildings with higher ceilings that include:
- Retail Showrooms
- Grocery Stores
- Shopping Malls
- Restaurant, Bar and Hospitality
- Sporting Facilities, Fitness Centers, Water Parks, Pools
- Indoor Pools
- Office Buildings
- Lobby Areas
- Fire Stations
- Airport Terminals
- Aircraft Hangars
- Automotive Maintenance Facilities
- Warehouses and Distribution Centers
- Manufacturing spaces
- Animal housing such as dairy barns and animal rearing pens
In addition to the energy savings from this technology, HVLS fans can in some cases offer demand reduction of displaced fans as well as staging, downsizing, or removal of electric HVAC equipment, as is indicated in the tonnage reduction claims by MacroAir.
Macro Air, AirVolution-D Gearless Fans
AirMotion Sciences, Big Smart Fans (with Variable Pitch Blades)
Big Ass Fans, Big Ass Fans
Rite Hite, HVLS Fan
Humongous Fan, Humongous Fan
Sky Blade, STOL and ST3 Series
Envira-North Systems Ltd, Altra-Air HVLS Fans
Go Fan Yourself, Large Diameter Fans
Swifter, HVLS Ceiling Fans
Serco Entrematic, ATEC HVLS Fans
Kelley Entrematic, WAVE HVLS Fans
Patterson Fan, High-5 HVLS Ceiling Fans
Standard practice for providing convective cooling for building occupants is with conventional, small ceiling fans. Convective cooling of farm animals is typically achieved through multiple smaller blowers. De-stratification is typically achieved with conventional ceiling fans or with ceiling mounted blowers that direct warm air from the ceiling to the floor in a more forceful manner in unoccupied spaces.
HVLS fans have been commercially available for since the late 1990’s, but haven’t been widely adopted in the commercial marketplace. The first applications were in the agricultural sector for use in dairy barns to provide comfort to cows. Many of the manufacturers of HVLS fans offer features to differentiate their products from their competitors. Some of these features can have an impact on energy consumption by improving fan performance or providing a dedicated solar power supply. Other features include:
- Solar electric package
- Gearless or gearbox elimination (direct drive AC or DC motors)
- Variable pitch
- Wireless controls
- Built-in lighting for small commercial and residential applications
There are several non-energy benefits of HVLS technology, including indoor air quality (IAQ), increased occupant comfort and improved product quality. IAQ benefits are due to a continuous mixing air more thoroughly within occupied spaces to avoid stale, stagnant air and potentially can eliminate condensation buildup and sick building syndrome (Boyd, 2013). Increased occupant comfort from HVLS fans can also be beneficial due to improvements in morale, which can have a positive impact on productivity. In the dairy sector, cows that are more comfortable produce more quantities of higher quality milk. In distribution warehouses or retail spaces where products are stored, HVLS fans can potentially reduce mildew damage to the following: paper files, office furniture, drywall, cloth products and product packaging such as cardboard (Boyd, 2013).
End User Drawbacks:
There can be drawbacks to HVLS technology due to its size and weight. Because the HVLS fan blades can have a radius of over 12-feet, designers and installers need to be cognizant of surrounding structural building components or equipment such as lighting fixtures or fire suppression systems. Air Motion Sciences claims that a smaller diameter HVLS fan of 15-foot or less should eliminate crowding with lighting fixture spacing. They also claim that with a variable pitch blade design, a 15-foot variable-pitch HVLS fan can provide a comparable amount of airflow to that of a 24-foot HVLS fan with fixed blade pitch. Structural modifications to a building may be needed due to support the weight of the fan support structure, motor, gearbox, fan blades and electrical. Obstruction of existing building structural components may also pose a problem, and will have an effect on placement and size of the fans.
HVLS fans can potentially cause a strobing effect if the blade arc (from the fan blade movement) passes between a lighting fixture and the ground. This can be a distraction to occupants and could affect those with epilepsy. HVLS fan manufacturers are aware of this issue and can offer fan selection guidance. Smaller HVLS fans for residential and small commercial applications can come with LED lighting installed in the fan hub, which can potentially eliminate the strobing problem altogether. The issue of strobing may be resolved with alternative lighting designs that avoid ceiling lights above the fans.
Another potential concern previously presented by fire officials is that HVLS fans might possibly block fire suppression sprinklers, reducing their ability to put out a fire. Authors of a study by the Fire Protection Research Foundation (Palenske, 2011) concluded that HVLS fans would not affect the performance of early suppression fast response (ESFR) sprinklers and their ability to put out fires.
Operations and Maintenance Costs:
Some minimal maintenance costs are incurred with HVLS fans such as visual inspection of blades (for cracks and damage), and support structure including “guy wires” and safety cables to ensure that they are secured properly. Other regular maintenance could include blade cleaning depending on the presence of dust and/or grease. There may be an additional cost of doing these types of inspections if the owner of the HVLS fan(s) doesn’t own scissor lifts to access them.
The Efficiency Maine TRM manual states that the HVLS fan technology has an expected lifespan of 15 years. 10-year warranties are common with HVLS manufacturers.
Multiple conventional high-speed propeller, box, or panel fans
Reference and Citations:
The State of HVLS Technology
The Construction Specifier
Technology Spotlight: High-Volume, Low-Speed Fan Technology
Energy Services Bulletin, Western Area Power Administration
Bonnema, et. al.,
Technical Support Document: Development of the Advanced Energy Design Guide for Medium to Big Box Retail Buildings – 50% Energy Savings
National Renewable Energy Laboratory
Maintaining and Cleaning High Volume, Low Speed Fans
CM/Cleaning and Maintenance Management
Avoid Sick Building Syndrome with HVLS Fans
Decrease Bacteria, Mold, Mildew and Spoilage with HVLS Fans
2015 Integrated Resource Plan: Advisory Council Meeting
HVAC for Large Spaces: The Sustainable Benefits of HVLS (High Volume/Low Speed) Fans
Architectural Record, Continuing Education Center
High Volume\Low Speed Fans and Sprinkler Operation
Aon Fire Protection Engineering
Reducing Heat Stress with HVLS Fans
Occupational Health & Safety
Serco HVLS Fans Pack Enough Efficiency to Help Keep Luggage on Route
“Green” HVAC Contractor Reduces AC Tonnage by 25%
Eubanks, et. al.,
2014 ASHRAE Technology Award Case Studies: Climate-Adapted Design for California School
HVAC Manufacturer Finds a Cool Solution with HVLS Fans
Efficient, Effective Air Movement: How to Justify HVLS Fan Systems
Minnesota Department of Commerce,
Technical Reference Manual for Energy Conservation Improvement Programs, Version 1.0
Minnesota Department of Commerce
Efficiency Maine Trust,
Commercial Technical Reference Manual, Version 2015.2
Efficiency Maine Trust
Low-Speed Fans Lend a Hand in the Showroom of a High-Speed Business
Heating/Piping/Air Conditioning Engineering
Destratifying Heat With Large-Diameter, Low-Speed Fans
Heating/Piping/Air Conditioning Engineering
Large-Diameter, Low-Speed Fans Ensure Comfort, Reduce Energy Use in Gym
Heating/Piping/Air Conditioning Engineering
HVLS Fans Deliver Energy Savings From the Top Down
Ask the Expert: How Can High Volume, Low Speed (HVLS) Fan Technology Help Reducing Heating Costs In the Winter?
American School & Hospitality Facility
Fire Protection Industry Bulletin: High Volume Low Speed (HVLS) Fan Shutoff for Fire Alarm Installations
City of Fresno [CA] Fire Department
Schirmer Engineering Corporation,
HVLS Fans and Sprinkler Operation, Phase 1 Research Program - Final Report
National Fire Protection Association
James, et. al.,
Are Energy Savings Due to Ceiling Fans Just Hot Air?
Florida Solar Energy Center