How High Volume Low Speed (HVLS) Fans Can Reduce Facility CO2 Emissions

Executive Summary

A common agreement on climate change:
There is compelling scientific evidence from the Intergovernmental Panel on Climate Change1 showing that climate change is caused by human activity and is more serious than ever before. Climate model projections indicate that the global surface temperature will rise significantly by 2100 if changes aren’t implemented “…the consequences could vary from disruptive to catastrophic”2. The first commitment period of the Kyoto Protocol ends in 2012 and while negotiations at the United Nations Climate Change Conference in Copenhagen (COP) 5 in December 2009 did not agree on the next framework for an international agreement to reduce Greenhouse Gas (GHG) emissions, some progress was made and it is only a matter of time before we have one.3

Business is becoming more aware of how climate change is providing opportunity and return on investment. This demonstrates that governments must implement a comprehensive international incentive program to entice businesses to invest in the change to a low-carbon global economy. Businesses that fail to address the need for reduction of greenhouse gases will be sure to experience devastating short and long-term risks.

Many fortune 500 businesses are not only measuring their own carbon footprint but are also measuring those further down the supply chain. Large retailers are making a commitment to reduce their carbon footprint and are analyzing and encouraging their suppliers to do the same. Wal-Mart is in the process of working on a sustainability index that will rate the greenness of all products it sells. Wal-Mart states that their objective is to “accelerate change towards sustainability,” which means that everything Wal-Mart touches will have to have some eco-improvements. This will ultimately affect the supply chain, whether it is in the manufacturing of goods or warehouse and distribution centers.

Companies also recognize that current and upcoming regulations aimed at reducing carbon emissions will be imminent. Businesses that fail to recognize this will not prosper in years to come. For this reason alone, businesses in the supply chain will be encouraged to reduce their green house gas emissions.

About 40 percent of the world’s energy is consumed by the building sector and about 37 percent of this is for heating, cooling, and ventilation.4 Since air circulation is important to improve energy efficiency with HVAC units, high volume low speed (HVLS) fans can improve the efficiency within large open spaces. Whether you utilize HVLS fans by themselves or in conjunction with an HVAC unit, the HVLS fan helps lower utility costs and reduces CO2 emissions.

HVLS fans reduce thermal loads, electricity use, and mechanical heating and cooling times. Because HVLS fans circulate air so efficiently, they reduce the load of a building’s HVAC system in many ways. In spaces with large, relatively open floor plans, air-conditioned air can be moved farther with less ductwork and even reduced tonnage. Heated air from radiant heaters can be circulated more efficiently with HVLS fans, reducing or eliminating pooling, and increasing the efficiency of the heaters while potentially reducing the number of heaters required. Thanks to the destratifying effect (mixing of air in order to eliminate layers of air at different temperatures) of HVLS fans, thermostats can be adjusted to more energy-efficient settings. The same number of air exchanges, which means the same air quality, can be achieved with fewer ventilation fans due to the high volume of air moved by energy efficient HVLS fans.

When used as a stand-alone cooling system, HVLS fans can provide a cooling effect equal to a reduction in temperature of up to eight degrees F. within the fan’s coverage area of up to 20,000 square feet per 2 horsepower 24-ft fan.5

More efficient, lower horsepower HVLS fans, 3/8HP to 1HP, often with six blades, 6-ft to 24-ft in diameter, deliver non-disruptive cooling that helps improve productivity and comfort in the work environment. AMCA testing (non-certified) shows that one manufacturer’s 24-foot, 6-blade, 1HP HVLS fan produces 275,694 CFM. When installed at a height of 18-ft, as in the AMCA test, this provides an effective coverage area of over 15,000 sq. ft., with an average calculated airspeed of only 609 ft/minute. By comparison, another manufacturer’s 30-inch high-speed 1HP fan delivers 12,000 CFM at an average calculated airspeed of 4,800 ft/minute. When used in conjunction with air conditioning or evaporative cooling systems, these lower-horsepower HVLS fans can efficiently circulate cooled air throughout the structure.

With the use of HVLS fans, business are able to significantly reduce heading costs. In most commercial and industrial buildings, heaters are mounted overhead so as to not interfere with working space. Unfortunately, this results in a heat gradient differential or heat stratification of ten degrees Fahrenheit to 35 degrees F from the floor to the ceiling depending on the height of the ceiling. While running an HVLS fan in forward mode will draw heated air down, more air is drawn in from the sides of the fan than the top, leaving some warm air undisturbed close to the ceiling. On the other hand, an HVLS fan that runs in reverse clears warm air from the ceiling, pushing it to the walls and down to the floor, which provides a more even distribution of heat from top to bottom — especially important when employees are working at different levels within a generally open structure.

Due to the Coanda effect, which is the tendency of a fluid jet to be attracted to a nearby surface (in physics, air is considered a fluid), fresh air tends to travel from the inlet opening such as a door, window or vent to the exhaust fan along the path of least resistance, which is typically up the wall, across the ceiling, and out through the fan. This means that most of the air that is exhausted from the building is the fresh air that has just been drawn in instead of the stale air that should be exhausted. Since HVLS fans continually mix the air in a space, stale air gets mixed with the incoming fresh air and exhausted, so less incoming air is required to produce the correct number of air exchanges in any given building.

This reduced volume requirement:

• Reduces the number of high-speed exhaust fans needed, in some cases eliminating them altogether, cutting exhaust fan power consumption accordingly.6

• Reduces the loss of heated or cooled air since less “virgin” air must be drawn in from outside — thus reducing heating or air-conditioning costs.

Energy Efficiency of HVLS Fans:
Calculations based on ASHRAE (American Society of Heating, Refrigerating and Air Conditioning Engineers) data and conservative facility design criteria (see Heat Savings Chart 2 ) show a five year return on investment after installing HVLS fans of $11,530 in Minneapolis, MN, and $5,350 in St. Louis, MO. In one actual before and after study, data shows average energy cost savings averaging 49 percent plus consequent reductions in the generation of CO2 and carbon (see table 1: CO2, Carbon and Cost Savings After Installing HVLS Fans).

HVLS fans are best suited for large, mostly open spaces with a minimum ceiling height of 15 feet. Studies by mechanical efficiency experts show that HVLS fans are the most energy efficient air circulating fans available.5 High-speed fans focus on using their speed to increase air displacement. According to the fan laws, a common subset of the laws of physics, the power to drive a fan is equal to the cube of the speed. If you double the speed of a fan, it requires (two times two times two) or eight times the amount of electrical power. For example, a high speed commercial fan delivering air at 20 mph requires about 64 times as much power as one of the same size delivering air at five mph. HVLS fans, on the other hand, focus on using size, not speed, to move air. The Air Movement and Control Association International (AMCA), the body that certifies fan performance, has defined airflow (CFM) as a function of fan diameter and thrust. Under this AMCA formula, increasing either diameter or thrust results in an increase in CFM; increasing thrust requires more input power, while increasing diameter does not. Regardless of diameter, all HVLS fans in the same series (for example, 1 HP fans) use the same motor and draw approximately the same current through the controller. This means that doubling the size of a fan requires less than twice the power. (see Psychrometric Chart 1)

The implementation of carbon policies in procurement of energy efficient systems still has a long way to go in order to meet global expectations. However suppliers that take the initiative today to reduce CO2 emissions will reap the benefits in the long run. Installing energy efficient HVLS fans either as a standalone system or in conjunction with HVAC suppliers can significantly reduce CO2 emissions within the supply chain. Suppliers will be forced to improve their carbon footprint either through government regulation or by retailer initiatives. The bottom line is suppliers that take the initiative to improve CO2 emissions have a better chance of sustaining in a global market.

1Intergovernmental Panel for Climate Change (IPCC) Fourth Assessment Report, 2007 (


3Carbon disclosure Project Supply Chain Report 2010

4For more on these statistics, see the May 2009 World Business Council for Sustainable Development (WBCSD) document, “Energy Efficiency in Buildings Report.” Visit See also the 2008 U.S. Department of Energy (DOE) Building Energy Databook at

5”Report on Measurement of the Air Velocities from Industrial Ceiling Mounted and Floor Mounted Fans for HVLS Fan company.” Marietta, GA 2001.

ASHRAE, ASHRAE Standard 62, Comprehensive Summary

Jaylin Krell, Marketing Administrator

Macro-Air Technologies

(909) 890-2270