HVLS fan Cow comfort, speed and spacing recommendations in dairy barns

Large-diameter ceiling fans have been incorporated into the architecture of freestall dairy facilities throughout the last 10 to 15 years. High-volume, low-speed (HVLS) fans were first built and utilized in massive commercial warehouses and manufacturing buildings. The first livestock application was for riding arenas in the United States' major equestrian markets. HVLS fans were then tested in dairy barns and found to be quite successful in improving cow comfort.

They don't provide as high airspeed as panel fans, but they effectively cool a much larger area.

HVLS fans serve two functions depending on whether they are in the forward or reverse. When the fan runs forward, it blows a column of air the same size as the fan diameter immediately downward. It then radiates a wave of air roughly 4 feet high in a 360-degree pattern from the fan.

The air rushes at high rates due to the length of the fan blades, which can be up to 30 feet in diameter, generating a velocity cooling effect for the animals as it passes over them.

Variable speed advantage

HVLS fans are controlled on a variable-speed basis with an automatic temperature controller in hot weather. This will start the fans at a predetermined interior temperature and adjust their speed or slowness based on changes in the interior temperature. Automatic speed control is especially useful in the spring and fall. Outdoor temperatures can fluctuate substantially over 24 hours.

Recommended speed

For mature livestock, AmeriWind recommends starting the fans around freezing. Have the fan speed  flatline at minimum ventilation speed until approx  65° F . Only then start  ramping to full speed  by 80°

Minimum ventilation keeps air moving and dries off floors most of the year.

While working in reverse during below-freezing weather, HVLS fans push air upward. Upward moving air destratifies any heat stuck along the ceiling and gently recirculates it throughout the structure.

Reversing is often accomplished by using a variable-speed control and running the fan at a constant speed of about 20%. An added benefit when working in reverse in a natural ventilation system is: The air passes over the inside of the sidewall curtain fabric and lowers the risk for moisture development in cold weather.

Electricity rebates

HVLS fans have lower running expenses than most high speed panel fans because they cover a bigger area. The HVLS fans use a three-phase motor with a variable speed drive which lessens the electric consumption at slower speeds.

Electric companies in many parts of the country offer electric efficiency rebates between $500 to $2000 per fan to encourage the installation of HVLS fans. This amount and the ease of getting it varies per electric company.

As off 2023, PA's PPL Electric offers Agricultural rebates that instantly apply to the fan at the time of purchase. It is straightforward for farmers to get a discount when purchasing HVLS fans, as It requires minimal documentation from the end user.

Birds and flys

Several operators have discovered that because birds can see the slow-moving blades, they are less likely to enter the barn when these fans are running. This, however, is not always the case. Birds may still roost and nest if perch sites are built where the fans are installed.

HVLS fans can play a significant function in an all-encompassing fly control program. During hot weather, the high-speed airflow they create within the building can also reduce the number of flies.

Considerations for Design

If you have a freestall dairy with huge sidewall curtain openings, ideally, the fans blades are installed above the curtain opening. Due to the length of the blade, flexing can occur in windy circumstances, causing the blade to fatigue.

HVLS fans are available in diameters ranging from 8 to 30 feet, with the smaller models proving more wind resistant. It is recommended to utilize Fan Chief with wind sensor input so that the fans shut down automatically in windy weather.

Cows will tend to stand immediately beneath the fan where the air is coolest in hot weather, thus avoiding placing fans within the structure over locations over aisle connectors which can cause blockages.

Avoid mounting a fan immediately under a light fixture. The motion of the fan blade can provide a strobe light effect, producing an annoying visual element for you and your cattle.

Get your air moving

Like with any other aspect of your dairy's ventilation system, get references and speak to other producers who have installed HVLS fans.

We have a ventilation specialist who can advise you on the size and configuration of HVLS fans that will work best for you and your cows.

Contact us for the references, and we will give our best effort to help you layout the ideal system for your barn.