Now, his data for the last three years confirms lower HVAC maintenance costs of more than 20 percent for a building with thermally powered VAV diffusers over a similar building with part constant volume and part VAV box systems.

MORE THAN ONE VAV BOX NEEDED

This discovery came about when Koury was experiencing problems in a 90,000-square-foot office building with a major tenant. One thermostat controlled a VAV box for five offices. As a result, only one person was comfortable at a time. The firm tried using VAV diffusers and decided that they worked quite well.

As Greer is the first to admit, comfortable tenants are important to the goal of low operating costs. When tenants are not comfortable, the maintenance staff must spend time resolving its complaints, said Greer.

Thermally powered VAV diffusers are designed to provide comfort because each is a zone of temperature control with a built-in thermostat and damper to vary incoming airflow. According to Greer, the even temperature distribution and room air movement due to the almost constant discharge velocity of the VAV diffusers further enhance comfort. Maintenance for repair and recalibration is also eliminated, he explained, due to the durability and dependability of the aerospace wax motor thermostat/actuator.

SOME PERSUASION NECESSARY

When Greer decided to use VAV diffusers in other buildings, he still had to convince Koury's engineers and contractors. They had no experience with VAV diffusers and a typical claim was "They do not work." Still, Greer knew they worked because he had tried them.

Next was the claim that VAV diffusers cost much more than standard air diffusers. However, when an actual first-cost comparison was made, it was clear that the installed cost of VAV diffusers was comparable to conventional VAV systems.

"I had to be very persistent with our engineers and contractors to get Acutherm's Therma-Fuser diffusers installed," said Green.

The result is that eight Class A office buildings, with a total of 443,465 square feet, are now conditioned with over 1,000 VAV diffusers. The system uses interoperable VAV diffusers that tie in with a building management system and allows Greer's maintenance staff to monitor and reset the temperature without going into the room. Greer has had about 200 interoperable VAV diffusers installed in two buildings, totaling 77,964 square feet.

"With Therma-Fuser diffusers, we can keep all of our tenants happy and give them individual control. And with the new EF interoperable units, a happy tenant is a phone call away," he said.

According to Greer, Koury's major tenant complaints have always been HVAC comfort and roof leaks. VAV diffusers haven't resolved any roof leaks, but they have reduced HVAC complaints. "In two years, we have had a grand total of three calls regarding Therma-Fuser diffusers," said Greer.

THE SAVINGS

According to Greer, actual data taken over the past three years shows over 20 percent lower HVAC maintenance costs for a building using VAV diffusers compared to a building with part constant volume and part VAV boxes. He collected and compared data from two Greensboro office buildings that are almost the same size.

The Brookhollow Plaza building has 91,000 square feet on four and one-half floors with air distribution that is part constant volume and part VAV boxes. The 84,000-square-foot, three-floor Grandover Office Building is an all VAV diffusers building.

According to Greer, HVAC maintenance costs for the Grandover building with VAV diffusers were 26 percent lower in 2002, 21 percent lower in 2003, and 22 percent in 2004. Electric utility costs for the same all-VAV diffusers building were also lower in each year.

Even though the lower operating costs of VAV diffusers are impressive, Greer emphasized that the comfort they provide is still most important.

"We all have to make money. That is the name of the game. But if we do not have tenants, low operating cost won't help," he said.

Publication date: 06/19/2006