If a duct system in a 10-SEER unit isn’t installed properly, the equipment probably isn’t delivering 10 SEER, said Stevenson. “In fact, it may be more like 6 SEER,” he said.

“Basically, what we are trying to achieve is installing heating and cooling in mass-produced homes to a level of quality that we would be happy with if it was installed in our own homes,” Stevenson said.

Leakage and airflow

“What we do is measure the airflow and static pressure on all supply air outlets and return air inlets, to ensure the system is operating the way it was designed to operate,” Stevenson said.

“Another thing we do — one of the most important things we do — is fully duct all our returns. We no longer use shafts, soffits, and furred walls as a method of routing return air. We have experienced lower static pressures on the return side when the return air is correctly ducted.”

The company also installs volume dampers. “There is a big gate valve where the ducts attach to the furnace’s plenum that allows us to adjust the amount of airflow in the trunk line,” Stevenson said.

MJB also seals the system to prevent leakage, and does a certified air balance on the systems it installs to make sure that the house is getting the proper capacities for efficiency.

Stevenson said he believes his company is providing an hvac system that exceeds his area’s Industry Standards, and provides his customers with the comfort they expect.

“Square footage is expensive here, and rather than take up space in the garage or closet, we install horizontal forced-air units in the attic.”

According to Stevenson, attic forced-air unit installation is usually better anyway. When a furnace is installed in the upflow position in a closet or garage, a platform is used for the return air and his experience has been that those platforms leak.

“That affects the static pressure of the furnace, which affects the capacity of the unit,” he said.

Advance preparation for new standards

“One of the issues the hvac industry is dealing with in California is leakage,” Stevenson said. “Because some contractors are not ducting supply and air correctly and the connections are not right, the equipment leaks.”

The State of California is planning on introducing new standards this summer with which a house has to comply to get a certificate of occupancy, according to Stevenson.

“The new standards will require that a house must not exceed a certain percentage of leakage, and they want a certified air balance report that verifies the unit is operating at its designated capacity,” he said.

“We started researching the proposed standards and changing our methods of installation to adjust for them. Now that we are ducting return air from both the first and second floors, installing volume dampers for air balancing, and sealing all duct connections, we have noticed a dramatic decrease in airflow problems.”