Decarbonization and electrification have become buzzwords in the HVAC industry. Multiple local and state governments are legislating against gas appliances as they try to reduce pollution and decarbonize the economy. In 2022, air-source heat pump shipments were at an all-time high at over 4.3 million.

What does that mean for the HVAC contractor? At the recent ACCA Conference & Expo, Wes Davis, ACCA’s director of technical services, presented on what HVAC contractors need to do to make heat pumps a success.

“The transition to heat pumps is not going to be a huge success unless we do our jobs as contractors,” he said. “Heat pumps aren’t magic. They are going to require some work.”

Davis presented five items HVAC contractors need to keep in mind when quoting and installing a residential heat pump.

1. Insulation

 Improving the insulation in a home is an important way to reduce the load. The typical house is leaky and poorly insulated.

“We can put in a heat pump that will deliver enough heat for the space but that is much bigger than it needs to be,” Davis said. “Putting insulation in is a way we can do our jobs better.”

This does not necessarily mean that HVAC contractors need to get outside of their comfort zone. Many contractors decide to partner with another company to do the insulation rather that complete that line of work themselves.

“If you walk up into the attic and you are not seeing any insulation or it is underinsulated, then hook up with an insulation company,” Davis said.

2. Tightness

Insulation alone is not enough. Air sealing is also a requirement to make sure the load of the house is reduced.

“While insulation is good, you need to make sure you air seal first,” Davis said. “Insulation can’t completely stop air.”

This includes sealing the gaps around lights, electrical outlets, and plumbing.

3. Duct leakage

How much the average duct leaks is up for debate. But what is not up for debate is that the number is substantial. Before putting in a heat pump, HVAC contractors need to make sure the leaky ducts are fixed so they do not end up putting in a larger system than needed. If there is no access to the ducts, a product like Aeroseal could be the answer.

“You need to have tight ducts that are sized correctly,” Davis said. “Sealing the ducts can really change the load and allow a smaller unit. You need to follow Manual S for size guidance. Size those ducts correctly so we get the right amount of air into the space. This needs to happen if heat pumps are going to have a chance to succeed.”

4. Supply Registers

It might sound simple, but don’t blow air on people. It is not comfortable.

“This is what we learn with Manual P,” Davis said. “With heat pumps, we have a much higher discharge temperature than the one we did before. But still, you don’t want drafts on people.”

This is done by making sure the right diffusers and return grilles are used. It also keeps the system quiet.

5. Moisture

It is fair to say that 74° with 70% relative humidity is a lot different than 74° with 47% relative humidity. HVAC contractors need to get rid of moisture both for comfort of the homeowner and to prevent mold.

“When heat pumps are sized for heating, they are usually oversized for cooling,” Davis said. “You need to have a strategy to deal with moisture when the heat pump is in cooling mode, especially during the shoulder seasons.”

This could be the function of the cooling system or a dehumidifier. The key is to keep the house comfortable, including when temperatures are mild outside.

The key for HVAC contractors is to remember these five items and manage customer expectations. If they can accomplish that, the heat pump installation will be a success.

The presentation was a part of the Codes and Coffee series. ACCA’s Codes and Coffee is a monthly webinar focusing on the latest codes and standards issues facing the HVACR industry. Visit www.acca.org for more information.