Heat pumps: teach your buyers well
Air source heat pumps are one of the choices used by builders seeking to deliver an energy efficient home. They use less power than baseboard or furnace systems. Or at least, they should.
The trouble is, homeowners may not understand how their heat pump system works, and may not set or maintain the controls properly. If this happens, they won't see the efficiency level they were promised, and that could lead to higher energy bills and frustration.
Certified energy advisor Wendy Smith of Performance Energy Advisors has worked with a number of B.C. builders using air source heat pumps. She also has an air source heat pump in her own home. Here are some tips for making sure your buyers get the most from their pump — and the least on their bills.
Not your traditional heating method
The key challenge in helping people use heat pump systems effectively is helping them understand how the system works compared to traditional forced air heat, says Smith.
"Gas furnaces are high temperature, low volume systems. They force heat into your home at 120 degrees Farenheit, and you can put your toes over it and you'll get nice and warm," says Smith. "In comparison, heat pumps are low temperature, high volume systems. They spill the air into the house at 95 degrees, so in order to actually heat up the house well enough, the volume has to be greater."
In the name of energy conservation, we've trained people to turn down their thermostats whenever their home needs less heat — all day when they're at work, all night when they're asleep. Unfortunately, this variation in temperature causes problems for heat pump systems.
"If the thermostat [on a heat pump system] senses that it's got, say, five degrees to move the temperature of the house up to the set temperature that you want, it's going to take a really long time at 95 degrees Fahrenheit. The result is that the system goes into backup," says Smith.
All air source heat pumps are installed with a backup (usually electric or gas) system. Backup systems can adjust the home's temperature quickly, but they consume more energy than the heat pump does, driving up bills.
Smith says even with her background, she made mistakes with her own heat pump. She knew that a more than two-degree setback would force the system into backup mode, but she still turned down the heat at night.
"We did just like everybody else because that's what we're used to," she recalls. "We found out the hard way that was a stupid thing to do."
When Smith's in-laws moved into the extra suite and needed a stable temperature all day, she discovered the sweet spot for heat pump efficiency.
Set it once, then don't touch
"What you really want the heat pump to do is just maintain the temperature constantly," says Smith. "It's not making up a big temperature deficit. The ideal comfort situation is to be constantly adding a small amount of heat all the time to the house, so your body constantly feels the same warmth.
"It's a real comfort benefit I've found; it doesn't go on and off. But the real issue here is that people are used to those on-and-off systems."
Smith says builders can also contribute to their homeowners' successful experiences with heat pumps by choosing the right systems for their needs.
"It should be a matched system [heat pump and backup], or else you'll be in backup more frequently. If it's not a matched and tested and rated set, you will most likely be in backup a lot more than you would expect," she says.
Smith also says it's important to choose systems appropriate to the climate. "The biggest market in air source heat pumps in the U.S. is for cooling, mostly. A system that is efficient on the cooling side of the equation may not be designed to be efficient on the heating side."
Making sure your buyers understand that they are saving — not wasting — energy by leaving the thermostat alone. It's the key to helping them operate their system for the lowest cost.
Smith says if people want it a bit cooler at night, they can set it back perhaps a degree or two. But she has found a better trick.
"If you want a cooler bedroom, just crack your window a little bit, cool your face a little. But don't cool the whole house."