We recently installed a heat pump system in our 1,500-square-foot house, built in 1940.
Although I researched beforehand, unexpected questions and challenges popped up during the installation, as is often the case with major home projects. Here’s what we learned from our experience. It might make the process a little easier for others considering similar projects.
Prepare your home: The better weatherized your home, the more efficiently a heat pump will operate. A small investment in a home energy audit can help identify issues that might cause a heat pump (or any other heating/cooling system) to work harder than it should.
Do the research: Most leading heat pump brands can handle a typical New Hampshire
winter. Our Mitsubishi system will produce heat when the outside temperature is as low as -30 degrees, and we’ve had sufficient heat as low as -8 degrees. Mini-splits come in many different configurations, including floor, wall, and ceiling mounts. Knowing the viable options ahead of time will help the installer design a system that better matches your aesthetic and performance preferences.
Get multiple quotes: This is good advice for any significant home project but especially for heat pumps, as there will be multiple ways to configure the system for any given home. In our case, the estimates had a wide range of prices and design choices, so we opted to have an independent engineering firm design the system and work with the installer.
Read the manuals: Once you’ve hired an installer and know what heat pump equipment you will have, find the user manuals online and read them. The Mitsubishi user manuals provide only basic information on settings and maintenance, and they are not always accurate. Make a list of questions to ask your installer to clarify anything you don’t understand in the manual. The installer should go over operation and maintenance once they’ve completed the work, but I found I had unanswered questions later.
Hire your own electrician: Most installers will do the required electrical work but usually with a mark-up. We hired our own electrician at a significant discount.
Think through installer suggestions: Any reputable installer will want to make sure the
system is efficient while trying to keep costs down. However, every house comes with unique challenges, and an installer might make a suggestion that isn’t best for yours. For example, one installer wanted to put the outdoor unit on our deck. It would have made installation easier and cheaper without sacrificing efficiency, but the trade-off would be more noise in the house. Our outdoor unit is behind the garage, and we cannot hear it in the house.
We also decided to use a ceiling cassette unit in an upstairs bedroom. During installation, we discovered that the original choice of a ceiling mount would not fit in the space between the ceiling joists. In 1940, those joists were a full two inches wide; the cassette unit was sized based on thinner modern joists. We could have avoided this problem if the installer had confirmed the unit would fit before beginning the project. Think through every choice the installer presents, ask questions about trade-offs, and make sure everything will work as planned.
Install thermostats: Our installer suggested using the remotes that come with the mini-split units rather than thermostats. It sounded like reasonable advice, so we were happy to take that expense off the list. However, the mini-splits did not always maintain the temperature setting on the remotes due to the way they tell the room temperature without a thermostat.
With a remote, the mini-splits sample the air temperature near the unit. That air might be
cooler or warmer than the air in the living area. A thermostat wirelessly sends the temperature it reads at its location to the mini-split. After installing thermostats near our living areas, the system maintains heat consistently at the settings we choose. Thermostats cost a few hundred dollars each plus labor to install, but are well worth it.
Have a backup strategy: Your strategy might be to have no backup at all, but we wanted a
backup heat source in case of power outages or to assist during extreme cold. That’s our
woodstove, which was also the backup to our steam boiler.
Speaking of power outages, most portable generators will not support a heat pump system. A whole-house generator might be OK, but you should confirm that with whoever services the unit.
Assess the effects of removing the old heating/cooling system or using it less: The only source of heat in our basement was our steam boiler. When it doesn’t run, the basement temperature drops about 10 degrees, which was a cause for concern during this recent cold snap. We installed a small resistance heat unit as it was the most cost-effective way to ensure the basement temperature stays above freezing.
If you want to learn more about heat pumps, the Peterborough Renewable Energy Project
(PREP) is hosting a heat pump workshop at 10 a.m., March 21, at the Peterborough Library’s Eben Jones Classroom. Iris Waitt of Design Day Mechanicals, which provides HVAC engineering services, will provide an overview of modern heat pump systems and answer questions.