The National Weather Service office in Gray put it plainly in its Thursday morning forecast discussion: a cold front crosses Friday, Friday night lows drop into the lower to middle 30s in the interior valleys with patchy frost, and temperatures stay below average through much of next week with frost or freeze possible on any given night. For a lot of houses in Maine and New Hampshire, this weekend is the first time the heat comes on since April. If you are under contract on one of those houses, that matters more than it used to.
The heat in the house you are buying may be a heat pump
Efficiency Maine says Mainers have installed over 200,000 heat pumps, and its heat pump program page notes they are now more common than oil heat in new homes. We see three kinds of houses: the older home with an oil boiler and a couple of wall-mounted heads added later, the newer home where the heat pumps are primary and the boiler is backup, and the new build with no combustion heat at all.
The seller of any of the three has probably been running those heads in cooling mode since June. A September showing on a 70-degree afternoon tells you nothing about how the house heats. That is the gap a fall inspection has to close.
What an inspector is actually required to do with the heating
The InterNACHI Standards of Practice, section 3.4, are direct about it. The inspector operates the heating system using normal operating controls, describes the energy source and heating method, and reports any heating system that did not operate. The same section says the inspector is not required to determine the size, capacity or supply adequacy of the system, and is not required to run a heat pump when conditions could damage the equipment. So a fall inspection can tell you whether every heat source turns on and produces heat. It cannot tell you whether that equipment will carry the house in January.
What we do on site is unglamorous. Every indoor head gets switched out of Auto and into Heat and left to run while we work the rest of the house, then we come back and confirm warm air is moving. Efficiency Maine’s user tips warn against Auto mode for the same reason we do: a head in Auto will happily air condition a sunny room in January or fight a wood stove. We pull the dust filters and photograph them. We check the outdoor unit for clearance, a stand or bracket that keeps it above where snow will pile, a drip line that will not ice it, line-set insulation that has not rotted off in the sun, and a disconnect within sight. If there is a boiler or furnace too, it gets run as well.
The cold-climate question, and the backup question
Not every heat pump is built for a Maine February. ENERGY STAR’s cold climate air-source heat pump designation requires third-party verified performance tested down to 5 degrees, and the program notes that a unit keeps working below that, but that pairing it with a backup heat source is the most efficient way to heat the home on the coldest days. The report will describe the make and model on the data plate. Whether it is a cold-climate model is a question for the seller and for the installer whose sticker is usually on the outdoor unit.
The second question is what happens if it stops. If the house has an oil boiler demoted to emergency backup, ask when it last ran and whether it has been serviced. Efficiency Maine’s tips include a warning we repeat to every buyer of an older house: turning off a boiler or furnace in an insufficiently insulated basement raises the risk of frozen pipes. We look at where the water lines run relative to the foundation walls and the sill, and we say so in the report.
If there is no backup at all, ask about the outage plan. Heat pumps run on electricity, and rural Maine and New Hampshire lose power in winter storms.
Rooms with doors
A single head in an open living area does a fine job with the open living area. Bedrooms down a hall with the doors closed at night are a different story, and it is a complaint we hear back from buyers the following winter. Efficiency Maine’s rebate rules give a useful benchmark: to qualify, a home’s heat pumps must be sized for at least 80 percent of its peak heating load, or 100 percent in combination with supplemental heat. We do not calculate heat loads on an inspection. We do walk every room and note which ones have no heat source of their own, so you can decide whether that is acceptable or a negotiating point.
What you can check yourself
None of this needs a license. At the showing, switch a head to Heat and give it ten minutes. Go outside and look at the outdoor unit: is it on a stand, is anything growing into it, is the line-set insulation intact. Ask the seller for the installation invoice and any rebate paperwork, which will name the model and the installer. Ask which rooms they actually heat in winter, and what they paid for electricity and fuel last year.
Buy it in the fall, live in it in January
We run the heat on every inspection, in every mode the house has, and we write down what we found and what we could not determine. Focused Property Inspections covers Maine and New Hampshire, from Greater Portland to the Sebago Lakes region and Lewiston and Auburn. Darryl Chandler has inspected Maine homes for thirty years, and the home inspection covers the heating system as part of the same visit. Call (207) 839-6595.