Andy Duncan has a very simple way to check whether a house is less than energy-efficient.

“Take a sheet of toilet paper and meander your house, holding it by doors. If it moves, you’ve got a draft,” he said.

Duncan – an instructor at Lakes Region Community College and associate with Foster Sustainable Energy of Concord – shared other ideas for keeping homes warm and cool, depending on the season, at an “NHSaves Button Up” workshop Thursday hosted by the Dublin Town Library. Early on, Duncan made two simple points.

“New Hampshire is the ninth-most-expensive state for energy,” he said, a fact echoed by chooseenergy.com and Statista. “And if we do better with energy efficiency, we won’t have to build more power plants.”

The 90-minute presentation included information such as that an electric water heater is only one-third as efficient as a heat pump system to heat water, and that purchasers of Energy Star appliances are eligible for rebates.

A worthwhile test for all of one’s appliances, said Duncan, is to use a watt meter to see how much energy a device is using.

“Pretty simple – you plug the device into the watt meter, which you then plug into the wall, and it will tell you, and many local libraries have them for people to check out,” he said.

His slides had other suggestions such as keeping a humidifier at 60% to 70%, not 100%, installing low-flow shower nozzles and faucets and lowering the temperature on a water heater to 120 degrees.

A typical household of three or four people uses about 600 kilowatt-hours of electricity a month, Duncan said, with a kilowatt-hour being 1,000 watts of energy over an hour.

Certain tips for saving energy may seem obvious, but Duncan said that doesn’t mean people follow them.

“I saw that in my neighbor’s house the other day; he had an air conditioner window unit in. It had been in all winter. Earlier I’d have suggested ‘remove it – you’re losing heat through the gaps,’ but at this point in the year… .” he said.

The air conditioner point was part of a larger theme of the evening.

“Focus on the building envelope first, then the heating and cooling systems inside,” said Duncan. “Many houses lose more heat from leakage than from a lack of insulation.”

“Heat always moves from hot to cold,” said Duncan, sharing slides suggesting air flow in houses, and he had a bit of information that caused one member of the audience to frown. “Brick, stone and concrete are heat conductors; it will escape structures made of this more easily,” he said.

With regard to insulation, Duncan said that the key point to be aware of is the “R factor,” which is its thermal resistance to the transfer of heat. The higher the R factor, the better. A blower door test is a good method for identifying areas where heat is escaping or the cold coming in, and infrared cameras can also help with this, said Duncan.

For all the emphasis on making homes airtight, Duncan also said that “Fresh air is needed for a healthy home,” explaining that “For a typical home, about one-third of the home’s air should be exchanged every hour.” This can be accomplished with a high-quality bathroom fan or a heat recovery ventilator.

“Most homes in New Hampshire are two to four times too leaky,” he said, but this does not lead to good ventilation; it makes homes “nosebleed dry” during the winter months.

Heat pumps are an increasingly popular method of controlling interior temperatures, and Joe Blount of Twin Oaks Electric in Bennington shook his head when a common belief of heat pumps – that they are not as effective in extremely cold weather – was mentioned.

“Heat pumps work at temps as low as 20 degrees below zero,” Blount said, adding that some recent models he has installed are efficient to 31 below. “We’re doing whole houses with them – no backups,” noting that no other heat source is required for the home.

“A good place to start in terms of assessing a building’s energy efficiency is an energy audit,” said Jack Landry of the New Hampshire Homebuilders’ Association, which can assist individuals in finding auditors and contractors at nhhba.com.

Duncan also introduced a new term to many in attendance – “negawatts,” as in negative.

“The greenest energy is the energy you don’t use,” he said.