Sealing up your home can save money and fight climate change

Illustration by Brock Kaplan, Star Tribune

An Edina woman knew her house could get drafty in the winter, so she signed up for a home energy audit to find out where cold and heat were getting in.

MMike Childs was on the hunt for heat loss.

Childs, who conducts home energy audits for the Center for Energy and Environment, showed up at a rambler in Edina at the invitation of owner Rachel Boeke. Boeke wanted to save money on her power bills, and she also wanted to stop energy from wafting out of the house. In the process, she was also confronting one of the biggest sources of climate-warming pollution.

Childs placed a large red fabric panel with a fan in the front door to pull air out of the house. Then he took a thermal camera to find where cold air was leaking in.

He walked into an ocean-themed bathroom with decorative fish on the blue walls. Childs aimed the camera toward the ceiling over the shower. A dark purple splotch popped up on the camera screen.

"There's something at the top of this cavity that's letting cold air down into the wall," he said.

The solution is obvious, yet remarkably effective: insulation.

Heating and cooling buildings and running the appliances inside of them account for roughly a quarter of global carbon emissions, according to the International Energy Agency. In Minnesota, a significant amount of the energy spent in buildings is used to keep them warm in the winter, with homes here using the fourth-most heating energy per household of the 50 states, according to a 2020 survey.

Minnesota's Climate Action Framework has set a goal of cutting emissions from existing buildings by half in the next 11 years. One of the best ways to do it is insulation, which ensures climate control in your house doesn't wreck the global climate.

Starting an audit

Boeke's home is colorfully decorated with political posters, Elvis Presley memorabilia and portraits of her three children. When she moved in 14 years ago, she said, almost nothing had been done to the house since it was built in 1967.

Since then, she had replaced the water heater, roof, and the furnace — twice. Parts of Boeke's house still felt drafty in the winter. An old friend, Stacy Boots Camp, an outreach coordinator at CEE, had encouraged her to figure out if her home needed more insulation.

The home energy audit program is a popular one, with appointments usually booked six weeks out, Childs said. Xcel Energy and CenterPoint Energy contract with CEE, which completes the audits. In Boeke's case, CenterPoint partnered with the city of Edina to cover her $100 audit fee.

Childs checked to ensure the water heater and gas furnace were venting correctly so carbon monoxide and other dangerous gases weren't building up. He also inspected the attic insulation to rule out the presence of vermiculite, which might contain asbestos. The age of the house made it unlikely, and indeed, after clambering up a ladder in the garage and poking a flashlight into a space above the door to the house, he confirmed that it was blanketed with cellulose, or ground-up newspaper.

But its 7-inch depth was about half of what's needed, he told Boeke.

Insulation in the attic is so important in part because of the wintertime "stack effect," said Patrick Huelman, who studies safe and efficient housing at the University of Minnesota. Warm air rises, and if it's drifting up out of a house through cracks or thin attic insulation, colder air gets pulled in through any cracks or gaps in the house lower down.

Insulating an attic well doesn't always save a homeowner the most money, he said, but "it's the right place to start the process" of air sealing and insulating. There are often gaps or holes in the attic that aren't apparent from below but still let hot air escape, Huelman said.

Searching for cold

As Childs scanned the house with his camera, small but unexpected areas of cold kept showing up. A single electrical outlet was a point of invasion for chilly air. A large swath at the top of a living room wall also showed up cold.

Another problem area was a gap between a wall and the brick facing of a fireplace in the basement. Boeke had already put plastic over a window nearby, because that corner of the basement was always so drafty.

Childs said this and other wall cracks could be easily filled in the acrylic caulk.

But it turned out that many of the escape routes for heat were actually in Boeke's ceiling. As Childs pointed his camera at the recessed lighting, the area around the fixtures was a dark purple on the screen. When the lights were turned on, the heat from the bulbs masked the effect, turning the areas bright yellow on the camera's screen.

Anything that spans the boundary between the conditioned living space of a house and an attic should be targeted for air sealing, Huelman said. Since lights produce heat, "you have to be careful about how you seal and insulate them," he said.

Hoping for warmer days ahead

Boeke's home avoided some of the more complex problems that can crop up with retrofitting older houses. It is new enough that there was no knob-and-tube wiring, an antiquated electrical system that requires airflow and limits in-wall insulation.

Boeke also didn't have single-pane windows — one of the only kinds that CEE actually recommends replacing, because windows are so expensive.

What CEE did stress — that the attic needed more than twice the current insulation — wasn't a cheap prospect. A contractor quoted Boeke $9,460 for the job, which included installing boxes in the attic that would cover and insulate all of her recessed lighting.

But with a rebate from CenterPoint and matching funds from the city of Edina, the total was knocked down to $6,860. CEE helped Boeke find a contractor who could apply the CenterPoint rebate before she paid for the work.

And Boeke decided on her own to get new windows for her bedrooms, mostly because the frames swelled so much in the summer heat that the windows were hard to open and close. That would by far be the costliest improvement, at around $23,000.

To pay for it all, she planned to refinance her home. "I'm hoping it's all going to help the house feel warmer," Boeke said.

Resources to get started

If you are interested in getting your own home energy audit, your electric or gas utility might be a place to start.

Xcel and CenterPoint customers should sign up with the Center for Energy and Environment's Home Energy Squad.

Minnesota Power offers rebates for a similar service with participating auditors.

The Minnesota Department of Commerce also publishes a home energy guide that can help you make decisions about how to insulate.