Taking stock of energy losses

But a thermal image recently taken of his house as part of an ongoing study by the state Department of Energy Resources, Sandeen said, revealed a problem spot that he said no contractor had ever detected.

By recording differences in the temperature of the surface, or envelope, of his 40-year-old home, the camera revealed there was no insulation behind its brick walls.

“The picture of my house really was quite amazing,’’ Sandeen said. “On the first floor behind the brick, the house is just gushing energy. Who would have known?’’

Sandeen’s home is one of hundreds in Lexington and Arlington that have been checked for heat losses by a state-hired contractor over the last month as part of a “Smart Building’’ program aiming to increase energy efficiency and reduce energy costs.

Using part of a $350,000 federal grant, the Department of Energy Resources has hired Woburn-based Sagewell Inc. to collect the thermal images of residential, commercial, and municipal buildings in several communities across the state.

Sagewell will use the images to analyze the quality of energy efficiency in the structures, and the information will be used by the state to help train builders about how to identify cost-effective improvements, according to the energy agency.

Pasi Miettinen, president and chief executive officer of Sagewell, said his company completed its thermal imaging of buildings and homes in Lexington last month, and the company spent much of last week completing thermal imaging of hundreds of buildings in Arlington.

His company uses thermal cameras that are mounted on vehicles that drive along the street “reasonably fast’’ while taking images of the facades of the buildings, he said.

The camera’s images illustrate warmer temperatures with brighter colors. An exterior wall with a high temperature is often indicative of poor insulation.

Miettinen said Sagewell conducts the thermal imaging in neighborhoods that offer a sufficient representation of the building types in the community. He said that before the work is completed, residents could make requests that Sagewell either include or not include their homes in the survey.

Once Sagewell takes the thermal image of a home, the property’s owner can access the image online at a password-secured company website.

The thermal image reports of each home can only be seen by the homeowner, but a report will be published this summer that will analyze patterns and energy-efficiency opportunities for all types of buildings included in the study, Miettinen said.

The opportunity to show people a picture of where their homes are leaking energy is why Jeremy Marin, cofounder of the Arlington Home Energy Efficiency Team, got involved with helping Sagewell get the word out to local homeowners about the thermal imaging study.

Arlington HEET is a nonprofit group that uses volunteers to assess and address the energy efficiency of homes in town, and Marin said while residents often recognize that their homes are cold during the winter, they don’t realize how much heat they are losing.

“If a picture is worth a thousand words, then these thermal images are going to speak volumes about what we can do to improve our homes,’’ Marin said.

Miettinen said about 30 to 50 percent of the energy lost by buildings occurs through the building envelopes, and so far the thermal imaging study has found the age of a building is not necessarily the best way to predict its energy efficiency.

An old home with good insulation may have few problems, while homes built in the last 20 years often have trouble spots where energy is escaping, he said.

Charlotte Milan, a member of a nonprofit environmental organization known as Sustainable Arlington, said the town passed a sustainable action plan in 2006 that set goals for residents to reduce the carbon emissions of their homes in an effort to improve the environment.

By showing residents thermal images of their homes and the amount of energy that is being wasted, Milan said, she’s hoping homeowners will be stirred to take action and reduce some of the emissions caused by the wasted energy.

“The more information they have, the less tentative they will be about taking the next steps,’’ Milan said.

Sandeen said Lexington is trying to reduce the town’s carbon emissions by 20 percent by the year 2020, and the Sustainable Lexington Committee is working to reach the goal.

About 45 percent of all of the energy used in Lexington is consumed by residential buildings, Sandeen said, and the committee thought the thermal imaging study would be a good way to help residents learn more about energy efficiency, and how to make improvements to their homes.

Sandeen is hoping residents will put the thermal images of their homes up on their refrigerators as a clear reminder that they need to do something to address energy leaks.

“We all know our houses are using too much energy, but what do we do about it?’’ he said.

“The thermal imaging camera drove by and found out in 10 minutes what I’ve been living in the house for 15 years without knowing.’’