Glare from energy-efficient windows can melt siding, vehicles
Posted May 5
Updated May 6
Apex, N.C. — Energy-efficient windows make up more than 90 percent of all new window installations in the U.S., according to a survey by the National Association of Home Builders. But they can become problematic for homeowners when sunlight bounces off the windows and is so intense that it can melt siding on houses and parts of vehicles.
Weeks after moving into a new home in Apex in December, Michelle Curtis noticed that plastic parts of her SUV had bubbled and melted.
“It was pretty unbelievable,” she said. “It’s like, could this really be happening? Could the reflection of the sun on a window of a house do this kind of damage to a vehicle?”
Experts say it is possible. The windows, which use low-emissivity glass, can act like a magnifying glass and reflect the sun’s rays. Clear glass reflects about 10 percent of sunlight's energy, but low-e windows, which have a green tint, reflect 30 to 50 percent, according to NAHB.
Low-e windows are generally mandated by modern building and energy codes for new construction.
"Low-e window glass is coated with a thin layer of metal or metallic oxide. Visible light is passed through low-e windows without difficulty, but the metallic layer blocks the passage of heat inducing ultraviolet light into the home, reflecting that light outward," David Crump, NAHB director of construction liability and legal research, wrote. "This keeps the home cooler in summer. In the winter, the effect is reversed, with interior heat blocked from passing outward."
Reports show the coating used on the windows to reflect the sun, combined with a concave effect in some windows, magnifies and intensifies the beam up to 200 degrees Fahrenheit. The problem is worse in late fall, winter and early spring due to the low angle of the sun.
Problems with low-e windows have been reported across the country. The beams have melted vinyl siding, plastic and paneling on cars and garbage cans. Reflections from the windows burned people at a pool at the Vdara hotel, a high-rise in Las Vegas. The windows on a London skyscraper were blamed for melting part of a Jaguar XJ. The Consumer Product Safety Commission said beams from sunroom roofs have started fires on cedar shingles in at least four homes.
Home builder Dan Tingen is on North Carolina's Building Code Council, which spent more than a year and a half investigating low-e window complaints in the state.
“I just hate telling people that we can’t help, and in this case, we haven’t figured out how to help," he said. “It’s just the collision of technology. It’s a problem, and there’s not an easy solution to it."
Tingen says window manufacturers have "done exactly what we asked them to do" by creating high-efficiency windows, but the new technology "has created an unintended consequence."
That consequence caused siding manufacturers to take the extra step of changing their warranties to exclude damage from external heat sources, including low-e windows. Homeowners who complain can have a hard time finding someone to take the blame.
In Curtis’ case, she contacted her builder, the window manufacturer and her car and homeowner’s insurance about the damage done to her SUV.
"No one's taking responsibility. They're (saying), ‘Contact this person. See what he says. Contact this other person,’ and (I'm) kind of getting the runaround,” she said. "If anything, we should be warned that this can happen. There should be some kind of safety warning. We certainly wouldn't have parked our vehicles here if we had any kind of warning.”
After 5 On Your Side got involved, Curtis' builder offered to replace the low-e windows in question with regular glass. Although it doesn't meet code, many industry experts say it's the best solution for now. Other options could include adding screens or shrubbery to diffuse the beam.
For homeowners who are worried that their low-e windows might damage their neighbors' property, legal experts say they should switch to regular glass, which costs about $150.