NFRC Decides to Look at Window Comfort Rating

Jim Larsen started off with a simple question. He wanted people to raise their hands if they felt the room they were sitting in was too cold or warm. Most hands stayed down. "Less than 5 percent of us are uncomfortable," Larsen said.

Larsen was right. Very few of the attendees at his Thermal Comfort Task Group held during the National Fenestration Rating Council (NFRC) meeting in Austin, Texas, had a problem with the temperature. A few of them did have concerns with the idea of the NFRC setting up some type of guideline to tell consumers how windows would affect the comfort level in their homes. But Larsen's detailed presentation went a long way to calming those fears.

For Larsen, this topic has become a passion. He joked after the presentation that he "bulldozed my house because my windows were so bad." That, of course, was only part of the reason. But he did spend a lot of time trying to convince NFRC attendees there was a way to label windows for comfort level. In fact, he went through mounds of technical information on the issue and distilled it into a half-hour format for his seminar.

He started out with a look at the seven stages of comfort (ranging, not surprisingly, from cold to hot). Of course, no one thing determines comfort. Using a sophisticated modeling system, Larsen demonstrated that air temperature, air velocity, relative humidity, metabolic rate and clothing all play into how a person feels when they're sitting in a room.
While all of these topics are relevant, NFRC attendees don't really care about whether someone is sporting their insulated winter coats or sleek summer rain jackets. They care about windows. And, windows playing a big role in a building occupant's comfort. A person's proximity to the window, the size of the glazing and its temperature plays a big role in comfort.

The question was how to indicate window comfort. Larsen proposed that hours of discomfort, thermostat offset versus window type, what it feels like at a certain temperature, the coldest (or hottest) outdoor temperature at the comfort limit and how far a person would have to move away into a comfort zone would work.

The Thermal Comfort Task Group's job wasn't to get into those specifics though. It was to determine whether to pursue a goal of putting thermal comfort information on windows. While a majority seemed to support the idea during discussion, saying that it would help consumers and decrease air conditioning and heating loan (which would save energy).

"We can bury our heads in the sand or we can do something to help limit energy use," one unnamed, yet committed, attendee said.

Others weren't so sure these ratings would help, saying there were way too many variables in a room to assign temperature comfort to windows, rating could bring possible liability to NFRC, and that the NFRC had other priorities.

"I'm wary of the NFRC taking on the responsibility of determining thermal comfort [when there are so many things to do]," one attendee said.

Eventually this attendee and others who opposed the thermal rating lost and the group decided to send the idea of rating windows for comfort on to the NFRC's technical committee.

Even if the technical committee approves the idea of a rating, Larsen wouldn't speculate on whether the rating would be a simple number, a fact sheet or even guidelines.