Designing for Ultimate Comfort
Temperature sensors are becoming smaller and better connected

by Tracy Ostroff
Associate Editor

How do you . . . evaluate individual temperature control systems?

Summary: The science of thermal comfort—what accounts for someone feeling comfortable or not comfortable in a space—is remarkably poorly understood, notes Scott Frank, a partner at the New York City engineering firm Jaros, Baum, & Bolles. Frank shares an overview of some of the changes in store for controlling personal environments and how these new technologies and methodologies fit into larger environmental contexts.

“There’s an increasing awareness of something we all know intuitively, and that is that people have different preferences for their personal environment,” Frank says. “And temperature is one of those parameters that can be controlled.” Frank notes that the LEED® program has been a “big help in trying to encourage this notion of the development or configuration of systems that avail individual control over temperature.”

Under-floor distribution systems allow some influence over the immediate temperature and local environment

One fairly effective approach that is being used now in office buildings, Frank says, is under-floor distribution, supplying air to the space coming from under floor plenums. “Every person has his or her own air outlet right next to the work station. Those systems allow some influence over the immediate temperature and local environment.”

More broadly, Frank says, engineers and architects have had the ability to provide individual temperature control for an individual enclosed office or a conference room. Most often, he says, it’s becomes a cost issue, because even in Class A office space, each thermostat needs additional controls and air valves to provide the dedicated control. “Often that can’t be supported by the business side of the equation,” he explains.

Barnacles on a wall no more
“One constant struggle that we as engineers have with architects is–when you talk about more conventional systems—where do you locate the temperature sensors that really want to be mounted in the space that is being served? They have gotten a lot smaller, and arguably more aesthetically pleasing, but still they are these barnacles that you have to stick on the side of a column or a wall,” Frank says. “And then you get into a lot of high-end applications where you have stone wall covering or other kinds of non-standard finishes and it becomes almost impossible to locate them.”

There are now very tiny temperature sensors, almost as small as a pencil eraser, that can be really hidden

Frank says technology has evolved to try to address some of these issues. There are now very tiny temperature sensors, almost as small as a pencil eraser, Frank explains, that can be readily hidden, even in a stone finish. They can be connected to a building management system to provide temperature sensing. There are also infrared sensors that can be placed a little further away that can view the temperature condition of a space from some distance, “like a little camera that sees warmth.”

Another area of rapid change, Frank says, is getting the sensors to connect automatically over a wireless network. “And if you talk to the manufacturers, they’ll tell you that they are looking down the road at some really imaginative ideas, like sensors that employ nanotechnology, which is essentially the design of systems at the molecular level. With pinhead-sized sensors with wireless connectivity to the building network, the sensors could be poured into paint and painted on the wall.”

Disconnect in perception
The cutting edge of the science of thermal comfort is trying to understand what influences people’s perception of comfort. “What they’re trying to figure out is if it’s a cold winter day we intuitively have expectations that it may feel a little cooler, and therefore when we walk into a space we’re not expecting it to be warm, and therefore are more comfortable or have the feeling of comfort even if it is cooler,” Frank says. “The whole idea is how do you engineer a space and try to keep as many people as possible happy?”

“The whole idea is how do you engineer a space and try to keep as many people as possible happy?”

The industry standard, Frank notes, is to create a design that will satisfy the greatest number of people at any given time, but also accounts for the demand of extreme summer and winter conditions. “There is another nuance to this, which I think is becoming increasingly important. With a renewed emphasis on energy conservation, there’s already recognition that it is essentially wasteful or can lead to energy waste if you design systems for the absolutely worst day when it is 90 degrees and very humid, so that you can still maintain exactly the same 75 temperature inside.” That kind of capability, Frank says, means you have a very large system that for all the rest of the hours of the year are running at greatly reduced load, which can lead to inefficiencies. With new and significant objectives for reducing greenhouse gas emissions “there is going to be a growing tolerance for even a little less thermal comfort during peak seasons.”

Frank says current standards are already accounting for this comfort in demand situations. “Instead of designing for one afternoon that is the worst, you design for something that happens maybe even 10 times a year, recognizing that there is a tradeoff. For a small number of hours a year the system will be taxed and you won’t be able to maintain that design condition in the space, and therefore people may feel a little discomfort. But that’s a reasonable tradeoff looking at energy conservation that you would have to pay all year long for even being a little out of spec.”