A few years ago Bill Spencer was a DuPont Corp. employee working on the company’s new miracle fiber, Tyvek. The substance serves as a protective wrap under a building’s exterior facade, acting as an air barrier, keeping warmth in and moisture out. Figuring that the same principals that keep a house warm and dry could work as well for people, Spencer sought a more practical use for the fiber. He found it on a cold, wet weekend while his son Erik was packing for a soccer tournament. Spencer stitched the fabric into a long-sleeved shirt to go under Erik’s jersey.

When Erik stayed warm and dry, his soggy teammates asked for their own shirts. That led to requests from other athletes. In 1999 Spencer bought the patent rights to the material, and started a thermal sportswear business in Chester with partner Jerry Wofford.

They launched Zyflex Thermal Sportgear in Jan. 2000 with one product — stretchy shirts that fit neatly under uniforms while repelling water and trapping air for warmth. Before the launch, Spencer spent about four years testing and perfecting the material. He sent samples to college coaches such as James Fritz, head lacrosse coach and assistant athletic director at North Carolina’s Pfeiffer University, and asked for feedback. Fritz has tried similar breathable, water-resistant fabrics, and says Zyflex is the best: "I think it’s absolutely amazing. It’s better. It does wick away the sweat and it enables you to breathe through the shirt. Not only does it generate a great amount of heat, it keeps [the players] dry."

Spencer attributes the fabric’s breathability to its ultra micro-fibers that are roughly the size of red blood cells. "Put on our product and go run in it and you’ll say it breathes just like cotton," he says.

Plus, Zyflex shirts seem to be more durable than others. "They hold up extremely well. I’ve had some shirts now for two years," Fritz says. "We have college athletes who use this every single day. We throw them in our industrial washer and dryer every day and they hold up."

Although retailers such as Target and Kmart, as well as outdoor outfitters sell similar products, you won’t find Zyflex among them. Selling there would drive up prices to more than $30. Spencer wants to keep his products affordable. "If you’ve got a little kid playing soccer out in the cold, you’re probably willing to pay $17 or $18 to see if it works," he says. "When you get up to $35, you’re talking about serious athletes."

Cutting out the middleman retailer hasn’t hurt sales. By December Zyflex had sold 8,500 shirts — more than double expected sales.