A heat pump petting zoo? This fair helps Americans green their homes. [Video]

WASHINGTON — A loose line of people snaked from a doorway in the side of a cargo truck. One young boy wandered over to examine several bales of hay stacked nearby while others craned their necks to get a peek inside. A small sign in the shape of a barn stuck over the open door read, “Petting Zoo.”

But the queuing visitors weren’t there to meet pigs, goats, or sheep. What they wanted was hands-on experience with a different kind of beast: heat pumps.

“We have heat pump everything,” said Vanessa Bertelli, head of the nonprofit Electrify DC, as she walked through the D.C. Armory, an indoor arena, on a recent Saturday.

To her right, is a showcase of two brands of heat pump water heaters. In another exhibit, a heat pump dryer. Inside the “petting zoo,” a converted truck designed to look like the interior of a home, heat …