Two design tweaks ensure that the Hot's surface stays cool. An insulating polymer sheath separates its two 10-inch-high ceramic heating elements from the device's outer walls. And the outer walls themselves are lined in foil to reflect heat back inward. The Hot's design also lets it heat more effectively than a conventional space heater. Most space heaters have weak fans that allow the hot air to rise to the ceiling instead of circulating through the room. In contrast, the Hot's motor, located in the heater's base, pushes air up through a thin slit running the perimeter of the device's loop, creating a strong current that streams across the room. As a result, the Hot can warm a 145-square-foot room from 45ºF to more than 60º in just 20 minutes.