Empire Comfort System: Mantis has a 93% efficiency rating, making it one of the most efficient gas units on the market. The unit has a power-vented exhaust and intake made from PVC, which reduces the installation cost and requires a smaller opening in the home’s exterior. A pump re-circulates the heat to extract as much as it can before it vents. It offers 28,000 BTUs. www.empirecomfot.com.

Nigel Maynard is senior editor, products, at BUILDER magazine.