The boiler's hot water will be put to use in other systems, too. Separate zones will feed supplemental radiant floor heat under the house's entire first story and in the bathrooms. And to warm up hot water, an additional zone from the boiler will circulate through a heating coil in an indirect water tank. With this setup, the water tank itself doesn't need a burner, and therefore it has no flue where heat can escape. "It acts like a giant thermos bottle, with very little standby heat loss," says Richard.
Hybrid HVAC Equipment
Since they were adding central air-conditioning, John and Sally scrapped the old radiators and boiler, opting to let the new ducts carry both AC and heat. TOH plumbing and heating expert Richard Trethewey designed a unique and highly efficient forced-air heating system that uses hot water as the "fuel" to heat the air supply. The water is warmed in a Lochinvar condensing boiler, which captures and uses heat from its own exhaust system, making it about 96 percent efficient—better than any furnace. This heated water will travel through insulated PEX pipes to two air handlers in the house. There, the water warms the air that's then channeled through 2-inch high-velocity mini ducts supplying heat to each room.
Shown: Richard Trethewey connects a mini duct to the main trunk line. These smaller ducts will be snaked through the house's 24 wall framing to deliver heated (or cooled) air.