Page 42 - November 2015 Green Builder Magazine

The Homeowner’s Handbook SIXTH EDITION

Heating & Cooling07

40 The most demanding systems in a home.

The energy savings and High-Efficiency Boiler

increased comfort far outweigh Hot water Flue
Boiler gases
the upfront cost of an energy- Cold
water
efficient HVAC system.
www.greenbuildermag.com 11.2015 Burner
AT THE HEART of most home heating systems is a
furnace, a boiler or a heat pump. A furnace burns Virtues Caveats
fossil fuel to heat air that’s forced by a blower fan
through a series of ducts to the living spaces; a ■■ Quiet operation—no air blowing ■■ Up to 50 percent more expensive
boiler heats water that’s then pumped to a hydronic, than a conventional boiler
or water-based, distribution system. Most heat ■■ Relatively easy to zone
pumps run on electricity. They don’t create heat, but rather extract ■■ There are fewer high-efficiency
it from the air or the ground. Heat pumps are available for use ■■ Lack of fan means lower electric boilers to choose from than
with forced-air and hydronic distribution systems. If you want use than a forced-air system there are high-efficiency
to minimize your fuel bill, an Energy Star rating is a minimum furnaces
standard for these appliances. ■■ Distribution system takes up
much less space than ductwork
GAS FURNACE
Super Efficiency include variable-speed blower fans with high-efficiency electric
A modulating gas furnace is the most technologically advanced motors. The ability to vary airflow and flame intensity also allows
fossil fuel-burning furnace you can get, with efficiencies as high for nearly constant room temperatures and better air circulation.
as 97 percent (that’s the percentage of the fuel’s potential energy
delivered as heat). It achieves this feat with a series of technical
innovations. Gas is not as clean as we once believed, however,
now that dirty methods of “fracking” are used in some extraction.
The pollution may simply be happening at the front end of the
process. No fossil fuel gets an environmental free ride. It’s a finite
resource, not a renewable one.

One way that new technology squeezes more heating power from
gas is with an exhaust heat exchanger. This exchanger steals back
heat from the furnace’s waste byproducts. Another feature, flame
modulation, adjusts the flame size, based on demand. These furnaces

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