Modern boilers are more efficient than older boilers for several reasons, but their main advantage is that they “condense”. A condensing boiler recovers more heat from the exhaust flue gases and uses it to heat central heating water, making it more efficient than older boilers. Heating air requires more energy than heating water. Because of this fact, furnaces tend to use more fuel for a shorter period of time than boilers.
When it comes to the cost of heating equipment, boilers tend to be more expensive, but they can also be much more durable than furnaces. This, of course, will also depend on the maintenance of this equipment by the owners. ENERGY STAR certified gas boilers have annual fuel efficiency ratings (AFUE) of 90%, approximately 8% more efficient than the federal standard. During your online search, you may have discovered a variety of “high-efficiency gas boiler models”.
Because a high-efficiency boiler doesn't require higher temperatures to ventilate, it can do the same job of heating a home as a conventional boiler, while using much less fuel to do so. Improvements in energy efficiency will save you money on a new furnace or boiler, since you can purchase a smaller unit. Condensing boilers cool exhaust gases so much that they can be vented with CPVC or polypropylene (plastic) tubes, instead of the steel vent required by conventional boilers. A home's heating system not only includes the boiler, but also all the pipes, valves, pumps and heat distribution.
The boiler's high-efficiency heat exchangers are made of stainless steel for long life and exceptional reliability. Because this condensate is acidic, heat exchangers in a high-efficiency boiler must withstand a low pH. A high-efficiency boiler has a lower chimney temperature because it is designed and built to withstand the condensation of a lower temperature operation without negative effects on the boiler. But to make sure that you make the most efficient choice, you should choose the right type of boiler for your home.
Condensing boilers generally operate more efficiently in homes with low system temperatures, such as those with radiant floor systems or in homes with high-volume cast-iron radiators of high water volume. The condensate drains to the bottom of the heat exchanger and exits the boiler through a condensate drain. The most efficient boilers keep heat in the house instead of letting it escape through the chimney or vent pipe. Steam, gas, and hot water boilers cost about the same, but steam boilers operate less efficiently, so this is something to consider when considering which boiler is best for your home's energy needs.
In addition, high-efficiency boilers are usually much smaller and lighter than conventional boilers, so they can often be hung on a wall, rather than mounted on the floor. Because this condensate is acidic, heat exchangers in a high-efficiency boiler must withstand a low pH.