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Central Heating

Both furnaces and boilers are common central heating systems in Vermont.  Furnaces heat air (“forced hot air”), distribute it through ducts and deliver it to registers throughout a building.  Boilers heat water and distribute it (either as water or steam) through pipes that feed radiators. These are generally considered “central” heating systems.  A variety of fuel choices are available for these systems. Depending on the unit’s design, they are generally built to burn a single source of fuel, such as propane, fuel oil, wood pellets, firewood, or natural gas. There are some hybrid boilers and furnaces that can work with more than one kind of fuel.

How well your system converts the fuel to delivered heat (its efficiency) is affected by the unit’s design and operation, how effectively the heat is distributed, and the type of thermostat you use.  Regardless of the system or fuel type, there are steps you can take that may help improve efficiency, reduce your energy use and/or save money. For example, regular maintenance of your heating system can help to ensure that it operates as efficiently as possible for as long as possible. There are some maintenance items that can be done by someone with basic familiarity of heating systems, while other maintenance items may be more appropriate for a heating system professional. Maintenance typically includes:

  • Making sure the thermostat is in good working order

  • Changing furnace filters at least once a season (A clogged filter can make a furnace have to work harder and can cause issues with motors and blowers.)

  • Avoiding blocked registers and radiators to allow for the free flow of heat to the room

The lifespan of these systems varies, but technology continues to improve the efficiency of new designs. If you’re thinking about replacing your system, it may be worth considering energy efficient replacement models that may help you save energy. Avoid features that often indicate inefficiencies such as:

  • A natural draft up a chimney that creates a flow of combustion gases

  • Continuous pilot light

  • Heavy heat exchanger

  • Large diameter flue pipe

  • A boiler that is turning on and off frequently (short cycling), instead of adjusting to your actual heating demand

  • Heating ducts that travel through unheated spaces

One way of comparing systems is the annual fuel utilization efficiency (AFUE) rating, which works like the “miles per gallon” sticker on new cars. Older furnace and boiler systems had efficiencies in the range of 56% to 70%, while modern ones can achieve a 98.5% rating. A primary difference between a furnace and boiler is that a furnace system’s ductwork can also be used to deliver cool air from a central air conditioner. This versatility may be a factor in your decision.

Electric Resistance

Electric resistance heating has gradually been displaced in Vermont, due to its high energy cost and demands on the electric grid. These older heating system types include electric baseboard heaters, electric furnaces, electric thermal storage and electric wall heaters. They can be considered "central" or "space" heating systems, depending on whether they have a central thermostat or controls for each individual room or device. If you heat with electric resistance, you may benefit from a switch to another heating source. An energy assessment completed by a qualified energy professional can help identify options for saving energy in your home or business.

Starting in 2020, electric resistance heating is not allowed in new construction, including additions or renovations, except in very limited circumstances including having a well-insulated and air sealed building shell, and having cold climate heat pumps as a primary heating system that can carry most of the heating load.

Some Benefits

  • Well-planned and executed energy efficiency upgrades, combined with an appropriate high-efficiency heating system, may be able to cut fuel bills and pollution from heating system emissions.

  • As compared to older models, a “sealed-combustion” type furnace does not use indoor air for combustion, which will lessen the likelihood of backdrafting and reduce pressure-driven air leakage from outside. A sealed combustion furnace or boiler will bring outside air directly into the burner and exhaust flue gases (combustion products) directly to the outside, without the need for a draft hood or damper. Furnaces and boilers that are not sealed-combustion units draw heated air into the unit for combustion and then send that air up the chimney, wasting the energy that was used to heat the air. Sealed-combustion units avoid that problem and also pose no risk of introducing dangerous combustion gases into your house (backdrafting). In furnaces that are not sealed-combustion units, backdrafting of combustion gases can be dangerous.

Some Considerations

  • Before buying a new furnace or boileror modifying your existing unitconsider first making every effort to improve the energy efficiency of your building and having a heating contractor size your furnace to meet the new, reduced heating load.

  • When shopping for high-efficiency furnaces and boilers, look for the ENERGY STAR® label.

  • High-efficiency sealed-combustion units generally produce acidic exhaust gases that are not suitable for old, unlined chimneys (there are also other potentially harmful gases in the byproducts of combusion in a furnace or boiler), so the exhaust gases should either be vented through a new wall vent or the chimney should be lined.

Some Next Steps

Undertaking energy-efficiency improvements first has the potential to help you save money when buying a new furnace or boiler, because you may be able to purchase a smaller unit. If you think it is time to upgrade, check with your fuel dealer about the possibilities for your existing set-up. However, the costs of retrofits should be carefully weighed against the price of a new boiler or furnace, especially if replacement is likely within a few years or if you wish to switch to a different system for other reasons, such as adding air conditioning. If you choose to replace your heating system, you'll want to consider the opportunity to install equipment that incorporates the most energy-efficient heating technologies available. To learn more about the current line-up of ENERGY STAR® certified Heating & Cooling products, visit the ENERGY STAR® certified product pages.  

A properly sized furnace or boiler can operate very efficiently. You'll want to choose a dependable unit and compare the warranties of each furnace or boiler you’re considering. You may also be able to reduce the size and cost of a new system by adding zoned heating/cooling or supplementary heat sources, such as highly efficient heat pumps and wood stoves.

Anytime you maintain, retrofit, or replace a heating system you need to be concerned with air quality. The combustion process creates several byproducts that are potentially hazardous to human health and can cause deterioration in your home.  You can help protect yourself from these hazards, as well as maintain energy efficiency, by ensuring that your chimney system functions properly and that your heating system has adequate air to burn effectively, or by selecting sealed combustion equipment when replacing a heating system.  For more information on health and safety considerations, visit the Health & Safety page.  You may also want to visit the Tools & Resources page and discuss your concerns with your heating professional.

Learn More

Visit the pages below to learn more about Heating & Cooling: