Furnaces

Furnaces

Whether you are investing in a new furnace or improving the performance of an existing one, reducing the amount of energy you use to heat your home will save you money, conserve natural resources and improve the comfort and air quality of your home.

Gas furnaces are available in more efficient models than oil furnaces and require less maintenance.

If your home is drafty and under-insulated, do the air sealing and insulation you need to do first, and then replace your heating system.  You’ll be able to downsize the system, and save even more!

You can also get considerable savings by properly maintaining your unit and setting the thermostat low at night or when you are away.

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What are my options?
How to buy?
Energy-Saving Tips

What are my options?

Condensing Furnaces.  Recommended by the American Council for an Energy Efficient Economy (ACEEE), a condensing furnace has an AFUE 90% or higher. ENERGY STAR qualified oil and gas furnaces have (AFUE) ratings of 83% and 90%, or higher, about 15% more efficient than standard models.

Variable Speed Furnaces.   These units can operate at a lower fire and fan speed, giving them a lower heating capacity when full capacity is not needed.  But they also offer certain advantages such as:
A quieter heating process.
Slower airflow, which uses less energy.
Better temperature control.

Sealed Combustion Furnaces.  These contain an air-intake pipe as well as an exhaust pipe, preventing damage to the unit caused by vapors from home laundries and reducing the danger from back drafts (exhaust gases down a chimney).

Costs.  Condensing units cost more than non-condensing units, but their higher efficiency will lower your energy bill and thus save you money in the long run.

High-efficiency units usually cost just $500 to $1,000 more than mid-efficiency units, and some utilities offer rebates that cover the difference.  The payback period for savings depends on local energy costs, the price of the unit, the climate, and the difference in efficiency between the old and new furnaces.

Fuel Type.  Most furnaces are powered by oil, gas, or propane.  Oil is generally as readily available in this area as gas or propane, but may have some disadvantages:
Nozzles can become clogged or worn out.
Oil furnaces need to be cleaned more often and the fuel filter must be changed.
Oil furnaces generally cannot be fitted for variable firing rates.
Oil furnaces may consume more electricity than gas furnaces and usually are not available in very high efficiency or condensing designs.
Per btu, fuel oil is now more expensive than natural gas
Fuel oil is a dirtier fuel than natural gas, with approximately 40% more CO2 emissions.

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How to buy?

Sizing a Furnace. Determining the appropriate capacity of the furnace is crucial.  Furnaces that are too small will not heat the house properly in the coldest weather, while furnaces that are too big will cost more and operate less efficiently.  They can also lead to temperature swings that create discomfort. The capacity will depend on the amount of Btu/h (British Thermal Units per Hour) needed to generate sufficient heat for your home.

The size of the house is one of many factors that will determine the appropriate size of your furnace.  Other factors include:

• Size, shape, and orientation of the house.
• Local climate.
• Insulation levels.
• Window area, location and type.
• Type of house construction and configuration.
• Air infiltration rates.
• Heating needs of the occupants.

You should use a professional to install the system.  When sizing a new system, make sure the contractor uses a sizing tool such as ACCA Manual J to calculate the heat loss that will occur during the coldest possible weather.

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Energy-Saving Tips

Efficiency. The efficiency of a furnace is indicated by its Annual Fuel Utilization Efficiency (AFUE).  This is the ratio of the heat output compared to the total amount of energy consumed. Although this rating does not account for some heat loss in the ducts, furnaces sold today are typically between 78% AFUE and 96% AFUE.

Below summarizes the general ranges of heating systems in relation to their efficiencies:

Old, low-efficiency gas heating systems:
Natural draft that creates a flow of combustion gases.
Continuous pilot light.
Heavy heat exchanger.
68% -78% AFUE.

Mid-efficiency gas heating systems:
Exhaust fan controls the flow of combustion air.
Electronic ignition (no pilot light).
Compact in size and weight to reduce cycling losses.
Small-diameter flue pipe.
80%–83% AFUE.

High-efficiency gas heating systems:
Condensing flue gases in a second heat exchanger for extra efficiency.
Sealed combustion.
90-96% AFUE.

Efficient furnaces cycle on and off less often and have more advanced controls to provide the desired temperatures throughout your home. Various efficient furnaces, like sealed combustion units, harness the products of combustion, reducing the exhaust temperature and providing more heat for your home.

Replacing your old furnace with a 90% AFUE furnace could reduce your energy consumption and costs by more than 30%.

For Retrofitting Furnaces.  By adding certain devices to your existing system, you can increase the efficiency and save money on your energy bill. 

Addition of a vent or flue damper. Prevents chimney losses.
Closes off vent when furnace is not on.

Intermittent ignition devices.  Eliminate a continuous pilot light.
Applies to older systems that are equipped with a continuous pilot light.
Are difficult to install: Be sure to use a professional
Cost about $250 and typically have a payback period of less than 10 years.
Save money in fuel costs, but are not always cost effective for aging equipment.

Derating Gas Burners.  Reducing the size of the burner.
Applies to the commonly oversized systems.
Reduces the heating capacity of your gas furnace making it operate more efficiently.
Reduces the size of the gas burner orifice, and possibly also the baffles.
Difficult process that should only be performed by a qualified technician.
The modifications should cost less than $100 and can save up to 15% of your fuel costs.

Conservation and Efficiency Tips. The easiest way to lower your energy bill is to conserve the generation of heat.

Thermostats. Set backs save money.
At night and when you are away from home, turn down the thermostat.  You can save about 1% of your heating bill for every degree that you lower the thermostat for at least 8 hours each day.
Turning down the thermostat from 70°F to 60°F saves about 10% ($100 saved per $1,000 of heating cost).
 
Programmable digital thermostats. With this device, you can adjust the times you turn on your furnace according to a pre-set schedule. This way, the unit does not operate as much when you are asleep or when the house is not occupied. Programmable thermostats store and repeat temperature settings based on a weekly schedule.

Maintenance.  Improves furnace efficiency.
Clean or replace the air filters within the system.
Clean registers and make sure the return and supply registers are kept clean and not blocked by furniture, carpets, or drapes.

Tune up the unit regularly.  Oil-fired systems should be tuned up and cleaned every year, gas-fired systems tuned up every two years, and heat pumps every two or three years.
Regular tune-ups cut heating costs and also increase the lifetime of the system, reduce breakdowns and repair costs, and cut the amount of carbon monoxide, smoke, and other pollutants emitted into the atmosphere.

Duct Sealing.  Reduce energy losses. In homes heated with warm-air heating, ducts should be inspected and sealed to ensure adequate airflow and eliminate loss of heated air. Ducts can often leak as much as 15-20% of the air passing through them.
Leaky return ducts can bring additional dust and humidity into living spaces. Thorough duct sealing can cost several hundred dollars but can cut heating and cooling costs in many homes by 15-20%.

Check the airflow.  Airflow through the unit should be checked to meet manufacturers specs. High airflow can result in an increased duct leakage and does not provide maximum home comfort.  If airflow is too low, distribution efficiency drops and accelerates the wear on system components, leading to premature failure.

Wasted Fan Energy. If your furnace is improperly sized or if the fan thermostat is improperly set, the fan may operate longer than it needs to. If you're getting a lot of cold air out of the warm-air registers after the furnace turns off, have a service technician check the fan delay setting.

Benefits to You and Your Community. Investing in an efficient unit can save you money, increase the comfort of your home, and conserve natural resources.  Reducing consumption or moderating the amount you heat your home as well will result in long-term economic benefits for you, your family and the environment.  It will also lessen dependence on imported oil and gas.

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