Increase Furnace Efficiency - Retrofit it
Furnaces and boilers can be retrofitted to increase their efficiency. These upgrades improve the safety and efficiency of otherwise sound, older systems. The costs of retrofits should be carefully weighed against the cost 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 gas heating system, you'll have the opportunity to install equipment that incorporates the most energy-efficient heating technologies available.
Other retrofitting options that can improve a system's energy efficiency include installing programmable thermostats, upgrading ductwork in forced-air systems, and adding zone control for hot-water systems, an option discussed in the Heat Distribution Systems section.
Gas-Fired Furnaces and Boilers
Gas furnaces and boilers can be fueled by either natural gas or propane with simple modifications accounting for the different characteristics of the fuels. Many furnaces and boilers operate on either natural gas or propane. Propane is usually more expensive as a fuel, but is available throughout the United States. Natural gas supplies depend on having a natural gas distribution system in your area, and areas at the end of the pipeline (such as the Northeast) tend to pay higher prices for natural gas.
A number of retrofits are possible for gas-fired furnaces and boilers, but before pursuing any retrofits you should consider the potential added benefits you could receive by simply replacing the furnace. The following retrofits are possible:
Vent dampers
The most common retrofit is the addition of a vent (or flue) damper. A vent damper prevents chimney losses by closing off a boiler's vent when the boiler isn't firing. Steam boilers benefit from vent dampers more than hot-water boilers, and bigger boilers benefit more than smaller ones. Vent dampers, however, may not be cost effective with properly sized, newer furnace models.
Intermittent ignition devices
Older furnaces and boilers with a continuous pilot light can be retrofitted with intermittent ignition devices. These devices are difficult to install and should only be installed by professionals. They cost about $250 and typically have a payback period of less than 10 years.
Although these intermittent ignition devices can save you some in fuel costs, they are not always cost effective when installed on aging equipment. If it's possible to turn off your furnace's pilot in the spring and to turn it on again in the fall, you can usually save the same amount of money as you would using one of these devices.
