Q _ My furnace needs to be replaced and I want to get a new super-high-efficiency model. What are the highest efficiency models available and how can I determine whether gas, oil, or a heat pump is my best choice? T.J.
A _ There are many new super-high-efficiency heating systems available. Some have efficiencies as high as 96%. This means that only 4 cents of each energy dollar is lost out the flue. Your existing furnace may lose as much as 45 cents of each dollar out the flue.The highest-efficiency gas and oil furnaces utilize a special secondary condensing heat exchanger. This heat exchanger captures the remaining heat from the flue gases after they leave the primary heat exchanger. The comfort level in your house is also better with these furnaces.
Water vapor (steam) in the flue gases, which normally goes up the flue, is condensed into water in the condensing heat exchanger. This change of state from vapor to liquid releases additional heat for your house.
Since most of the heat is removed from the flue gases and they are cool, they are vented outdoors through a small plastic pipe. This is great advantage when switching from electric heat to gas or oil. You do not have to build an expensive chimney or insulated vertical flue pipe.
In order to exhaust the cool flue gases (they are not hot enough to naturally rise up and out), a special induced draft blower forces them outdoors. This is also a very safe feature because it minimizes the chances of flue gases and carbon monoxide backdrafting into your house.
These new-super-high-efficiency furnaces also often utilize a special variable speed blower. This feature is usually needed with the new high-efficiency central air conditioners too.
The efficiency and reliability of heat pumps has been greatly improved over the past decade. Variable-speed blowers and compressors, and the new quiet scroll compressors, cut electricity usage considerably.
Your most efficient choice depends on the relative gas, oil, and electric rates in your area. Your heating contractor should have a cost comparison chart of operating costs for each system at various efficiencies and rates.
You can compare the operating costs yourself. The heat content of fuels is - 1 cubic foot of gas equals 1,025 Btu, 1 gallon of oil equals 138,700 Btu, 1 kilowatt-hour of electricity equals 3,413 Btu. Based upon your local rates and the efficiencies of each type of furnace or heat pump, you can determine the cost per Btu of heat output for each system.
You can write to me for UTILITY BILLS UPDATE No. 102 showing a buyer's guide of the super-high-efficiency gas and oil furnace and heat pump manufacturers, model numbers, capacities and efficiency levels, and a fuel cost comparison chart to determine which type of system is best for you. Write to the Deseret News c/o James Dulley, 6906 Royalgreen Dr., Cincinnati, OH 45244. Please include $1.00 and a self-addressed STAMPED BUSINESS-SIZE envelope.
Q - I am redecorating my living room and I plan to hang a large mirror. Will it save much energy to hang the mirror on an outside wall so it reflects the heat indoors? M. G.
A - A standard glass mirror reflects visible light, but does not reflect much heat radiation. A polished aluminum or other metal surface reflects much more heat indoors away from the outside wall. Although the glass mirror reflects little heat, it will create a narrow air gap between itself and the wall. This reduces the convective heat losses from air movement.