Heated debate: When is it wise to replace a furnace?


The decision to replace a furnace or heating system can be one of the most challenging homeowners ever face, especially if the old unit isn't completely defunct.

Energy and utility experts talk about efficiency ratings and paybacks, but what most people have to decide is how comfortable they will be, physically and financially.

A Baltimore homeowner wrestling with the problem of saving energy costs writes: "My major energy waster is an oil-fired burner originally built to burn coal. . . . Although I replaced most of the windows in the house with double-paned windows and we turn down the heat at night, we don't seem to be making much progress in cutting consumption."

This homeowner has already done a lot of research. He called his local utility supplier, Baltimore Gas & Electric Co., for an energy .. audit, and at its suggestion, he called the previous owner's oil supplier to find out how much oil they burned in a heating season (980 gallons). He figures his old furnace operates at 67 to 70 percent efficiency, that is, 67 to 70 percent of the fuel burned results in heat supplied. Since December he has used 450 gallons of oil, so he's probably operating the old unit about as efficiently as possible.

Should he replace it? The estimated cost of a new, more efficient gas-fired unit is $2,700. The homeowner figures his yearly savings at $300-$400, meaning the cost of the system would be paid back in seven to nine years.

The question of payback is not how much, but how long. Will the homeowner live in the house long enough to recoup the investment? Most don't.

"It's almost never cost-effective to replace an existing furnace or boiler that still runs reasonably well," said Gustin Kiffney, of Energyworks, a Baltimore energy-consulting firm.

When an old furnace breaks down and has to be replaced, Mr. Kiffney said, it's worth spending an extra $500 or so to upgrade to a 90-percent-efficient unit; but it may not be worth spending a few thousand dollars on a state-of-the-art unit (95 percent efficiency and above), because the payback period is so long.

It may be possible to shorten the payback period. BG&E; is offering a new "Residential Rebate Program" for customers who install high-efficiency heating and cooling equipment. The rebates range from $80 to $700, depending on what kind of equipment is installed.

The rebates "help offset the incremental costs of going from mimimal efficiency to high-efficiency," said Bob Martin, BG&E; conservation specialist. "So they get a good portion of the incremental cost back initially, plus they will save annually because their operating costs are going to wind up being lower."

The program operates through local contractors; interested homeowners will have to do a fair amount of research to make sure the program is for them. It's important to start with a good bid; the rebate won't do much good if you're paying too much for the equipment.

The homeowner had also gotten a suggestion that, instead of replacing the entire unit, he install a flame-retention burner in the old unit; he was told it would raise the efficiency to about 80 percent. However, the energy auditor questioned whether a boiler already modified from coal to oil would benefit that much from a new burner.

The problem with an older boiler, said Steve Strain, owner of Modern Heating and Air Conditioning of Baltimore, is that the fuel has to heat a huge amount of water. Newer systems apply the heat more directly. Increasing the efficiency of a burner in an older system won't reduce the amount of water that has to be heated. You've still got an old boiler. The 80 percent efficiency may apply only to what's going up the flue, and not to the total efficiency of the system.

So there's no clear answer here; a start would be to calculate the payback on an expenditure of $570 if the efficiency goes from 70 to 80 percent.

The homeowner wondered about a couple of other options. How about a wood-burning stove that would heat only the most-used areas of the house? But he was concerned about the stove's impact on indoor air quality and its impact on the environment.

The main problem with a wood stove is that the wood is usually not free. A cord of wood can cost $100 or more, and Mr. Kiffney said the stoves are rarely more than 50 percent efficient. He also said there will be some products of combustion introduced in the house; you may not notice smoke, but there will be small particles. He also questioned the wisdom of burning trees for heat: "It's renewable, but not as fast as people are burning them."

Mr. Kiffney also noted that some states require a catalytic device in the stove chimney to remove pollutants.

Finally, the homeowner wondered if it would be worthwhile to turn the heat down further at night, from his current 60 degrees to 55 degrees, and heat the sleeping area with an oil-filled electric heater.

The answer to this one is an unqualified yes.

"Anytime you can utilize a warm-room concept, do it," Mr. Martin said. You can always save by not heating the whole house.

As for setting back the thermostat, Mr. Martin said, the saving is 3 percent per degree over a 24-hour period. "So if you used to keep it at 60 and now you keep it at 55, all the time, you're going to knock off 15 percent of your annual heating bill."

Next:Tackling bathroom moisture problems.

Mr. Johnson is construction manager for Neighborhood Housing Services of Baltimore. Ms. Menzie is a home writer for The Sun.

If you have questions, tips or experiences to share about working on houses, write to us c/o HOME WORK, The Sun, 501 N.

Calvert St., Baltimore 21278. Questions of general interest will be answered in the column; comments, tips and experiences will be reported in occasional columns.

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