Ask The Experts


I discovered that the brick chimney for my furnace is leaking water and ruining the nearby plaster in the house. My roofer insists that the seal at the roof is good and the furnace is new, but it is a very old chimney. Do I need a whole new chimney?

If the water leakage continues, the old chimney could become severely deteriorated and you might indeed need a new chimney. At this point, however, you may simply need to have the chimney relined. Houses from the early 1900’s or older usually have unlined chimneys. The interior surfaces of unlined chimneys, which are exposed to the exhaust gases from the furnace, are just bare brick. Brick is reasonably durable and resistant to deterioration from the hot gases that were produced by old inefficient furnaces. But modern furnaces extract more heat from the fuel, resulting in a cooler and wetter exhaust. Burning natural gas produces a lot of moisture. The moisture in this cooler exhaust condenses in the cold portion of the chimney in the attic and above the roof line. The moisture soaks the brick, deteriorating the masonry, as well as adjacent interior finishes. More recent masonry chimneys include a clay tile flue liner. The liner is much more durable and moisture resistant, but even so water can build up and damage can occur. High efficiency furnaces should never be vented to a masonry chimney due to the moisture. Modern mid-efficiency furnaces may be vented to a clay tile lined chimney if certain critical conditions are met, but never to an unlined chimney. In any case, if your chimney is getting excessively wet, the furnace was improperly installed. There are two possible solutions. One is to reline the chimney with a new stainless steel flexible liner. The new liner is typically installed from the top of the chimney down and tied directly to your furnace exhaust. The other method is to abandon the chimney and vent the furnace exhaust directly out the side of the house, using a special power blower unit to force the exhaust gases through the vent pipe to the exterior. Either method may work for you, but as houses become tighter and furnaces more efficient, chimneys will become obsolete. Power vents will be the more common way to vent exhaust gases from homes.

My heat bills have gotten ridiculous. I see ads for miracle portable heaters. Are these really as good as they sound?

The primary advantage of portable electric heaters is that they can provide heat right where you are located in the house, allowing you to turn down the thermostat on your whole house heating system. The energy saved by allowing the rest of the house to be cooler will result in lower overall heating bills.

There is a downside however. You won’t be saving money under all circumstances, and you may be uncomfortable. For example, when you move from one room to another, there will be a warm up period for the new location. Also, it won’t work well for you if you have a larger family using multiple rooms at the same time. In most cases, depending on your utility service provider, electric heat is significantly more expensive per unit of heat introduced into the house than other energy sources, such as gas or oil. So placing several electric heaters around the house may increase your overall heating costs, not lower them.

Another issue is the cost of the portable heaters themselves. All of the electricity that we use in our homes ultimately converts to heat. No portable electric heater is really any more efficient than any other. Every watt of electricity consumed by any portable heater converts to an equivalent unit of heat. The advantages of one heater over another might include nicer appearance, quieter operation, more even temperatures, and better distribution of heat, but not more heat per dollar spent on electricity. Radiant electric heaters may make you feel warmer for slightly less money than units with resistance coils and blowers, because the heat is radiating toward your body directly, rather than simply warming the air around you. But in any case no high priced “miracle” heater is any more efficient at converting electricity to heat energy than a cheap portable electric heater from the discount store.

We have a very large house with just my wife and I home now. We closed the registers in the extra rooms to save on our heat bills, but it doesn’t seem to be saving us any money.

Closing off some rooms to save heat can be a good energy saving idea. By concentrating heat in a smaller portion of the house, less heat will be lost through the envelope of the house to the exterior. There are a few things to watch out for however. First, it is important that the thermostat be in one of the rooms that you keep heated. If the thermostat is in a room with the heat supply closed, it will remain cool and will be continuously calling for heat, which the furnace will be unable to satisfy. Your furnace will be working harder and your heat bills will go up.

Another concern is that furnaces need a good flow of air to ensure efficient heat transfer. If you close too many registers, the overall air flow through the furnace is reduced, and heat transfer from the furnace to the air around the heat exchanger is also reduced as a result. The furnace will run hotter and may even overheat. When a furnace runs too hot, a higher percentage of the heat goes up the chimney, and you run the risk of damaging the heat exchanger. This could be a safety hazard as well as an added expense.

As heated air enters the rooms in the house, air should be returning from other registers in those rooms back to the furnace for reheating. Depending on the overall design of the ductwork, closing off several rooms may significantly unbalance the return air, resulting in some rooms that pull cold air in from the exterior through cracks and gaps in the windows and finishes, and other rooms that push heat out of the house through cracks and gaps.

Closing off a couple of rooms in a house may be very helpful, but shutting down heat to a larger portion of the house should be evaluated by a knowledgeable heating contractor to make sure that doing so will result in the safe and efficient operation of your heating system.

I just received my latest fuel oil bill and went into shock. I can’t afford to heat my house at this cost. What other type of heating system would be cheaper?

There are many different options that may be available to you. Assuming that you heat with forced hot air, we can make some simple comparisons that might be helpful when reviewing these options. At the present time the cost per BTU for fuel oil heat in a modern standard efficiency furnace is roughly equivalent to the cost of basic electric resistance heat at NYSEG residential rates. Electric resistance heat, except in local special rate districts, has been by far the most expensive heat type for many years, so it is no wonder you went into shock.

High efficiency oil furnaces tend to be problematic, if available at all, so your best bet is probably to change fuel type. Propane is roughly equivalent in cost to oil in a standard efficiency furnace, but with propane you can upgrade to a high efficiency furnace which will lower the cost per BTU to heat your house at present rates by 15 to 20 percent. Given the volatility of the markets though, this cost advantage could disappear.

If you are lucky enough to have natural gas available, you would be wise to convert. With a standard efficiency furnace you would pay less than half the cost of oil heat. With a high efficiency gas furnace you would save even more, resulting in heat at a third the cost of fuel oil per BTU. We know that natural gas prices are likely to go up, but we suspect that the cost will remain considerably below that of fuel oil.

Your other choices generally involve space heating rather than central forced air heat, and will require some attention and physical labor on your part to keep them running. But they can save significant money. Wood heat at 60 percent efficiency at current prices per cord is roughly one third the cost of fuel oil heat. Wood pellet heat at 80 percent efficiency at current prices per ton, and coal heat at 75 percent efficiency are also one third the cost of fuel oil. If you’re shopping for a new heating system, please remember that the efficiencies quoted above are common for the heat source type but may vary, resulting in higher or lower heating costs.

Whatever type of fuel you use, don’t forget to better insulate and seal your house to conserve heat.

We have a two story 3,900 sq. ft. home built in 2005 with 19 foot ceilings in the Great Room. Our propane bills are way too high, and the furnace cycles on and off all the time. Our house is tight and well insulated. What could be the cause of such high bills?

Historically, propane has been the most expensive of the standard fossil fuels. This, combined with the size of your house, probably accounts for most of your high heat bills.

However, the rapid cycling of the furnace that you mentioned can reduce its efficiency and increase your costs. This is usually caused by either of two problems. One is insufficient air flow through the furnace. If too little air moves through the unit, it will overheat. A safety device then shuts down the burners, which turn back on as soon as the furnace cools a little. Clogged furnace filters, a clogged AC evaporator coil, too few return air registers, too many closed registers, or registers covered with boxes or other clutter, all slow down air flow through the furnace.

Another potential cause for the cycling of the furnace that you mention may be a misadjusted heat anticipator in the thermostat. This device places a small electrical current through the coil in the thermostat to turn off the furnace slightly before the thermostat actually reaches its set temperature. This helps prevent wide swings in room temperatures, but if out of adjustment, can cause the furnace to turn on and off way too frequently.

If the furnace overheats or turns off before the blower delivers much heat to the rooms due to cycling, you’re going to lose your heat and your money up the chimney. Have your furnace serviced with these issues in mind. You may be able to save some dollars after all.

Is it acceptable to run the exhaust ducts from my bathroom ventilators to the roof overhang, or do they have to go directly outside? My contractor says it’s okay to go the eaves; my buyer’s inspector says it isn’t.

The bathroom ventilators are intended to exhaust warm moisture laden air from the bathrooms out of the house to prevent excess moisture and resultant mold and decay. The ventilators should exhaust directly to the exterior, not into the attic or the overhangs. The attic should be kept as dry as possible. When warm moist air enters the attic in winter, the moisture condenses on cold surfaces, resulting in mold and decay. If your ventilators exhaust into the attic, you’ve simply moved the problem from the bathroom to the attic. Even though there are vents in the overhangs of most homes, the exhaust will not leave the attic if directed to these areas. This is because air normally enters at the ventilated eaves and leaves the attic at the ridge or gable vents near the peak. This natural flow of air simply pulls the moisture from the ventilator exhaust ducting right back up into the attic.

The best approach is to direct the exhaust from the bathrooms to the exterior directly through the roof, or through a gable end wall. We have occasionally found ducts in the attic that are full of ice or water, making the ventilators useless. The ducting should be insulated and should be as short a route as possible to avoid moisture buildup in the ducting itself.

I have forced air heat and my house is very dry in winter. What type of humidifier do you recommend?

We actually would recommend against installing a humidifier if at all possible. Whole house units in particular are usually poorly maintained since they are out of sight and out of mind. They can become contaminated with mold, viruses, or bacteria, they often leak, causing damage to the furnace, and they may add too much moisture to the house if poorly adjusted. If a humidifier is absolutely necessary, we would suggest using a small portable unit, since it will be far more likely to receive adequate maintenance.

The type of heating system does not affect the humidity in a house, but there is usually a correlation with the age of the house. Older houses are generally drier than newer homes because they require more heating. When we heat the cold dry winter air that enters our house, we lower the relative humidity. The relative humidity is lower because warm air is capable of holding more moisture than cold air. So, if we warm a smaller total volume of air, or reheat it less frequently, by better sealing and insulating the house, we will reduce the dryness and save money at the same time.

We add moisture to the house as we breathe, cook, bathe, wash clothes, water plants, etc. This moisture can be sufficient in a “tight’ house to prevent excessive dryness. The key is to keep the cold dry air out, and keep the moisture that we naturally generate in, by maintaining a well sealed and insulated house.

I’m planning on installing a humidifier on my furnace so the house won’t be so dry this winter. Is there a brand or type that you would recommend?

In most cases we would recommend against installing any whole house humidifier at all. Most whole house humidifiers mount on the furnace ductwork and use the forced air furnace to blow moisture from the unit through the house. While most older homes do tend to be too dry for personal comfort in winter and humidifiers can alleviate the discomfort, they bring their own set of problems. Most humidifiers do not adjust themselves to appropriate moisture levels based on outdoor temperature, and because whole house humidifiers are out of sight and mostly out of mind, we don’t usually adjust them properly either. Consequently, as the exterior temperature drops, excess moisture tends to condense on the colder surfaces in the home, resulting in condensation on windows, in walls, and in attic spaces. This process can result in mold buildup, stains and decay. In addition, we don’t maintain and clean them adequately. Most humidifiers eventually leak due to mineral buildup and clogging. Depending on the location, the leakage can destroy an otherwise good furnace. Most importantly, poorly maintained humidifiers can pose a health risk. One of the most common humidifier designs consists of a plastic “hamster wheel” with nylon mesh wrapped foam applied around the circumference. This then dips into a pool of water, picking up the moisture which is blown into the ductwork as the furnace blower operates. The problem with this is that the foam acts as a filter and collects mold, bacteria and viruses which then proliferate in this constantly warm moist medium, only to be blown through the house on the next cycle.

If you must add moisture to the house, one option would be to purchase a room sized unit that you will be filling frequently, and which you will presumably monitor and clean as necessary as you add water. If you believe that a whole house unit would be appropriate for you, we recommend the type that uses a vertical mesh with a drain at the bottom. Water dribbles through the mesh from the top, and any that doesn’t get picked up as the air blows through simply drains out the bottom. You will need a floor drain nearby, or a condensate pump to handle the unused water.

I am getting conflicting information regarding salvaging my flooded appliances. Do the gas water heater and furnace have to be replaced, or can they be repaired?

All of the authorities with which we are familiar, including the American Gas Association and the Consumer Product Safety Commission, agree that the gas safety valves for appliances that have been submerged must be replaced to ensure proper safety function. These valves control the pilot flame and main burner flame. A thermocouple tells the safety valve if the pilot flame is lit, ensuring that the gas will ignite when the automatic safety valve opens. The proper function of gas safety valves is critical in preventing gas leakage or explosion. While the unit may function after being dried-out and cleaned up, it does not mean that critical parts will operate properly when needed to prevent a safety malfunction. Since water heaters generally have a relatively short life and other parts may also be damaged, including the insulation, and since replacing the valve is a significant percentage of the cost of a new unit, it is almost always the best decision to replace the water heater. The furnace or boiler may be worth salvaging, depending on age and type, but expect to replace any pumps or motors and any other safety devices or controls, in addition to the gas safety valve. Any motor that you manage to salvage will be likely to have a significantly shortened remaining life.

Incidentally, electrical breakers or fuses should not be salvaged either, according to the Consumer Product Safety Commission. In most instances, this would mean that replacement of the electrical service panel is recommended if it has been submerged. The wiring itself will probably be acceptable once all outlet and junction boxes are opened up and all connections cleaned and inspected.

In any case, extreme care should be taken when energizing any equipment that has been submerged. Shock hazards are very likely. We highly recommend professional help.

I had someone in to service my furnace. He says the heat exchanger is bad, and I need a new furnace. How do I know if this is true? I can’t afford a whole new furnace.

It would be nice to be able to trust what your service person tells you, but we are aware of several instances where homeowners were misled about the condition of their heating equipment and had the equipment replaced unnecessarily. The heat exchanger is a critical component in your forced air furnace and is a serious concern if defective. In essence it is a metal vessel inside your furnace that contains the combustion process. The flame and exhaust gases are contained within, and the forced air from your rooms is blown around the outside of this metal container, picking up the heat that is produced. If the heat exchanger is cracked or otherwise breached in any way, exhaust gases, potentially containing carbon monoxide, may escape into the air you breathe, rather than just go up the chimney. In almost all instances, if the heat exchanger is bad, the only cost effective and sure repair is to replace the furnace.

It would be very difficult for you to directly confirm if the heat exchanger is bad, but you can try. The crack or hole may be readily visible by looking up through the inlet area, where you can see the flame, but more often than not it is out of view. Soot buildup in the heat exchanger or around the inlet area is a clue that a breach may have occurred, causing poor flame quality and resultant soot. If the flame significantly changes its appearance or lifts off the burners when the blower kicks on, the heat exchanger is likely to be bad. There are other tests, such as using a small smoke producing device in the burner area to see if the smoke shows up at the registers, or using a combustion gas detector in the plenum or at a register, to help confirm the diagnosis. For your purposes though, we can only suggest that you let your service person know that you are concerned about the cost, and would like him or her to show you the crack or hole. While it may not be visible to you now as the furnace sits, it should definitely be visible once the unit is removed or the jacket taken off, if indeed there is a defect.

If it is any consolation, replacing the furnace with a new more efficient unit will very likely be cost effective, whether the heat exchanger was defective or not, if the furnace is 25 years old or older.