QUESTION: My gas water heater is leaky and doesn't provide enough hot water for morning showers. What are the highest-efficiency gas water heaters made and will they provide enough hot water?
ANSWER: Your water heater uses more energy than any other equipment in your home except for your furnace and central air conditioner. It typically accounts for 20% to 25% of your annual utility bills.
Installing a new super-high-efficiency water heater can save more than $100 a year and pay back its cost over its lifetime. The heating recovery time is quick, so there should be plenty of hot water in the morning. For a 50-gallon tank, heating rates are as high as 46 gallons per hour.
There are several new types of super-high-efficiency gas water heaters. One design uses a submerged chamber burner design. The other type utilizes an enlarged conventional heat exchanger area with pre-heated combustion air. Both have very high efficiency at about 85%.
In the submerged burner design, the heat exchanger is totally surrounded by water in the bottom of the tank. This greatly improves the heat transfer from the burner to the water in the tank so less heat is lost up the flue.
There are other advantages of a submerged chamber burner design. Since the burner is totally enclosed, it is much quieter when the burner is on. Also, you can set the water heater directly on the floor without any feet or locate it against a wall (zero-clearance).
The other new super-efficiency design has an extra-large, conventional combustion chamber area. The expanded heat exchanger area allows for more heat transfer to the water and less energy lost out the flue.
The combustion air, from your utility room or basement, circulates past the combustion chamber walls before it actually mixes with the gas and is burned. This pre-heating of the air improves the efficiency.
Whenever you select a new water heater, check the specifications for the amount of insulation in the tank walls. There can be considerable heat loss from the tank itself. The tanks with the highest insulation values, up to R-16, use foam insulation, not fiberglass.
You can write to me at the address below for Utility Bills Update No. 353 listing names, addresses and telephone numbers of manufacturers of super-high-efficiency gas water heaters, product information and specifications, and a chart showing the dollar savings. Please include $1 and a self-addressed stamped business-size envelope.
Old Insulation OK but Check for Asbestos
Q: I just bought an older house and I wanted to add some attic insulation. Is it necessary to remove the old rock-wool insulation before adding the new insulation?
A: If the old insulation is not damp or badly deteriorated, you should be able to add new insulation over it. Check under the old insulation for a vapor barrier attached to the insulation or for plastic film lying on the floor. If is has none, you may need additional attic ventilation to minimize the chance of condensation.
Since it is old insulation, it may have some asbestos mixed with it. Wear a mask and protective clothing when you are near it. Before you work up there, you should have a sample of the old insulation tested for asbestos. A polarized light microscopy test costs about $30 to $40 and it is well worth the small expense.