Home Improvement : CUT UTILITY BILLS : Water Heater Able to Warm House as Well

QUESTION: I need to replace my hot water heater soon. Are there any types of energy-efficient water heaters that can also heat my house through the central air-conditioner forced air system?

ANSWER: There are several natural or bottled gas combination systems that can heat your house and hot water. These are an ideal fit with the milder heating needs of your climate. Several of the smaller output systems are at the high-efficiency levels--about 85%. Some of the large systems are at the super-high-efficiency levels--about 94%.

The super-high-efficiency systems are of a condensing heat exchanger design. The cool exhaust flue gases are vented outdoors through a plastic pipe. Therefore, you do not need a chimney. This makes them an excellent replacement for an electric system where no chimney now exists.

One of these systems is basically a large heavily insulated water heater. It circulates the hot water through a heat exchanger coil in the furnace air blower section. When your wall thermostat calls for heat, a small pump flows the hot water through the heat exchanger.

The other super-high-efficiency system is basically a boiler with a heat exchanger coil in the blower. When you need hot water, a pump circulates the very hot water through a heat exchanger in the water heater tank.

The smaller high-efficiency systems use a more-standard hot water heater. It is connected to a heat exchanger coil in the furnace blower. The water temperature of about 140 degrees F circulates to the heat exchanger which heats the air. It is still about 120 degrees when it returns to the water heater. This is hot enough for most household hot water needs.

These smaller systems are a good fit with an existing heat pump. During the very mild weather, the heat pump is very efficient. When the weather gets a little colder, the gas water heater provides less-expensive heat.

One high-efficiency combination unit has the blower and duct connections built into the top of the water heater. All you have to do is attach the forced air ducts. This saves floor space and is easy to install.

With any of these combination systems, a central air conditioner is used as usual. The evaporator coil from the outdoor condenser unit is located in the air handler blower section. During the summer, the water heater only heats water and the water is not circulated to the blower.

You can write to me at the address below for Utility Bills Update No. 012 showing a list of manufacturers and output specifications for the large super-high-efficiency and the smaller high-efficiency combination water/space heating systems. Please include $1 and a self-addressed stamped business-size envelope.

Adding Insulation Long-Range Investment

Q: My house is constructed with brick veneer and insulated 2 by 4 studded walls. I would like to increase the wall R-value to at least R-19. Is it worthwhile to add more insulation to the indoor wall surface?

A: Generally, unless you are going to stay in your house for a very long time, it would probably not be feasible to add foam insulation board indoors. If you are involved in a remodeling job that requires the removal of much of the interior wall surface, then it may be feasible.

Another option is to add insulation to the exterior surface of your walls. This is the most efficient location for insulation. It blocks many of the air leaks into your house and your existing wall provides thermal mass. Several companies make special complete exterior insulation systems.