These clever devices give you a new way to zone a forced air heating or cooling system. They're cheaper than motorized dampers, equally automatic, and easier to install. Balloons in your ducts can mean substantial savings but their big benefit is a more comfortable home.

By EVAN POWELL

Chances are most rooms of your house are empty at any given time, yet your heating and cooling system probably sends as much of its output to the empty rooms as to those that are occupied.

That's only one problem with standard forced air heating and cooling. In some houses there are others: An upstairs may be perpetually overheated unless the downstairs is kept uncomfortably cool. A south-facing room may be too hot every sunny afternoon. Or the kitchen may be oppressive whenever someone's cooking. The answer to all these problems is to divide the house into zones that you can heat and cool separately. With hydronic (hot-water) heat distribution, zoning is a common practice.

Now, with a new system developed by Retrozone Systems Corp. of Plano Texas, it may become more common with forced-air distribution too. The system, called Airzone, uses inflatable dampers in the ducts. When a zone's thermostat calls for heat (or cooling in summer), the FlexDampers are deflated, allowing the air to flow through freely. Meanwhile, dampers in ducts to zones that need no conditioned air are inflated by an air pump, puffing up to block airflow. Solenoid valves and a control panel run the show.

The Airzone system can be used with a heat pump as well as with gas, oil, and electric furnaces, and with air conditioners. I installed one in my house and have found it to be the best answer yet to maximizing both efficiency and comfort. The Airzone equipment is relatively inexpensive, and installation is simple enough that most homeowners can do it themselves.

While zoning a hydronic heating system is easily done with valves, to zone a forced-air system you have to install motorized dampers. They work, but they're expensive, and installing them is tedious: You cut out a section of metal duct at each branch run and insert a damper. In newer homes with flexible ducts, you have to install sections of metal ducting to hold them.

Rubberlike dampers seal ducts as they fill with air-via a pump, fortunately.

Before the Airzone system came along, I had installed manual dampers to divide my home into living and sleeping zones and maintained the latter at cooler temperatures in winter. These dampers balance airflow, but do not open or close zones.

They did save energy, but left a problem: A room on the north side of the house that has glass on two sides was always too cold in winter and too warm in summer. Even adding a third supply duct didn't cure the problem but the Airzone system did. The reason: By cutting airflow to areas that don't need it, there's now more available for that room. In effect, I've increased the capacity of my furnace and air conditioner. In larger houses, zoning can mean that one heating or cooling system will suffice where two would be required without it.

 The inventor of the FlexDamper, Jerry Tartaglino (now president of Enerzone), set out to solve his own problem. Then a regional manager for a company that installed energy-management systems in large commercial buildings, Tartaglino wanted a scaled-down version in his own house. "I lived alone and didn't want to heat and cool the whole place," he says. But when he analyzed his ducting and priced motorized dampers, the cost was prohibitive.

He's not sure how the idea of inflatable dampers came to him, but he started experimenting. "I stuffed kids' punching bags into the ducts, and rigged a compressor from a little tire inflator," he recalls.

When this inventor talks about losing sleep over his ideas, he means it. "Several times I was awakened by explosions," he relates. "You can't imagine how well noise carries through ducts until you have a big boom in the middle of the night." Those punching bags burst after a few inflation / deflation cycles.

Nevertheless, Tartaglino applied for and got a patent on the inflatable damper concept, and eventually got two $45,000 development grants from the Department of Energy.

One of the biggest barriers to commercialization was UL approval, Tartaglino reports. Eventually, he interested Du Pont in his concept, and that company developed a synthetic elastomer material that could undergo indefinite inflation cycles (no more midnight booms) and would not contribute toxic gases in case of fire. The now-UL-approved material, which

Read Page 2