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after October 31, 1999
Claudia Chandler (916) 654-4989
Media and Public Communications Office
1,089 Words
(Fifth in a series of 10 feature articles for 1999)


Leaky Ducts Can Cost Big Bucks


One of the bathrooms in Susanne Garfield's Northern California home had no heating vent. "The room was always uncomfortable - too hot in the summer, too cold in the winter," she complained. So she hired an air conditioning company to install a heater outlet in the bathroom.

When the technician crawled under the house, he discovered ductwork was already in place leading to the bathroom. It snaked across the ground, open and unconnected at the far end.

"The original contractor who installed the central air conditioning system apparently forgot to cut the hole and install the bathroom vent as he planned," said Garfield. "As a result, conditioned air was pumping out of the end of an open duct. It turned out that for more than a year we'd been wasting money by heating - or air conditioning - our crawl space and the great outdoors!"

When the open duct was attached to a properly working vent, Garfield's bathroom was finally comfortable. Better yet, her summer electricity bill dropped by $15 a month.

Such horror stories illustrate why properly working heating and cooling ducts are an important factor in energy efficiency. By sealing duct leaks, a homeowner can save an average of 10 percent of the energy required to heat and cool a new California home, according to field research performed by the California Energy Commission.

Today's ductwork consists of insulated flexible tubes that snake across the attic floor or under the house. Unfortunately, heating ducts are out of sight and therefore out of mind. Homeowners wouldn't put up with leaking water pipes. But ductwork - carrying air instead of water - can leak for years, without anyone knowing it.

Ducts can leak for reasons as simple as a protruding nail in the attic that snags and tears the duct when it's being installed. Then, too, joints and junctions where two pieces of duct come together may separate over time. Scientists at the Lawrence Berkeley National Laboratory late in 1998 made a startling discovery - ever-popular duct tape was useful for hundreds and hundreds of tasks, but holding ducts together wasn't one of them.

Over three months, researchers tested duct tape and 31 other sealants under accelerated laboratory conditions that mimicked long-term use in the home. They blasted air heated to nearly 170 degrees and cold air chilled to below 55 degrees through ducts. They baked them at temperatures up to 187 degrees to simulate the oven-like conditions of a closed attic under a hot summer sun.

"Of all the things we tested, only duct tape failed. It failed reliably and often quite catastrophically," said Berkeley Lab division head Max Sherman.

Instead of duct tape, the researchers recommended sealing ducts with mastics, gooey sealants that are painted on and allowed to harden.

Problems also occur when ducts are blocked or kinked. Just as a pinched garden hose cuts down the flow of water, a kinked duct drastically reduces the flow of air. This can happen when ducts are forced into tight places under the floor or in the attic.

Design is important as well. Improperly designed systems may have ducts that are too small for the amount of air they are supposed to carry, or a duct that is too large in one room may siphon off conditioned air that should be going to another part of the house. The air conditioner or heater may be either undersized or too large for the duct system, providing too little or much more pressure than the system was designed to handle.

Sacramento resident Patti Berg discovered both of those duct nightmares - poor design and blockage - after she and her husband moved into a new apartment. Very little conditioned air came through the register in their bedroom, leaving the room too hot in summer. When she removed the grill, she discovered that a previous renter had blocked off most of the duct with cardboard. "I guess it was the other tenant's way of trying to adjust a duct system that wasn't very well designed, but it was causing us to run the air conditioner much more than we need to now," said Berg.

Her experience demonstrates why it's a good idea to have your duct system examined for leaks, blockages, and just poor design. Air conditioning companies familiar with duct testing can perform the examination, and your local utility may give you a sizable rebate when you have it done. You may be amazed at the monetary savings and the dramatic increase in comfort.

The State's residential energy efficiency building codes were revised this summer to reflect the importance of duct systems. The California Energy Commission now gives energy efficiency credits to California builders who properly design, install, seal and test duct systems.

These energy credits provide builders with added flexibility in design, giving them more of a selection of what energy efficiency features they can provide in new homes. Studies by the building industry show that improving duct systems can be a less expensive way to comply with energy efficiency building standards than some other options that have been available.

The new code revisions were supported by the building industry as a way to improve construction practices, and to help safeguard against potential construction defect litigation.

Across the country, heating and air conditioning accounts for a whopping 44 percent of the energy used in U. S. homes. Thanks to our milder climate, Californians use on average only 30 percent of their energy to heat and cool their homes; but even at that figure, consumers can cut their utility bills considerably by preventing waste. When it comes to the quality of home duct systems, the opportunities for improvement are substantial, and the rewards - in both comfort and reduced energy bills - can be great.

Heating and cooling systems have markedly improved in efficiency over the past two decades, in part because of California's increasingly strict building standards. New products were developed that use less energy. Forced-air heaters offer a perfect example: 20 years ago, natural gas models were 60 percent to 70 percent efficient. Because of energy requirements, today's designs are as much as 97 percent efficient, producing more heat for much less money.

Since the Energy Commission introduced the first Energy Efficiency Building Regulations back in 1977, home construction techniques have also evolved. Today's homes are better insulated, with improved weatherstripping to keep heat inside during the winter. Windows have become increasingly more sophisticated, with high-tech coatings and gases between multiple panes of glass that improve their insulating value. As a result, energy savings can be startling - providing your duct system isn't squandering the benefits.


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This article is based on the California Energy Commission's Home Energy Guide, to be published early in 2000.

You can find additional information about energy in California on the Energy Commission's Web Site at www.energy.ca.gov.

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