Ask Energenie

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1. What is the advantage of purchasing gas-filled glass windows? Does the gas leak out over time, and if so, how does that affect how well the window insulates?
2. I have a large west window that gets a lot of sun in the summer. I'm thinking of purchasingadjustable blinds to restrict the sun as well as provide privacy. Which would work better, horizontal or vertical blinds??
3. With the increase of gasoline prices to over $1.50 per gallon, I need to improve nay gas mileage.Can you review those tips given out during the later 1970s and 1980s?
4. What is the R-value of soil?
5. What are some advantages and disadvantages of using multiple window air conditioners rather than a central system?
6. I have trouble finding the 40-watt fluorescent lamps anymore. Seems like they are all 34- or 32-watt lamps. Can I use these as replacements in my old light fixtures?
7. Which type of fan is the most economical to use for summer cooling?
8. What should I do with my humidifier during the summer?
9. What can I do to reduce humidity in nay home and ease the load on my air conditioner?
10. Is it cost-effective to buy high-efficiency air conditioning units?

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1. What is the advantage of purchasing gas-filled glass windows? Does the gas leak out over time, and if so, how does that affect how well the window insulates?

"The advantage of having argon gas between the panes of glass is that argon has a higher thermal resistance than air does," said Richard Nelson, extension speciahst at Kansas State University.

Nelson explained that argon has a higher R-value because it is denser than air. This reduces heat transfer within the air space.

"Argon-filled glass windows have insulating values anywhere from R-2.5 to R-3.2, while air-filled windows have R-values slightly over two," he said. "For homes with a significant amount of window area, say 25 to 40 percent of the house's square footage, this R-value difference can cut energy costs significantly."

Over time, argon gas may leak out of the space between the panes of glass, Nelson said.

The amount lost depends on how well the window was manufactured and the quality of materials used.

He said argon leaks are usually caused by failure of the seals between the glass and the edge spacer. Also, some gas is lost because it diffuses through the seals.

"Even if the argon gas does leak, the window's thermal performance isn't affected much as long as there is no noticeable failure of the seal."

Tests have shown that if an argon-filled window leaks five percent of its gas each year, it will lose only 12 percent of its R-value after 20 years.

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2. I have a large west window that gets a lot of sun in the summer. I'm thinking of purchasing adjustable blinds to restrict the sun as well as provide privacy. Which would work better, horizontal or vertical blinds?

"Both types, when fully closed, are equally effective, assuming they have the same reflectivity," said Doug Walter, president of Kansas Building Science Institute, Manhattan.

Horizontal bhnds, however, must be completely closed whenever sunlight strikes the window.

Walter said this is necessary because the sun is very low in the sky when it strikes west windows late in the afternoon.

"On the other hand, you can adjust vertical blinds to block direct sunlight but still allow a view through the window," he said.

The angle of vertical blinds should be perpendicular to the sun's position. You may have to make several adjustments throughout the afternoon and evening.

"Choose blinds with a light or reflective surface," Walter said. "Also, keep in mind that external shading is more effective than internal shading."

External shading options include awnings, solar screens, shutters and vegetation.

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3. With the increase of gasoline prices to over $1.50 per gallon, I need to improve nay gas mileage.Can you review those tips given out during the later 1970s and 1980s?

"Joining a car pool, walking instead of driving, and owning a fuel-efficient automobile are some of the best ways to reduce your cost of gasoline," said Gene Meyer, extension mechanical engineer at Kansas State University. "Remember to plan your driving to minimize trips."

Here are several other tips to help improve you car's gas mileage.

• Have your car tuned. An engine tune-up can improve car fuel economy by an average of one mile per gallon.
• Keep your tires properly inflated. Underinflated tires can decrease fuel economy by up to one mile per gallon.
• Slow down. The faster you drive, the more gasohne your car uses. Driving at 65 miles per hour rather than 55 miles per hour reduces fuel economy by about two miles per gallon.
• Avoid jackrabbit starts. Abrupt starts require about twice as much gasoline as gradual starts.
• Pace your driving. Unnecessary speedups, slowdowns and stops can decrease fuel economy by up to two miles per gallon. Stay alert and drive steadily, not erratically. Keep a reasonable, safe distance from the car ahead of you and anticipate traffic conditions.
• Use your air conditioner sparingly. The use of air conditioning can reduce fuel economy by as much as two miles per gallon under certain speeds and operating conditions.
• Avoid lengthy engine idling. Turn your engine off when you are delayed for more than a couple of minutes.

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4. What is the R-value of soil?

"The resistance of soil to heat flow (R-value) varies a great deal, depending on the type of soil and the moisture content," said Gene Meyer, extension mechanical engineer at Kansas State University. "In general, soil is not a good insulator."

For a fine-grained soil with 20 percent moisture content, the R-value is about I per foot, roughly the same as concrete.

"Because of this low R-value, it is important to insulate foundations, including slabs-on-grade, crawl space walls and full basements. Insulating the first few feet below grade is the most critical area, but we recommend full-depth insulation."

Additional information on insulating foundations is available by calling 800-KSU-8898.

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5. What are some advantages and disadvantages of using multiple window air conditioners rather than a central system?

"If you wish to continually cool your entire home, a central system is more convenient to operate," said Richard B. Hayter, director of Engineering Extension Programs at Kansas State University.

Another advantage of a central system is that it runs quieter.

"Generally speaking, the energy efficiency of top-of-the-line central systems will be higher than that of window units," Hayter said.

However, you can buy window units that have higher efficiencies than some central systems.

Compare the Seasonal Energy Efficiency Ratio (SEER) when selecting units-the higher the SEER, the higher the efficiency under similar conditions.

Hayter said the main advantage of window units is that you can operate them individually.

"This allows you to cool only occupied rooms instead of the entire home," he said. "So, if you're careful, your annual air conditioning cost should be lower if you use multiple window units."

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6. I have trouble finding the 40-watt fluorescent lamps anymore. Seems like they are all 34- or 32-watt lamps. Can I use these as replacements in my old light fixtures?

"The standard 40-watt, four-foot fluorescent tubes have been all but replaced by energy efficient 34-watt lamps," said Gene Meyer, extension mechanical engineer at Kansas State University.

The Energy Policy Act of 1992 mandates that energy efficient lamps be sold for general service fluorescent application. Exceptions exist for lamps used in low-temperature applications and certain other situations.

"The 34-watt lamps should operate fine in most fixtures," Meyer said. "If the ballasts are very old, they may fail soon after the installation of the energy-efficient lamps. However, ballasts of that vintage are very inefficient and replacing them with energy efficient lamps and ballasts will reduce your energy costs."

Consider replacing lamps and ballasts with the newer T-8 style lamps and electronic ballasts.

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7. Which type of fan is the most economical to use for summer cooling?

"Selecting a fan involves more than just looking at operating costs," said Bruce Snead, extension specialist in residential energy at Kansas State University.

He said these factors will affect your choice of fan: volume of air to be moved (measured in cubic feet per minute), speed and configuration of the airflow, nature of the space, and activity that occurs in the space.

Other factors to consider include safety features, quietness, appearance and price.

"The wattage rating of the fan determines its operating cost," Snead said. "The lower the wattage, the lower the operating cost."

The following list will help you compare different types of fans by operating costs. The costs are based on one hour of operation at a rate of 8 cents per kilowatt-hour of electricity. At this rate, a table top oscillating fan would use a penny of electricity, a ceiling fan about a penny and a half, a box fan two cents, whole-house fan three to four cents, and a small window air conditioner five to six cents.

"Each type of fan has limits to its use, and you must consider these before making a purchase," Snead said.

"For example, oscillating and ceiling fans only circulate air, so they are not effective in exhausting air or drawing a fresh supply inside," he said.

Another example of limited use is a ceiling fan, which creates air motion in a fixed location. On the other hand, oscillating and box fans are portable. When a-box fan is set in an open window, it can exhaust or supply air, giving it added versatility.

Snead said whole-house fans are fixed and only exhaust air, but draw cooling breezes throughout the house.

"Fans are a low-cost cooling option, but their effectiveness depends on the temperature of the air theyare moving."

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8. What should I do with my humidifier during the summer?

"Because you seldom need humidifiers in the summer, you should clean them and store them dry," said Gene Meyer, extension mechanical engineer at Kansas State University.

"If yours is a room humidifier, simply drain the water," he said.

Clean out scale with a mild detergent and inspect the media element and clean or replace it if necessary.

The media element is the surface, such as a foam pad or metal grid, that is kept wet to allow for evaporation.

"Always unplug your humidifier before cleaning," Meyer advised.

If you have a central humidifier, shut off the power and water to the unit. Wash any scale or debris from internal parts. Again, you may need to clean or replace the media element before you use the humidifier next winter.

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9. What can I do to reduce humidity in nay home and ease the load on my air conditioner?

"If you have an older, leaky home, the primary source of moisture is humid outside air that enters," said Doug Walter, president of Kansas Building Science Institute, Manhattan.

This often happens if you open storm windows for ventilation and do not close them later when the air conditioner is running.

"If you air condition your home most of the summer, manage the house as if it were winter," Walter said. "Keep storm windows closed and lock primary windows to increase their air-tightness."

With the house tightened, you should try to minimize the amount of moisture you generate inside.

Because most of this moisture originates in the kitchen, bathrooms and laundry, run exhaust fans in these areas whenever you generate moisture. Also, make sure you have vented your clothes dryer properly to the outside.

Because house plants also generate moisture, consider moving them outside to a protected area during the summer.

Poor surface drainage around your house can be a source of unwanted moisture. Make sure the ground slopes away from your foundation. Downspouts should have extensions that divert rain water several feet away from the foundation. If you have a crawlspace under all or part of your house, place a 6-mil plastic vapor barrier over the soil.

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10. Is it cost-effective to buy high-efficiency air conditioning units?

"Yes, if the unit serves a home or business that air conditions throughout the summer rather than on an intermittent schedule," said Gene Meyer, extension mechanical engineer at Kansas State University. "The additional cost of the higher efficiency units can be justified from the energy savings.

The minimum Seasonal Energy Efficiency Rating (SEER) is 10, but the Department of Energy is considering increasing the minimum to a SEER of 12.

Homeowners and business operators can justify the purchase of air conditioners with a SEER of 13 or 14 in applications where energy costs are high or the cooling season is long.

"In buildings used less frequently, such as churches and meeting rooms, energy savings usually won't offset the cost of the highest efficiency units," Meyer said.

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Ask Energenie is produced by the Kansas Energy Extension Service through Kansas State University. This material was prepared with the support of the U.S. Department of Energy (DOE) Grant No. DE-FG48-97R802102. However, any opinions, findings, conclusions, or recommendations expressed herein are those of the author(s) and do not necessarily reflect the view of DOE.