Ask Energenie

July 1998

Table of Contents

1. What are "CFC's" and what effect do they have on our atmosphere?
2. Which vines or other plants shade windows or walls best during the susmer?
3. We are getting ready to re-roof our home. Is it best to use light or dark colored shingles?
4. If I berm my new house, how do I make sure I won't have water problems?
5. Why does my basement seem warmer when I run my dehumidifier? I thought it was suppose to feel cooler if the room was less humid.
6. Are there any quick checks that I can do to assure my air conditioner is working properly?
7. In the summer, is it cheaper to open my windows at night when it's cool outside or to just let my air conditioner run all night?

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1. What are "CFC's" and what effect do they have on our atmosphere?

CFCs are chlorofluorocarbons — a family of chemicals that contain chlorine, fluorine and carbon. They are used in a variety of products, possibly the best known being air conditioners.

"The recent concern with CFCs is the effect they have on the ozone shield in the earth's stratosphere," said Richard B. Hayter, director of Engineering Extension at Kansas State University.

"There is a variety of CFCs. If they are released to the atmosphere they eventually break down under exposure to ultraviolet rays, in turn releasing chlorine atoms," Hayter said. "These chlorine atoms break down the ozone molecules in the the stratosphere."

The ozone layer filters the ultra-violet rays produced by the sun and protects the earth from overexposure. The CFCs that are of greatest concern are those that are fully halogenated.

"CFCs that are not fully halogenated, such as most of the refrigerants used in residential and commercial air conditioning are not as harmful to the ozone layer," Hayter said. "Those that are not fully halogenated break up in the lower atmosphere and have a short lifespan."

However, they still have a limited effect on the ozone layer and thus will be phased out with time.

CFCs were once used in a variety of applications such as sterilizing agents, solvents, plastic foams, refrigerators and freezers, and automobile air conditioning and blowing agents in food packaging and other foams.

As a result of the international agreement commonly known as the Montreal Protocol, the compounds that had the greatest impact on ozone depletion are no longer manufactured in developed countries. New compounds and equipment have been developed that minimize or eliminate the potential for damage to the ozone layer. In addition, technicians who service equipment which use the compounds are well trained and certified in the techniques for minimizing release to the atmosphere. Also, the CFCs in equipment which is being serviced is recycled or captured rather than released to the atmosphere.

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2. Which vines or other plants shade windows or walls best during the susmer?

"Both horizontal and vertical shading can be created by plants, but most plants require a support structure to hold them in position," said Bruce Snead, extension specialist in residential energy at Kansas State University.

Horizontal shading by wisteria, roses, muscata or concord grapevines requires a fairly strong arbor or trellis. Silver lace vines can grow on cord or rope with some training of the tendrils.

Training involves manually setting the vine in the right direction so it will move along the lattice or string in the proper pattern as the vine matures.

Vertical shading of the west wall or windows can be accomplished by training vines to grow up lattices or a network of string. Virginia creeper, ivies, euonymus, and morning glories are good vines for vertical shading.

"The primary advantage of using plants to shade the windows of your home is that plants are better matched to the cooling season," Snead said. "Overhangs, awnings, and other fixed shading devices are effective, but as the path of the sun drops in August and September, more sun shines in, adding to cooling costs."

Plants provide shade throughout the hottest months. They leaf out at the beginning of the cooling season in May or June and remain that way until late September.

Plants, however, require proper care and may need to be trained to grow in certain paths if they are to be effective. ¶Contact your county extension agent or local nursery for more information.

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3. We are getting ready to re-roof our home. Is it best to use light or dark colored shingles?

"A light colored shingle will be the best choice," said Gene Meyer, extension specialist in small business energy at Kansas State University. "This will help to minimize your cooling costs, especially if your roof is not shaded.

"Dark shingles will increase the cooling load but will not significantly reduce your heating requirements," Meyer said.

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4. If I berm my new house, how do I make sure I won't have water problems?

"You can avoid below-grade water problems by a combination of good surface drainage, below-grade drainage and waterproofing of surfaces in contact with the soil," said Doug Walter, president of Kansas Building Science Institute, Manhattan.

Good surface drainage can be established by grading the soil away from your house at a five percent slope for at least 15 feet.

"Thick turf-grass or other dense soil covering also aids surface drainage," Walter said. "Roof eaves should be guttered and the downspouts directed well away from the foundation."

You create subsurface drainage by installing a perforated plastic drain pipe around the perimeter of your foundation below the level of the floor. You must install the drain pipe in gravel to prevent plugging with soil and grade it at ¼-inch drop per foot of run to a sump pump or, if the site permits, to a grade-level drain.

"Waterproofing of below-grade surfaces is essential to avoid water problems," Walter said. "Damp-proofing with asphalt-based products provides only temporary protection."

Waterproofing products are available in a variety of forms, ranging from brush- or spray-applied coatings to rubber membranes.

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5. Why does my basement seem warmer when I run my dehumidifier? I thought it was suppose to feel cooler if the room was less humid.

A dehumidifier removes moisture by cooling the air below the dew point, allowing the moisture to condense and collected in a pan or run down a drain. An air conditioner removes moisture in the same way.

"With an air conditioner, the heat removed from the inside air is released to the outside by the condenser," said Gene Meyer, extension mechanical engineer.

"With a dehumidifier, the condenser is located inside so it releases the heat back into the room. The dehumidifier's compressor also releases heat into the room, so the room temperature actually increases.

"You are correct in your observation that a room with less humidity should feel cooler than a humid room," Meyer said, "but only if the rooms are the same temperature."

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6. Are there any quick checks that I can do to assure my air conditioner is working properly?

"It is generally a good idea to have a professional look at your cooling system at the beginning of each year," said Gene Meyer, extension specialist in small business energy at Kansas State University. "However, there are a few checks that can be done by the homeowner," he said.

If you have a sight glass on your refrigerant line, check to see if there are any bubbles. A sight glass will be located on the small line coming from the outside condensing unit.

"Bubbles should appear only as the unit starts up and should disappear in a few seconds as the sight glass fills with clear refrigerant," Meyer said.

At the same time, carefully touch both refrigerant lines.

"The smaller line should be warm to the touch but not so hot that it can't be held," he said. "The larger line should be cool but there should be no frost."

If you have a small thermometer, check the temperature of the air coming from the vents.

"It should be 15 to 20 degrees cooler than room temperature," Meyer said. "If the unit has just started or if the humidity is high, the temperature difference may be less."

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7. In the summer, is it cheaper to open my windows at night when it's cool outside or to just let my air conditioner run all night?

"You will save energy any time you can open your windows and avoid running your air conditioner, even if you use a whole-house fan to pull air into your house," said Doug Walter, president of Kansas Building Science Institute, Manhattan.

"In fact, a whole-house fan can make it easier and more effective to cool your house with outside air," Walter said.

Because your house and its furnishings pick up humidity from the outside air when you cool with outside air, you should try to keep your air conditioner off for as long as possible — at least four hours before you start it up again — in order to maximize your savings.

"Many people who cool with outside air at night wait until mid to late morning before they turn their air conditioners back on," Walter said.

"However, you should close your house up as soon as the outside temperature is greater than the inside temperature."

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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-FG47-92-CE60210. However, any opinions, findings, conclusions, or recommendations expressed herein are those of the author(s) and do not necessarily reflect the view of DOE.