Ask Energenie

May 2000

Table of Contents

1. Should I turn off my furnace’s pilot light during the summer?
2. Will I save energy by turning off my air conditioner when I leave home, or am I better off just letting it run?
3. Why does soil make such a good insulator for earth-sheltered homes?
4. I've heard that the production of some refrigerants will stop. What about the refrigerant used in my heat pump?
5. What should I do to maintain my daytime solar air heater, especially during the summer?
6. What is the cost of operating a gas clothes dryer compared to an electric dryer?
7. Water trickles out of the bottom of my furnace when the air conditioner is running. Is it leaking?
8. How effective is aluminum foil at reducing heat gain through windows?
9. ?
10. ?

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1. Should I turn off my furnace’s pilot light during the summer?

"Yes," said Gene Meyer, extension mechanical engineer at Kansas State University. "Turning off the pilot in the summer will save on energy costs."

Follow the instructions printed on your furnace to properly extinguish and light the pilot.

"If your furnace has no instructions or if they are unclear, consult a service technician or your gas utility," Meyer said.

The Institute of Gas Technology tested gas and energy consumption for a standing pilot light. Researchers found that during the summer, pilot energy is wasted if the furnace doesn’t have air conditioning. If the furnace has air conditioning, 136.9 percent of the pilot’s energy consumption is wasted.

In an air-conditioned building, return air circulates through the furnace. If the pilot is on, its heat places an extra load on the air conditioner.

"The pilot also creates a stack draft effect in the chimney," Meyer said. "The stack effect increases air infiltration through windows and around doors, thereby increasing the air conditioning load."

In the past, you may have heard that turning out the pilot light decreases a furnace’s life. Meyer said recent tests indicate that the possibility of damaging your furnace is minimal or nonexistent.

On the other hand, turning off the pilot will not extend the life of your furnace either.

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2. Will I save energy by turning off my air conditioner when I leave home, or am I better off just letting it run?

"If you plan to be gone for four hours or more, you will save energy by turning off your air conditioner or turning up the thermostat," said Doug Walter, president of Kansas Building Science Institute, Manhattan.

"During the day, keep windows shut and close curtains or blinds on any windows that will be exposed to sunlight," he said.

The thermal mass of the house will probably keep the indoor temperature well below outdoor temperature, and your house should cool quickly when you restart the air conditioner.

"You may want to use a programmable thermostat or timer to turn on the air conditioner 30 to 45 minutes before you plan to get home," Walter said. "If your home is still warm when you arrive, turn on a fan to create air movement."

Moving air can make the air feel about four degrees cooler than it really is.

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3. Why does soil make such a good insulator for earth-sheltered homes?

"Soil does not make a good insulator, but a good moderator," said Richard Nelson, extension specialist at Kansas State University.

Because of soil’s moisture content and density, it has a high heat capacity, which means it can absorb a considerable amount of heat but increase only slightly in temperature.

Another condition that adds to soil’s "insulating" ability is the delay, or lag time, between the time heat is absorbed at ground level and when a temperature change occurs below the soil surface.

Nelson added that the degree of temperature change decreases with soil depth.

"Between May and August, the average daily air temperature increases 20 degrees," he said. "Fifteen feet below ground, soil temperature may increase only a few degrees."

The means that during summer, the ground temperature at this depth is lower than outside air temperature and room air temperature. Ground temperature near the soil’s surface is higher than it would be 15 feet below, but it is still cooler than room temperature.

In the winter, soil is still holding heat absorbed over the summer. So, average soil temperature is higher than outside air temperature, but still lower than room temperature.

"Thus, heat loss to soil is less in an earth-sheltered home than it would be in an above-ground home, where walls are exposes to outside air," Nelson said.

He added that earth-sheltered homes still need insulation, especially ones that are only earth-bermed and not fully earth-sheltered.

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4. I've heard that the production of some refrigerants will stop. What about the refrigerant used in my heat pump?

Most residential heat pumps and air conditioners use R-22.

"R-22 is a hydrocholorfluorcarbon (HCFC)," explained Gene Meyer, extension mechanical engineer at Kansas State University. "There are no plans to quit making this refrigerant until the year 2020."

Production of R22 for use in new equipment will cease in 2015 but production to service existing equipment will continue until 2020.

Researchers are presently looking for environmentally safe alternatives for R-22 and other refrigerants.

Meyer said new regulations affect the use of R-22.

No intentional venting of HCFCs has been allowed since July 1, 1992. Beginning no later than the end of 1995, R-22 and all other HCFCs must be recovered and recycled.

"These restrictions may affect the cost and way that your heat pump is serviced," he said.

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5. What should I do to maintain my daytime solar air heater, especially during the summer?

"If it is a space heating only type system, cover your collector for the summer, particularly if it is a sloped or wood-frame collector," said Bruce Snead, extension specialist in residential energy at Kansas State University.

Snead said you can cover collectors with anything from cloth to particleboard, as long as the material blocks sunlight.

"Covering or shading prevents overheating, which can cause degradation of some materials," he said.

Covering collectors that have fiberglass or plastic glazing will extend the life of the collector and reduce potential yellowing of the glazing. The covering will also protect the system from hail.

"While you are preparing your solar heating system for the off-season, check and replace air filters," Snead said. "Clean the air registers of any dirt and dust."

This is also a good time to check fans and pumps and make sure they are properly oiled.

Snead added that you should turn off electricity to the unit before handling any components.

When getting your system ready for the heating season, clean the glass so maximum sunlight reaches the collector.

"A typical rain shower will not keep the glass clean enough," Snead said. "Use a squeegee or sponge to clean grime and dirt off the glass."

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6. What is the cost of operating a gas clothes dryer compared to an electric dryer?

"You can operate an electric clothes dryer for about $10.40 a month if you run it for 30 loads," said Doug Walter, president of Kansas Building Science Institute, Manhattan. "The energy cost of a natural gas dryer is about $7.15 for the same number of loads."

He said nearly half of the energy a gas dryer consumes is for the pilot light. A gas dryer with a pilotless ignition costs only $3.30 a month to operate.

"A gas dryer operating on propane costs $11.60 a month with a pilot light and $5.00 if it has a pilotless ignition," Walter said.

The rates used in these comparisons are 7.7 cents for a kilowatt-hour (kWh) of electricity, $5.50 for one thousand cubic feet (MCF) of natural gas, and 85 cents for a gallon of propane.

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7. Water trickles out of the bottom of my furnace when the air conditioner is running. Is it leaking?

"No," said Gene Meyer, extension specialist in small business energy at Kansas State University. "The condensate drain on the cooling coil is probably plugged."

Meyer explained how a plugged coil drain can cause water to collect in the furnace.

"During the cooling process, water vapor is removed form the air," he said. "A hose or line carries this water from the cooling coil drain pan furnace to a drain."

If the line is plugged, the water backs up and overflows a pan in the furnace.

"When this occurs, you need to clean out the line immediately," Meyer said. "If the condition continues, it can cause furnace failure."

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8. How effective is aluminum foil at reducing heat gain through windows?

"Placing foil or other reflective materials inside windows exposed to direct sunlight can reduce heat gain and cut cooling costs," said Bruce Snead, extension specialist in residential energy at Kansas State University.

Snead explained that foil acts as a radiant heat barrier, reflecting the sun’s energy back through the glass. Foiling windows is a low-cost, temporary approach that works best for west-facing rooms that are seldom used during the day.

"The major disadvantage of this energy-saving method are loss of sunlight inside your home, and the appearance of the foil from outside your home," he said.

If you apply foil to thermal pane windows, the glass may crack or seals may break due to uneven expansion. If this is a concern, check with the window manufacturer before covering them with foil.

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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.