Ask Energenie

December 1999

Table of Contents

1. Do Christmas lights take a lot of energy? I'm talking about the typical strings of lights you put on a Christmas tree or across the front of the porch.
2. Which type of window should I use in my new home: triple-glazed or double-glazed with a low-emissivity coating?
3. My central humidifier does not seem to be providing as much humidity as it once did. Why?
4. I'm building a new home. What R-value do you recommend for the walls?
5. We built a new house several years ago and installed quality windows. Unfortunately, they leak an enormous amount of air. The air doesn't leak around the window sashes. It seems to be coming through the openings for the springs on the side channels of the windows. We have had several architects and window representatives come to our house, but they cannot determine where the air is coming from. We have lots of windows on the north and the winter is brutal in our new home. Can you help with any suggestions?
6. An electrical water heater warms the water for my washing machine. How much is this costing me, and what is the cost difference between heating with electricity and natural gas?
7. I've heard there's a way to make a simple, low-cost timer for setting back a thermostat at night. Does the device really work? If so, can you tell me where I can get plans for building it?

| Return to Ask Energenie home page |

1. Do Christmas lights take a lot of energy? I'm talking about the typical strings of lights you put on a Christmas tree or across the front of the porch.

"A few strings of Christmas lights do not take much energy," said Doug Walter, president of Kansas Building Science Institute, Manhattan.

A standard string of Christmas lights consumes about four watts of electricity per foot of length. Sets with miniature lights consume less energy per bulb, but the bulbs are more closely spaced. Thus, a string of miniature lights uses about the same amount of electricity as a string of standard Christmas lights.

"So, with a 50-foot string on the tree and a 50-foot string across the front of your porch, you have about 400 watts of Christmas lights," Walter said.

"If you operate them five hours per night for 20 nights, the total cost of electricity will be about three dollars, based on a rate of 7.6 cents per kilowatt-hour," he said.

If your Christmas display includes spotlights and other types of bright displays, total wattage can jump quickly.

Walter suggested using a timer to control outdoor displays.

An outdoor timer will prevent you from leaving them on all night, wasting energy, and will automatically turn them on if you're gone for an evening.

A plug-in appliance timer (available at hardware stores) works well for Christmas displays.

"For outside lighting, be sure to use lights and cords approved for outdoor use," Walter added.

Back to Top

2. Which type of window should I use in my new home: triple-glazed or double-glazed with a low-emissivity coating?

Bruce Snead, extension specialist in residential energy at Kansas State University said the double-glazed windows with a low-e coating are probably the best choice.

"The R-value rating of a low-e window is usually equal to or greater than that of a tripled-glazed pane," he said. "Also, the greater R-value comes without the increase in weight and frame size associated with the third pane."

Other advantages of double-glazed, low-e windows are reduction of summer heat gain and simpler manufacturing.

Back to Top

3. My central humidifier does not seem to be providing as much humidity as it once did. Why?

"Several things may explain the reduced performance of your humidifier," said Richard B. Hayter, director of Engineering Extension at Kansas State University. "And you may be able to correct most of them with simple maintenance."

First check the setting on the humidistat if your system is equipped with one. Be sure it is in the "on" position and is set at a comfortable level but does not produce excess humidity.

Hayter said persistent condensation or frost on windows is a sign that the humidifier is set too high for the outdoor conditions.

"As outdoor temperatures drop, you should lower the humidity level to prevent condensation within the walls of your home," he said.

"Seldom is it necessary to have humidity levels above 30 percent, and even lower levels may be necessary during cold weather to prevent condensation."

Next, you should check the humidifier.

Many models require periodic maintenance. Once or twice a season, you should clean the humidifier to remove mineral deposits.

If your unit has metal or fabric pads, clean them with a solvent sold for this purpose. The solvent may be available from the supplier of your humidifier or from a hardware store. You can also use vinegar to clean the pads.

With some humidifiers, you need to periodically drain the reservoir to remove mineral deposits. Other units may have a foam belt or drum that you can replace as deposits build.

Your central humidifier will probably be attached to a water line in your home. Typically the attachment to the water line is through a small hand valve, sometimes called a tapping saddle.

"At times small particles can clog this valve," Hayter said. "Simply opening and closing the valve may remove the particles."

Similarly, the electric solenoid valve on the humidifier may have malfunctioned so that it does not open when the humidistat activates it.

If you determine that this valve is the problem contact a plumbing contractor who can replace it for you.

Back to Top

4. I'm building a new home. What R-value do you recommend for the walls?

"The recommended level of wall insulation will vary from a R-13 in Southeast Kansas to an R-19 in Northeast Kansas. If heating fuel prices are medium to high, higher insulation levels are recommended. If natural gas prices exceed $6.50 per MCF, propane exceeds $.60 per gallon, or your average electric rates exceed $.055 per kilowatt-hour, insulation should range from R-19 in southeast to R-24 in northeast Kansas," said Gene Meyer, extension mechanical engineer at Kansas State University.

Meyer said R-13 is achievable with conventional 2x4 construction and batt or cellulose insulation. To achieve higher R-values, you should use 3/4 to one inch insulated sheathing on the outside of the studs. To obtain even higher R-values, 2x6 construction and insulated sheathing are needed.

"Insulated sheathing is a rigid, foam-type insulation placed between a home's siding and outside wall frame. It completely covers the studs and greatly enhances the walls performance," Meyer said.

"Because it is difficult to add insulation after construction, consider insulating to higher R-values to avoid paying for increasing fuel costs later," Meyer said.

In both the R-19 and R-24 wall sections, the insulated sheathing also keeps the batt or cellulose insulation temperature above the dew point, minimizing moisture problems. For more information on residential insulation, check out the new fact sheet available soon on Engineering Extension's Web site at http://www.oznet.ksu.edu/dp_nrgy/.)

Back to Top

5. We built a new house several years ago and installed quality windows. Unfortunately, they leak an enormous amount of air. The air doesn't leak around the window sashes. It seems to be coming through the openings for the springs on the side channels of the windows. We have had several architects and window representatives come to our house, but they cannot determine where the air is coming from. We have lots of windows on the north and the winter is brutal in our new home. Can you help with any suggestions?

"You need to have someone conduct a blower door test on your house to determine the source and cause of the air leaks around your windows," said Doug Walter, president of Kansas Building Science Institute, Manhattan. "A specialist will use the blower door to create an artificial pressure difference between the inside and the outside of your house, allowing his to trace and locate air leakage pathways."

A blower door is a large fan mounted in an expandable frame that is installed in an outside doorway to conduct the test. For a list of individuals certified to conduct a blower test in your area, contact the Kansas Housing Hotline at 800-752-4422 or visit the Kansas Energy Star web-site at www.ink.org/public/kesp/index.html.

"It is likely that the windows were installed without having the space between the window frame and the rough frame opening properly sealing," Walter said. "If this is the case, sealing the windows will require removal of either the interior or the exterior window trim and filling the cavity all around the window with a non-expanding foam sealant.

"It's possible you will find some fiberglass stuffed into the cavity. If so, be sure to remove it before installing the foam sealant."

Back to Top

6. An electrical water heater warms the water for my washing machine. How much is this costing me, and what is the cost difference between heating with electricity and natural gas?

The cost of heating water for washing clothes depends on the volume of water used (for full or partial load) and the price you pay for electricity and gas.

Richard Nelson, extension specialist at Kansas State University, said washing a full load of clothes takes approximately 17 to 20 gallons of water for the wash and rinse cycles. Washing a partial load requires 9 to 12 gallons of heated water per cycle.

"Washing clothes in a hot cycle requires that the water temperature increase from 70 degrees to 125 degrees," Nelson said.

Assuming electricity costs 7.5 cents per kilowatt-hour and natural gas costs about $3 per thousand cubic feet, the cost of washing a full load with natural gas is about 33 percent less than if using electricity.

"Heating the water for a partial load would cost you almost five cents using natural gas versus 19 cents for electrical heating," Nelson said.

Back to Top

7. I've heard there's a way to make a simple, low-cost timer for setting back a thermostat at night. Does the device really work? If so, can you tell me where I can get plans for building it?

"Yes, the device works, and you probably don't need plans," said Doug Walter, president of Kansas Building Science Institute, Manhattan. "If you can plug in an extension cord, you can 'build' the timer."

"The device works by creating a small heat source below the thermostat to fool it into thinking your house is warmer than it really is," Walter said.

A night-light provides the heat, and plugging it into an appliance timer allows it to come on automatically, at the time you have specified. You'll also need an extension cord to connect the timer and night-light.

If you want to have a set-back only at night, Walter said you can get an appliance timer that has only one "on" and one "off" setting in a 24-hour period.

"If you want more than one set-back period, you should purchase a timer that has at least two settings," he said. "Some have a tab for every hour."

You can purchase an appliance timer at most hardware stores for about $7.

The extension cord should be long enough to reach from your thermostat to the nearest electrical outlet.

The female end of the extension cord should have a flat surface so you can stick it to the wall below the thermostat. Walter said double-stick carpet tape works well for this.

The night-light should be the basic four-watt variety that points up when plugged in. Avoid night-lights with light sensors.

"Program the timer to come on whenever you want the temperature to be set back," Walter said. "Then plug it into the outlet nearest the thermostat."

Plug the night light into the extension cord and mount it on the wall so the top of the light is about two inches below the bottom of the thermostat.

Next, plug the extension cord into the outlet on the appliance timer and make sure that the night light switch is in the "on" position.

To test your new set-back device, use the manual override switch on the timer to turn it on, then observe the temperature on the thermostat.

"After a few minutes, it should read about eight to 10 degrees above the normal comfort temperature," Walter said. "If it is above or below this, remount the night light further or closer to the thermostat to obtain the desired set-back temperature."

If necessary, you can override the set-back by simply switching the night light off.

Walter said you could also use this device in the summer to control your air conditioner.

"Simply program it in reverse so the light is off when you want to raise the temperature of your house," he said.

Back to Top| Home |

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.