Ask Energenie

March 2000

Table of Contents

1. I need to replace the boiler in my home. What features should I look for in a replacement?
2. The crawlspace under my house is always damp or wet, even though there are several vents to the outside. Do I need to add more vents or install a ventilation fan?
3. What is the recommended hot water temperature for my home?
4. I've heard a little about using compressed natural gas as an alternative fuel in vehicles. What are the advantages of using natural gas instead of gasoline and diesel fuel?
5. What direction should I orient my house to take advantage of the sun for passive solar heating?
6. I've lowered the temperature on my hot water heater to 120 degrees. Is there anything else I can do to reduce water-heating costs?

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1. I need to replace the boiler in my home. What features should I look for in a replacement?

"Today's residential boilers have many of the same features as modern furnaces," said Gene Meyer, extension mechanical engineer at Kansas State University. "These boilers can have a standing pilot light and atmospheric vent, or they may be fitted with sealed combustion systems."

Beginning in January 1992, all residential-size hot water boilers must have a minimum efficiency of 80 percent.

Meyer said many manufacturers have added an intermittent ignition system to obtain the higher efficiency.

"Eliminating a standing pilot light reduces fuel consumption," he said.

Another way manufacturers have increased boiler efficiencies is by improved venting. In an open venting system, air is warmed inside the boiler, rises and escapes up the stack. Room air is then drawn in to cool the boiler.

"Besides using up room air that has already been conditioned, atmospheric vent systems increase air leakage into the home," Meyer explained.

There are three ways to reduce the negative effects of atmospheric venting.

The first is to use a vent damper, which blocks the vent when the boiler is off, reducing warm air loss from the boiler. The second method uses a fan to draw combustion products out of the boiler and up the stack. The draft-inducing fan stops when the burner shuts off, blocking the escape of air from the boiler.

"With both of these venting systems, combustion air comes from inside the home," Meyer said. "This air must be replaced with outside air."

The third type of venting uses a sealed combustion system to eliminate the combustion air problem. In this system, a combustion air intake supplies the burner with outside air for combustion. The combustion products are then vented directly outside, usually with the help of an induced-draft fan.

Meyer said boilers with intermittent ignition and some type of vent control will have efficiencies from 80 to 85 percent.

"The most efficient type is the condensing boiler, which lowers flue gas temperature until moisture condenses," he said. "These boilers can achieve efficiencies of 90 to 95 percent."

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2. The crawlspace under my house is always damp or wet, even though there are several vents to the outside. Do I need to add more vents or install a ventilation fan?

"Probably not," replied Doug Walter, president of Kansas Building Science Institute, Manhattan. "Ventilating a crawlspace doesn't work well because soil is usually cooler than outside air in the spring and summer."

Walter explained that instead of drying the soil, humid air entering the crawlspace adds more moisture because it condenses on the cooler surfaces.

"If you notice standing water in your crawlspace, you probably have a problem with surface drainage," he said.

To correct this problem, pack clay-based soil around the perimeter of your house, creating a slope away from the foundation. Then plant a thick ground cover, such as turf grass, in this soil. The turf will slow the percolation of surface water into the soil.

"Also, make sure the rain gutters on your roof are clean and that downspouts direct water at least two feet away from the foundation," Walter said. "You can buy gutter extensions or place splash blocks under the spouts, if necessary."

To prevent any remaining dampness from damaging your floor structure, install a heavy plastic vapor barrier over the crawlspace soil.

Walter suggested using plastic at least four, preferably six, mil. thick.

"Overlap seams about six inches and weight them down with sand or soil," he said. "Do the same around the perimeter of the crawlspace, allowing six inches of plastic to extend against the foundation wall."

You can buy sheet plastic in compact rolls at discount stores, hardware stores and lumber yards.

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3. What is the recommended hot water temperature for my home?

The ideal hot water temperature in a home is 120 degrees.

"Water temperature is also an important safety consideration if you have young or elderly occupants in your home," said Richard B. Hayter, director of Engineering Extension at Kansas State University. "Higher temperatures can easily scald."

Many dishwashers have auxiliary electric heaters that warm the water if it is not hot enough for dishwashing purposes.

"You should set the water temperature to 140 degrees if you have an automatic dishwasher and are using natural gas for water heating," Hayter said. "If you have an electric water heater, it is more economical to use the dishwasher's auxiliary heater and lower water temperature in your water heater to 120 degrees."

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4. I've heard a little about using compressed natural gas as an alternative fuel in vehicles. What are the advantages of using natural gas instead of gasoline and diesel fuel?

"Probably the greatest advantage is reduced emissions," said Bruce Snead, extension specialist at Kansas State University.

"Compressed natural gas will burn much cleaner than gasoline and diesel fuel," he said.

The Department of Energy estimates that by using existing pipelines, the United States could potentially supply enough natural gas to displace close to one million barrels of gasoline and diesel a day. This amount would run approximately seven to eight million vehicles.

"Another advantage is that it costs less to maintain a vehicle equipped to run on natural gas, and use of CNG may potentially promote longer engine life," Snead said.

Several large fleet operators such as United Parcel Service and Federal Express have run a portion of their trucks on CNG, and many other communities through the Department of Energy’s Clean Cities program have both cars and trucks running on CNG.

"Purchasing a vehicle which runs on CNG costs an additional $3,000 to $5,000, which is a substantial investment," Snead said. "However, most states, including Kansas, have alternative fuel tax incentives that help lower these costs."

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5. What direction should I orient my house to take advantage of the sun for passive solar heating?

"Your house should face true south, not magnetic, or compass, south," said Bruce Snead, extension specialist in residential energy at Kansas State University.

Snead said true south is the center line of the sun's path over the planet. In Kansas, true south varies from eight to 11 degrees east of compass south.

"A good rule of thumb would be to orient your house 10 degrees east of compass south," he said.

This adjustment will slightly reduce exposure to hot western summer sun and increase morning heating in the winter.

"Remember that shifting the orientation up to 20 degrees east or west of true south reduces average solar radiation on the south wall by only about 10 percent," Snead said.

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6. I've lowered the temperature on my hot water heater to 120 degrees. Is there anything else I can do to reduce water-heating costs?

"There are two more things you can do to reduce the amount and cost of energy to heat water," said Richard B. Hayter, director of Engineering Extension at Kansas State University.

First, cover the water heater with an insulating jacket if the unit is in an unheated area.

Hayter said insulating jackets are inexpensive and easy to install.

"The other thing you can do is periodically drain two to three gallons of water from the tank drain valve," he said. "Doing this removes accumulated sediment from the bottom of the tank."

Draining a portion of the water tank from gas-fired water heaters is particularly important in areas with hard water. Even a small amount of sediment in the bottom of the heater will increase both energy consumption and the time it takes to heat up after heavy use.

To drain sediment from the heater, place a bucket under the drain valve, or use a hose and bucket if there isn't enough space next to the heater. Slowly open the valve, drain two to three gallons from the heater and then close the valve.

"If there is a lot of sediment in the bottom of the bucket, you may have to repeat this step several times," Hayter said.

He suggested draining your water heater at least twice a year.

Unless the heater is new, the drain valve may leak after opened, especially if it has not been used for a long time.

"Use a threaded cap to stop the drip, or replace the valve if necessary," Hayter said. "You don't want a leaky valve to waste all the energy you've saved!"

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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.