Extension and Ag Research News


NDSU Offers Tips to Reduce Home Heating Costs

Using supplemental heaters and reducing air leakage can help cut home heating costs.

As the cost of staying warm continues to go up, people try to find ways to reduce the impact on their budget.

Ken Hellevang, North Dakota State University Extension Service engineer, offers tips for reducing heating costs, including zone heating with a supplemental heater and reducing air leakage.

Zone heating involves keeping some areas of the home warmer and some cooler. That can reduce heating costs because heat loss is related to the temperature difference between indoors and outdoors. Therefore, if the house temperature is kept at 60 F rather than 70 F when the outside temperature is 0 F, the heat loss will be reduced by 14 percent, Hellevang says. The savings might be 50 percent if the house is at 50 F rather than 70 F when the outside temperature is 30 F.

Reduce the house thermostat setting and use space heating in portions of the house. In homes with a central heating system, close heat vents or dampers and doors to reduce the amount of heat supplied to a room or area.

However, high humidity and mold growth can be problems in cooler parts of a home. A 20-degree drop in temperature will double the relative humidity. For example, if the relative humidity is 35 percent in a portion of the house at 70 F, the relative humidity will be about 70 percent in a room or area at 50 F. The potential exists for mold growth at relative humidity levels exceeding about 70 percent. Monitor the levels using an electronic humidity meter available at most hardware and general stores.

Hellevang urges consumers to investigate advertizing claims before purchasing heaters to provide supplemental heat.

An electric space heater provides 3.4 British thermal units (Btu) per watt of electricity used. Therefore, a 1,000-watt (1 kilowatt) heater will produce 3,400 Btu of heat each hour and a 1,500-watt heater will produce 5,100 Btu per hour. An electric heater is 100 percent efficient, converting all the energy coming into the unit to heat. The amount of heat produced is the same regardless of whether it is from an electric resistance element or an infrared bulb.

The cost to operate the heater is the electric cost per kilowatt-hour (kwh) multiplied by the kilowatts (kw) of the heater. For example, the cost to operate a 1,500-watt (1.5 kw) heater with an electric rate of 7 cents per kwh is 10 cents per hour. Most electric heaters that can be plugged into a common house electrical outlet are 1,500 watts or smaller. A 1,500-watt heater will draw 12.5 amps on the electrical circuit, which is nearly the maximum for most house electrical circuits.

Do not use unvented combustion heaters in a home because they produce numerous pollutants, including carbon monoxide and water vapor. Select only vented combustion heaters and follow manufacturers’ guidelines for venting combustion gasses outdoors, Hellevang advises.

Comparing the cost of fuel and heating efficiency can help you chose the most economical heater. For example, electric resistance heat at 7 cents per kwh is equivalent to natural gas at $1.89 per 100,000 Btu in a high-efficiency furnace, No. 2 fuel oil at $2.01 per gallon in a 70 percent efficient furnace, propane at $1.74 per gallon in a high-efficiency furnace and corn at $6.35 per bushel in a 65 percent efficient furnace.

Do not forget to include the purchase price of the heater and labor associated with using it when comparing the cost, Hellevang says.

Publication AE-1015, “Fuel Cost Comparison Chart,” which is available from the NDSU Extension Service, can help you make comparisons easily. It is online at http://www.ag.ndsu.edu/pubs/ageng/structu/ae1015.htm.

Here are some other factors to consider. Room temperature and the temperature of surfaces, such as walls and windows, can affect thermal comfort. You feel colder in a room with cold wall surfaces, even though the air temperature is the same, because of radiation heat loss from your body, Hellevang says. Closing draperies creates a warmer inside surface, which increases the feeling of warmth. Adding insulation to a wall or ceiling also can help because it decreases the heat loss and creates a warmer inside surface, which increases the comfort level.

Air leakage causes the largest heat loss from a home. A well-sealed house will have an air leakage rate of about 0.5 air changes per hour (ACH), while a poorly sealed house may have an air leakage rate that exceeds 1 ACH. The difference between a well- and poorly sealed home, an air leakage of 0.5 ACH, will increase the fuel use by about 500 gallons of propane or 460 therm for one heating season. A therm is the energy equivalent of burning 100 cubic feet of natural gas.

Hellevang suggests sealing openings in the wall and ceiling to reduce air leakage. Places to check in walls include between the sill plate and foundation, and around windows, pipe penetrations and electrical outlets. Look for openings, feel for a draft or use a lighted stick of incense to check spots for a draft. Use weather stripping or caulking to seal openings.

Windows with sliding parts typically have higher air leakage than windows that seal by compressing the weather strip. Install plastic over the window to reduce air leakage. Reduce air leakage through doors by installing weather stripping and using a storm door.

Recessed lighting is the most common location for air leakage through the ceiling. Use approved enclosures or seals for recessed lights.

Fireplace dampers also should be sealed to reduce air leakage. This can be done with a chimney cap, fireplace plug or draft stopper.

However, some air exchange is required to remove indoor moisture, odors and pollutants. The recommended minimum ventilation rate is 0.3 ACH. The relative humidity should be 30 percent to 40 percent for most of the winter. Observe the rate of odor dissipation and measure the relative humidity to monitor the amount of air exchange. Use an electronic relative humidity meter or note the amount of condensation on windows. Use ventilation to reduce the humidity level if window condensation runs off the window onto the framing.

Do not vent a clothes dryer into the home to save energy because this will put excessive amounts of moisture into the air that normally will cause condensation and other moisture problems.

NDSU Agriculture Communication

Source:Ken Hellevang, (701) 231-7243, kenneth.hellevang@ndsu.edu
Editor:Ellen Crawford, (701) 231-5391, ellen.crawford@ndsu.edu
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