Energy Usage and Conservation Within the Household Darryl Birtwistle Energy, Society, and Climate October 7, 2002

Facts  The energy consumed within the US increased exponentially from about  Projections indicated US would be using energy at a rate of 160 Qbtu/yr by 2000 (Q= 10^15).  By 1996, we only used energy at a rate of 93.8 Qbtu/yr.  Buildings and appliances now use about 38% of the total energy consumed in the nation. (industry: 36%, transportation: 26%)

Energy Uses and Sources

Space Heating  Uses largest amount of energy in US households (20%).  Natural gas is the predominant source used.  Household heating is a very inefficient process as hot air leaks out roof, through cracks in walls and windows, through doors, and out the basement.

Furnaces, Stoves, and Fireplaces  Most use natural gas  Furnaces are 60-90% effective. (50% for older units)  Alternatives are electric resistance heating and the use of electrically powered heat pumps.  Electric resistance heating is 100% efficient, however, costs more to operate.  Electrically powered heat pumps can be used in places where temperatures are not too low. May also act as air-conditioner.

Fireplaces  Are inefficient unless used to heat small part of house while thermostat is down.  Efficiency of 40-65%.  Open fireplaces have negative efficiency: they remove more heat from the house than they provide.  Heat enters fireplace then goes out the flue.

Efficient Fireplaces  Some fireplaces are constructed with connective passages around back of firebox so air is air is drawn close to it, heated, then sent back into the room.  This type of fireplace is more efficient.  Firewood provides energy at rate of 12 to 30 mil. Btu per cord.  Cord = 128ft 3 stack  Higher density wood has more heat per cord.  All wood is about 8600Btu/lb.

Solar Heat  Heat can be gained through direct light through south-facing windows.  Light not reflected back out converts into heat.  Conversion efficiency from light to heat is usually around 60–90%  Transmission of sunlight through glass and insulation factors need to be taken into account.

Effective Design

Standards for Home Heating

Space Heating and Conservation  Most important factor for conservation is thermostat settings.  Normal settings have dropped from 72 to degrees as comfortable living temp.  Settings should be turned to around 55 at night, then brought back up before needed.  The many critics of this idea are falsely informed.  Buildings should be properly insulated.

Insulation  With perfect thermal insulation and no leakage of air, no energy source would be needed to keep a constant temperature.  However, this is not possible.  Well designed houses have been built that require no separate heating system.  They are heated by existing internal sources such as lights and stoves.  Insulation is important in controlling heat loss.

Insulation - Building Materials

Air Infiltration  Accounts for a complete change of air in a house about once per hour.  Also accounts for 1/3 of heat loss.  Air exchange occurs around doors, windows, leaky siding, and other cracks.  Fireplaces chimneys and furnace vents also account for loss of warm air.

Heat Loss

Air infiltration  Leakage can be reduced to about 10% by caulking, weather stripping, the addition of automatic flue dampers, and closure of fireplace and openings and chimneys.  Must keep dangerous gases such as carbon monoxide and radon in mind when completely sealing a house.

Air to Air Heat Exchanger  Gets rid of harmful gases without heat loss.  Heat is transferred from warm to cold air by conduction through a thin barrier.  Brings incoming air up to temperature as well as gives it moisture.

Water Heaters  About 10-20% energy consumed in house.  Usually gas or electricity heats a gal. Tank of water to temp range of F  Gas heaters loose heat through flue.  Pipes carrying water take away heat.  Steady expenditure of energy is required to maintain the water temperature.

Ways to Conserve  Reduction of the amount of hot water used.  Lowering heater’s thermostat to 120 deg reduces energy consumed and still provides hot enough water.  Insulation can be added to the tank and pipes.  Electric igniters eliminate energy wasted by pilot light.  Flue damper can be installed.

Air Conditioning  About 60% (57 million) of US households now have air conditioners.  75% of new homes have central air conditioners.  Takes output of 7 large power plants to provide energy for US air conditioning.  Air conditioners should be turned down when not needed, doors and windows should also remain shut to prevent loss of cool air.

Air Conditioning  Central air conditioners are rated by there seasonal energy efficient ratio (SEER).  Typical SEER ratings have increased from 6 or 8 some years ago to 8.5 or 9.5 recently.  Cost of energy to operate air conditioners is enough to motivate people attention to good house design and insulation.

Appliances  Main energy consumers –Refrigerators –Clothes dryers –Air conditioners  Many appliances thought to waist energy such as electric carving knives and toothbrushes really use a negligible amount of energy.

Appliances - Energy Consumption Chart Water Heater: 6,000 A/C: 4,300 Refrigerator: 1,300 Washer: 1,080 Dryer: 1,060 Lighting: 844

Appliances – Energy Leakage  Appliances drain energy even when they are off in order to maintain settings, display clocks, and keep remote control alert.  TV’s drain energy to keep tubes warm.  12-volt power transformers for many appliances drain energy when off.  Typical house drains continuously about 50w of electric power when all switches are turned off.  This leaked electricity costs about $3 billion per year nation wide.

Energy Guide  Must be posted on all new appliances.  List energy usage and cost for appliance for one year.  Allows consumer to compare increased cost of energy conservative appliance to savings in energy usage.

Refrigerators  Companies began to minimize insulation to provide more space.  Made refrigerators less energy conservative.  1972: 1700kWh/yr were used ($130)  1997: 690kWh/yr ($50) is the standard.  Projected 2001 standard is 535kWh/yr, down 30% from 1997.

Clothes Dryers  Consume about 15% of household electric energy.  Energy can be conserved by hanging clothes outside.  Air from electric dryer can be vented back into the house to conserve heat.

Lighting  20% of electric energy is used for lighting.  Standard light levels in public schools have increased from 20 lumens/sq ft. to 60 (suggested level for reading).  Many office buildings have lighting levels of 80 to 100 lumens/sq ft, including corridors and stairways.  Many office buildings have single switches that turn on whole floors at once.

Lighting (light choice)  Fluorescent light produces about five times more lumens per watt than incandescent lighting. –15 w fluorescent bulb = 75 w incandescent bulb  Some people complain about quality of light of fluorescent bulb, this is being fixed  Fluorescent lamps last about 10,000 hours, ten times longer than conventional light bulbs.  Lower energy usage and longer lifespan account for greater price of fluorescent light bulbs.

Lighting Chart

Lighting - Conservation  Choose efficient light fixtures.  Use effective lighting design.  Use switches allowing lights to be individual controlled, allow for dimming.  Corridors and stairways should use less light.  Users should remember to turn off lights or use automatic controllers to turn them off.

The Energy-Conservative House  Study done on 1200 sq ft California house to determine energy conservation in relationship to cost.  Largest effect was for space heating which went from 120 mil Btu/yr to 35 mil Btu/yr, for an expenditure of $1600. (2/3 reduction)  Total energy used was also decreased from 235 to 100 mil Btu with an investment of $2700

National Affect  If the conservation steps taken in this experimental house were used across the nation, the 36 QBtu used nationally per year for buildings and appliances could be reduced to 15 Qbtu/yr, with a cost of about 150 billion dollars.  Demonstrates the potential for energy conservation in homes and buildings.

Recycling  Recycling is important in reducing garbage but also in conserving energy.  Takes only 1/3 amount of energy to form a beverage can from recycled aluminum as it does from virgin aluminum.  Less energy to just reuse and existing container.  Takes also 1/3 less energy to form steel products from scrap than from ore

The End