Heating & Cooling Systems:
Saving Energy and Keeping Safe


This worksheet helps you identify possible problems with your home heating system, duct system, and the house envelope (the foundation, floors, walls, ceilings, and roof). By keeping your system in proper order, you can avoid unhealthy situations, reduce energy bills, increase your comfort level, and prevent structural damage.

This assessment is divided into three parts:

  1. Combustion Heating Appliance Ventilation Safety
  2. Energy Consumption
  3. Energy Efficiency (heating/cooling systems, air-sealing and insulation, and domestic hot water)

What do you expect from your house?

Your house should be a safe, comfortable place that is affordable and durable. How a home is constructed, insulated, and heated and cooled directly affects how it meets these objectives. A house is affordable only when costs for heating and cooling are reasonable. Energy bills are lowest if a home is tightly air-sealed and properly insulated and if all mechanical systems are operating efficiently. (Before extensively air-sealing your home, it is critical to ensure that doing so will not cause health or moisture problems. See part 3b, which begins on page 100, for more information.) Above all else, your home must be a healthy place to live.

Part 1. Combustion Heating Appliance Ventilation Safety

If your furnace, wood stove, boiler, or water heater burns gas, oil, wood, or coal, it is important that the venting system, which carries combustion gases out of the house, is properly functioning. (This also applies to a gas clothes dryer.) Part 1 explains how venting systems work and what will keep them safe. At the end of part 1, fill out the assessment table to identify potential risks with your system.

Are your combustion appliances safe?
When fuel (gas, oil, coal, or wood) is burned, carbon dioxide and water vapor are given off. If the burner is not functioning perfectly, carbon monoxide and other harmful pollutants are also produced (see chapter 9, "Indoor Air Quality," for more information about combustion byproducts). Most combustion appliances are vented to remove combustion byproducts from the home. However, improper maintenance can lead to problems such as blocked vents (Where did that bird put its nest?) and cracked flues. Vents or flues should be checked annually to make sure they are in good working order.

The three types of venting systems are natural-draft, power-vented, and sealed-combustion. Natural-draft or atmospheric-vent systems rely on the natural tendency of warm gases to rise. Natural-draft appliances always vent into a vertical flue (either masonry or metal) and have a draft hood, which draws extra in-door air into the flue. Natural-draft appliances are particularly susceptible to backdrafting. This problem occurs when exhaust equipment such as a clothes dryer, central vacuum, or exhaust fan draws air out of a house, creating a negative pressure within the house. This can cause combustion byproducts to backdraft, or be pulled into the house instead of going out the vent (See Figure 1)

With power-vented systems, a small blower exhausts combustion byproducts from the house. Flue gases from power-vented appliances rarely backdraft. The newest furnaces and water heaters use sealed-combustion systems. With this type of system, air needed for combustion is brought in from outside through an intake pipe. Flue gases are vented outside through a second pipe. No chimney is needed. These systems are completely isolated from inside air, and as long as the intake and vent pipes are not blocked or damaged, sealed-combustion appliances are immune to backdrafting.

Unvented appliances, including gas fireplace logs, should only be used in well-ventilated areas. If you must use unvented appliances, open a window in the room at least 1 inch.

Do your appliances get enough air?

For safe operation, it is critical that combustion appliances have enough air to work properly. The National Fire Protection Association (NFPA) codes (or more stringent local codes) must be followed to ensure safe installation and operation of combustion equipment.

Sealed-combustion units draw air directly from outside the home. However, natural-draft and power-vented units draw air from the indoor space in which they are located. If you have combustion equipment in a closet or other confined space, make sure the appliance gets enough air. This is often accomplished with louvered doors. Do not place anything inside or outside of the confined space that might block air flow.

Assessment 1 -- Combustion heating appliance ventilation safety

If you have a combustion appliance, complete the table below. For each question, indicate your risk in the right-hand column. Some choices may not correspond exactly to your situation, so choose the response that best fits. Refer to part 1 if you need more information.

Assessment 1 Table 1. Low Risk / Recomended 2. Medium Risk / Potential Hazard High Risk / Unsafe situation Your Risk
Vent system for combustion No combustion appliances (all electric) or sealed combustion NA - Unvented space heaters
- Unvented has logs
- Any signs of damage to vent pipes
- Rist or carbon present on top of appliance, below draft hood
Vent system for combustion Chimney or flue inspected annually Inspected only once in past five years Chimneys, flues not inspected or inspection record unkown .
Adequate air for combustion [does not apply to sealed-combustion appliances] All combustion equipment located in a well-ventilated space e.g. attic or garage Combustion equipment located in a well-sealed basement. This situation is worse if exhaust e.g. such as a clothes dryer as also located in the space. Combustion equipment located in a small space (e.g. closet) and openings are blocked .

Responding to Risks

Your goal is to lower your risks. Turn to the Action Checklist on the back page and write down the high and medium risks you identified. Refer to the recommendations in Part 1 to help you make plans to reduce your risks.

Part 2. Energy consumption

The amount of energy consumed in your home depends on many factors, including how well the home is insulated, the efficiency of appliances and equipment, the local weather and climate, and your lifestyle. This section describes how to calculate your energy use and determine if it is high or low. At the end of this section, fill out the equations in assessment 2. If your energy consumption is low, that's good news. If it is high, or if there are ways you could save more energy (and money), continue to part 3.

Does your house use too much energy?
Your family's lifestyle will affect how energy is consumed in your home. The best and most accurate way to determine the energy efficiency of your home is to have a home energy audit done by a service professional. Without an audit, it is not easy to know if your energy consumption is "too much." Contact your local utility to see if they offer a residential energy audit or can provide data on average energy consumption for houses similar to yours. Alternately, you can ask them to quote you a monthly payment plan that will indicate the average energy consumption for a house in your geographic location.

Typical distribution of residential energy use. Data taken from U.S> Congress, Office of Technology assessment, Building Energy Efficiency, OTA-E-518, 1992.

When you call, be sure to describe your energy and fuel uses. For example, you may have an all-electric home, or you may heat with gas and cook with electricity. It is also important to specify whether or not you have air conditioning. Make sure the utility understands that you are trying to determine typical energy usage for a home the size of yours. Otherwise, they may quote you a monthly payment plan based on your past energy usage.

Assessment 2 -- Energy Consumption

Use the equations in the assessment on the following page to evaluate whether your energy costs are high or low. First, check your records or call your utility to determine how much you spent on energy bills over the last twelve-month period. Then divide your energy costs for one year by twelve to arrive at your average monthly energy bill.

Compare this with the monthly bill of an "average" home or with the monthly payment plan amount quoted to you by your utility company. If your current bill is much greater, then there are probably many opportunities for improving the energy efficiency of your home. If your bills are lower than the average home, there may still be certain opportunities to make your home more energy efficient.

There are three key strategies to increase energy efficiency: air-sealing (leak-proofing) your home, adding insulation and efficient windows, and using more efficient appliances and equipment. Each is covered in part 3.

Part 3. Energy Efficiency

The average home in the United States wastes 30 to 50% of the energy it uses. If every home installed energy-efficient equipment and was well-insulated, individual homeowners and the national economy would reap tremendous savings. The following sections will help you identify where energy is being lost and how you can prevent future losses. Complete the assessment tables at the end of each section to see where improvements can be made.

3.1 -- Improving Heating & Cooling Systems

The single greatest energy consumer in your home is the heating/cooling system (furnace, boiler, heat pump, wood stove, or air conditioner). This system has three parts: (1) heating/cooling unit(s), such as furnaces and air conditioners, (2) ducts or other distribution mechanism, and (3) a thermostat to control output. You can save energy in all three areas.

Table 1 -- Are Your Energy costs High or Low?

Use this table to calculate and compare your energy consumption:

Total of hearing/cooling bills for the past (year) (12 months) $________
Average monthly bill $________(A)
Average monthly bill for energy efficient houses simillar to yours $________(B)

In Table 1, if A is larger than B, it may indicate that your home is using more energy -- and costing more money -- than it should. By increasing energy efficiency, you can cut your bills and save significant amounts of money over the long run.

How old are the parts of your system?
If your primary heating/cooling unit is over fifteen to twenty-five years old, it is probably not very energy efficient. Even if it still works, you may benefit by replacing it with a new energy-efficient model. A new device can pay for itself in fuel savings in only a few years. Or, if you find long-term financing for the new equipment, the dollar value of the monthly energy savings may exceed the monthly payment for the equipment, which would result in a positive cash flow.

Is your system getting proper maintenance?
All machines work more efficiently-- and more safely-- if they are inspected and maintained. Your furnace, air conditioner, and other heating/cooling equipment should be checked and serviced every year by a qualified professional. Monthly maintenance, such as inspecting and changing air filters, is recommended during the heating or cooling season. A forced-air system includes an air filter, which removes dust and debris before it reaches the air blower and heat-exchange coils. Dirt on the coils reduces efficiency, so you should change or clean your air filter on a regular basis.

Are you using your thermostat to save energy?
One of the easiest ways to save energy is to set thermostats at a lower temperature in winter and a higher temperature in summer so that the heating/cooling system runs less often. If a house is caulked and weather-stripped to prevent cold drafts, most people-when dressed appropriately-will be comfortable at 68 degrees Fahrenheit during winter. To save more energy, temperatures can be turned down to 50 or 60 degrees while you are sleeping or when the house is empty. During the summer, a thermostat setting of 72 degrees or higher is recommended. During times when the house is unoccupied, a summer thermostat setting of 80 to 85 degrees is recommended.

Digital or clock thermostats (also called automatic set-back thermostats) can be programmed to adjust the temperature in your house automatically (figure 10.3). For example, they can turn the heat down every night at 11 P.M. and bring the temperature back up by 6 A.M. before you get out of bed. The newest kind of residential thermostat, a home energy manager, allows many temperature settings throughout the week. Depending on your lifestyle, these set-back thermostats can pay for themselves in energy savings in as little as one or two years.

Figure 10.3 Digital or clock thermostats can be programmed to adjust automatically

Is your distribution system working well?
Unless there is a heating/cooling unit in each room, you probably have a system to distribute hot or cool air from a central heater or air conditioner. Over 90% of central heating systems and virtually 100% of central residential cooling systems in America have forced-air distribution systems that use air ducts to move warm (or cold) air to the rooms of the house. If the duct system leaks, it can waste large amounts of energy.

Any ductwork located in an unheated space (such as an attic or crawl space) has a high potential for heat loss. Ducts in such spaces should be insulated. Also, all joints in the duct system, everywhere in the house, should be properly sealed to make sure all the warm or cool air gets where you want it to go.

Besides providing supply registers in each room to deliver heated/cooled air, there must be a return duct to allow air to get back to the heating/cooling unit. Many newer homes do not have a return register in every room, but rely on the space under a closed door to allow supply air to return to a centrally located return. If you have a room that is uncomfortable (hard to heat or cool) when the door is shut but is fine when the door is open, you probably have an air distribution problem. You can increase the cut under the door or call a heating and cooling specialist to resolve the problem.

The second most common heat distribution system uses hot water that is distributed through pipes to radiators or convectors. Pipes carrying hot water should be insulated everywhere--from boiler to radiator. Use a quality insulation material. Cheap materials degrade over time.

Assessment 3.1 -- Improving Heating/Cooling Systems

Use the table on the following page to identify areas where energy can be saved. Indicate your potential energy-loss level in the right-hand column. Although some choices may not correspond exactly to your situation, choose the response that best fits. Refer to the sections above if you need more information to complete the table.

Assessment 3.1 Table

1. Low Energy - loss 2. Medium energy - loss 3. High energy - loss Your Loss Potential
Age of heating/cooling equipment Less than 5 years old 5 to 15 years old 15 years old or older .
Maintenance of heating/cooling equipment Air filters changed every month during use, and equipment serviced at least every 2 years. Filters changed occasionally, and systtem maintained on an irregular basis filters not changed or rarely changed, and system not maintained .
Air - temperature thermostat Modern thermostat with variable temperature set-back. Routinely used to minimize energy consumption Newer thermostat installed, but not used to regulate temperature at night and when house is empty Older thermostat in place. Set to maintain a constant temperature .
Duct location All dust work located in heated/cooled space Some duct work in unheated space All duct work in unheated space .
Return duct Air-return ducts in every room, or bedroom doors left open One "central" air-return. Bedroom doors shut at night but 2" or greater space under bedroom door. One "central" return. Bedroom doors shut at night, little space between bottom of door and floor .
Air-sealing ducts and registers Seams in duct system caulked or sealed, especially where air registers enter rooms No visible gaps in duct system Gaps visible in duct system of around room air registers .
Air-intake or air handler Located in heated space Located in unheated space (crawl space or attic) Located in garage* .
* If your air handler is in your garage, NEVER leave your car rumming in the garage. The air handler can pick up car exhaust fumes and distribute them to the house through the duct system.

Responding to Your Potential Losses of Energy
Your goal is to reduce the amount of energy that is wasted. Turn to the action checklist on page 105 to record the high and medium loss potentials you identified in the table. Use the recommendations in part 3a to help you identify ways to increase energy efficiency.

Safety Note
Your home receives outside air from all small holes and cracks in the structure including any holes in the duct system that are located outside the conditioned space (such as an attic or crawl space).

Sealing a leaking duct system will reduce the amount of outside air that leaks into the home. While this will reduce energy consumption you must also be aware of how it might affect combustion appliances and air quality within the home. The precautions listed under the "Safety Note" on page 102 apply here also. Duct sealing is a job best left to a professional.

3.2 -- Preventing Loss of Heated (or Cooled) Air
Once you have reached a comfortable temperature indoors, your aim is to keep it that way. Preventing unwanted air leaks and blocking heat transfer are two important approaches to making your home even more energy efficient.

Have you air-sealed your home?
Every house has openings through which outside air can enter. Some openings, such as open windows and doors, are obvious pathways for air entry. Others, such as cracks around window frames, are unintended pathways for leaks (figure 10.4). This uncontrolled leakage of air, known as infiltration, can account for a large portion of the total heat loss in a home-typically about 30% of the total heating bill. Cold (or warm) air entering a home must be heated (or cooled) if the home is to remain comfortable. Sealing your home against air leakage is not difficult, but it does require detailed information to be done right. For details on how to reduce air leaks, contact your local Cooperative Extension office or the U.S. Department of Energy's Energy Efficiency and Renewable Energy Clearinghouse (EREC). (See "For More Information")

Does your home need more insulation?
Even if you air-seal your house, you still need to prevent the transfer of heat or cold through walls, floor, or ceilings. Insulation acts like a blanket to retain the heating or cooling your system produces. Insulation materials are assigned an "R-value," which is a measure of how well they "Resist" the flow of heat energy into or out of your home. The larger the R-value, the more heat (or more cool air) is kept where you want it.

The recommended amount of insulation for a home varies with geographic location. If you have extreme temperatures, you will need more insulation. Your local building supplier should be able to provide you with your good recommendations. The EREC publication "Insulation Materials and Strategies" describes various insulation products available and provides insulation recommendations for all areas of the United States by zip code. It also helps you to decide if you should attempt the job yourself or have it done professionally.(See "For More Information")

Assessment 3.2 -- Air-sealing and Insulation

As before, put your potential energy-loss level (1,2, or 3) in the column labeled "Your Loss Potential." Although some choices may not correspond exactly to your situation, choose the response that best fits. Refer to the information above if you need more information to complete this chart.

Assessment 3.2 Table 1. Low Energy Loss 2. Medium Energy Loss 3. High Energy Loss Your Loss Potential
Attic Allpotential leak points are sealed or weather - stripped Only some potential leak points are sealed Most potential leak points are not sealed .
Windows & doors All sealed with caulk and weather-stripping, and tested for leaks. Newer, well-sealed windows installed, with tight storm windows. Only some windows and doors caulked and weather-stripped. Older, or leaky storm windows used. Some windows sealed in winter with plastic sheets Older windows. Not sealed. Storm windows may be absent .
Basement or crawl space Sill plate, service entrances, windows, and wall cracks sealed with caulk or foam Leaks detected, but not fully sealed No sealing attempted .
Attic insulation Insulation equal to or greater than recommended for the region. . Insulation well below recommende lovels, or not insulated. .
Insulation in walls (above ground) Wall cavity insulated with loose fill or 3 1/2 inch to 5 1/2 inch batt . No insulation in wall cavity .
Insulation in heated basements Walls insulated with rigid foam or batt, according to the regional recomendations . Walls not insulated .

Responding to Your Potential Energy Losses
Your goal is to reduce the amount of energy you use. On the Action Checklist, record the high and medium loss-potentials you identified above. Use the recommendations in Part 3.2 to help you find ways to increase energy efficiency.

3.3 -- Increasing efficiency o domestic hot water systems


After heating and cooling your home, heating water for domestic consumption is the next largest energy user. There are several ways to reduce the amount of energy you use to heat water.


**Proceed with caution**. As stated before, your home must be a healthy place to live. Air- sealing may save energy, but it can cause unhealthy air to be trapped inside. Leak-proofing can cause a dangerous situation by reducing the air available for combustion appliances. Do not attempt to leak-proof your home until after you have taken care of these problem areas:

  • Gas or kerosene heaters, or gas fireplaces--if unvented--must be removed or vented outdoors.
  • If you have a gas cook stove that is not vented to the outside by a power vent hood, do not extensively seal your home.
  • If you have a high level of radon in your home, take steps to reduce it before sealing.
  • If you have natural-draft appliances, do not extensively leak-proof your home without seeking the advice of an energy services professional.

The simplest thing you can do to save energy used for water heating is to turn down the water heater temperature. Each 10-degree reduction in water heater temperature will save you 3 to 5% on your annual water heating bill. Lowering the water temperature will also increase the lifetime of your water heater and reduce the risk of someone being burned by the hot water. Children and the elderly are most at risk of being scalded from water that is too hot.

Most water heaters are factory set around 140 degrees Fahrenheit. For most household uses, that is higher than necessary. Usually, 120-degree water is adequate unless you have an automatic dishwasher without a temperature booster. In this case, you may need to keep the temperature set at 140 degrees for optimal dishwashing performance.

Wrapping your water heater with insulation can reduce water heating energy use by 4 to 9%. Except for some new water heaters that come with high levels of foam insulation and do not need any more, the addition of insulation usually pays for itself in less than one year. Water heater insulation blankets are widely available at hardware stores and come in standard sizes to fit 40-, 60-, and 80-gallon water heaters. Be sure to follow the manufacturer's instructions for installation.

Reducing hot water consumption will reduce the amount of energy needed. Fix any leaking pipes and consider installing low-flow shower heads. Washing laundry in cold rather than hot water will also save energy.

Hot water pipes should be insulated wherever they are accessible. Either preformed foam insulation or wraparound fiberglass insulation can be used.

Assessment 3.3 Table 1. Low Energy Loss 2. Medium Energy Loss 3. High Energy Loss Your Loss Potential
Thermostat setting Thermostat is set at 120°F. Thermostat is set at 130°F. Thermostat is set at 140°F or higher. .
Insulation A new, highly insulated water heater or water heater blanket is installed. . An older water heater with no added blanket is in use. .
Water conservation Low-flow shower heads are installed, and there are no leaking faucets. A conscious effort is made to conserve hot water. There are no leaking faucets. Some effort is made to minimize hot water use. There are leaking faucets, and no low- flow fixtures are installed.d .
Pipe insulation All accessible hot water pipes are insulated. Some accessible hot water pipes are insulated. There is no insulation. .

Responding to Your Potential Energy Losses
Your goal is to reduce the amount of energy you use. On the action checklist (see page 105), record the high and medium loss potentials you identified above. Use the recommendations in part 3c to help you find ways to increase energy efficiency.


Go back over the assessment tables and make sure that you have recorded all high and medium risks and energy-loss potentials. Next, list the improvements you plan to make. You can use recommendations from this chapter or from other sources to help you pick actions you are likely to take. Write down a date to keep you on schedule. You don't have to do everything at once, but try to eliminate the most serious problems as soon as you can. Often it helps to tackle the inexpensive actions first.

List High and Medium Risks & Energy-loss Potentials What can you do to reduce risks and energy losses? Target date for action
Water heater not insulated
Buy a ready-made insulation blanket at the hardware store. One week from today: (March 8, 1997)
Your Home: . .

For More Information

Energy Efficiency and Renewable Energy Clearinghouse . The U.S. Department of Energy provides energy information through the Energy Efficiency and Renewable Energy Clearinghouse (EREC). EREC will send detailed information on the topics in this assessment, and much more. Call them toll-free at (800) DOE-EREC (800-363-3732, 9am - 7pm, Eastern time.

American Council for an Energy Efficient Economy.The American Council for an Energy Efficient Economy can provide information on energy-efficient appliances. Contact them at 2140 Shattuck Avenue, Suite 202, Berkeley, CA 94704; (510) 549-9914. Ask for a current list of publications.

Resources and Publications. --

Home*A*Syst Helps Ensure Your Safety

This Home*A*Syst assessment does not cover all potential risks and concerns related to energy conservation which could affect health or environmental quality. It is meant to serve as a starting point for identifying and addressing the most apparent risks. There are other Home*A*Syst worksheets -- on a variety of topics -- to help homeowners examine and address their most important environmental concerns.

This Home*A*Syst handbook covers a variety of topics to help homeowners examine and address their most important environmental concerns. See the complete list of chapters in the table of contents at the beginning of this handbook. For more information about topics covered in Home*A*Syst, or for information about laws and regulations specific to your area, contact your nearest Cooperative Extension office. Contact the National Farm*A*Syst/Home*A*Syst Office at: B142 Steenbock Library, 550 Babcock Drive, Madison, WI 53706-1293; phone: (608) 262-0024; e-mail: HOMEASYST@MACC.WISC.EDU.

This publication is based on Home *A* Syst: An Environmental Risk-Assessment Guide for the Home developed by the National Farm *A* Syst/Home *A* Syst Program in cooperation with NRAES, the Northeast Regional Agricultural Engineering Service. Permission to use these materials was granted by the National Farm *A* Syst/Home *A* Syst office.

This publication was written by Lori S. Marsh, Associate Professor and Extension Engineer, Department of Biological Systems Engineering, Virginia Polytechnic Institute and State University.

For more information, contact the National Farm*A*Syst / Home*A*Syst office at: B142 Steenbock Library, 550 Babcock Dr., Madison, WI 53706-1293 Phone: (608) 262-0024
Email: farmasyst@macc.wisc.edu