Over 30 pages of energy saving tips on buying, using and maintaining window air conditioners and on using and maintaining central(whole house) air conditioning to help you have more energy efficient A/C


Types of Room Air Conditioners
Energy Saving Tips for Buying and Using Room Air Conditioners
Energy Saving Tips for Using Central Air Conditioning
Build Roofs Over Condenser Units and Through-the-Wall Air Conditioners

Types of Room Air Conditioners

Air conditioners that are not large enough to cool an entire house are
commonly called “room air conditioners”. There are basically two types: conventional room air conditioners, which use the “refrigeration cycle” to generate cool air and the much less common “evaporative coolers”. These use a completely different technology, which is explained below.

In the section below, Energy Saving Tips for Buying and Using Room Air Conditioners, almost all of the measures apply to both types of air conditioners. In the refrigeration cycle, refrigerant is pumped through an evaporator coil where it expands to become cold. Air is blown past the evaporator coil while it is cold to become cool, and then enters the home. The refrigerant is pumped from the evaporator coil to the condenser coil, where it is compressed. This makes it hot. Air is blown past it to the outdoors, cooling it down.

There are three types of room air conditioners that use the refrigeration cycle: “window-mounted air conditioners”, “through-the wall air conditioners”, also called “built-in air conditioners”, and “portable air conditioners”. Through-the-wall air conditioners are designed to be installed in a hole in a wall. Their advantage is that they don’t block the view through a window. They are similar to window air conditioners, but can have larger cooling capacities, as large as 22,000 Btu’s. The largest models can cool a small apartment.

Portable air conditioners rest on the floor next to a window, on wheels or casters. They are much less energy efficient than window air conditioners, but have the advantage that you can move them to the room you are in. However, you will need to use a long, heavy gage extension cord if any of the rooms do not have enough extra electric capacity.

Portable air conditioners remove heat from a room by creating hot air through the air conditioning cycle and blowing it out the window. Air that is cooled in this cycle is blown into the room. Single hose models only blow out the heated air, but dual-hose models draw in air through a second hose to make up for the heated air. 

Single hose models produce less cool air for the same electricity used. When they blow out the air, the air pressure in the room becomes lower. This draws in warm air, mainly through gaps around doors. 

Dual hose models draw in outside air through the second hose, so the room’s air pressure remains the same. 

Each circuit it will be plugged into must allow the unit’s high amperage, or you must use a very long 14 gage extension cord, often plugged into a 20-amp kitchen outlet. In most homes, few if any of the outlets in bedrooms and the living room would have enough extra electrical capacity for a portable air condition, but an extension cord could be plugged into a kitchen outlet that is used for small cooking appliances.

Portable air conditioners have the disadvantage that they collect water, which must be emptied each day.

Window evaporative coolers cool the air that passes through them by allowing water contained in them to evaporate into the air. They are only effective if the climate is very dry, because only dry air absorbs enough water to significantly lower the temperature of air passing through it. Their effectiveness varies from day to day based on the outdoor relative humidity. They use about one-fourth as much electricity as conventional units.

In the climates where they are commonly used, they can lower the temperature of the air passing through them by as much as 20º. They are only effective in dry climates because only dry air can absorb much water. There are units that are mounted to the wall of the house behind a window with a box similar in size to a window air conditioner sitting on the window sill.

The picture shows one of these units. The box in front is mounted in the window opening and the remaining part is mounted outside of the house. These would be difficult for most homeowners to mount, and a water feed tube must be connected to a house water pipe. There are also portable units which sit on the floor next to a window, requiring no installation. With these you pour in the water. They are much less effective and energy efficient.

Ductless Split System Air Conditioners

Ductless split system air conditioners use the refrigeration cycle and can be installed to cool more than one room, by each room having a separate evaporator (the unit containing the cooling coil). These air conditioning systems have a condenser that rests on the ground outside of the house and a small evaporator mounted to the wall, normally near the top of the wall.

They are more energy efficient A/C than room air conditioners because their condensers release the heat more effectively. A 3” diameter hole must be cut through the wall behind the evaporator for the refrigerant tubes and their insulation. This type of air conditioner is more expensive to buy and operate than any type of room air conditioner if only one room is cooled, but a condenser can be used with up to four evaporators, cooling four rooms, and can be less expensive than the other types if two or more rooms are cooled. They are sold and installed only by heating and air conditioning contractors.

energy efficient air conditioning
Ductless Split System Condenser
energy conservation tips for air conditioners
Ductless Split System Evaporator


Room SizeAir Conditioner Cooling Capacity
100-150 sq. ft.5,000 Btu
150-250 sq. ft.6,000 Btu
250-300 sq. ft.7,000 Btu
300-350 sq. ft.8,000 Btu

Buy air conditioners with many energy saving features, such as:

        • Digital thermostats. These keep the room’s temperature constant.
        • 24-hr timers. In bedroom air conditioners, timers can be set to turn on the unit an hour before going to bed and turn it off in the middle of the night when the home is cooler.
        • Three fan speeds. Using a lower fan speed can save electricity.
        • Three cooling settings (cooling speeds). Using a lower setting can save electricity.
        • Slanted louvers for more uniform cooling. This could allow you to set the fan speed at a lower level.
        • Remote control. This can allow you to turn it off from in bed when you otherwise would allow it to run, saving energy.
energy efficient air conditioning
Strapped-On Air Conditioner Cover

An air conditioner’s energy efficiency is given as its “Energy Efficiency Ratio”. This indicates how much heat it removes for the electricity it uses. The energy efficiency ratios of room air conditioners are given in Specifications on the retailers’ and the manufacturers’ websites. They range from about 8 to about 10. ENERGY STAR air conditioners all have high energy efficiency ratios.

Before buying a room air conditioner you must check if the electric circuit it would be using has enough extra amperage capacity. A rule of thumb is to buy an air conditioner which draws no more than 50% of the circuit’s amperage capacity, but if a circuit is used only for lights and appliances such a radios, which draw very low amperage, you may be able to use more than 50% of the circuit’s capacity.

First, check if the circuit you want to use is a 15 or 20 amp circuit. This will be written on the circuit breaker switch or the fuse (the higher-amperage circuits are not for 115-volt wall outlets). To check how much amperage a circuit is using, turn off its circuit breaker or remove its fuse and check which outlets and lights go off. They should be near each other, but occasionally an outlet or ceiling light in the basement is on the circuit. If an extension cord must be used, it must be a 15-amp (14 AWG) cord. These may be called, “appliance cords”. A lower amperage extension cord is a serious fire hazard.

Energy Saving Tips for Buying and Using Room Air Conditioners 

      • If an air conditioner is left in the window in winter, cover it on the outside with a plastic tarp fastened with “all-weather” duct tape, or with a strapped-on air conditioner cover. Strapped-on air conditioner covers are sold in the weatherization sections of home centers and plastic tarps are sold in the paint departments.

        Plastic tarps are more economical because they are made from heavier plastic and thus more durable, and because several covers can be cut from a tarp. Also, air conditioner covers are not air-tight if they are strapped on as they are designed to be, but tarps are air-tight if taped on tightly.
Quilted inside air conditioner cover
Quilted Inside Air Conditioner Cover
      • If an air conditioner is left in the window in winter and cannot be covered on the outside because it is on an upper floor, cover it on the inside with transparent plastic sheeting. Double-sided tape is available in hardware stores. You could also cover it on the inside with a quilted inside air conditioning cover, which are sold at some home centers.
      • If an air conditioner is left in the window in winter, replace the plastic side panels with rigid insulation. Side panels have frames and thin plastic pleated sheets that unfold to fill the opening. Tear the sheets out of the frames and replace them with rigid insulation, taped on with all-weather duct tape. If rigid insulation can be cut with a knife, but it may only be available in 48”x96” sheets.
      • If you have a window air conditioner in a metal case that is mounted to the wall, caulk between the case and the air conditioner with clear, interior/exterior caulk.
Door Sweep
Door Sweep
Door Weatherization Bottom
Door Weatherization Bottom
      • If a room with a window or through-the-wall air conditioner is kept cooler than the rest of the house, mount a door sweep or weatherizing door bottom to the bottom of the room’s door. This will prevent the cooler air that settles to the bottom of this room from flowing out from under the door.
Outdoor Thermometer
Outdoor Thermometer
      • In rooms with air conditioners, mount outdoor thermometers to the window frames so you can see when the temperature outside is low enough to turn off the air conditioners and use less air conditioning. In the evenings, if the outdoor temperature falls to well below the rooms’ temperature, you can set the control to “fan”, to blow in the outside air. At this setting the unit may use about one-tenth of the electricity.
      • Check the filters each month. If they are torn or filled with pet hairs or dust, replace them. If they are washable and they are dirty, wash them with dish soap and water and let them dry. Washing or replacing a filter will improve the energy efficiency of an air conditioner because a dirty filter reduces the airflow and can allow the condenser coils to become dirty and less effective. Also, a dirty filter can damage the unit.

        If a filter is torn, dirt will reduce its efficiency and damage it. Filters which must be cut to size are sold in home centers and hardware stores, and filters of the correct size can sometimes be ordered from the manufacturer.
      • Clean the evaporator and condenser coils once each year, and more often if your air is dusty. An air conditioner is less efficient if these coils are dirty because they cannot release heat as easily, a layer of dust is insulation. Lay a plastic drop cloth on the floor to catch water spill, remove the front access cover and remove the air conditioning unit from its case.

        Wash it or vacuum it. To wash it, take the unit outdoors and wrap the fan motor, electrical control box and electrical terminals in plastic. Clean and hose out the coils and water pan. Wait 24 hours before turning on the air conditioner. To vacuum it, use a vacuum cleaner with the brush attachment.
      • If an air conditioner is in direct sunlight much of the day, plant shrubbery to block the sun. The condenser coils in the back release heat, and operate much less efficiently when heated by the sun.
      • If your home has forced air heating or central air conditioning and there are rooms with air conditioners, close the registers in those rooms when using the air conditioners. This will prevent cooled air from escaping.
      • If a room with a window air conditioner has windows on different walls, mount the air conditioner in a north-facing wall, where it will receive no direct sunlight, or mount it in any window where it will be shaded from the sun. Before plugging it into a different outlet, check if the outlet is on a different circuit (has a different circuit breaker or fuse). Also, there are code requirements you must follow. These normally include:
        • The outlet must be grounded.
        • The unit may not draw more than 50% of the circuit’s amperage capacity. The circuit will be either 15 amps or 20 amps, as indicated by the number on the circuit breaker of fuse. If the power used by the air conditioner is given in watts, its amperage can be found by dividing it by 120, the home’s voltage. (wattage=amperage x voltage).
24-hour plug-In timer
      • In bedrooms with an air conditioners, install 24-hour plug-in timers in the outlets the air conditioners are plugged into. They may be called, “Heavy Duty Appliance Timer”. Set them to turn the air conditioner on an hour before going to bed and off in the early hours of the morning. They are available at heating and air conditioning stores and in some hardware stores and home centers.
      • If the side panels are torn, replace or repair them. Air conditioner side panels are sold in some home centers. To repair them, use “all weather duct tape”.
      • If you have a through-the-wall air conditioner, remove it and inspect the insulation. This is often foam rubber, which loses its shape and lets in air. Also, if the condensation water is not draining from the tray, the insulation may have become saturated and deteriorated. If the insulation is ruined, replace it with a 1¼” x 1¼” foam rubber insulation strip. These are sold in the weatherization departments of home centers and hardware stores and may be called, “Window Air Conditioner Seal”.
      • If an air conditioner is used more than necessary because the other window in the room will not open and a window fan could be used in it, pry open the window. The cause will be that the sash was painted shut. Use a utility knife to cut the paint around the sash, and pry the sash loose using a stiff blade putty knife, being careful not to leave marks in the window sill.

        Occasionally, windows don’t open because they were painted shut from the outside, so the paint must be cut from the outside. If you can’t cut from the outside, remove the window stop on the side that is stuck and slide a stiff blade putty knife between the sash and the window frame to break off the paint.
      • If you leave an air conditioner running all night instead of leaving a window open for fear of crime, secure another window in the room at 6” open. For more airflow, also secure the upper sash at 6”. One method is to install a “window vent latch”. This locks the window while it is partially open. These are not available in most home centers and hardware stores so they may need to be ordered. Another method is to open the sash by 6” and drill a hole through both sashes on the left and right sides, and insert 3½” nails into the holes. The nails must fit snugly.
Dual Window Fan
      • If an air conditioner’s fan setting is used frequently, mount a window fan in another window to use in place of it. Using the fan setting is much less effective than using a window fan because the air is drawn through the coils.
Window evaporator cooler
Window Evaporator Cooler
      • If your climate is very dry, you could replace small window air conditioners with window evaporative coolers. As explained above in Types of Room Air Conditioners, they use about one-fourth as much electricity, but cannot be used on humid days.
      • Plant a tall bush to the west of an air conditioner on a west wall to shade it in the evenings as the sun sets. Plant one to the east of an air conditioner on the east wall.
      • Buy a portable dehumidifier to reduce the moisture in the home, allowing you to set the thermostat temperature slightly higher with the same comfort level. They range in price from $150 to $250 at home centers. The cost to operate a dehumidifier may be greater than your savings in air conditioning costs, but consumers use them dry the air to reduce mold and mildew, making the air cleaner and healthier, and reducing allergy symptoms. On some models the water drains through a hose and on others the water fills a bucket that must be dumped. See the Topic of Home Energy Conservation, Dehumidifiers.
      • To cool two or three adjacent rooms more efficiently than buying individual air conditioners, buy a “ductless split system” air conditioner. This has a small condenser that rests on the ground outside of the room and a small unit that creates cold air (evaporator) mounted to the wall. A 3” diameter hole is cut into the wall behind the evaporator.

        They are more expensive than window units if only one room is cooled, but a condenser can be used with up to four evaporators, cooling four rooms, and can be less expensive than a window unit if two or more rooms are cooled. They are sold and installed only by heating and air conditioning contractors.
      • If you need to cool the air in only one or two rooms on most days and you run the central air conditioning to cool these rooms, buy window air conditioners for those rooms so you can turn off the central air conditioning. This will save electricity and reduce repair and replacement costs. Also, a window unit can cool a room rapidly, so you can turn it on when you enter the room. Since central air conditioning cools the house slowly you may be leaving it on all day.

Energy Saving Tips for Using Central Air Conditioning
If you take measures to reduce your use of central air conditioning, you will cut your electricity costs and also reduce the high costs of equipment repair and replacement. A condenser may last only 12 years if used often, and is usually over $2000 to replace. If on the roof, a crane must be used to replace it.

      • Set the temperature 1 or 2 degrees higher and notice if you can sense any difference. The electricity used could be reduced by as much as 3% for each degree the temperature is raised. The percentage of reduction is highest in the mildest climates, because 1 degree is a large fraction of the temperature difference between in the home and outdoors.
      • Install a programmable thermostat. These control the air conditioning when you are not home, allowing you to use less air conditioning. The basic types are:
          • 7-day programmable – a different schedule for each day of the week
          • 5-2 day programmable – one schedule for weekdays and one for weekends
          • 5-1-1 day programmable – a schedule for weekdays, for Saturdays and for Sundays
          • Smart thermostats – control your heating and cooling from your cell phone, also programmable
          • WiFi thermostats – has the features of smart thermostats plus many other smart features such as, senses when you’re not home during the day and uses less utilities.
      • Inspect the insulation that covers the two tubes leading from the condenser, which is outside of your house. If insulation has fallen off, remount it or replace it. Replace it with 1/2“thick rubber foam insulation, which is sold in home centers.
      • Have a service inspection performed every one or two years. This can extend the life of the air conditioning unit and the condenser, and improve their efficiency. The service technician will check if the refrigerant is low, oil the fan and compressor to prevent the bearings from failing, calibrate the thermostat, and more. If the refrigerant is even slightly low, the efficiency will be significantly reduced.

        Service inspections are most important for older units, which often leak refrigerant. Ask the technician to check the airflow rate through the air conditioning unit. The airflow rate often decreases over time, reducing the unit’s efficiency. Some utility companies offer service inspections at a discounted price.
      • Set the fan speed to “high” on days that are not humid. Air conditioners operate most efficiently at this setting, except when the humidity is very high. On very humid days, (or periods of the year in some regions), the fan speed should be set at “low”. This should be explained in the owner’s guide.
      • Check the air conditioner filter at the intervals it was designed to be replaced or cleaned. A clogged filter greatly reduces the efficiency of an air conditioner and can cause damage. The intervals range from monthly to yearly: 1” thick flat spun glass filters are designed to last 30 days; 2” thick flat spun glass filters are designed to last 60 days; and pleated filters are normally designed to last 90 days. If the filter also removes mold, smoke, etc., it becomes less effective after the period it was designed for.
Condenser unit not cleaned
Condenser unit not cleaned
      • Clean off any leaves that are stuck in the top grille or caging of your condenser unit.

        The condenser unit is in your back yard or on your roof. It releases the heat taken from your house through its fins. Air is drawn in from the top, so leaves can be pulled into the grille or caging. Grilles have slats, caging is made from heavy wires. If the airflow is even slightly blocked as it passes through the fins or if the fins’ surfaces are dirty or badly bent, the air conditioner will operate less efficiently and cost more to run.
      • Clean the fins in the condenser when they appear dirty. Dirty fins allow much less air to pass through, and can greatly raise your electric costs. First, turn off the power to the condenser at the circuit breaker. It is normally a small panel box mounted to the wall of the house, close to the condenser.

        Remove the side panels or caging to expose the fins, and remove the caging or panel on the top. Clean out the dirt and debris that is stuck between the fins. Spray the fins from inside out with a garden hose at low pressure. Straighten any bent fins. A tool for this is sold at hardware stores.
      • If you don’t want to clean the condenser yourself and it appears dirty, hire a contractor to do it.
      • Cover the condenser unit with an air conditioner cover in winter to keep the fins and the grilles or caging clean. These are sold in the weatherization section of many home centers. If unavailable, buy a tarp in the paint section of a home center and secure it with duct tape.
      • Remove any plants or large objects within two feet of the condenser unit. These trap the heat that radiates from the unit and block wind that cools it.
      • If the condenser unit is in direct sunlight, build a roof over it to shade it or plant a tree close to it. Condensers release heat much less efficiently when under direct sunlight. See How to Build a Roof for a Condenser Unit. Build an attractive small wooden fence around it, or plant tall shrubbery to block the sun from striking it at a low angle in the mornings and evenings. These will also add to the beauty of your home.
Cooling coils (evaporator coils)
      • Clean the dust from the cooling coils (evaporator coils) in the air handler inside the house once each year. These are the large coils, with many small fins which the air passes through to become cool. Air conditioners operate less efficiently when these are dirty. Shut off the power to the air conditioner at the circuit breaker panel box inside your house (not the circuit breaker outside, next to the condenser) and remove the screws from the side panel to gain access to the cooling coils. Use a vacuum cleaner brush attachment to clean off the dust.
      • Turn off the power to the air conditioner at the end of the cooling season. If the power is left on, the heating elements will be energized until the next cooling season, wasting electricity. Check your owner’s manual. Turn off the power at the switch. If there is no switch, turn it off at the circuit breaker panel.

        When you next use the air conditioning, turn on the power 24 hours before turning on the air conditioner to prevent damaging the compressor. You must post a sign next to the switch (or circuit breaker panel) to remind the other residents to turn on the power 24 hours in advance.
      • If the air conditioning system uses the same duct system as the heating system (has the same registers), a damper, which controls how much air flows through the ducts, is usually required to be set differently for air conditioning and heating. The damper is set to optimize the system’s efficiency. Without adjusting the damper, the first floor may become much cooler than the upper floors.

        The damper has a control lever, and there should be marks on the duct to indicate where to set control lever in the heating season and in the cooling season. If there are no marks, ask a service technician if the damper should be set differently for the heating and cooling seasons, and to draw marks to set it.
      • If your second floor is warmer than your first floor when the air conditioning is running, try to balance the temperature if it is wasting electricity. It is wasting electricity if the thermostat temperature is set to make the second floor comfortable. You can balance the temperature by partially closing off all of the registers on the first floor.

        If you have registers in the basement, and few homes do, they will cause the second floor to not get enough cooled air. Try closing off the basement registers. The large grilles at the top of walls are not designed to close. These allow air to return to the furnace or air conditioner.
      • If a return vent is in a room instead of in the hallway where they normally are, leave the door to the room open if possible. When the door is closed, the air pressure becomes lower in that room due to air being drawn into the vent.

        Warmer air may be drawn in through gaps around the windows, and if the room is on the top floor, hot air may be drawn in from the attic. Both make the system less efficient. You could cut 1/2” from the bottom of the door in place of leaving the door open, or you could post a sign, PLEASE LEAVE THIS DOOR OPEN WHEN A/C IS RUNNING
      • In the rooms you don’t cool, close the registers and the doors. If registers don’t close, oil them. However, closing off more than 25% of the space in the house could damage the air conditioner.
      • If you live in an apartment, mount a door sweep or weatherizing door bottom on the apartment’s front door to prevent cooled air from escaping under the door.
      • If you use many recessed lights or lamps with incandescent or halogen bulbs, without dimmer switches, either install dimmers or replace the bulbs with LED bulbs. Incandescent and halogen bulbs produce more heat than light, increasing your home’s use of air conditioning.
      • If you have rooms that are warmer than the rest of your house and you lower the thermostat temperature to cool these rooms, increase the flow of air through these rooms to balance the temperatures. Cut off ½ ” from the bottom of these doors and set a box fan inside or outside of them to blow air out of the rooms. The fans will draw cold air from the rooms’ registers across the rooms.
Air deflector mounted to register
Air Deflector Mounted to Register
      • If the registers are at the bottom of the walls, install air deflectors on the registers with their fins facing upward. The fins will direct the cool air upward. If you also have forced air heating, reverse the direction of the fins in the heating season to improve the heating efficiency. The air deflectors are attached by magnets and easily reversed. The manufacturer of at least one brand recommends that they be reversed between the cooling and heating season.
      • If your home has transoms above the doors, repair them if they will not open. In most homes with transoms, they have been painted closed and can be made to open by cutting the paint with a utility knife. If you open them when the doors are clo sed and the air conditioning is on the temperature will be more uniform throughout the house. Raise the thermostat temperature by one degree and check if you have the same comfort level.
      • If your climate is very dry you could replace your central air conditioner with an evaporative cooler. These use about one-fourth of the electricity, but can only be used when weather permits. Where they are commonly used, they typically cool the air by about 20º before it enters the duct system, but it becomes warmer as it passes through the ducts, depending on the size of the house.

        Thus, if the outside air is 95 degrees, an evaporative cooler may cool your home to about 80 degrees. If it is not a dry day the cooler will be less effective. Furthermore, they cost less than half as much to buy as air conditioner units.

        Evaporative coolers cool the air by causing water to evaporate into the air as it enters the house. Only dry air can be cooled effectively because it can absorb much more water. Their advantage to some homeowners is that they draw in fresh air, while air conditioners recycle the air. They are mechanically simple, so you don’t need to pay for service inspections, but they require homeowners to do much more maintenance than air conditioners.

        Some homeowners don’t install them because they may allow dust mites to enter the home. Also, they use very much water, so they should not be used if the home’s water is in limited supply.
      • If your home or a room with a portable air conditioner uses more air conditioning than heating, and has recessed lights with incandescent or halogen bulbs, replace them with CFL (compact fluorescent) or LED bulbs. Also, replace high-wattage bulbs in torchier lamps with lower-wattage bulbs. Incandescent and halogen bulbs create much more heat than light, increasing the need for air conditioning.
      • Hang white shades or blinds at windows where there is direct sunlight, to reflect the solar radiation. Curtains and drapery which are not light-colored absorb solar radiation, heat up and radiate energy into the room.
Skylight blinds
Skylight Blinds
      • Mount very light-colored drapes or curtains across patio doors.
      • On skylights, mount skylight blinds or skylight shades. These are sold in stores specializing in window shades and can be ordered online.
      • Hire a contractor to install awnings on the windows of a wall that receives much sunlight, if this would beautify your home. Attractive awnings can increase the property value of your home. For maximum effectiveness there should be a gap between the top of the awnings and the house to prevent hot air from being trapped.

        To block the direct sunlight while allowing residents to see through the windows, it is recommended that the awnings cover 65% to 75% of the window on the east and west sides of the house, where the sunlight enters from a lower angle and 45% to 60% of the window on the south side of the house.
      • Mount a windsock in your yard to show the direction and strength of the wind. Sometimes when the wind is blowing strongly you could turn off the air conditioning and open some windows. If the wind is blowing north, for example, you would open windows on your north and south walls. Directional wind socks are cloth cones that rotate to show the direction of the wind and the wind’s strength. Wind socks with baskets and ribbons also show the strength and direction of the wind.
      • Plant trees to shade your house in summer. If the winds are strong in winter the trees will also shelter the home from the wind, lowering your heating costs. A local nursery can advise you on which trees grow well in your area. To provide shade without waiting many years for the trees to mature, plant evergreen trees to the east and west of the house. These will soon be large enough to shade the house in the mornings and evenings when the sun is low.
      • Plant vines to cover your walls if you have brick walls. Vines insulate the house from the sun in summer and provide good thermal insulation in winter. Do not plant vines on a house with wooden siding because vines hold moisture, causing wood to rot. Also, vines can be harmful to the mortar of very old structures. Brick walls built before about 1940 have softer mortar, which can be damaged by vines. A nursery can recommend which vines to plant.
Pergola Covered with Vines
Pergola Covered with Vines
      • If your home has a deck or patio that is often in direct sunlight, build a covering
        over it so you can use it often and turn off your air conditioning. A large canvas beach umbrella can be mounted on a round picnic table that is designed to support it, or a large, retractable awning could be installed. You could also build a pergola over the patio and cover it with vines for shade. Building a pergola is a “do-it-yourself” project. Plans are available in do-it-yourself web sites and magazines.
      • Improve your back yard so you can spend more summer evenings outdoors and turn off the air conditioning. Build a deck or patio. Plant many small trees around the patio to create a cool “microclimate” from water vapor escaping from their leaves. Buy a picnic table, lawn chairs and gas grille for the lawn. Build a wooden fence around the yard. Set up a volley ball net.
      • If your home has a Victorian or early twentieth-century cupola on the roof and the window sash below it will not open, try to repair the sash to allow it to open. This is normally no harder than cutting through several layers of paint.

        The purpose of a cupola is to allow air to escape on warm days to cool the house, and they are very effective because the wind draws air out of the house. After opening the sash, weatherstrip it to prevent warm air from escaping in the heating season.

        When the outside temperature is in the 70’s at the end of the day, turn off the air conditioning, open the sash and leave it open all night. It will help to open second floor windows, and if opened in bedrooms, these rooms will cool the bedrooms by bedtime. The air inside will become cooler all night long, so less air conditioning will be needed the following day. Opening a cupola will also lower the humidity in the home because the outside air that enters is much less humid than the inside air, except on the day of a rain.
      • Do all that you can do to lower the humidity in your home and then raise the thermostat temperature by one or two degrees and notice if your home is still as comfortable. As mentioned above, for each degree that you increase the temperature you could save approximately 3% in air conditioning costs. To lower the humidity in your home:
Foundation Wall with Crawl Space Vents
        • In the months that your central heating is off, open your crawl space vents. In warm climates these should remain open all year. Crawl spaces often have 100% relative humidity due to water vapor rising from the ground.

        • If you have a crawl space with a dirt floor and no covering, cover it with 6-mil plastic sheeting. This will stop most of the water vapor from entering the home. They are sold in 10’ x 100’ rolls in paint departments and paint stores.

        • Fix a broken kitchen exhaust fan. These vent humid air. If it is a very old fan mounted in the wall, it is likely that the damper has rusted and remains open or closed. This may be easy to repair.

        • Check that the attic fans (attic ventilators) are working. To test an attic fan, set its temperature control to its lower limit. It should turn on. If not, use a voltmeter to check that it has power. If it has power, replace the fan. Buy a similar model at a home center and follow the instructions. They range in price from $65 to $100.

        • When taking a shower in the morning, open a bathroom window to vent the humid air.

        • If you dry your clothes indoors on a rack or clothesline, move it outdoors in the summer.

        • If your roof does not have a gutter, install one. This will reduce the home’s humidity and may also protect the basement from water damage. A do-it-yourselfer can easily install gutters and downspouts with the help of a do-it-yourself book or website.

        • If your clothes dryer vents into your home, make an exterior vent. Clothes dryers that vent indoors put all of the water from the wet laundry into the home’s air as water vapor. The dryer vent could pass through a window or wall and end at a dryer vent hood.

          To put the vent hose through a window, replace the pane of glass with a sheet of transparent polycarbonate with a 4” hole cut into it. Home centers and hardware stores have high-strength, polycarbonate sheets which are used to substitute for panes of glass. The vent hose can be passed through a brick wall by removing two bricks and applying mortar to form a 4” hole. It can be passed through a frame house with any type of siding by cutting a 4” hole in the siding, the sheathing and the interior surface material.

Build Roofs Over Condenser Units and Through-the-Wall Air Conditioners

How to Build a Roof Over a Condenser Unit


        • Sledge Hammer
        • Hacksaw
        • Drill
        • Hammer
        • Framing Square
        • Saw
        • Tape measure


        • 1/2” thick plywood or 1” thick boards
        • (7) 8’ 2×4’s
        • 12d nails or 3” deck screws
        • Package of shingles
        • ¾” roofing nails
        • 8d nails or 2” screws
        • 4’ of ½” EMT pipe (sold in the electrical dept. of home centers)


        1. Cut the pieces of the frame from 2×4’s. The top should have a slight slope, be a foot above the condenser (so heat isn’t trapped), and be large enough to shade the condenser throughout the day. If the condenser is east or west of the house, the roof should be large enough to shade the condenser when the sun is low.

        2. Using 3” deck screws or 12d nails, build the top of the frame and mount the legs. Nail or screw on a piece of 2×4 as a diagonal (not shown on dwg). Place it over the condenser. Drill two ¾” holes through each piece of the frame that rests on the ground, and nail or screw these to the legs (see drawing).
        3. Cut ½” EMT pipe into four 12” pieces to use as stakes, with one end of each cut to 45º to penetrate the ground. Flatten 1” of the other end with a sledgehammer and bend it over. This end will hold down the board. Pound the stakes through the hole until the ends rest on the boards.

        4. Using 1/2” plywood or 1” boards, cut the wood for the roof. Fasten it to the frame using 8d nails or 2” screws.

        5. Cut the shingles with a utility knife and nail them to the roof with ¾” roofing nails.

How to Build a Roof Over a Through-the-Wall Air Conditioner:


        • Saw
        • Metal shears (if sheet metal will be used)
        • Drill
        • Framing square
        • Tape measure
        • Hammer (if wall is brick)


        • Two 8’ pressure-treated 2”x 2” boards
        • Exterior paint (if plywood will be used)
        • 2’x4’ piece of heavy-gage galvanized sheet metal or ½” exterior plywood
        • 3” deck screws
        • 1¼” exterior screws
        • 2½”masonry nails (if wall is brick)


        1. Nail or screw a 2×2 board to the wall above the air conditioner. If wall is brick use 2½” masonry nails, nailed between the bricks.

        2. Cut three pieces for the left side of the frame. Join them to form a right triangle using 3” deck screws, and nail or screw it to the wall. If wall is brick use 2½” masonry nails, nailed between the bricks. If wall is not brick, use 3” deck screws. These should be long enough to penetrate the sheathing behind the siding. Repeat for the right side of the frame.

        3. Cut a piece of 2×2 board to fit between the right and left sides of the frame (the right triangles), to support the bottom of the awning. Join it to the sides using 3” deck screws, after drilling pilot holes for the screws.

        4. Cut the roof piece from sheet metal or plywood. If plywood is used, paint the top edge with exterior paint to protect it from absorbing water (the rest will be painted last).

        5. Mount the roof piece to the frame using 1¼” exterior screws.

You can enjoy having energy efficient A/C if you do many of the small things explained above.