How to Use Less Electricity with Air Your Conditioning

Many energy saving tips on buying, using and maintaining window air conditioners and on using and maintaining central (whole house) air conditioning to help you use less electricity with your air conditioning

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Types of Room Air Conditioners

Air conditioners which are not large enough to cool an entire house or apartment 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 “window evaporative coolers”, also known
as “swamp coolers”. These use a completely different technology, which is explained below.

In the topic,
Energy Saving Tips for Buying and Using Room Air Conditioners, most of the energy tips apply to both types of room 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.

Conventional Room Air Conditioners

There are three types of conventional room air conditioners: window-mounted air conditioners; through-the wall air conditioners, also called “built-in air conditioners”; and portable air conditioners. As mentioned, these use the refrigeration cycle. Their
advantage over central air conditioning units is that you can turn one on to cool a room while you occupy it then turn it off to save energy.  

Window-mounted air conditioners have several disadvantages: they block most of the view from the window; you may remove them in the cold months, to have a view through the window and if you haven’t insulated them well. Also, there normally won’t be enough extra electrical capacity in the nearby outlet, so a new circuit must be created.  

Through-the-wall air conditioners are installed in a hole in a wall so they don’t block the view through a window. They can cool a room better than the other types because they can be larger.
They can have cooling capacities as large as 22,000 Btu’s, great enough to cool a small apartment. A new circuit normally must be created for each because they are normally larger than window-mounted units, but the cable that feeds
the circuit can often be mounted to the outside wall running to the basement. 

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 be easily moved from room to room. You will need to use a long, heavy gage extension cord if any of the rooms do not have enough extra electric capacity. They have the disadvantage that they collect water, which must be emptied each day.  

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 long 14 gage extension cord. Normally, a 20-amp kitchen outlet or a 20-amp outlet used for a window air conditioner will be sufficient. In most
homes, few if any of the outlets in the bedrooms and living room have enough extra electrical capacity for a portable air condition.

To determine if an outlet has enough extra electric capacity, turn off it’s circuit breaker and check which outlets lose power. These are the outlets on that circuit. The circuit breaker will have 15 or 20 written on it, indicating
that the circuit has a maximum load of 15 or 20 amps. Add the air conditioner’s required amperage to everything using those outlets to estimate how many amps the circuit would need to provide. Basically, you are only checking if
anything on the circuit uses many much power, such as a TV computer or space heater. 

Window Evaporative Coolers

Window evaporative coolers, also called “swamp coolers”, or “evaporative air conditioners” 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, also called “mini splits” or “ductless mini splits” also use the refrigeration cycle, but the condenser is outside the house and the air conditioning
units (evaporators) are in the rooms they cool. A system will have one condenser and two, three or four air conditioning units, one for each room being cooled. The condenser rests on the ground outside of the house or is mounted
to the wall. 

They use less electricity than room air conditioners because their condensers release the heat more effectively. A 3” diameter hole must be cut through the wall behind each evaporator for the refrigerant tubes and their insulation.

Energy Saving Tips for Buying and Using Room Air Conditioners 

Energy Saving Tips for Buying  Room Air Conditioners

Energy Saving Features Available In Room Air Conditioners:

  • 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.

  • Smart air conditioning. These models can be paired with your smart phone for remote control. You conserve electricity by turning off your A/C when away from home.

Buy the Correct Size Model for Maximum Energy Efficiency

A model that is too large will cycle on and off too often, wasting electricity. A model that is too small is efficient but of course will not always make the room cool enough. The table below shows the correct cooling capacities recommended
by an air conditioner manufacturer. 

Cooling Capacities for Maximum Energy Efficiency 

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 a Model With a High Energy Efficiency Ratio.

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.

Create a New Circuit for the Air Conditioner If It Would Use Too Much Electricity.

Before buying a room air conditioner you must check if the electric circuit it would be using has enough extra amperage capacity. If not, you must buy a smaller model or install a new circuit. 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 as 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 estimate 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.

Buy Energy Star Air Conditioners

ENERGY STAR products are very similar to other products but use energy more efficiently. Thus, they use less to do the same thing. They must meet energy efficiency criteria set by the EPA or the Department of Energy. 

Energy Tips for Using Window Air Conditioners 

  • If a window mounted air conditioner conditioner is left in the window in winter, cover it on the outside with an air conditioning cover or with a plastic tarp fastened with “all-weather duct tape”. 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 are 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.

  • 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.

    Plant a tall bush to the west of an air conditioner on a west wall to shade it in evenings as the sun sets. Plant one to the east of an air conditioner on the east wall to shade it in mornings.

  • If an air conditioner is left in the window in winter and will not be covered on the outside because it is on an upper floor, cover it with either transparent plastic sheeting or a quilted air conditioning cover. Quilted covers 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 pleated sheets out of the frames and replace them with rigid insulation, taped on with all-weather duct tape. Rigid insulation may only be available in 48”x96” sheets. Use the remainder for other types of insulation, such as inserting behind radiators.

  • If a window air conditioner is in a metal case that is mounted to the wall, caulk between the case and the air conditioner with clear, interior/exterior caulk.

  • 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.

  • Check the filters each month. If they are torn or filled with pet hairs or dust, replace them. If they are washable and dirty, wash them with dish soap 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 are cut to size are sold in home centers and hardware stores, and filters of the correct size can sometimes be ordered from the manufacturer.

  • When the outside air is cooler than the inside air in the late evenings, change the setting from “Cool” to “Fan” . Check the outside air temperature either with a smart phone or by mounting an outdoor window thermometer to the window frame.

  • 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.

  • Either wash or vacuum the evaporator and condenser coils once each year, or 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, because a layer of dust is insulation.

    To wash the coils, 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 a window air conditioner or through-the-wall air conditioner is in direct sunlight much of the day, mount a plywood or sheet metal roof over it to shade it. The condenser coils in the back release heat, and operate more efficiently when shaded from the sun.

The outlet you plug it into must be grounded. Also, check if it is on a different circuit. If it has the same circuit breaker it is on the same circuit. It should draw no more than about 50% of the amperage of the circuit it is on. See,
Create a New circuit for the Air Conditioner if it will use too much Electricity

  • If you often need to cool the air in only one or two rooms and run the central air conditioning for this, 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.

  • 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.

  • Inspect the insulation around “through-the-wall” air conditioners by removing them from the wall. They often have foam rubber insulation, 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 the side panels are torn, replace or repair them. Air conditioner side panels are sold in some home centers. To repair them, use white “all weather duct tape”.

  • If an air conditioner’s fan setting is used frequently, mount a window fan in another window to use in place of it. A window fan will bring in much more air because a fan draws the air into the house through its coils.

  • If you leave an air conditioner running all night instead of leaving a window open for fear of crime, try turning off the air conditioner and securing a different window in the room at 6” open and run a stand fan next to it.

    One way to secure a window is to prop it up with a 6” piece of 2″x 3″board. To prevent an intruder from raising the sash, jamb in very tightly a 2″x 3″ board above it vertically. Paint the boards white.

    Another way 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. This should probably only be done with wooden sashes. The nails must fit snugly.

  • 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 sash was probably painted shut. Use a utility knife to cut the paint and pry the sash loose with 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. 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.

  • 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. The cost to operate it may be greater than your savings in air conditioning costs, but they also 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 post, ”
Guide to Dehumidifier Energy Conservation”.

  • If your climate is very dry, you could replace small window air conditioners with window evaporative coolers. These use about one-fourth as much electricity, but cannot be used on humid days.

They are explained in the topic, ”
Types of Room Air Conditioners“.

Energy Saving Tips for Using Central Air Conditioning 

If you take steps to lower the energy consumption of your central air conditioning, you can cool your home for less money and reduce the high costs of equipment repair and replacement. A condenser may last only 12 years if used often
and costs over $2000 to replace. If on the roof, a crane must be used to replace it.

  • Turn off the power to the air conditioner at the end of the cooling season. If 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. 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.

  • Clean off any leaves stuck on top of the condenser unit and rake up leaves in the yard. The condenser draws in air at the top, forces it past its coils and fins and releases it out the sides. This releases the heat taken from your house through its fins. Since air is drawn in from the top, leaves are pulled against it and pieces of leaves are drawn through and clog up the fins.

    If the airflow is partially blocked at the top or as it passes through the fins, the air conditioner will operate less efficiently and cost more to run.

  • Remove any large 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.

  • 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 larger fraction of the temperature difference between in the home and outdoors.

  • 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.

  • Install a thermostat with many energy-saving features. The types of thermostats include:

  • 7-day programmable – let’s you program a different schedule for each day of the week

  • 5-2 day programmable – lets you program a schedule for weekdays and another for weekends

  • Smart thermostats – you can control your heating and cooling with your smart phone and are programmable

  • WiFi thermostats – have the features of smart thermostats plus other smart features such as sensing when you’re home.

  • 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.

  • Always replace the filter for your HVAC system (called “air filters” or “furnace filters”) at the end of it’s recomended life. Some are designed to last only 30 days, some for 1 year. If clogged with dirt they slow the airflow and make your air conditioning cost more. Shut off the power at the switch or turn off the system at the thermostat before replacing a filter.

    Generally, the thicker the filter, the better it cleans the air, but the more resistance to airflow it creates. The higher it’s resistance to airflow, the more it costs to use your air conditioning, 1” thick spun glass filters create the least resistance and thus save you the most.

    A filter’s MERV rating indicates how well it cleans the air, and FPR ratings are similar.

  • Clean the fins in the condenser when they appear dirty. You can do this yourself or hire an HVAC contractor. 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 also 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.

  • 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.

  • 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 the topic, How to Build a Roof for a Condenser Unit.

  • If the condenser unit is in direct sunlight, build a 4′ high wooden fence around it or plant tall shrubbery to block the sun from striking it at low angles in the mornings and evenings. Either should be 2′ away. These will also add beauty to your home.

  • 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 fins; the air passes through them 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.

  • If your heating and air conditioning use the same HVAC ducts and registers, set the main HVAC damper (the valve that controls airflow to the house) at “Cooling” at the beginning of the cooling season and “Heating” at the beginning of the heating season

    This may not necessary for single story homes. In multi-story homes it prevents the first floor from receiving too much cold air.

    The damper has a control lever, and there may 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.

    Very large homes may have more than one HVAC duct taking air from the furnace and air conditioner, and each will have a damper.

  • If your second floor is warmer than your first floor when the air conditioning is running, and you set the thermostat temperature to make the second floor comfortable, try to balance the temperature.

    You can balance the temperature by partially closing off all of the registers on the first floor. Experiment with this on a very cold day.

  • 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.

  • Mount magnetically attached air deflectors on registers at the bottom of the walls. These direct cool air upward. In the heating season they can be reversed to direct warm air downward.

  • 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 into these rooms to balance the temperatures. Cut off ½ ” from the bottom of these doors and run a box fan inside these doors to draw in the cooler air while you occupy the rooms.

  • If you have registers in the basement, keep them tightly closed. Air flows out of them and returns to the air conditioner in a short path with less friction, causing the top floor will receive too little air.

  • If your home has transom windows 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 you use more air conditioning than heating and your ceilings have 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.

  • Mount blinds or skylight shades on skylights. Blinds and shades designed for skylights are sold in stores specializing in window shades.

  • If you spend almost all of your time in one or two rooms, buy window unit air conditioners for those rooms and turn them on in place of the central air conditioning. This will help you conserve electricity.

  • Hang white shades or blinds at windows which are under 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.

  • Mount very light-colored drapes or curtains across patio doors.

  • Have awnings mounted on the windows of walls that receive 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 weathervane in your yard to show when the wind is blowing fairly strongly and in which direction. When the wind is blowing strongly in moderate temperature weather you could turn off the air conditioning and open some windows. It’s direction shows which windows to open. 

  • 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.

  • 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 umbrella can be mounted on a round picnic table, 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 spend more summer evenings outdoors and turn off your air conditioning. Build a deck or patio. Buy a picnic table, lawn chairs and gas grille for the lawn. Build a wooden fence around the yard. 

  • 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. They can be very effective when the wind blows because it 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 cupola’s sash and leave it open all night. It will help if you 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.

  • Using the cupola will also lower the humidity in your home because the outside air that enters is much less humid than the inside air, except on rainy days.

  • 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.

  • Do all you can 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:

  • In the months your central heating is off, open your crawl space vents to allow the humid air to escape. This is their purpose. Vapor rising from the ground makes the air in a crawl space very humid.

    Don’t forget to re-open them or the crawl space will be too cold in winter and the room above will be colder.

  • 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 shut. 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.

  • 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 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.

Ways to Vent a Clothes Dryer Through a Wall

  • If there is a nearby window with a small pane of glass, replace the pane with a sheet of transparent polycarbonate and cut a hole in it for the hose. This material is very strong, but for added security screw a 2×4 across the sash. A jigsaw will cut the hole.  Home centers and hardware stores have polycarbonate sheets; they are commonly used to replace glass because they are unbreakable. 

  • Open the window and stick the hose through while drying clothes.

  • If the nearby wall is brick, make a hole through the wall. This requires a few tools and should only be done by someone with experience. Only one brick need be removed; the hose will be compressed a little to fit through the opening and mortar should be applies around the hose.

    A reciprocating saw can be used to cut through the plywood sheathing and drywall, but they must first check that no wiring is in the wall!! 

  • If the nearby wall is of any other material, except stone, an experienced person can cut a 4″hole through it using a reciprocating saw or a 4″ hole saw. They must first assure themselves that (italics)no wiring is in the wall!   

How to Build a Roof Over a Condenser Unit or a Through-the-Wall Air Conditioner

How to Build a Roof Over a Condenser Unit


  • Sledgehammer

  • 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. sssssssssssssss ssssssssssss sssssssssss sssssssssss sssssssssss
  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).
    sssssssssssssssss sssssssssss ssssssssssss sssssssssssssssss 
  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. sssssssssssssssssssssss ssssssssssssssssssss ssssssssss
  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). sssssssssssssssssssssss ssssssssssss ssssssssssssss
  5. Mount the roof piece to the frame using 1¼” exterior screws.

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 brick wall)


  • 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. ssssssssssssss sssssssssssssssss sssssssssssssssss ssssssssssssssssssss          
  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. sssssssssssssssssssssss sssssssssss ssssssssssssssssss ssssssssssss                 
  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. sssssssssssssssss ssssssssss sssssssssssssssssssssss ssssssssssss  .                
  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). sssssssssssss sssssssssss ssssssss sssssssssssssss ssssssssssssssss 
  5. Mount the roof piece to the frame using 1¼” exterior screws.

Cooling your home could become much less expense if you do many of these energy tips which help to use less energy with air conditioning. You will save energy and enjoy much lower energy bills. 

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