Energy Efficient Air Conditioning

In the temperate and warmer latitudes, energy efficient air conditioning systems are a major part of keeping ourselves comfortable year ‘round, but especially during the warmer summer months.  The bad news is that air conditioning is one of the more expensive home comfort costs we will have.  The good news is that there is much we can do to keep these costs down and still keep ourselves comfortable.

As a young person growing up in the mid ‘50s in hot and humid Midwestern U.S. summers, we actually functioned quite well without energy efficient home air conditioning – either in our home or in our cars, though I doubt I would want to do it now.

Floor Standing FanWe had a nice system going where we would open the house at night and use one large floor-standing fan blowing out to draw in the cooler evening and night air through the open windows in the rest of the house.  Then, when we got up in the morning, we would turn off the fan, close the windows, and the drapes, to keep the house comfortable all day.  Then, in the evening, we would repeat the process.  Now, with my own home, I still try to use our energy efficient air conditioning as little as possible – for two reasons, 1) I really don’t like air conditioned air, and 2) it keeps the cost down.  We just use it when we need it.

This was one step above the most energy efficient, “ventilation,” or letting natural air movement keep our homes comfortable and livable.  This simply relies on the fact that heat rises.  By keeping windows or other existing paths open high up in the home, heat can, “escape” through these windows and vents. This will then naturally draw cooler air into the lower portion of the home – and it costs NOTHING.  Simply opening windows and vents high in the home encourages this to happen... your home actually performs like a chimney bringing cool air in at the bottom, and allowing hot air to escape out the top.  For many people, this type of cooling, though not energy efficient air conditioning, can still be very effective, and it definitely saves on energy and money. If we remain aware of ventilation as a way of cooling and use it on days when temperatures are not excessive, we will save money... and the fresh air is great.

The next step from natural ventilation, and one that is still not very expensive, is forcing ventilation with fans; window, ceiling, and whole house.

Window Fan

Window fans are best used to draw cool air in and drive hot air out. Also, place the fan in a window so it will work with any natural breezes that are blowing – don’t make the fan work against natural breezes; use the fan to augment them.  Close windows near the fan, and open windows further from the fan that face any breeze that is blowing.

Ceiling fans are not energy efficient air conditioning, so actually do not cool a room or bring in any cool air; they only circulate air within a room.  The moving air within a room gives a “wind chill” effect so people in the room feel cooler.  This then tells us that if no one will be in the room for a while, we should turn the fan off to save energy and save money.  I feel that ceiling fans many times defeat natural ventilation by blocking the natural flow of air through the home, so evaluate each situation and make sure the fan is doing what is best to keep people feeling comfortable.

Ceilng fan
Whole House Fan

Whole house fans are large units, usually located in attic or crawl space above the house.  They actually augment natural ventilation by quickly helping move more heated air out of the upper areas of the house and therefore bringing in more cool air in the lower rooms.  As I mentioned above, this is how we were cooling our home during my younger years in hot and muggy Midwestern U.S. summers – drawing in cool air at night, and closing up the house to keep it cool during the day.  Before energy efficient air conditioning, this worked very well.

Another fairly energy efficient way to keep you home cool during warmer months is, “Evaporative Cooling” sometimes called, “Swamp Cooling.” This works best in less humid locations as it relies on evaporating water to create cool air that is circulated to keep comfortable. For homes in more humid areas, this process can be pretty inefficient and not offer much actual cooling.

Home cooling with actual energy efficient air conditioning is the most energy expensive method, so as with so much else in keeping our homes comfortable, the first step in adding this more powerful cooling comfort to your home is a home energy audit..

Home Energy Audit WorksheetAnd the good news here is that this is something we can easily do for ourselves.  One of the major advantages of doing our own home energy audit is the ability to keep records of what needs to be done as we do it, and by comparing our energy efficient updates, we can directly see the impact of the work we have done – it will show up in lower energy utility bills, and because utility bills today usually will show us direct comparisons of past months, before our improvements, and current months after improvements.  Proof in print of the energy and money we are saving.  Also, we can prioritize what we should do first against the costs so we can make energy and money saving improvements and still keep our budgets under control.

As a part of your energy audit, you find and seal any air leaks or cracks where cool air can leak out of your home.  We don’t want to spend our money trying the cool the outdoors, so make sure all the cracks and leaks are well sealed.  This also is good for efficient heating of our homes.

What type of energy efficient air conditioning is right for you?  There are really only three different forms that home air conditioning takes:

Central Air Conditioner

Central Air Conditioning – a chilling unit, usually found outside the home, supplies cool liquid that is circulated in a heat exchanger in the air handling system, moving cool air throughout the home.

Split Air Conditioning – as its name implies, the cooling unit which supplies the chilled liquid to the cooling coils, is outside where the noise is less distracting, and a small air mover is mounted inside the room.  Chilled liquid is cooled outside, and piped inside to the air mover.  This is similar to Central air Conditioning in that the cooling “compressor” coils are located outside the house, and the “evaporator” coils that chill the air moving through the home are inside, but instead of the whole house, split units cool only one, two, or three rooms.

Split Air Conditioner
Window Air Conditioner

Portable Air Conditioning or Window Air Conditioning – a smaller, self-contained individual unit is placed in a window to cool a single room, though several rooms may benefit from larger units if there is a way for the cool air to circulate freely between the rooms.  This can sometimes be aided with free standing fans.

Whatever energy efficient air conditioning system you plan to use, work with sales people to insure that it is correctly sized for your needs, from room sized to whole house sized.  Too large a unit will not actually cool your home efficiently and cost you more money, and too small a unit will have to work too hard and... cost you more money.

No one system is necessarily better than the rest and the choice between them is more one of convenience and installation cost.  Central Air Conditioning will keep the entire home comfortable so as you move from room to room, you will not be hot in one room and comfortable in the next, but adding it to a home that does not already have the necessary ductwork installed can be challenging and costly.

Between Split Air Conditioners and Window Air Conditioners, the split variety generally is more expensive to install as you must use a professional installer.  Window units can be purchased and placed as needed, and with proper maintenance can run fairly economically for years.

And what is the key to any good energy efficient air conditioning system? It must be properly maintained!  This mainly consists of making sure that the air filters are kept clean and washed or replaced as often as needed.  Also, check the aluminum cooling fins on both the inside and outside.  For room units, this is just the front and back of the unit.  For split or whole house units, the compressor fins will be on the outside unit and subject to all the dust and debris in the air around the unit – these should be cleaned at least once a year.  On the house side, which will be the inside facing side of window units, inside the duct of whole house units, and in the air handler part of split units, make sure the fins are clear of dust and debris, and they should be cleaned at least once a year.  All this care and cleaning keeps your air conditioning system operating at peak efficiency, and saves you a lot of energy – and money.  Also, for your central air conditioning and split units, at the beginning of each cooling season, you will want a professional to make sure that they have the proper amount of coolant.

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