Why does my air conditioning system cost so much to run when it still doesn’t keep me comfortable?

In the heating and air conditioning industry, we are beginning to understand the cause-and-effect relationships between inefficient building practices and wasting energy and money through energy losses.

New studies demonstrate that indoor air quality is degraded and biological allergy-causing agents are introduced into our homes by leaks in walls, ceilings, windows and air conditioning systems.

All over the country heating and cooling systems are running excessively never achieving acceptable levels of comfort or efficiency because houses are leaky and so are air conditioning duct systems.

Discomfort is rampant as high humidity takes over in homes built with new techniques and new materials but the air conditioning systems are not designed properly for these new homes. As the energy “footprint” decreases in a home, the size of heating and cooling systems should decrease proportionately. Ask the average HVAC contractor how many square feet can be cooled by a ton of air conditioning and he may very well tell you 500 square feet per ton is the standard. This could be an indication of faulty design practices. A casual rule of thumb that can have serious negative consequences.

 A Simple Example

 My house, for example, was built in 1977. If you were to calculate the amount of cooling capacity it would take to cool that home as built with R-19 rock wool insulation in the attic, R-13 fiberglass batts in the walls and vintage double pane aluminum windows, you would find that 500 square feet of that home could be cooled by one ton of air conditioning.

If however you took the same size house and built it today achieving the minimum requirements of today’s more efficient building codes, you would find that the more efficient building structure would allow you to decrease the amount of cooling needed so that the square feet per ton ratio would be close to 750 square feet of living space per ton of cooling equipment. This is common sense rule of thumb reasoning.

To illustrate the point, imagine two glasses of iced tea on your kitchen table. One is a 16 ounce glass mason jar mug the other is a stainless steel vacuum insulated travel mug with a screw top lid. It doesn’t take a degree in rocket engineering to figure out which container will keep the iced tea cooler longer.  To put it another way, which mug will have more ice left in it after one hour? You guessed it! The travel mug wins. So it is with your super insulated house; it is easier to cool with less cooling power. So this is a more with less equation. If you build a house with more insulation and more efficient windows, you can cool the same size house with less air conditioning plain and simple.

Old Homes Waste Energy

The median age of the existing homes built in America is about 1974. That means that half the homes that we live in today were built in a different era; before the energy crisis of 1973.

        How does this affect the we way we design our indoor comfort systems?

First of all, the way we approach the problem of design depends very much upon the way the house was built in the first place. When energy was cheap and conservation was not such a big concern in our culture, houses were built inefficiently. Air leaks were just a consequence of common construction practices. In older homes weatherization efforts must be undertaken to wisely control energy costs.

In newer homes, especially those built since the year 2000, much of that attention to detail such as caulking, sealing and enhanced levels of insulation has been required by minimum building code standards. 

Since there is such a variation in the efficiency of the building envelope of any particular house, critical attention must be paid to the performance of a home in order to properly match it with the right heating and cooling system.

The craft of air conditioning in this country is in many ways underdeveloped. Many contractors lack the basic skills to overcome the challenges that we face today concerning energy usage and the principles of true indoor comfort. Increased competition in the mass production home market inevitably results in lower prices and lower prices means cutting corners.This downward spiral in quality craftsmanship brings us to the point where we are today. 

Poor Performance of HVAC Systems is the New Normal

According to research conducted by the National Comfort Institute, the average performance of a typical air conditioning system installed in this country is 57%. That means that 43% of the energy consumed to cool a typical home is not translated into cooling and comfort but is wasted. In a time where we are all more conscious of the long term cost of wasting precious natural resources something needs to be done about this problem.