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Size Does Matter!

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Happy, Happy, Joy, Joy — we made it to another Friday! Welcome everyone and I think it’s safe to say that summer is in full swing when you walk out your front door at 6:15 am and your glasses immediately fog up from the humidity. According to my weather app, at the time of this writing, it is not yet 7:00 am and the temperature is 84 degrees with a feels like of 94 degrees and the humidity is at 82%. Considering that the sun is barely up, I think it’s going to be a warm one today and probably every other day until October! The temperature vs. humidity discussion is my segue to the size does matter discussion when it comes to air conditioning.

First and foremost, you cannot guess when it comes to properly sizing and designing an air distribution system for a home or building. Years ago, before we know what we know now, the old rule of thumb was for every five hundred sq. ft. you needed 12,000 BTU’s of cooling, or more commonly known as a ton of air conditioning. In my usual tradition of imparting some useless trivia, the term ton dates back to the old days when people used to cool buildings with ice that was harvested from rivers and lakes, and someone far brighter than your humble author discovered that it takes 286,000 BTU’s to melt a ton of ice over a twenty-four hour period. When you do the math and round up a little, you get the magic number of 12,000.

Fast forward to today where we have been blinded by science and there is a lot more to sizing a system than just the square footage. We take into consideration the direction the home sits, the color and type of roof, how much insulation is in the attic, whether or not there are other heat reduction methods in the attic, the window size and type, and what type of construction is the home and the duct system. If you think it sounds complicated, you’d be correct. The question is, why does it all matter?

The first answer is the obvious one, in that if an air conditioning system is too small it is not going to properly remove the heat and cool our space correctly. The second is a little more complex in that if an air conditioning system is too big for the space you will have humidity issues. This is caused by the unit not running long enough to properly dehumidify our environment. Please remember that air conditioners themselves are not true dehumidifiers, however, one of the by-products of a properly sized air conditioning system is you get good dehumidification. This is especially true when you look at variable speed air handlers which I have discussed in the past.

Bottom line, if you are in the market for a new air conditioning system and whomever comes to give you pricing doesn’t run a load calculation on the building to ensure proper sizing, you might want to choose another contractor. We will always run a load calculation before we will let you purchase a new system. If you need a new heating and cooling unit give us a ring at 1-800-475-1504, visit or drop me an email at

Ice, Ice Baby… House Whisperer out!!


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