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Why is My AC Running All the Time?

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Air conditioning can be problematic in a Houston summer, and units can run all day long without ever really cooling to your desired temperature.

As we head into ever hotter days, we rely more on our home’s cooling systems, but we may not be as comfortable as we like. Houston would not be as large as it is without the aid of air conditioning. It is simply to hot and humid here. As the days become hotter, one call that I receive more than most is about AC units running all of the time, but the house is no cooler. What can we do? Is the unit broken? Then you hire a HVAC professional, and he tells you that it is fine. You are left not knowing what to do. I have been there.
    I am not sure if this is a true fact for all air conditioning units, but it is a rule of thumb that I keep hearing over again: your AC cannot cool the house down more than twenty degrees Fahrenheit from the outside temperature. If you have a 100F day, like my thermometer read yesterday, then the home cannot be cooled more than to 80F. I have seen exceptions to this statement, but generally it has applied to most homes that I inspect. This rule has been mentioned to me by builders and HVAC technicians. Not a comforting thought. I have seen homeowners increase the size of their AC systems in the hopes of improving this situation; however this has not always helped. Here are the steps that I have taken to ensure better cooling:

1) I set my programmable thermostat to a reasonable range. To me this means between 77F to 79F. I have it go warmer at night, and cooler when the family needs it during the day. I keep it within a few degrees, because big swings cause the AC unit to work harder. Since I am seeing exterior temperatures in the 90F to100F range, the high 70s appears achievable.

2) I make sure that my air conditioning system is in good shape. Yearly maintenance can be a big help. For me, there was one issue this year that I always mention on my home inspection reports: deteriorating insulation around the refrigerant pipe. This line should be insulated all the way from the compressor to the evaporator coil in the attic.

3) Adequate insulation which covers your ceiling joists. For Houston, you probably should have an R48 amount of insulation in your attic. I hardly ever see this when inspecting a home. I have around an R60 above my living areas with an R26 over my attached garage. To prevent thermal bridging, I have insulation covering my ceiling joists. On top of this set-up, I have a radiant barrier. I also insulated my garage doors. Even new homes will not be fully insulated. Builders do not insulate over attached garages, and I have been told by a few builders that they can leave up to 2% of the attic uninsulated. Any area without insulation can make your insulating efforts useless. 

4) I am an avid caulker, sealing any joint. I want to prevent loosing my conditioned air, so I caulk around windows, doors, and wall joints. I also have weather stripping in place. I notice that many homes forget to do this around attic doors. I also have insulating pads behind electrical outlets on exterior walls. I do not have a fireplace, but remember to keep the damper closed. My kitchen range vent has all of its coverings in place to help prevent loss.

5) I run my ceiling fans. We feel more comfortable (cooler) with air movement, so ceiling fans help.

6) I added insulation to my ducts, and they are sealed. During my home inspections, I am grateful for the cool air in the attic coming from a duct, but this is not a good  thing for a homeowner. This happens in many homes.

7) Keeping the door closed. If you have children, then you know what I mean. Even my dog will open the back door. He has not figured out how to close it.

8) Solar screens over windows along with awnings. Double or triple paned windows are the best, but older homes have single paned windows. There is a window screen material that helps prevent radiant heat from coming into the room. Window awnings also help prevent the sun’s heat from entering the home. I did an awning for entire wall sections to keep the walls cooler.

9) Plant trees and bushes for shading. Plants cool an area better than an awning. Trees blocking the sun from the south and east help in Houston.

10)Shading your compressor. I have never heard of anyone advocating this method, but it occurred to me last year. Last year I had serious AC issues. With my wife quite upset, I decided to take cold water from my garden hose to bring the temperature of the fins down. This had a noticeable effect on the interior cooling. This year I setup a shading system for my compressor. The principle is simple. The compressor takes hot refrigerant from the evaporator coil, and cools it down by running the refrigerant through tubes with fins while a fan forces air over them. The air takes away the heat, leaving cooled refrigerant to return to the evaporator coil. These fins are being heated by the sun’s rays, so the air has to take away that heat and the heat of the coolant. When I watered my compressor, I was assisting in removing heat with the water. By shading the unit, I am preventing  heat from being there.

11) Improved attic ventilation. I find that the better the air flow through the attic helps cool the house. Better ventilation removes the heat from the attic, which will stop that heat from effecting your living areas.

Those were my steps to improving my AC for this summer. You can use this blog’s search function to find articles on specific topics with more details. Keep cool.

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One Response to “Why is My AC Running All the Time?”

  1. because of the radiant heat build up in our attics and garages we here in arizona have developed the GF-14 garage and attic cooling fan. radiant heat is everywhere interest is everywhere and rising

© Frank Schulte-Ladbeck Professional Home Inspector Houston, Texas
Frank Theodor Schulte-Ladbeck
home inspector, TREC# 9073
Houston , Texas , 77063 United States

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