Many times when I visit with families, I will make a side comment about the temperature in our home and their eyes get wide with wonderment. They don’t understand how we can be comfortable with the thermostat at 78 during the summer when they have theirs at 74 and are miserable.
The Problem
The secret is that it is not the temperature but the humidity that makes you uncomfortable in your home. This is why 78 degrees in Houston feels so much worse than 99 degrees in Palm Springs. Houston has humid air while Palm Springs is hot and dry.
For years, air conditioning systems were designed by a rule of thumb or were over-sized to make sure they “worked” properly. Early in my career, I remember homeowners asking us how much more it would be to upsize their systems to make sure they could keep their homes cool. We would often oblige and offer that as an option.
Now we know better and actively discourage the upsizing of air conditioning systems. We have learned that those practices made our homes less comfortable, as they failed to properly remove the humidity from the home’s environment.
The humidity is what was creating a majority of the discomfort not the actual air temperature.
What Happens?
An over-sized system will short cycle as it blast cools the home to the temperature set on the thermostat.
This is when the system comes on, runs for a short period of time and then turns off. This short run time does not allow for system to remove an adequate amount of humidity.
Although your home’s temperature may be at a desired level, the higher level of humidity may keep you uncomfortable. This often leads to homeowners continually lowering the thermostat to keep the air conditioning system running until they are comfortable.
The lowering of the thermostat keeps the system running so that it is able to remove the humidity, while dropping the temperature. The humidity makes your home feel warmer than it really is.
Over Sizing Can Cost You
Oversized units may not only cost you in comfort but can cost you in dollars as well. Compressors need recovery time, if your system is constantly coming on and off in a short cycle pattern, it can damage the compressor and other systems. This may require costly repairs and/or compressor replacement.
Powering up a compressor repeatedly to come on and off can raise you’re monthly electric bill.
You will often pay more for the larger equipment at installation as well. Here is an article that discusses these matters in greater detail;
http://www.proctoreng.com/articles/bigger.html
The Viscous Cycle
When homeowners feel uncomfortable they keep turning down the thermostats until it the system runs enough to make the home comfortable. As the air dries out and the house temperature continues to drop the home starts to feel more comfortable.
As the home becomes cooler, you will often have a family members complain the house is too cool and ask you to turn the AC off. They will tell you to turn up the temperature and the system will shut off allowing the humidity level to rise.
Have you ever wondered why you’re wife will be perfectly comfortable outside on a fall day when it is 75 but needs a sweater in your home when the thermostat says it is 74 degrees. It is because in your effort to make the home comfortable you ran the system so long, the air dried out as well as dropped in temperature which exasperates the feeling of coolness.
Often one of the homeowner’s will complain it is too cool and turn the temperature back up. This keeps the system off for awhile and the humidity begins to rise again and the cycle repeats itself.
Longer Is Better
Air conditioning systems remove the moisture from the air as they operate. The longer a system operates the more humidity it removes. The desired outcome is for the system to take its time cooling the home down so it can remove the humidity as it slowly cools.
In other words, the longer the system runs the more humidity is removed and the more comfortable you feel, even though the temperature may not be 74 degrees on the thermostat.
What Can You Do?
How do you make your home’s system keep you’re home more comfortable? That can be harder to do with an existing system, however, there some intermediate steps.
1 – Keep your filters and coils clean and units properly serviced.
2 – Run vent fans when showering to remove humidity from the bathroom. It is recommended you run them for at least 20 minutes after your shower.
3 – Use your vent fan at your cook top to remove smoke and humidity from meal preparation.
4 – Keep your interior doors open so air flows through your home unobstructed.
5 – Make sure your vents and return airs are clean and clear of obstructions.
6 – Make sure your vents/ducts are not leaking and are properly insulated.
7 – When adding on or remodeling, have your existing systems reworked instead of adding another compressor.
8 – When the time comes to change out your system, have a qualified AC technician complete an accurate and thorough load calculation to see if you can down size your system and/or redesign your system to be more efficient.
9 – Inspect your home for breaches that allow warm moist air to enter or cool dry air to escape, such as weather-stripping, windows, doors, etc… Seal the leaks!
Just Right
With a properly sized and operating air conditioning system, you can make 78 feel like 72. This does not only apply to your existing home but to your new home. Quiz your builder on how he/she designs the air conditioning systems. Do they have a load calculation completed? Do they up size the systems “just to be sure”? Do they know what a short cycle is?
Your air conditioning system is one of the largest energy users in your home. Having a well designed and operating system will not only save you money but it will also keep your family more comfortable.
Thank You
Having a properly sized air conditioning system means sometimes bigger is NOT better. Make sure your contractor understands all the science that goes into the design and installation of a system. If you are building a home, make sure your builder understands as well.
If you have a question on how we can help you build a custom home, please feel free to email your questions to our offices. Garabedian Properties is a full service building firm serving the Dallas/Fort Worth Metroplex. We offer new luxury homes, premium remodels, green building/remodeling, home care services, storm/roof repairs and commercial building contracting.
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