Why Air Conditioning Works Overtime in Hot Attics
AC Can Use over 60% of the Electric Bill for Fla Homeowners
I found this article apparently written by Allison Bailes, PHd the grandson of the inventor of Air Conditioning... Willis Carrier... In any event, he founded the Energy Vangard Group, which is all about teaching energy efficiency. I could have re wrote this, or just wrote it from scratch, but instead here is a link to their site.
Their site is huge, and goes into great details about heat transfer, and keeping Fl homes cooler. It recognizes the difference we have here in the south, with heat and humidity. Also, it recognizes the value of proper AC sizing, and cooling the attics. That is why we spend a lot of time on:
Understanding the Benifits of Attic Cooling
Sealing Leaky AC Ducts
Installing Radiant Barrier and Solar Attic Fans.
After this is done, then we can discuss installing Solar PV
Bright Energy Central
Anyway,here is an excerpt from the article from The Energy Vangard Website
An air conditioning system is an amazing thing. I spent the years 1988 to 1998 living in Louisiana and Florida driving a car without an air conditioner, so I appreciate cool air. If you've been a reader of this blog for a while, you probably know that I also appreciate HVAC systems done right.
The Fundamentals of Air Conditioning
An air conditioner is a device that moves heat from one place to another. It picks up heat from inside your home and moves it to the outside. In other words, it pumps heat from one place to another. Although we could call it a heat pump, we usually reserve that term for air conditioners that can pump heat in either direction - inside to outside or outside to inside. (I wrote about the paradox of getting heat out of cold winter air a while back.)
When you put your face in front of that AC vent, it may seem that an air conditioner creates cold, but in reality, it's removing thermal energy from inside your house and sending it outside. This transfer of heat from your home's air does indeed make the air cooler, and the air blowing out of the supply vents does feel cold. It's best to think of the process, though, as a heat flow from inside to outside. (For more about this, read What IS Heat Anyway?)
The Refrigeration Cycle, Simplified
Step 1: Catch the heat from inside the house.
The inside part of your split system AC has a blower, that pulls air from the house and sends it over a very cold coil. This coil has cold, cold, cold refrigerant running through it, so the air passing over it gets cold. Well, OK, what's really happening is that heat from the air is flowing into the cold coil with the cold refrigerant.
When the air comes off the coil, the temperature has dropped about 20° F (if everything is working right). So if you're keeping your house at 75° F, the air coming off the coil is at 55° F.it goes through a special device before it enters the coil I talked about in step 1. This special device lets the warm, liquid refrigerant expand into a bigger volume, which causes the temperature to drop - a lot!
OK, if you are still reading this, then you are more committed than most. The main thing is, if the AC unit has to run the cold air thru a superheated attic, then the efficiency of that AC unit is severely compromised.
So what can you do in Florida to Cool Down That Superheated Attic?
There are a few choices...... The Best & Most Expensive:
Install spray foam under the plywood in the attic, remove the insulation, close off the soffit vents and seal all outside penetrations. The attic must be now completely sealed from the outside.....Once this is done, then the attic will be at the same temp as the home. What a difference this makes.
However, this is fairly expensive, so many people ask about cheaper options. Also, some homes are not built to have a spray foam job without extensive retrofit.
Many homeowners opt for the option of installing Radiant Barrier, more insulation and a few solar powered attic fans. This is not quite as effective as the first method, but it's about half the price.
The main point of any of my articles is to make a homeowner think. Most of this stuff is not that complicated in its basic form. That's why we keep trying to make the point, that running AC thru the hottest point of the house before getting it to the living space is CRAZY.
Mike Norvell Sr
Hope this helped. For more info on making your home more efficient, plz fill in the form to contact us...
Why Doesn’t My AC Turn Off In The Summer?
Maybe your attic is getting too Hot…. Get rid of that attic heat!