Do not skimp on your air conditioning. If it is 100 degrees
outside and your system will only cool 20 degrees, then your
house will be at 80 degrees during the hottest part of the day.
If it is 105 degrees outside, then you'll be at 85 degrees.
Frankly, my wife and I like to keep our home at 72 degrees.
That means when it is 105 degrees outside, the A/C unit needs
to cool our home 33 degrees. In order to accomplish this, we
need larger-than-normal units.
Most A/C people will tell you that you shouldn't design a home
to cool 30 degrees because during the warmer parts of the year,
the A/C units won't be running long enough to remove the humidity
from the air. That's where a two-stage unit like the Trane XL
1800 comes in. The XL 1800 has two compressors: a smaller one
for when your needs aren't that great, and a bigger one for
when you need full power. It also has a variable speed fan.
If you slow down the airflow, the system can pull more moisture
out of the air. That said, you need to be careful that you don't get too much air conditioning for your home because it will cause humidity problems.
Your choice of air conditioner will be an important one. I
recommend the Trane
XL19i that replaced the XL1800 I got when my home was built. The XL19i is a 19.5 SEER system with dual compressors,
two-stage cooling, a two-speed fan, and a sound insulator on
the compressors. If you combine it with the variable speed indoor
unit, it gives you better humidity control I mentioned. It is
backed by a 10 year warranty.
Do you really need an 18-19.5 SEER air conditioner? Probably not.
It is the Rolls Royce.
Efficiency levels for air conditioners
- 10 SEER — the minimum efficiency allowed by law for
new central air conditioning systems.
- 11 or 12 SEER — For my first home, I upgraded from
the 10 SEER to a 12 SEER and had very low utility bills. I
recommend a minimum of 12 SEER.
- 14 SEER+ — These units start to get expensive, but
their efficiency is outstanding.
Efficiency levels for Gas Furnaces
- 78% — The legal minimum for new furnaces on the market
- 80% — This is the minimum I recommend.
- 90+% — Currently the highest efficiency you'll find.
|Annual Cooling Bill
|6 SEER||10 SEER||11 SEER||12 SEER||14 SEER||18 SEER|
Don't spend a lot of money on a high-efficiency air conditioner
and then go cheap on your ducts. Specify R-6 flex air ducts
to ensure that you get well-insulated ducts. Most air ducts
will be in a hot attic. You can lose a lot of cooling power
to poorly insulated ducts.
Don't use duct tape
Well-insulated ducts won't do you much good if you have leaks.
The best way to get a leak is to use duct tape to the seal connections.
Under the extreme heat conditions that are typical in an attic,
duct tape can begin to break down in days. Make sure that your
contractor uses mastic or adhesive to seal any connections.
makes several good mastics and adhesives.
For your registers or grilles, I recommend Airmate
401, 601, 403, and 603 aluminum grills. They have dampers and
individually adjustable curved blades.
You want curved blades so that the air is projected horizontally
across the room and then falls down. If it blows straight down
on you, it is worse for allergies and is not as comfortable.
You don't want any air blowing straight down except from an
18 foot or higher ceiling.
For registers on the wall, you want the air to blow straight
Manual J Load Calculation
An air conditioning contractor who knows what he is doing will
perform a Manual J Load Calculation to determine what size air
conditioning and heating units you need for your home. A Manual
J Load calculation takes into consideration for every room in
- Average temperatures inside and outside during both winter
- Foundation/floor type and square footage
- Wall construction (total r-value and square footage)
- Ceiling type, square footage and height
- The duct location, length, and insulation.
- Number of people in room.
- Number and type of appliances or computer equipment. This is especially important for kitchens, laundry rooms, home offices, media rooms, and exercise rooms.
- Window/door sizes, number of panes, frame types, and BTUH
- Window, door, and wall orientation ( faces N, S, E, W, etc.)
Balthazar Custom Homes
If you are looking for a great custom home builder in Dallas,
check out John Balthazar of Balthazar Custom Homes. He is fair and
knowledgeable. His quality is first-rate. He uses great
You can contact John at 972-618-7653.
Come tell us about your experiences building or remodeling a home in our Discussion Forums.
This is also the best place to get your questions answered.