Advice for New Houston Construction
I know there are some Houston pros on here, as I have read many useful posts in the past. I am building a 5000 sf house in SW Houston. I will have a 4 ton unit down and a 5 ton unit up, and the builder is highly recommending Lennox. I have a few questions:
1. I am strongly leaning to a Lennox XC16 2-stage model. From what I have read, it should cut down on humidity versus a XC14 single-stage model. Is that right? Is a 2-stage a good investment in Houston?
2. I do not understand what a variable speed furnace does. Is it the same concept as the 2-stage AC -- that is, it runs at a low speed most of the time? Why are there so many recommendations to do variable speed furnaces?
The VS can be slowd to help remove humidity better.
A two speed AC system can help control humidity.
A variable speed blower, especially with the right thermostat, can also help control humidity.
However, when it comes to energy conservation and keeping comfortable, you need to look at the whole house, not just the AC system.
Some things that can make huge differences in how big your AC system needs to be - and the resulting energy bills.
Put the air handler and duct work in conditioned space - This can make a 30% difference in the cooling costs.
Design the house so the windows are shaded in the summer time. Any sun coming in a window is heat that you have to pay to remove.
Control infiltration. You want fresh air coming into the house, but you want to control where it comes in at and how much.
If close attention is paid to all of these things, you might be quite comfortable with AC equipment half the size you are looking at. And cooling costs cut in half as well.
There are two-stage furnaces that have a high and low setting for the blower and the burners. Not the same as a variable speed blower. Variable speed is nice because it will automatically adjust to provide intended airflow for the furnace and the AC. This protects the furnace heat exchanger and the AC compressor and provides the intended airflow for best efficiency and comfort. The two-stage furnace is also nice because it runs on low most of the time, which is quieter, and you also get more even temperatures. Not sure if two-stage is really more efficient.
I also agree that there's a lot more to efficiency and comfort that equipment selection. I recommend radiant barrier roof decking. It's not very expensive and is best installed with original construction. Also, properly sized and sealed duct work is very important. And get good windows. There are good double paned and not so good double paned windows.