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?

Many thanks.