In Atlanta this is probably not an issue but in any case a simple heat tape to the drainline will be enough to prevent any problem (per the installation instructions)this of course would include garages, attics, unconditioned crawl spaces etc. The mod has been aound for a good 8 years and has only improved with time. You will probably not find ANY complaints by anyone who owns one. The efficiency is pretty good but you are buying comfort with the mod in addition to the fuel efficiency. The 80+ VS 2 stage is a good compliment for the second floor.