I like Entry #13. I like both the colors. I thing the word "and" is way too bold, and the "Air" is way too weak. I like the boldness of "Heating".
Generally I am wanting something BOLDER. I think the Grey color you used for the fonts on the other logos would be stronger in a darker grey or darker color.
I really like Entry#12 also... I wonder if the flame behind and the wind could form some kind of circular "yin and yang" of hot and cold... flames going up on the left, and ice / wind dripping down on the right... which could go BEHIND the Text.
Just an idea.
Another thing we don't want to lose is the .com... we want to do the logo in a way that encourages people to go online.