Terracotta/Evaporation for cooling fermentation?

[sideshow_ben]

I'm going to brew a Kolsch and my basement is in the low 70's. Rather than warm up by kegerator to the 60's for fermentation, I was thinking of building a terra cotta (or pot-in-pot) evaporative cooler. Basically I'm going to find an unglazed planter pot that holds my Better Bottle, stick the carboy in the pot and fill the space with water, then have a fan blow on the outside of the pot. In principle the evaporation of water on the outside of the pot cools the inner water by 10-15 degrees.

Has anyone ever tried doing this?

 

[Ravenshead]

Yes though it's typically done with a t-shirt over the carboy to provide better wicking. Search "swamp cooler" for more info.