Yeah in building this system I also thought you could make a very efficient (to run) air con system for a house. Like
Bach-On!!! said, as they are testing this in a project house I don't feel so stupid for thinking about it now. If I build it exactly the same but on a much larger scale put a large oil type plastic tank deep underground and use a pump to circulate the water or coolant through large thin rads mounted in the cealing. Have user controlled fans to circulate the air. It may not be as cool as a real air con system but I'm sure it would be enough to make a house much more comfortable in the summer.
The best part over a real air-con system is that it would also be virtually "free" to run once installed and no nasty high pressure gasses in the system. I'm building a house ATM so I may seriously look into this in more detail. maybe connect a rad to my PC cooling tank to see if it can make my room cooler.
You guys ought to check the link I supplied in my second thread as this guy tried pipe and it heated up, it's really worth the download time.
I've put it below.
http://www.fatnfast.com/otherwebs/overclocked