Hey Graham! Forgot to pass on a REALLY GOOD website to research and pose your question at...it's at: http://www.facilitiesnet.com/fn A very good site that I subscribed to at my last place of employment (a start-up) I needed help then! I still get emailed newsletters from them. It has all kinds of resources dealing with buildings, and the care and feeding of...no offense to anybody, but I think you'll be able to learn more about your situation at that website, than from us assembly guys...(I'll admit it) There's a search function box on the opening page where you can type in something like "Air Conditioning" and you'll wind-up with all kinds of hits of past articles posted on the site...they also have a forum like us to ask questions. -Steve Gregory-