i'm having this problem too, my workshop is at the back of an extra long garage, the garage is one of those pre fabricated concrete wall jobbies with an asbestox lux corrugated type roof. when i started using it for turning i put 2x2 battens verticaly on the walls and then some normal roof insulation followed by some 1/2" insulation board, i did the same on the ceiling. Now this has had a good side and a bad side- the good side is that yes it is cooler in the summer and a 2' tube heater is all thats required to keep it frost free in the winter. the down side is that any heat prodouced inside the workshop stays there, my lathe lights etc all get warm, so i have started to use an input fan at floor level for fresh air and a shower type extrator fan to take the warm air out at the highest point..... but its still not enough so i'm now looking at installing a larger capacity extractor fan but they seem to rise steeply in price as soon as you go above 4"
I worked for a air conditioning expert recently and he kindly came to have a look at my situation his advice was to keep the air moving and that air conditioning such a dusty enviroment would be a waste of money.
Mine is un-insulated and the asbestos roof feels more like a radiator at times! Is your shop insulated at all? I reckon that would make a difference, even if you only did the roof at some point.
