I’m working in my loft laying chipboard. It’s summer here. It’s hot up there. There’s limited headroom - even in the middle I can’t stand up. Give me tips on how I can keep cool.
Is it well ventilated?
Do it on off times – like early in the morning. Early by meaning say 3am start time. Using it fan to circulate the air, even if it’s trapped air, will also help. Otherwise, not too much you can do other than say wetting a tshirt and then wearing that with the fan on, or soaking a clean snot rag and wrapping the wet rag around your neck - again with the fan on.
I’m in a terrace with young children next door, so very early starts are not on, likewise working in the evening. As for ventilation, there’s the trap door into the loft.
Wet washcloth! Apply directly to head!
Wet washcloth! Apply directly to head!
Wet washcloth! Apply directly to head!
P.S.: It will feel even cooler if you wet it with rubbing alcohol.
A leather jacket and a motorcycle is always cool. Also, get some kick-ass shades like this guy -> 
I recommend a cold, wet do-rag. Wet it and put it in the freezer for a bit before you go up. The handkerchief catches sweat and keeps it out of your face and if you have any sort of long hair, it keeps the hair off your neck (if you tie it a certain way).
I also suggest taking another cold, wet rag and tying it around your neck. Having something cold on the back of your neck is the bomb.