Heh, I've done a similar thing (new house, new boiler, redundant airing cupboard turned into a server room)
Don't know it it's possible in your place, but I've put a low rpm extractor fan in the cupboard ceiling that pulls the hot air into the roof and added a vent panel to the door. I've got a 24-port switch, couple of ups and two servers in there and internal temps are more than acceptable.
If you're going to run usb, vga, dvi whatever from your workstation into the office, you might consider buying a 2-gang termination block (similar to what you get in classrooms with IWBs and projectors) and mounting it on the office wall.
Regarding power use, I have wake-on-lan enabled, since I only use them at the weekend / evenings.
Are you at all concerned about condensation from pulling that hot air into the loft?
Originally Posted by pete
I have recently shifted our primary school servers (2x servers + 1 UPS) into a room a little larger than your airing cupboard (aprox. 2m x 2m x 3m high). I have put vents in the top and bottom of the door, but have got no extraction in there. The temperature reaches 27C in there.
However, this weekend will be the first full weekend with the door kept closed for longer than 18 hours. My backup plan, should the temperature be getting too high, will be to add an extractor into the ceiling into the loft space (which is absolutely massive!).
My loft was (in Spring at least) warmer than the airing cupboard with the servers running, even at night-time. We'll see how it goes in winter - I can always turn the fan off, since the major heat source for upstairs will be less prominent. The long south-facing wall + big skylights means I've never had the heating on upstairs because the sun heats the house sufficiently in the day to keep it warm all night.
Originally Posted by itwasntme
YMMV, of course.