We're moving into a new office in an old building in London (that's England :) and are walling off a 2m x 1.3m area where the router & telephone equipment currently terminates to use as a server closet. The closet will contain: 

* 2 24-port switches
* 1 router
* 1 VSDL modem
* 1 Dell desktop
* 1 4-bay NAS
* 1 HP micro-server
* 1 UPS
* Miscellaneous minor telephony boxes.

There is no central A/C in the office and there never will be. We can install ducting to the outside quite easily - it's only a couple of metres to the windows, which face a courtyard. 

My question is whether installing an extractor fan with ducting to the window should be sufficient for cooling? Would an intake fan and intake duct (from the window, too) be required? We don't want to leave a gap in the closet door as that'll let noise out into the office. If we don't have to put a portable A/C unit into the closet, that'd be perfect. 

The office has about 12 people; London is temperate, average maximum in August is 31 Celsius, 25 Celsius is more typical. The same equipment runs fine in our current office (same building as new office, also no A/C) but it isn't in an enclosed space.

I can see us putting say one Dell 2950 tower server into the closet, but no more than that. So, sustained power consumption in the closet would currently be about 800w (I'm guessing); possibly in the future 2kw. 

The closet will have a ceiling and no windows and be well-insulated. We don't care if the equipment runs hot, so long as it runs and we don't hear it.