So I was doing some reading and came across an article about Intel and their using outside air to supply a datacenter with "Air Side Economization". They did a 10 month experiment with running 900 servers in new mexico while not using any climate control, fancy intake filters, humidifiers, or dehumidifiers.
The results are quite interesting as they did not see a significant rise in the failure rate of the hardware, which is impressive since it varied in humidities from 4% - 90+% and temperatures from 64 - 92 degrees and made the servers collect a layer of dust.
Here is a link if you are interested:
Intel: Servers Do Fine With Outside Air « Data Center Knowledge