Free air cooling technology for data closets


Limp Gawd
Oct 2, 2004
Looking for recommendations and advice on applying free air cooling to closet sized datacenter. At this stage we are open to all ideas. Some HVAC folks we've contacted suggest mini split airconditioner systems with one condensing unit and an air handler for each closet as a quick and simple solution. AC most likely may be installed as backup anyway but if possible we want to provide the ability for full cooling without using the energy of a refrigeration cycle. Of course this all will be networked for monitoring and control.



The project requires cooling a 20ft x 16ft closet and a nearby separate ~10ft x 10ft closet that are on the ground concrete floor. Both have tall 18ft ceilings. The closets will have some racks and electrical appliances . No raised floors, no hot or cold aisles. The closets are located on the ground level at the corners of the building in the garage. and are on perimeter walls allowing easy ducting outside and the building is geographically in an ideal region that for most of the year free cool air will be available except for some hotter summer days.

Larger datacenters appear to be popularizing variations and expanded concepts of air-side economizers.

Are their any smaller scale ready to buy free air economizer solutions with or without evaporative cooling?

We haven't yet found appropriately small sized economizer solutions so we are also open to the idea of designing a custom simple yet effective system. The closets require intake air to be particulate filtered 24/7 to prevent dust accumulation etc. Cool outdoor air would pass through filters directed into the closets towards the front of racks. The closets would exchaust hot air into the building to warm the garage in the winter or exhaust hot air outside in the summer.

Ideally the system would have a central controller that accepts a variety of i/o and could be programmed to rely on sensors to intelligently automate air flow thru different fans and louvers depending on temperature variables and also to intelligently seal off free air and power on AC when required during summer heat waves.

Have any of you experience cooling closets with fresh air and are you able to offer suggestions and available options for premanufactured kits or components: sensors, fans, louvers, controllers and automation? Filters for particulates? HEPA or other that will remain effective in varying outdoor humidity and temperatures ranging to below freezing?

Last edited:


Aug 28, 2001
stupid forums lost my post...

the short of what I had typed was:

I know very little about this topic, but I wanted to look into it when we build our house. the concept makes perfect sense to me.

I'm interested in this topic, so hopefully someone can provide more insight.