[tghw]

I don't think you are. I came across this a number of months ago and looked into building one myself. You could pretty easily start out with a couple of sheets of acrylic and make a grid to separate them. Then you just have to drill a lot of holes. I think getting the grid right would be the hardest part as a DIY project, but you could pretty easily imagine a machine cutting slots so it all fits together nicely.

[krasin]

laser cutters are very inexpensive and accessible nowadays. Once somebody published a device, producing such a set of acrylic sheets with holes is not a problem at all.

[bluefinity]

Ponoko will laser cut and ship you acrylic for fairly cheap: http://www.ponoko.com/make-and-sell/show-material/19-acrylic...

[X4]

hmm.. you could use solar energy to heat the air coming through, otherwise the building would cool down right?

Also is it possible to let the air pass through into one direction only? I think strategically placing incoming/outgoing air-pass through windows, could make a decent air-flow (+heating) system.