Grate-type tiles work well in the data center if they're used correctly and if the parameters are well understood. You need to really understand your under-floor air flow when installing grate-type tiles because they can deprive other parts of your floor.
Remember, you're limited to the amount of air your CRAC can deliver. Most data centers lose a significant percentage of their air in uncontrolled leaks. Additionally, the under-floor air flow and pressures are uneven to begin with. Thus, it's highly unlikely that you have all the air your CRACs are delivering actually available at the tiles you install.
You not only need to be concerned about how much air goes through which tiles, but you also need to know the exact placement of grate-type tiles. If you put them in a place where air volume and pressure are already low, they're going to do little for you and will probably make things worse somewhere else. Other then trial and error, the best way to make these determinations is through CFD modeling.
Additionally, while the GrateAire tile offers 58% open area, this is only if the tile does not have a damper. Dampered tiles allow you to control the air flow at each location so that you don't waste air in places where less cooling is needed. However, the dampered GrateAire tile has a maximum open area of only about 33%. This is not a whole lot better than a fully open standard perforated tile, so we don't specify it very much. But since the 58% open tiles affect under-floor air volume and pressure, we use them very carefully and only after performing a thorough CFD analysis.
ABOUT THE AUTHOR: Robert McFarlane is a pioneer in the field of building cabling design. He has been asked to speak at countless seminars on building infrastructure for electronic communications, evolving technologies and the requirements of trading floor and data center design. Mr. McFarlane served for twelve years as President of Interport Financial, Inc., a firm specializing in designs for financial trading floors and critical data centers.