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Air changes for large warehouse to calculate infiltration loads

StephenJcan (Mechanical) (OP)
15 May 01 10:29
Hello everyone. Can someone help me by directing me to a reference for air changes for large warehouses?
A typical warehouse would be 500,000 square feet and 30 feet high with many dock doors.
I have tried calculating the infiltration using the crack method but I read somewhere that for larger buildings the easier way to design it would be to use an air change/hour number to figure out the infiltration.
Can anyone help me out?
PAN (Mechanical)
19 May 01 22:05
I recommend to use 10-15 air change. You may consult the roof ventilator supplier for more detail.
Guest (visitor)
21 May 01 12:18
All depends on heat load. ASHRAE says to ventilate at .15 cfm/ft2 (or 75,000 cfm total in your warehouse). That's ventilating only, not cooling. General rule for space conditioning is 1 cfm/ft2, but that may be off due to high ceilings. If it's new construction, insulate that roof because that's your main load. If I come across any added info I'll post...
leatherneck (Mechanical)
22 May 01 21:38
For figuring infiltration only (not ventilation), I've used 0.5 air changes per hour for large warehouses.  This is still a significant heat load.  
CliffClaven (Mechanical)
12 Oct 01 9:37
0.5 ach is a good number! ((0.5ach)*(500,000*30'))/60 = 125,000 cfm.

125,000cfm*1.08*20 = 2,700,000 btuh assuming you are using a 20 degree delta T.  This transalates to 270 gpm additional water flow to pick up just infiltration, assuming you are circulating water to terminal units and that it will be water and not a form of glycol to the terminals.  The gpm requirement will change with glycols.

Scary!

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