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66 66 P P a r t I I : a r t I I : C o n s u m p t i o n I s s u e so n s u m p t i o n I s s u e s

Windows
Most often, server rooms have no windows. If yours has none, you can skip this calculation.
However, if you do have windows, look at these formulas to determine which is most
applicable to your datacenter:
South Window BTU = South Facing Window Length (m) × Width (m) × 870
North Window BTU = North Facing Window Length (m) × Width (m) × 165
If there are no blinds on the windows, multiply the results by 1.5.

NOTE If you are in the southern hemisphere, swap these formulas. In the northern hemisphere, the
heat on south-facing windows is greatest. In the southern hemisphere, the heat on north-facing
windows is the greatest.

Add together the results of these calculations to get your final amount:

Windows BTU = South Window(s) BTU + North Window(s) BTU

People in the Room
You probably don’t have someone permanently stationed in the server room. If people
aren’t in there, you can skip this section. However, if you do have people located in the
server room, the heat load goes up about 400 BTU per person. Here’s the formula:
Total Occupant BTU = Number of occupants × 400

Equipment
Obviously, most of the heat generated is from your equipment. You can find the equipment’s
power consumption in its documentation or on the vendor websites, if it’s not written on a
sticker with the serial number.
Don’t forget to take into consideration any other equipment that might be in the room
(maybe there’s a photocopier or other additional equipment). Here’s the formula:
Equipment BTU = Total wattage for all equipment × 3.5

Lighting
Multiply the total wattage for lighting by 4.25, as shown in the following formula:

Lighting BTU = Total wattage for all lighting × 4.25

Total Cooling Requirement
Now, just add up all these numbers and you’ll get the total amount of cooling you’ll need
for your datacenter, as follows:

Total Heat Load = Room Area BTU + Windows BTU + Total Occupant BTU +
Equipment BTU + Lighting BTU