How to calculate Fresh Air Handling Unit Capacity using Formula with out using Hap Software--- For FCU's

Dear sir , I am working as hvac trainee engineer in an hospital so i need technical information will u plz my mail id

reagrds

shiva

FIRST THING TO 1. CALCULATING AREA  2. NEED TO CALCULATE SENSIBLE HEAT AND LATENT HEAT (btu) 3. AFTER CALCULATING THE TOTAL HEAT LOAD DIVIDE BY 12000 BTU .IT WILL GIVE THE TOTAL CAPACITY OF THE UNIT REQUIRED.