Exhaust hood usage formula

[keg]

I am installing multiple exhaust hoods in a new multi-story facility.Each hood has approximately 300-500 cfm capacity.
The building is divided among several tenants each with varying amounts of exhaust hoods.Multiple exhaust hoods are common to one exhaust fan on the roof.Rental space is based on square footage of floor space.How can I figure the amount of a surcharge plus or minus for cfm's lost for each exhaust hood?

 

[ChasBean1]

Get a baseline of operating cost from power consumption by the hood fan and divide the bill proportionally based on the number of hoods per tenant. Don't put flow stations in the ducts because you'll drive yourself crazy trying to calibrate and track them. Plus you shouldn't generally put extra stuff in hood exhaust ducts. Don't do this every month, but establish a norm and raise their rent by the operating cost divided by their proportion of the total number of hoods.