First, you're not going to use RCV. That's for single unit dwellings that serve as a primary residence. You're going to use ACV (RCV less depreciation).
Bottom line: You need to determine a good faith value for each building. If it's a "tear down situation", demolition value might well be used. Or you might use "functional building cost". Here's some info on these two approaches from our Flood Insurance Training Manual:
Functional or Demolition/Removal Cost:
...in the case of buildings used for ranching, farming, and industrial purposes, insurable value may also be determined by the functional building cost value or the demolition/removal cost value. [Federal Register /Vol. 76, No 200 – page 64178]
A.) Functional Building Cost Value:
...the cost to repair or replace a building with commonly used, less costly construction materials and methods that are functionally equivalent. For example, a farming operation would replace an old dairy barn currently used for storage with a storage building of pole, or some other type of less costly construction found currently in storage buildings.
B.) Demolition/Removal Cost Value:
The lender may calculate the insurable value as the “demolition/ removal cost value†that is the cost to demolish the remaining structure and remove the debris. The ‘‘demolition/ removal cost value’’ may be used when a building is not important to the ongoing nature of the business and as such would not be replaced if damaged or destroyed by a flood.
There's also an article at our website (free) entitled "Flood Insurance Insurable Value" that you can find in the "Lending Tools" box. I think you might find this helpful.
https://store.bankerscompliance.com/