We are converting our fourth commercial warehouse into self storage. 

If you have ceiling fans that is also a concern unless they are really high up  and out of the way like in a 15 ft tall warehouse space etc.Mixed use is harder to manage and lenders generally like  a lower LTV on the loan such as 65% ltv because a small investor is juggling 2 types or more of various asset classes in a single building.

Hi,How do I figure out how much commercial office and warehouse space go for in a given area?

Make sure you are not comparing office space and warehouse/industrial space.You also have to compare similar age of buildings,amenities,and sizes.1 mile is very far away for a comp.The seller always wants to overvalue.I wouldn't go that high on it.In Atlanta office has a very high vacancy and turnover rate is high.I would be more concerned if this income is based on established businesses that have been there for years and are on solid financial footing.

It was totally below grade and the temperatures there were 10-20 degrees different from the floor above. 

Temperature control thermostats that have a max,  we use a  landlord stat from Chicago temperature control.

Install is on second floor, temperature controlled, plywood floor.Can someone confirm that if i roll it I will be OK?

Another example, let's say I own one property and have renter's warehouse manage it. 

So getting a variance to make it multi-family would probably be easier then actually trying to use it as it is currently zoned as I am sure the locals would complain if this actually started running factory/warehouse operations.I have contacted some of the firms in my area to feel them out, and I have found one that is an all in one design and GC firm. 

Your first priority is to have the heating system repaired so that it maintains the temperature in the unit without having to use the fire place.If you do not want to maintain the fire place inform the tenant that you will allow him out of his lease.