No sure if this would work well in your region and how your building is oriented - but you should look at a Solar Wall. There are a bunch of brands out there but this website has a good description of the technology/system. Its not a recommendation of their product as I have never personally purchase a solar wall only heard really good responses from people who have. http://solarwall.com/en/products/solarwall-air-heating/how-it-works.php

New construction in the age of "End of Oil" and "Global Warming" requires a preliminary total UA (total heat loss/gain of building for the extremes of the location.  Long term WHAT IF'S  in regards to the escalating costs of electricity in your location (discussion with power company).  It seems you are staging the total plan over several building
sessions -  as the business develops.  Become familiar with floor radiant heating and zero-energy buildings of the future.  In Maine, the walls are approaching R=45 and the roofs R=70 to minimise the cost of present/future solar thermal and PV systems.  In your area a solar thermal storage with heat pump output may be required to get winter floor temps to the 90 F range.  Floor loading and the proper amount of structural steel/mesh should be specified by an engineering firm.  http://www.wirsbo.com/Header/System...ating.aspx
Backup heating in the future may be best done with an automatic pellet boiler interfaced with the radiant slab and a few convection heaters near doorways/overhead doors.  When overhead doors open, the vehicle should "mate" with the building using an air inflating bladder system otherwise a vehicle long "anti-room" to totally stop air infiltration in the winter.  Designing what you have been discussing will be a methodical challange requiring much help.  Look over the above web site and it will give you much information.  Obtain their design three ring binder for installation and design to help you with the graphs of energy flows and include also the snow melting portion.
    A previous post mentioned SIP's.  For your application this is really the only way to go and will pay off both in winter and summer on your future energy costs.  It may seem overly insulated, ranges mentioned above,  but you will survive the future as your competitors slowly secumb to the future energy crunch.  Be sure your building roof faces  5 degrees East of True South and angled for the winter sun angle (otherwise if low pitch or flat, collector and module racks will be neede. Engineered structurally before you start - now.)  No need to add solar right away for space heating as you will need all your funds to expand your business to the break even point as quickly as possible.  Good luck - I can tell you have the courage to pull it off!
   http://www.ases.org/index.php?optio...Itemid=164    Much to learn here.
Find a local Solar group and you will find it much easier and friendlier.
POA

I just read the blog and feel there are a number of things that need to be mentioned.
 "Green" is an ill defined concept for buildings that somehow or other are better built or impact the environment or make the world a little bit better.   There are a large number of things that can be done and some don't cost anything, some cost a little and some are not cost effective   at all.   Some of the advice you have been given is incorrect, some is good and some has been given by people that are trying to sell you something.
What you need to know is that a standard commercial building built by any average contractor will NOT perform the way you think it should nor will you get what you think you paid for.  50 Years in the construction business earns me  the right to say that.
"Commissioning" of  a building is the process of overseeing the design, construction and maintenance of a building by a third party.  LEED constructed buildings are commissioned buildings that have extra requirements for the enhancement of the environment  that may not have Return On Investment.
No one has suggested to you that you consider the monthly utility bills as part of the expense of building and operating the building.  What you build and what you equipment you chose can greatly impact the operating costs.  A cheaply built and poorly constructed building  the size you are talking about can raise the monthly cost from  $5000 to $20,000 a month.

Heat Pumps and the most efficient heating and cooling systems you can get.  Ground effect heat pumps that have the ground coils buried in a flat plane just under the surface will not work in your area.  However, a vertical coil in a deep well arangement will work for both heating and cooling.  You are looking at thousands of dollars a month difference compared to standard package units.

The amount of outside air that infiltrates into a building through cracks and vents and other leaks is a great thief of conditioned air that you have paid to heat or cool.  So the "tightness" of the building is as important as the "R" value of the wall.  Sips are good insulators but it is difficult to get them installed correctly and very difficult to get them to stay that way.  ICF walls are the most cost effective building system available.  They cost a little more to construct (5%) but they save you large amounts of money over time because the do not leak.  A light colored metal roof that is sprayed with open or closed cell foam is again the most cost effective system over time.

Interior light is a subject that has not been mentioned.  You can spend large amounts of dollars in lighting costs and still have a poorly lit building if you place the lights directly over the storage shelves.  The type of lighting that you have installed can run from pennies a square foot to  as much as a dollar a sq ft. 

Large storage racks make air circulation difficult and that caused hot and cold spots in different areas.  This greatly affects the heating and cooling loads on the building and also on worker comfort,   You should look into using very large ceiling fans to move the air.  As large as 30 to 40 foot in diameter.

You also need to consider the effect the materials that you are storing will have on the quality of the air inside the building.  Toxic out gassing from leathers and vinyl material is large when the material is new.  You will have "sick building syndrome" and poor worker health if you ar not careful.

Regards
Joe Redburn
LEED  AP BD&C
E3 Building Sciences
[email protected]

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any significant span would require a rediron frame, 40 ft. wide with center beam/post is about the maximum width as shown on this project using SIPs on roof that are 22' - 9" long, eave walls 16 ft. center peak at 24' - 4"