[Strawbale] Retrofit S/B on Wood Frame

[Carportman]

I recently bought an old frame structure and am trying to
 decide the most effective and least expensive method of
 insulation and finish.  The exterior is very old lap wood
 siding with a lot of open seams up to 1/2" high.  The 
interior is simply studs, no drywall, paneling or
 anything..........we just look out through the cracks.
My first thought was to spray the inside with about an inch
 of high density urethane to insulate and seal all the 
openings/cracks.  Then I thought regular batt insulation
 on the inside with vinyl siding on the outside.  Gypsum 
board would work as an interior walls.  Very conventional.
................no soul..............and not cheap.  
Mama suggested straw bales on the outside.  This would 
require my extending the old corrugated steel roof and
 setting some type of beam around the perimeter to support
 the bales.  Solid concrete would work, I suppose, but 
I'm inclined to set concrete piers every 8-10' and span 
them with something less expensive that would still work.
 
Tying the bales to the wood siding would be simple enough.
......I could use bamboo stays or like my straw house, I
 could use steel rebar.  

Looking for any suggestions on exterior and wall finish
 out on interior. Sheetrock has no soul..........But then,
 I have little money.  Keep in mind my Scottish tendencies.
 
Many thanks, Douglas
 

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