I’m located in Central NY and will be building a 30x50x12  pole barn shop this year and am trying to make a decision on insulation. 

I’ve been quoted R19 fiberglass batts  in the walls and R42 chopped fiberglass in the ceiling or R21 foam in the walls with R42 chopped fiberglass in the ceiling.  The spray foam would be $1,450 more than fiberglass.  I’m planning to heat with minisplits and will keep the shop between 50 & 65 depending upon how it is being used. 

Both options will have tyvek underneath the steel siding and liner panels for the interior walls and ceiling with rat guard at the base and appropriate trim in the corners and between the wall and ceiling to minimize any gaps and reduce potential airflow.  The exterior wall will also have rat guard at the base and vented soffits and baffles in the eaves to facilitate air flow over the chopped fiberglass ceiling insulation to the vented ridge.  I’m planning to surface mount the electrical in EMT to minimize penetrations.  

My contractor is recommending the fiberglass option as being more cost effective over the project life (20 years).  I tend to agree, but am looking for other’s opinions and experiences.   Cost is definitely a driver here, but so is comfort.  This will be my last shop (I’m 58) and I’d like to build something that will be good to work in for as long as I’m able to work in a shop.