We live in New England and have a 100 year-old 16'/28' shed/old blacksmith's shop with open peaked ceiling to 11-12 ft at peak. We use it for household storage and occasional workshop and art projects. We would like to seal it up and insulate it to keep out critters, dehumidify, and minimally heat with baseboard heating (we think) in winter. Walls are currrently open with true 2X4 studs and 2x6s in ceiling. What kind of insulation would you recommend? We are considering Icynene. Contractor says no ridge vents are needed and says it will be so tight you can heat with a candle! True? Should we worry about the building not "breathing"? Should we? If we go with a cement floor, will condensation collect there? How can you prevent that? Many thanks!