Masraum I was thinking no windows mainly for simplicity and partially as bad guy entry points
But we are in the country and very low crime area so may have to rethink that as you bring up good points about ventilation . When I say the compressor will be " outside " it will basically be a mini room off the existing building with an entry door from the inside . That way I can roll the compressor in or out if needed it already is sitting on a 4 wheeled platform I built for it in my previous garage .
So yes your diagram is basically how the building and the compressor room will be built . The studs will be 2x6 with plywood on the exterior and house wrap and OSB on the interior . Standard fiberglass insulation is the plan . Probably vinyl siding on the exterior for minimal maintenance . I will insulate the back of the compressor room door for noise suppression and even thinking about leaving a open space on top of the three perimeter compressor room walls of maybe 3 - 4 " and cover with window screen/hardware cloth of maybe 1/8 " or 1/4 " grid . My thoughts are two fold: one it will allow some noise to escape and two that will allow intake/cooling air for the compressor pump . Have any of you guys done something like this ? I would size the roof over the compressor room to allow coverage so wind driven rain would not come in .