I put a workshop in my hangar and insulated with foil faced insulation
with 1/4" of fiberglass. I have been amazed!

My main problem is the opposite of yours - heat. My plan was to install
an HVAC unit and insulate the hangar sized room. Since I have a metal
hangar, I looked at metal building oriented solutions. Radiant heat
gain/loss seems to be a primary problem. The metal walls radiate
outside heat into the space via infrared radiation. And radiate inside
heat out the same say.

Therefore, stuff like this:
http://www.steelbuilding.com/buildin...ories_foil.htm

works very well. I lined the room with the white faced side in (good
light reflection and general looks)and have the foil side facing out.
Without any HVAC operation, it moderates the the temp withing the
workshop unbelieveably well. It just never gets as cold or as hot as
the outside temp over a 24 hour period. The place is just a pleasure to
work in. Add some AC or heat, and it's like home.

Mass insulation and air infiltration work well. But my experience in a
metal building suggests that radiation control may be equally or even
more important. Someone with some engineering talent should be able to
set me straight.

By the way, the stuff goes up with double sided tape which also works
unbelievably well in my application. I could have thrown the staple gun
away.

The Visitor wrote:

With that vent in there it is gonna get cold.

I have a cieling with insulation on top. I had the sweaty airplane
problem but put in a cieling fan and things have been fine since. It has
not been turned off in 8 years! (2 actually)But with the air moving, it
can hold a lot more moisture and won't condense out. With my entire
hangar insulated the temperature does not get below freezing in the
winter. And it is cool in the summer also. The cieling fans are
fantastic! Also the floor is epoxy painted perhaps keeping out ground
moisture.