Just bought an 1880's Carriage house. It is two floors and roughly 1100 sq'. We took down the ceiling on the second floor gain more space. Now we want to keep the open space, but not quite sure how to insulated it.
Winter is right around the corner, and my head is spinning with all of the info; Radiant Barriers, baffles, fiber glass with sheet rock. We also noticed four venting holes in the brick on both sides of the Building. What do we do about that, since we took down the ceiling? Any advise would be greatly cherished.  Thank you! 

Thank you for your question.  

I am assuming your rafters are a minimum of 2" x 6" and NOT a true 2" x 4".  If this is true, you have some options:

First the holes at the two gable ends are there to ventilate the attic.  I would suggest that you put 2" x 6" rafters horizontally scabbed onto the original roof rafters approximately 4' down from the apex of the roof.  This will create a flat area of the ceiling and give you the proper ventilation for that attic area.
Regarding the slope ceiling (or the underside of the roof rafters below the newly installed flat ceiling), you will need to install baffles (proper vents or air chutes) on the underside of the roof  boards prior to installing any insulation.  If you have true 2" x 6" you could install 5-1/2" high density R-21.  The way you would install this is to stable the flange of the insulation to the face of the rafter.  Typically you see blanket insulation installed with the flange inside the rafter, but in your situation you do not have that 1/2" to give away.  This is the manufacturer's recommended way to always install blanket insulation, however, it is seldom installed in this manner due to the fact installing with this method prohibits the drywall from being glued to the face of the rafter. 

Since you cannot glue the drywall to the rafter you will need to run the screws (not nails) a maximum of 8" apart.  If you have larger rafters please inform me as to what they are and I can make you a better recommendation.
Hope this information is helpful to you.

Bruce Jones
The Insulation Doctor