This was a small coal burning Inglenook fireplace in a bedroom in a very old home. A 9x15 chimney ballloon was used to air seal the flue just above the firebox. This is a photo from the floor looking up the flue.
New York is increasing its energy standards and is investigating the possibility of implementing the Passive House Standard for new construction and retrofit projects. Interviewee: Ken Levenson, with NY Passive House Assoc and 475.