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Unusually Tight Construction

UNUSUALLY TIGHT CONSTRUCTION, as defined in the Mechanical Code, is construction where:
1. Walls and ceilings exposed to the outside atmosphere have a continuous water vapor retarder with a rating of one penn or less with any openings gasketed or sealed, and
2. Weatherstripping on operable windows and doors, and
3. Caulking or sealants are applied to areas such as joints around window and door frames, between sole plates and floors, between wall-ceiling joints, between wall panels and at penetrations for plumbing, electrical and gas lines and at other openings.
This term is important in live/work because in buildings of unusually tight construction, outside combustion air must be provided for gas appliances, an expensive proposition in many cases. Typically an existing building being remodeled for live/work will not have this problem. However, if it is a concrete building, is getting new doors and windows, and is being sealed on the outside, it is possible. Check with your mechanical engineer as the project proceeds.