Field Testing of Compartmentalization Methods for Multifamily Construction - Washington DC

BSC TO5 Task 2.1 Field Testing of Compartmentalization Methods for Multifamily Construction - Capitol Heights, MD 20743

A building comprising five vertical townhome units was built in the Washington, D.C., area; the townhomes were three-story slab-on-grade units (1700-2000 ft2) with a rear-facing "tuck under" garage. The three-story townhome design results in 3 ACH50 being equivalent to a stringent surface-area based target (0.16-0.17 CFM50/ft2 building enclosure).

The party walls between units were area separation walls, with a 2-hour fire resistance rating (Underwriters Laboratories U347 assembly; equivalent to U373 and U336). This assembly has a 1-in. vertical air cavity on each side of a 2-in. vertical gypsum panel in the middle of the assembly, resulting in an airflow network that is connected over multiple floors (despite nominal draft stopping), and has potential connections to exterior conditions.
The test townhomes were built with several experimental airtightness details, including taping of exterior sheathing as an air barrier closure detail (in particular, at area separation walls). Various measures were applied to the units for this experiment, including a "control" conventional construction unit and some units with "improved" detailing (without taped sheathing).