Increasing Innovation and Affordability in Housing: A Case Study on Townhome Area Separation Walls

Christine Barbour
James Lyons
Newport Partners, LLC

Consistently achieving cost-effective area separation walls (ASW) in townhomes that meet the fire protection requirements in the residential building code and air tightness provisions in the energy code can be a challenge for builders, architects, designers, trade contractors, and code officials. Townhome ASWs are complex and must serve several functions, including fire separation, limiting sound transmission, and limiting airflow. The typical townhome ASW is a 2-hour fire-rated gypsum assembly. Because townhomes are often a more affordable housing solution, cost is important. The energy code provisions reduce air leakage through the building envelope for energy and cost savings to the consumer and, at the same time, require additional steps to achieve and test reduced air leakage rates.

For cost-effective construction, builders need predictability and consistency. The fragmentation of the construction and inspection process with so many players with different roles means that the installation of any product or material may have unintended effects or consequences on the overall building performance. Historical examples, such as moisture accumulation within highly insulated walls or complications with attaching cladding over exterior foam insulation on walls, are often related to increases in one code that are not immediately reflected in other codes. In the case of ASWs, the gypsum assemblies are designed for fire protection. When the energy code is adopted, sealing the ASWs is needed to meet the air leakage requirements. This research demonstrates that air leakage is higher at the ASWs than the exterior walls on the end units, so ASWs must be air sealed to reach the air leakage requirements. Unless the air sealing material is part of the fire-rated gypsum assembly, a chance exists that the townhome will not pass the inspection.

To meet the fire protection and energy code requirements, a builder might face issues that can impact construction costs, including additional inspections that affect project scheduling, different interpretations of ASW requirements by various jurisdictions, construction setbacks, delays in certificates of occupancy, and lost energy savings. With the Inflation Reduction Act of 2022 and efforts across the country to reduce building greenhouse gas emissions by adopting zero energy codes, plus the strong market for townhomes, the need for cost-effective, code compliant ASWs is likely to increase. This article summarizes field and regulatory solutions to consistently design and construct cost-effective ASWs and serves as an example of the need to harmonize codes through a holistic lens and adopt innovations to reduce complexity and maintain affordability.