January 2010
This high performance Scope of Work explains three best practice approaches for a wall design with rigid insulating sheathing, a weather resistive barrier (WRB) and vinyl siding to effectively address moisture intrusion, air leakage, and thermal performance. Though lap-style vinyl siding is presented as the choice of cladding, other materials such as cement board siding could also be used with appropriate Scope of Work modifications. This particular wall assembly is presented because vinyl siding is commonly used in many markets, and rigid insulating sheathing is used as a means to significantly increase the r-values of walls and reduce thermal shortcuts from the framing. When rigid insulating sheathing is utilized, it is imperative to incorporate it successfully into the wall design to ensure durable and efficient homes that address thermal and moisture issues.
This Scope of Work details the installation of exterior rigid insulating sheathing, a WRB and vinyl siding, including flashing and waterproofing details, which play a critical role in the performance and durability of the wall system.
The Scope of Work details three separate trade contractor scopes: rigid insulating sheathing, WRB (house wrap) and vinyl siding. Depending on the design and the builder’s approach, this scope may be used in whole by a single trade contractor, or in sections, by multiple trade contractors building just a part of the wall assembly. This Scope of Work may also be used in parts by builders or trade contractors building different wall assemblies that include either rigid insulating sheathing, house wrap or vinyl siding.
Prepared by:
NAHB Research Center