“Best in Class” Report: Energy Efficient Exterior Wall Design (Mixed Humid Climate)
The design and implementation of a highly energy efficient exterior wall that is durable and cost effective is a critical component of a high performing home and can pose a challenge to production builders. As energy efficiency requirements increase for building codes and voluntary programs such as Energy Star and green building programs, the production builder must evaluate numerous designs and products in order to optimize framing, insulation, fenestration, and air sealing. An example of a successful energy efficient wall design is the implementation feature of this report.
The high performance wall design was implemented into K. Hovnanian’s Monmouth High Performance test home. This Building America test house, built in 2009, is a single story, slabon-grade design located in the mixed humid climate (climate zone four). While a primary goal of the project was to meet or exceed the Building America (BA) 40% Whole House Energy Savings target over the 2008 BA Benchmark, a secondary goal was to develop a wall system that would conform to future energy code requirements for the mixed humid and/or cold climates. The implementation of new products and practices to improve energy efficiency has the potential to create unintended moisture and durability issues and have increased cost implications. For this project, a number of wall frame/insulation/air sealing combinations were considered and modeled in order to meet the project goals. The features considered included site built versus panelizing, 2x4 versus 2x6 framing, OSB sheathing with and without exterior rigid foam, structural insulated sheathing (SIS), air sealing products and methods, and various wall cavity insulation types and densities of fiberglass batts, blown loose fill fiberglass, cellulose, and spray foam.
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