Energy Efficient Retrofits: An Exterior Approach to Improving the Performance of the Suburban Wall
As codes and advanced building standards expand what buildings can accomplish, we inevitably examine existing building stock to assess how to improve buildings. In the United States, only one percent of buildings are new construction each year; the rest is existing. Existing houses do not provide the performance expected of buildings today and must be retrofitted to improve their performance while also balancing the embodied energy, cost, buildability, and durability.
This thesis surveyed existing buildings in State College, PA, IECC Climate Zone 5, specifically single-family wood framed housing with no insulation. A representative wall assembly was modeled with retrofit strategies to determine exterior envelope retrofit strategies for existing homes. The findings were analyzed to find the most effective strategies using WUFI (hygrothermal), Flixo (heat transfer), RS Means (cost), EC3 (embodied carbon), and a custom buildability rubric.
This analysis resulted in 28 exterior wall assemblies that meet requirements. Of those 28, two were selected for superior performance: a prefabricated panel with cellulose insulation and ZIP R-9 sheathing for superior thermal performance, and a Larsen truss assembly with cellulose insulation and ZIP sheathing for superior balancing of criteria and the lowest embodied carbon.
This research has generated a list of retrofit strategies which can be applied to State College and can serve as a guide to homeowners or the building industry to retrofit walls in cool-humid climates to be more energy efficient. Moreover, the process documented in this thesis allows for exploration of other wall types and climate zones in future work.
Overview image of the retrofit structural solutions evaluated in this research
