Energy Efficient Retrofits: An Exterior Approach to Improving the Performance of the Suburban Wall
Open Access
- Author:
- Zimmerman, Holly
- Graduate Program:
- Architecture
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- February 29, 2024
- Committee Members:
- Lisa Domenica Iulo, Thesis Advisor/Co-Advisor
Rahman Azari, Committee Member
Ute Poerschke, Program Head/Chair
Ali M Memari, Committee Member - Keywords:
- energy efficiency
sustainability
embodied carbon
buildability
durability
retrofit
exterior retrofit
cost analysis
thermal performance
heat flow modeling - Abstract:
- As codes and advanced building standards continue to expand what high performance buildings can accomplish, we inevitably turn to the existing building stock to assess what should be done to improve a large quantity of buildings. In the United States, only one percent of building stock is new construction each year; the rest is existing buildings. Existing houses do not provide the durability, energy efficiency, or comfort expected of buildings today and need to be retrofitted to improve their performance while also balancing the embodied energy of the materials, cost, ease of assembly, and durability. This thesis surveyed the existing building stock in State College, IECC Climate Zone 5, looking specifically at single-family detached housing, specifically wood frame construction with little to no insulation. From the existing buildings, a singly representative wall assembly was identified which is modeled with retrofit strategies and simulated to determine exterior envelope retrofit strategies for existing homes. The findings were analyzed and compared to find any patterns which indicate which materials or strategies are most effective. Strategy analysis relied on simulation software such as WUFI (hygrothermal), Flixo (heat transfer/thermal bridging), RS Means (cost), EC3 (embodied carbon), and a custom rubric to evaluate buildability. This analysis resulted in the determination of 28 exterior wall assemblies that meet the defined requirements for State College, PA. 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 the five criteria and the lowest embodied carbon which can be completely offset by the carbon savings from reusing the existing wall structure. 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 people in the building industry for how to retrofit walls in cool-humid climates to be more energy efficient. Moreover, the process is documented in this thesis to make exploration of other wall types and climate zones possible in future work.