Informed Residential Retrofits through THERO (Thermal Resiliency Evaluation using OpenStudio-HPXML)

Abstract

Of roughly 111 million buildings in the US, 90% of the buildings are single-family homes. Therefore, residential building stock in the US consumes higher energy than commercial stock. The National Renewable Energy Laboratory (NREL) has proposed ten residential retrofitting packages to decarbonize the existing residential stock in the US. However, their study currently focuses primarily on energy efficiency. There is a catastrophic impact on the resiliency of buildings and the safety of residents due to rising global temperatures leading to uncertain weather. This research aims to evaluate these proposed retrofit packages across energy efficiency and thermal resiliency paradigms during future, extreme weather, and power outage conditions. To achieve this, a framework called THERO (THErmal Resiliency evaluation using OpenStudio-HPXML ) was built on the foundational framework by NREL, which expands the competencies to run batch simulations for indoor thermal comfort metrics. Simulations were performed on a sample of the energy models in Chicago (n = 500) and Phoenix (n = 200) for future, extreme, and power outage conditions. Three cases were considered from the retrofitting packages: the baseline, an upgrade with enhanced enclosure, and an upgrade with high-efficiency whole-building electrification. The indoor thermal resiliency was evaluated across the metrics of Energy Use Intensity (kWh/sq. mtrs.), Time Not Comfortable based on ASHRAE 55-2004 (hrs), Heat Index Hours (hrs), and Humidex Hours (hrs). We were able to successfully interact with the NREL database, perform batch simulations and compute thermal resiliency using THERO. The current studies show that for indoor thermal resiliency, an enhanced enclosure upgrade performs better in Phoenix, while whole building electrification with high efficiency performs better in Chicago, not only in the current but also in future and extreme weather conditions. However, in the case of a power outage scenario, in both cities, an enhanced enclosure upgrade performs better thermally than a high-efficiency electrification upgrade. Conclusively, this study establishes that indoor thermal resiliency and energy efficiency for residential building retrofitting does not always lead to similar recommendations. Additionally, this project enables the building science community to harness the potential of the rich NREL dataset while informing architects and policymakers on comprehensive retrofitting solutions that make the residential stock more resilient to climate change.