Article
Effect of Thermal Bridging on Buildings' Energy Performance: Comparison of Area-Weighted vs. Additive Thermal Resistance in Facades
Proceedings of the Facade World Congress 2020
(2020)
Abstract
Heat transfer through building facades can occur by any combinations of conduction, convection, and/or radiation. Conductive heat transfer depends on materials’ thermal conductivity (λ) and thickness (d), which influence building envelope’s thermal resistance (R-value). The most common approach for calculating R-value of building facades is based on the additive method, where material components of the facade in sectional view, their relative thickness and thermal conductivity are considered. However, in order to account for thermal bridging caused by framing, area-weighted approach should be used to determine more accurate R-value. This approach also considers plan view of building facade, and the properties of framing components. The main objective of this research was to investigate the effects of facades’ thermal resistance (additive vs. area-weighted R-values) on buildings’ energy performance. Research methods included data collection, modeling, simulations and comparative analysis of results. An existing Campus Recreation Building on UMASS Amherst campus was used as a case study building. First, the original construction documentation was reviewed to create a 3D model in Revit. Facade material components and specifications were used to determine properties of the opaque facade system, consisting of brick cavity wall with steel stud framing. R-values for this facade system were calculated using additive and area-weighted methods. Then, a building energy analysis simulation program Green Building Studio was used to calculate annual and monthly energy consumption for the case study building, where one energy model was created to analyze the impacts of two different R-values on the overall energy consumption of this building. Other inputs, such as building geometry, occupancy schedules, glazing materials, etc. were identical in both simulation scenarios. Energy modeling results were compared to actual energy consumption data, collected over a period of one year. Simulation results showed that energy consumption, cost, energy usage intensity, carbon emission, and heating loads were higher with area-weighted method, and lower with additive approach.
Keywords
- Facades,
- thermal bridging,
- energy consumption,
- simulations,
- actual energy consumption,
- R-value,
- thermal resistance
Disciplines
Publication Date
2020
Citation Information
Mahsa Farid Mohajer and Ajla Aksamija. "Effect of Thermal Bridging on Buildings' Energy Performance: Comparison of Area-Weighted vs. Additive Thermal Resistance in Facades" Proceedings of the Facade World Congress 2020 (2020) Available at: http://works.bepress.com/ajla_aksamija/191/