APPLICATION OF INFRARED THERMOGRAPHY ON THE IN-SITU MEASUREMENT OF BUILDING ENVELOPE THERMAL PROPERTIES
Open Access
- Author:
- Lu, Xinrui
- Graduate Program:
- Civil Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 04, 2019
- Committee Members:
- Ali M Memari, Dissertation Advisor/Co-Advisor
Ali M Memari, Committee Chair/Co-Chair
Farshad Rajabipour, Committee Member
Gordon Patrick Warn, Committee Member
James Freihaut, Outside Member
Somayeh Asadi, Committee Member - Keywords:
- Building Envelope; Infrared Thermography; Building Science; R-value
- Abstract:
- Building energy consumption accounts for about 40% of the total energy consumption in the U.S., and therefore approaches that can reduce building energy demand are of great interest. The building envelope system is one of the main elements in buildings that can be improved for better building energy performance, and it also plays a significant role in building energy simulation. The thermal resistance, i.e., the R-value, is the key thermal parameter for building envelope systems contributing to the whole building energy performance. While the R-value has been long introduced in the building science field, however, there is still a lack of sufficient research work in understanding its influence on the whole building energy simulation process and results. In particular, there is serious need for experimental methods to determine the real R-values for existing buildings in order to obtain the actual building performances instead of the theoretical values. The primary goal of this proposed research is to develop a quantitative infrared thermography approach to measure the R-values for building envelope systems on site. Achieving this would provide the industry with a more practical and faster alternative to measure the R-values for existing buildings. Traditionally, to measure the real R-value of building envelope systems, Hot Box Test Method is used in laboratory to measure building envelope mock-up assemblies. However, the Hot Box Test Method requires large testing facilities and also an envelope component to test, which will not be practical when measurements of existing buildings are of concern. Compared to new construction, for existing buildings, in-situ measurement of the building envelope thermal properties may be essential since in most cases drawings and details may not be known. The Heat Flow Meter Method is the generally known technique for in-situ measurement, which involves the use of a number of sensors and portable data acquisition systems. However, due to the unsteady natural conditions, the accuracy of Heat Flow Meter Method is not completely understood yet. To consider the influence of unsteady environmental conditions, some dynamic methods have been developed. The dynamic methods are so far not widely known or commonly used for in-situ measurement as their accuracies and performances are not completely explored. The infrared thermography has long been used for building diagnosis purposes to detect surface imperfections, moisture issues, air leakage and thermal bridge locations. Even though it has served as a powerful diagnosis tool for years, its application still remains qualitative and the interpretation of the image results can be somewhat confusing. However, the capability that infrared camera can catch the temperature distribution on the entire surface gives us the potential to use it as a quantitative tool for in-situ measurement of building envelope thermal properties. This research is focused on the development and validation of a quantitative methodology using infrared thermography for in-situ measurement. Several key difficulties, such as the exterior radiation and convection model, interpretation of infrared images and measurement of environmental conditions are discussed and explored. The results of this study can serve as a quick and effective tool for engineers and researchers to measure thermal properties of existing buildings, and therefore provide appropriate inputs for building energy simulation and energy retrofit. This research has been carried out through accomplishing several objectives. Initially, the influence of R-values for building envelope systems in the whole-building simulation process was studied, especially the detailed modelling approaches for several common techniques to improve the building envelope performance such as adding insulation materials and using advanced building envelope system types. This initial study helped better understand the importance of obtaining the realistic R-values instead of the “design values”. The next objective was to explore the existing methods to measure the building envelope R-values, using both the Hot Box Test Method and the Heat Flow Meter Method. By comparing the existing test methods and models, the most appropriate one can be used for on-site application to validate the results of infrared thermography method developed in this research. The final objective was to develop a quantitative infrared thermography testing method and calculation model that can be used for in-situ R-value measurement as a quick and practical tool.