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.

Since many buildings in Canada were built prior to the advent of national and provincial energy codes and standards, quantifying building envelope thermal performance in existing buildings is an important step in identifying retrofit opportunities. Due to the lack of building codes or standards for existing buildings in Canada, development of a rapid and robust quantitative approach to evaluate and rank buildings for vertical envelope retrofits is required. Hence, this dissertation sought to develop quantitative approaches to evaluate existing building envelope thermal performance in Canada and beyond. Following current professional practices, in Chapter 1, a comprehensive study was conducted on 49 campus buildings at the University of Victoria (UVic) to evaluate potential energy savings from vertical envelope retrofits, and to further validate those savings through more detailed energy models and parametric analyses for a subset of buildings. To this end, the thermal performance of a building envelope was quantified based on its heat loss coefficient (UA), obtained from multiplying its surface area (A) by its thermal transmittance (U-value). Heat loss calculations were used as a metric to inform envelope rehabilitation prioritization, while considering other data such as age and physical condition in parallel. Archetype energy models for selected buildings were used to evaluate the impacts of envelope retrofits on energy and GHG savings. The outcomes of this study allowed the University to weigh the benefits of improved energy performance from envelope retrofits against associated capital cost expenditures. Also, the implemented methodology and studied parameters unveiled a new horizon in evaluating the thermal performance of existing building envelopes in Canada, where a building code for existing buildings has not yet been established. Considering the economic findings of the envelope retrofits studied, it was concluded that in the absence of an existing building energy code, the University would likely require additional incentives, such as higher utility costs, higher carbon taxes, or qualifying for utility incentive programs to justify improving existing building envelope performance on the basis of energy only. The strength of the proposed methodology in Chapter 1 was in its balance of effort and ultimate decision-making utility, where reasonable thermal bridging approximations based on simulation models for existing buildings can yield data accurate enough to inform a ranking exercise on a large breadth of subject buildings. However, since numerical models do not consider degradation of building materials, real moisture content, and errors associated with manufacturing and installation, actual building envelope thermal performance differs from 3D simulation models. To study this limitation, in-situ thermal assessments of building envelopes were performed to quantify their actual thermal performances. To this end, Chapters 2 to 4 of this dissertation attempted to determine the viability of an external infrared thermography (IRT) survey technique for quantification of heat losses through the opaque building envelope, and also explores its potential application in identifying and comparing sources of air leakage. The experiments were performed on wood-framed wall assemblies commonly used in Canada due to growing interest among designers, builders, and governments to encourage the use of wood as a building material. In these studies, (Chapter 2 to Chapter 4), thermal transmittances (U-values) of wall assemblies were estimated with external IRT and compared with 3D computer simulations. Furthermore, the impact of the accuracy of U-values estimated with IRT on the deviation of energy simulation outputs with metered data was examined. Finally, a novel relative quantitative infrared index (IRI) was proposed as a means to facilitate rapid evaluation and subsequent ranking of building envelope thermal performance. From the experiments in Chapters 2 & 3, it was found that the U-values obtained with IRT were comparable with simulated values suggesting IRT can be a reliable tool for estimating the thermal performance of wood-framed wall assemblies. Results also demonstrated that thermal imaging artefacts including nonlinear characteristics of infrared (IR) camera focal array, a.k.a. non-uniformity corrections (NUC) and vignetting could have a substantial influence on the accuracy of results, in particular energy model outputs. This limitation was resolved by introducing a practical approach where thermal images were taken from different incident angle. Overall, IRI was found to be a reliable metric for relative quantitative comparison of building envelope thermal performance regardless of boundary conditions. Moreover, outcomes of the IRT air leakage study in Chapter 4 indicated that combined qualitative and quantitative IRT approaches could potentially be implemented by practitioners to identify sources of air leakage and thermal bridges in buildings and compare their relative severity. Since blower door testing is gradually being introduced as a building code requirement to measure building envelope airtightness in an increasing number of Canadian jurisdictions, performing IRT simultaneously is potentially valuable exercise in this context. Ultimately, the methodologies outlined in Chapters 2 to 4 can help decision-makers to characterize building envelope retrofits from a performance perspective, and potentially serve as a basis for governments to develop policies to improve existing building energy performance. The methodologies in Chapters 2 to 4 prompted opportunities to utilize the emergent technology of small unmanned aerial vehicles (UAVs) equipped with an infrared camera for quick thermal assessments of building envelopes. The last chapter of this dissertation, Chapter 5, outlines advantages and limitations of aerial IRT (UAV-IRT) surveys compared to conventional stationary IRT. Furthermore, a set of best practices for UAV-IRT were presented to minimize dynamic measurement uncertainty. It was concluded that with the current IR camera technology, aerial surveys for quantitative thermal assessment of building envelope are not as accurate as with conventional infrared thermography; further investigations by manufacturers and researchers are recommended.

This book is about the optimization of the characterization of the thermal properties of building envelopes, through experimental tests and the use of artificial intelligence. It analyses periodic and stationary thermal properties using measurement approaches based on the heat flow meter method and the thermometric method. These measurements are then analysed using advanced artificial intelligence algorithms. The book is structured in four parts, beginning with a discussion of the importance of thermal properties in the energy performance of buildings. Secondly, theoretical and experimental methods for characterizing thermal properties are analysed. Then, the methodology is developed, and the characteristics and properties of the algorithms used are explored. Finally, the results obtained with the algorithms are analysed and the most appropriate approaches are determined. This book is of interest to researchers, civil and industrial engineers, energy auditors and architects, by providing a resource which improves energy audit tasks in existing buildings.

The building sector has a major role to play in the mitigation of greenhouse gas emissions. Indeed, residential and non-residential buildings account for 40% total energy consumption in the European union. In addition, given that 80% of building energy demand come from heating, thermal insulation is a domain with great potential for energy savings.The estimation of the thermal performance of a building usually relies on theoretical calculations. When in situ measurements are performed, the results often show some discrepancies with predictions: this is the so-called “performance gap”. Thus, it is important to distinguish the contribution of each element of the building envelope to the overall energy losses. In particular, “thermal bridges” (insulation irregularities) generate locally additional heat losses. They may also alter the thermal comfort of inhabitants as well as lead to mould growth issues.This thesis proposes several methods for the in situ estimation of heat losses in a building wall or in a thermal bridge. The methodology consists in applying an artificial thermal load to the wall and to analyze its transient response. This “active” approach is usually faster and less sensitive to weather conditions than standard steady-state methods. In practice, the indoor air is heated, and both the temperature and heat flux are measured on the wall surface. An inverse method then estimates the thermal resistance of the wall by fitting a model (direct model) to these transient measurements. The well-posedness of the inverse problem is assessed thanks to several mathematical tools. Some model reduction steps are required for the parameters of the direct model to be estimable with the desired uncertainty.In the case of a homogeneous wall, temperatures and heat fluxes are measured with contact sensors at one specific location. For a non-homogeneous wall or a thermal bridge, these local contact measurements are extrapolated to the rest of the wall thanks to infrared thermography and the quantification of the total heat transfer coefficient. For this purpose, several methods were developed to measure this coefficient in situ. Thanks to this extrapolation procedure, the inverse method can estimate the thermal resistance (or thermal transmittance) of an equivalent homogeneous wall having the same behavior as the real wall.The methods developed were validated on four experimental campaigns. Measurements were carried out in laboratory, in a climate chamber, and in situ. Different types of wall (heavyweight internally insulated wall, lightweight insulated wall) were tested. Several types of material-related thermal bridges were also investigated (mainly high-conductive materials in insulation systems). The results were compared to reference values obtained from steady-state measurements. Indeed, several methods for the characterization of thermal bridges in steady-state were compared: some are inspired from the literature, others are original.

This book results from a Special Issue published in Energies, entitled “Building Thermal Envelope". Its intent is to identify emerging research areas within the field of building thermal envelope solutions and contribute to the increased use of more energy-efficient solutions in new and refurbished buildings. Its contents are organized in the following sections: Building envelope materials and systems envisaging indoor comfort and energy efficiency; Building thermal and energy modelling and simulation; Lab test procedures and methods of field measurement to assess the performance of materials and building solutions; Smart materials and renewable energy in building envelope; Adaptive and intelligent building envelope; and Integrated building envelope technologies for high performance buildings and cities.

A technique for measuring the thermal resistance (r-value) of large areas of building envelope is under development. It employs infrared thermography to locate radiant temperature extremes on a building surface and to provide a map of normalized temperature values for interpolation between locations. Contact thermal sensors (thermocouples for temperature and thermopiles for heat flow) are used to calculated the r-value at specific locations by summing the output from each sensor until the ratio between temperature difference delta T from inside to outside surface and heat flow converges to a constant value. R-value measurements of a wood frame insulated wall were within 13% of the expected theoretical value. Similar measurements of masonry wall were 31 and 43% less than expected. Experimentation demonstrated that a large delta T was the single most important variable affecting accuracy and speed of convergence. Thermal guards around heat flow sensors were of little value, according to both experimentation and computer simulation. Attempts to match the absorptivity of sensors with their surroundings may have been insufficient to diminish about 10% of the remaining error in measurement. Lateral heat flow and convection may have been significant problems for accuracy in the masonry construction. Currently, an investigator cannot rely on the literature for guidance in assessing the limitations on accuracy for in-situ building r-value measurement.

Infrared thermography (IRT) is a non-contact, non-invasive methodology which allows for detection of thermal energy that is radiated from objects in the infrared band of the electromagnetic spectrum, for conversion of such energy into a visible image (such as a surface temperature map). This feature represents a great potential to be exploited in a vast variety of fields from aerospace to civil engineering, to medicine, to agriculture, etc. However, IRT is still not adequately enclosed in industrial instrumentation and there are still potential users who might benefit from the use of such a technique and who are not aware of their existence. This e-book conveys information about basic IRT theory, infrared detectors, signal digitalization and applications of infrared thermography in many fields such as medicine, foodstuff conservation, fluid-dynamics, architecture, anthropology, condition monitoring, non destructive testing and evaluation of materials and structures. The volume promotes an exchange of information between the academic world and industry, and shares methodologies which were independently developed and applied in specific disciplines.