Everything above absolute zero radiates infrared energy in proportion to its surface temperature. When the objects are hot enough they radiate visibly and our eyes can see them glow. As they cool their radiation becomes invisible to the eye. We then can use infrared thermal sensors and scanners to measure their self-emitted infrared radiation and relate it to surface temperature. When the inside and outside of a structure are at different temperatures thermal energy flows through the walls and ceilings. The better the insulation, the less energy flow and the more is conserved. Changes in wall and ceiling surface temperatures are an indication of the thermal energy loss. This paper introduces the basic physical laws that make infrared thermal sensing instruments work, and explains how they are used to detect and measure heat loss in structures.

This session deals with meteorological effects of the real life world as these effects apply to the use of infrared to find heat loss or heat gain of buildings. Some of the common misreadings of thermal effects and the causes of the misreadings are described.

The steadily increasing costs of energy emphasize the necessity of efficient energy utilization and conservation. Energy conservation is the first approach to extending energy supply and slowing energy prices escalation.

Quantitative methods for measurement of absolute (kinetic) surface temperatures of roof surfaces from aerial thermal data are discussed. Methods of accounting for atmospheric variation, background reflectance, path radiance and roof emissivity effects are also discussed. The quantitative method has been tested on several research programs under the sponsorship of the New York State Energy Research and Development Authority and the U.S. Department of Energy. The results of these tests, which are presented here, represent a comparison of concurrent contact and aerial roof temperature measurements on a variety of roof surfaces. These tests indicate that kinetic roof surface temperatures can be measured from wholly-airborne data with a standard error of 1.0°C. The implications of these results for airborne measurement of building heat loss are presented in this paper.

The effectiveness of aerial infrared thermography as an energy audit procedure for residences having pitched ventilated roofs is investigated. Three adjacent unoccupied houses were instrumented to provide ground-truth comparison data under various weather conditions. Factors affecting the accuracy of this technique are identified and analyzed, and guidelines are presented concerning the recommended use of aerial infrared thermography as a procedure for assessing the thermal performance of residences. Keywords: aerial scanning; energy conservation; infrared halo analysis; infrared thermography; roof heat-loss survey.

A method is presented, using new infrared heat flow meters, to measure the heat flows and R-values in homes. Such defects as wet or missing insulation, air infiltration effects, and thermal bridges are readily evaluated. A new reference standard method simplifies the heat flow measurement. The procedure can be used by modestly skilled auditors to advise the homeowner regarding retrofit of new insulation, or repairs to the existing envelope. The procedure is sufficiently direct, that it is believed to be the lowest cost of all measurement-based energy audits. It is competitive with non-measurement survey methods which produce much less information.

Since 1975 the federal testing institute on heat and sound technique at TGM in Vienna carries out thermographic tests mainly to give advice on thermal insulation of buildings to reduce energy consumption for space heating in Austria.

This paper will offer a synopsis of a unique infrared mobile ground based heat loss scanning program undertaken by the City of West Allis, Wisconsin during the 1981 heating season. Nearly 25,000 structures were surveyed over a period of six weeks. Further, the paper will contain a brief introduction describing the 1979 pilot program which served as the base for the 1981 full City scanning program. Finally, the paper will discuss prescanning preparation, data acquisition, training programs, data dissemination and a summary of key points. An epilog will follow.

After the energy crises in 1974 rebuilding in Sweden has often included supplementary insulation of the thermal envelope. This has been done as the Building Code says that rebuilding is equal to building a new house at least from the codes point of view. Therefore the rebuilt house should have a quality equal to a new one. Moreover the government has given financial support to supplementary insulation in the belief that it would result in energy conservation for the built environment. This support has been given to buildings that ought to be badly insulated judging from their age and construction. Therefore many pretty buildings in our country has got new ugly overcoats with a thicker lining. Not necessarily because they needed the lining but because of the financial possibilities or the fact that the old overcoat was worn out.

In Sweden thermography has been used durinc the last 10 - 15 years to study air leakage and insulation problems. The method has been defined in the SIS standard No. SIS 02 42 10.

For several years, infra-red scanning has been utilized in energy audits in commercial/ industrial situations. With the advent of recent increases in energy costs, the residential sector has become increasingly aware of the high cost of home comfort. With this awareness, IRT has become an important tool in assisting homeowners to determine the most effective means of reducing the cost of comfort.

Naturally, there are varying opinions as to the degree of seriousness of today's energy problem, as well as the long range effects it will have on us all. As numerous as these opinions may be, so are the theories as to the most optimal course(s) of action that should be undertaken to relieve the situation. For example, there is no clear-cut consensus as to which alternative energy source we should most diligently pursue, how diligently should the pursuit be at this time, is there (or will there ever be) a need to significantly change our lifestyles and business expections, or will scientific discoveries relieve us all in the end? As complex and omnipresent as these queries may be, the paradox is the consensus among most of us as to the existence of an energy problem.

With an increasing interest in the United States, expressed by the National Bureau of Standards (NBS) and the Department of Energy (DOE), as to the cost effectiveness of carrying out quality control thermographic inspections on homes that have been retro-fitted with various types of building insulation and also in the technical proficiency offered by infrared (IR) contractors in this particular application, the New England Innovation Group (NEIG) was contracted to compile, analyze, and report on data supplied to the group by randomly selected infrared inspection contractors which would examine these Particular issues. The homes inspected under this NEIG/NBS/DOE/CSA program were for the most part single-family, low-income homes that were "weatherized" through the Community Services Administration (CSA) Program. Thirty-two homes in eight different cities across the country were inspected by a total of twenty-six different infrared inspection firms using various types of infrared inspection equipment, with baseline data on each of the thirty-two homes being supplied by NBS Personnel. The data supplied by the various private IR inspection contractors was then compared to that generated by the NBS baseline inspection data in the categories of: Method of Inspection, Equipment Operation, Thermal Interpretation, and Completeness and Accuracy in Evaluation. This applied research program, which examines the aforementioned issues as they relate to quality control thermographic inspections of residential buildings, was conducted through the 1978-79 and 1980-81 heating seasons. The results from both phases of the program reveal a drastic need for a standardization in the minimum level of technical exoertise as well as the manner in which IR contractors Perform and present quality control thermographic evaluations.

Diagnosis of the dynamic thermal performance of buildings requires specialized training in thermography. Due to the complex and transient nature of heat flow through buildings, it is critical that a thermographer be skilled in the fundamentals of building science and infrared technology. This paper presents the objectives and rationale for instruction in thermography, as well as the specific knowledge requirements of the training program developed by Public Works Canada (PWC).

The new ASHRAE Standard 101P, entitled "Application of Infrared Sensing Devices to the Assessment of Building Heat Loss", addresses the requirements upon infrared equipment when they are to be used for locating deficiencies which may exist in the thermal envelope of a building. Five categories of survey type are set up by the standard: imaging, airborne survey; non-imaging, spot radiometer; non-imaging, line scanner; imaging, exterior survey; and imaging, interior survey. It is intended that the standard will enable a prospective user of such equipments to better understand what level of information detail is obtainable from their proper application and show how the equipment specifications influence the conditions under which thermal measurements are to be made.

Methods to measure the heat loss are needed in order to evaluate the energy efficiency or the results of retrofitting wood frame buildings. Theoretical analysis with assumed building construction will give a measure of efficiency. Specific heat transfer measurements allow a more definitive analysis but only at preselected points. On the other hand, an infrared imaging instrument's data are global in nature and can verify the quality of the insulated areas through proper inspection. Such inspection requires a standard method which defines the requirements of training, gives definitions of anomalies, and lists the required procedures. This paper will discuss the status of such a thermographic standard which is currently being produced by a task force in ASTM C-16.30 for wood frame buildings. Voting on this Practice should begin this fall with passage expected in 1982.

Thermographic scanning has been a viable tool for investigating building envelope deficiencies for over ten years. One of the basic assumptions has been that a minimum temperature difference must exist between interior and exterior air before an inspection can be considered. It has also been assumed that the greater the air-to-air temperature difference (i.e., the greater the heat flow), the more accurate the inspection. However, for building exterior scanning, as ambient exterior temperature decreases, instrument sensitivity decreases at a rate faster than heat flow increases. In the past, manufacturers' specifications have been neither adequate nor standardized in respect to instrument sensitivity fall-off and instrument comparisons. Minimum resolvable temperature difference (MRTD) testing underway at Public Works Canada is helping to solve this problem.

The roof has always been one of the most important portions of a building envelope. It is, however, one of the most overlooked areas with respect to building maintenance. As long as the roof is not leaking into the building, it is thought to be functioning properly. This is an erroneous assumption as many problems occur long before they are evident as leaks into the building. Early location and repair of roof problems can mean the difference between a roof which must be completely torn off and replaced and one which will give years of service to the building owner.

Emissivity values were measured at 0°C for four modern building materials in the 2.5-5.6 μm region of the infrared spectrum. The materials consisted of various visible colors and textures of roofing shingles, fluoropolymer coated steel roofing, aluminum siding, and solid vinyl siding. The results varied significantly over the range of colors selected. Values for thin coatings on metal substrates were lower than expected for the coatings alone. The effects of temperature, texture and wavelength were not clear. Emissivity values for common building materials were compiled from the literature and are included for comparison.

For the past four years, the Architectural Sciences Division of Public Works Canada (PWC), under the direction of Mr. Peter A. D. Mill, has been developing techniques and procedures for building enclosure evaluations. During the winter of 1980 - 1981, the Architectural Sciences Division undertook a series of wall evaluations of fifty-three federally owned buildings. Thirty-three buildings were surveyed in the Western Region (Manitoba, Saskatchewan and Alberta) and twenty buildings in St. John's, Newfoundland (Atlantic Region).* A combination of aerial surveys and exterior and interior ground surveys were conducted by both PWC staff and private sector consultants.

Results of a thermographic study of roof surface temperature and heat loss are presented. The major finding is that a technique is demonstrated for obtaining quantitative temperature and heat transfer measurements from a thermogram using a thermally controlled reference surface within the area surveyed. The presence of the reference surface is shown to permit calculation of heat transfer rate with a quantifiable level of uncertainty. The present work also demonstrates that the representation of grey tone imagery in digital and graphical formats can be useful for both qualitative and quantitative purposes in energy conservation.

An infrared absorbing tracer gas technique using nitrous oxide has been developed by the Architectural Sciences Division to illustrate patterns of air flow from air-conditioning supply air diffusers. Air flow patterns are recorded in real time on videotape through the use of infrared cameras and an IR opaque gas. By identifying faulty air circulation, the quality of the interior environment may be improved. The approach was first recognized by Public Works Canada in 1978 as having great potential as another diagnostic technique for improving Canadian building performance. The tracer gas technique comes as an extension of the developmental work in thermographic diagnosis of enclosure deficiencies done by Public Works under the direction of Peter A.D. Mill. 1,2,3

We have developed a method for measuring R-values for large areas of building envelopes with thermography and contact sensors. The technique entails locating thermal extremes on a building surface with thermography. Contact sensors determine the R-values at these locations. A thermographic map provides the basis from which to interpolate R-values for all other locations within the area surveyed. This paper explains the interpolation technique we employed and demonstrates some of the difficulties of the method. Further experience will define the limitations of the technique more fully.

The Vietnam War surfaced an important fact: The ability to see at night as effectively as during the day is indispensable. During the conflict, the Army fielded the first generation image-intensified tube systems. These systems added a new dimension to the tactics of land warfare. Taking the night away from the Vietcong was the goal during the late sixties and the early seventies, and it was attacked with ingenuity, enthusiasm, and a sub-stantial number of research and development contracts to U.S. industry.

There is considerable information, usually of a complex nature, contained in a thermographic image. In building science diagnostics, it is necessary to quantify this information and upon occasion to improve or manipulate the image data. This is only feasible using digital processing techniques and devices, some of which are highlighted in this paper.

The Spot Radiometer is a non-imaging, infrared instrument designed to measure either the temperature of a well-defined surface area or the radiosity from that area. (Radiosity is defined as the total radiation which leaves a surface per unit time per unit area, and is the sum of emitted and reflected radiation.) Typically, the Spot Radiometer is a portable, battery-operated device consisting of a collecting lens or mirror, an infrared detector, an amplifier, signal processor circuitry, and an analog or digital display.

The Pyroelectric vidicon (PLV) is an infrared (8-14 micron wavelength) sensitive television-type camera pick-up tube. As can be seen from Figure 1, the tubes presently being produced can be configured into portable, battery operated, electronic imaging systems with full TV-compatible tape recording and playback capabilities. (The system illustrated is a laboratory modification of a "home recording", standard 2/3-in. vidicon camera system.)

This paper presents a compilation of information on the history and features of thermo-electric coolers, infrared detectors and their combination into detector/cooler packages. It shows their potential for utilization as the thermal infrared sensors in those measurement devices related to the problems of energy conservation in building envelopes. General sensor considerations are reviewed in light of present and future applications and features of a typical commercial instrument using thermoelectrically cooled detectors are presented. The history, evolution and features of the cooler detector package, which is the heart of the system is presented. The presentation highlights the desirable attributes of these often overlooked thermoelectrically cooled detectors. Features such as low cost, high reliability, low power, lightweight and long life make them more appreciated and attractive to future commercial instrumentation designs.

There are a number of equations that can be used for calculation of true object surface temperature from radiation measurements made with infrared imaging equipment. With careful analysis of the measurement situation it is possible to reduce the number of parameters involved in such measurements and still improve the accuracy. Practical methods also exist for measuring or estimating remaining unknown parameters

The quantification of industrial heat loss is of increasing importance because of the enormous amount of energy consumed by process industries, and the subsequent high cost of wasted energy. Thermography provides a relatively inexpensive technique for gathering the necessary data to determine heat loss. When other relevant data is collected at the time of the survey and simple data processing techniques are applied, the results can be quantified to establish a priority rating of energy-saving projects. Simple calibration techniques can be used to provide accurate figures on annual heat loss. These estimates are particularly useful if cost benefit (or return on investment) information is desired.

The Jet Propulsion Laboratory has used infrared thermography extensively in the Low-Cost Solar Array (LSA) photovoltaics program. A two-dimensional scanning infrared radiometer has been used to make field inspections of large free-standing photovoltaic arrays and smaller demonstration sites consisting of integrally mounted rooftop systems. These field inspections have proven especially valuable in the research and early development phases of the program, since certain types of module design flaws and environmental degradation manifest themselves in unique thermal patterns. The infrared camera was also used extensively in a series of laboratory tests on photovoltaic cells to obtain peak cell temperatures and thermal patterns during off-design operating conditions. The infrared field inspections and the laboratory experiments are discussed, and sample results are presented.

An innovative approach to the development of a model system for comprehensive industrial sector thermographic investigations and inspections will be taken during the winter of 1981-82 in Holyoke, MA. Infrared thermography techniques will be utilized for cost effective identification of building and process heat losses. The Holyoke program provides for a wide range of energy conservation services and will result in the implementation of no-cost, low-cost, and cost-effective capital intensive measures financed through a cooperative effort of government and private funding.

Thermography, currently being applied by utilizing the AGA 750, 720 and 782, has demonstrated its value as a maintenance and conservation tool. It is efficient because in the scanner's portable configuration, hand held or car hood mounted, large quantities of electrical equipment, square footage of thermal envelope, steam distribution piping, etc., can be covered. The severity of the problem can be estimated easily by measuring the object's temperature and cataloged for future action by quickly recording the situation with a photograph. It is a productive procedure which identifies problems which justify the cost of the survey in roughly 70% of the cases. Moreover, the problems located by the thermographic survey are usually corrected. This is because of the high impact of the polaroid pictures taken during the survey. The technicians correcting the problem, the engineering department, and the senior management personnel can all understand the situation because of the clarity of the photograph. Furthermore, feedback concerning the repairs can be easily obtained by rescanning the problems involved.

The application of infrared thermography (IR scanning) in utilities for aerial surveys, inspection of substation and overhead connections and equipment is well known. This paper describes a new application for infrared thermography--examination of underground secondary connections in manholes and service boxes. The analysis of over 300 potential failures detected by IR scanning, to date, has shown failure mechanisms in all which eventually would have caused the connection to fail. Infrared scanning of undergound secondary connections has been shown to be a viable method for preventive maintenance. Potential failures are detected before the occurrence of an emergency (customer outage) condition. Analysis of these potential failures by QA & R provides a check on the efficacy of the operator, equipment and procedure.

Since September 1978, Public Works Canada has been leading an interdepartmental Canadian Government project aimed at using thermography to diagnose problems in building performance in various climates. It has been demonstrated that the thermographic camera provides insight into how building systems actually perform, by "seeing" the thermal effects of various mechanisms of heat transfer. This insight is arrived at by either interpreting surface thermal patterns with IR cameras or thermal patterns of air movement using tracer gases. These results are significant in that they indicate how buildings perform rather than how they are built, thus encouraging new ideas in building design and services.