Building Air Leakage Research Articles

Development and experimental evaluation of new building air leakage measurement methods: measurement of interior air leaks and comparison to conventional methods

Building air leaks (both through exterior and interior surfaces) can have a significant impact on energy consumption, indoor air quality, fire safety, and moisture accumulation affecting structural durability. Blower door testing has been used to measure leaks in buildings, but commonly used testing methods do not directly measure interior leaks. In this paper, new testing methods (guarded interior test and zonal multipoint pressure testing method) are presented that directly measure these interior leaks, utilizing common blower door equipment for both single and multi-point testing. These new methods are compared to conventional methods in terms of the information provided, limitations and time/effort needed. In addition, building leak measurement results are analyzed to reveal (a) coupling between power law model values (exponent and coefficient) for an ensemble of buildings, (b) the error in using single point testing when estimating low pressure leakage, and (c) how building power law models vary from low to high pressure ranges.

Building air leakage characteristics and airtightness durability of single-family dwelling

In this study, we focus on the leakage characteristics and composition of openings associated with building airtightness in wooden single-family dwellings. The proposed parallel combination models for leakage are equal to or better than the power law in terms of compatibility with measured values. Unlike reinforced concrete housing complexes, wooden single-family dwellings indicate variability in terms of the coefficient of leakage characteristics, including in highly airtight units. Dwellings constructed approximately 10 years ago do not exhibit a clear declining trend. However, the airtightness decreases in dwellings that have undergone renovations on the outer walls, such as through the addition of an attic or the installation of additional heat pumps.

Application of reference-free natural background–oriented schlieren photography for visualizing leakage sites in building walls

Air leakage in buildings can cause health and comfort concerns for occupants and can contribute to mold growth on building materials, or in extreme conditions, rot of building materials. Unwanted air leakage through the building envelope also contributes to approximately 4 quadrillion Btu (1172 TWh) of energy consumption per year in the building sector in the United States. Locating and sealing leakage sites can improve the energy efficiency, comfort, air quality, and moisture durability of the building stock. Typical methods of finding leakage sites, such as infrared imaging and smoke tracing, rely on concurrent blower door operation, which can also measure the total leakage rate of the building. Smoke tracing can be disruptive to occupants, and infrared imaging and smoke tracing cannot measure the contribution of individual leaks to prioritize sealing efforts. In this work, an optical fluid flow imaging technique, reference-free natural background–oriented schlieren imaging, was adapted to visualize air exfiltration. This is the first step in developing a method to noninvasively locate and measure exfiltration or infiltration sites so that sealing efforts can be prioritized. Experimental results of this technique are presented, demonstrating the method's applicability to visualizing exfiltration through three common building claddings in an outdoor environment. Key variables impacting the performance of this technique when applied to building leakage are also discussed.

Energy and emissions effects of airtightness for six non-residential buildings in Canada with comparison to contemporary limits and assumptions

Building air leakage is often a significant contributor to the energy consumption of a building and is difficult to characterize. Unlike the thermal performance of building envelope components, the high variability of airtightness of building assemblies and their interfaces makes air leakage of buildings difficult to predict. This publication describes the process and results for identifying leakage rates and locations within six non-residential buildings using airtightness testing, specifically six commercial buildings. Infrared (IR) scanning was used to visualize locations of air leakage in the building envelope. The energy and emissions effects from the measured performance were quantified and compared to the assumption in the relevant Canadian building code.The air leakage rates for all buildings tested in this work were less than the ASHRAE 90.1 standard limit of 2.0 L·s−1 m−2 @ 75 Pa, while three were less than the Air Barrier Association of America (ABAA)/United States Army Corps of Engineers (USACE) standard limit of 1.25 L·s−1 m−2 @ 75 Pa, and two were less than the National Energy Code of Canada for Buildings (NECB) assumption of 1.5 L·s−1 m−2 @ 75 Pa (a different area normalization is used for the NECB). The effects of airtightness on energy use intensity and annual operational emissions were quantified and found to be substantial and varied. The incremental energy use intensity ranged from a reduction of 47 kWh/m2ᐧyear to an addition of 64 kWh/m2ᐧyear.The most common location of leakage is between connections of building assemblies, especially the roof wall connection, and building components, particularly doorways, as well as at various envelope penetrations, such as for pipes and ventilation inlets/exhausts. The process of testing was documented and showed that the use of currently-available commercial equipment enables tests for typical small to medium-sized commercial/non-residential buildings to be completed efficiently. The results showed there is notable variation in airtightness levels between buildings and there are opportunities for improvement.

A measured energy use, solar production, and building air leakage dataset for a zero energy commercial building

This paper provides an open dataset of measured energy use, solar energy production, and building air leakage data from a 328 m2 (3,531 ft2) all-electric, zero energy commercial building in Virginia, USA. Over two years of energy use data were collected at 1-hour intervals using circuit-level energy monitors. Over six years of solar energy production data were measured at 1-hour resolution by 56 microinverters (presented as daily and monthly data in this dataset). The building air leakage data was measured post-construction per ASTM-E779 Standard Test Method for Determining Air Leakage Rate by Fan Pressurization and the United States Army Corps (USACE) Building Enclosure Testing procedure; both pressurization and depressurization results are provided. The architectural and engineering (AE) documents are provided to aid researchers and practitioners in reliable modeling of building performance. The paper describes the data collection methods, cleaning, and convergence with weather data. This dataset can be employed to predict, benchmark, and calibrate operational outcomes in zero energy commercial buildings.

Reliability of quantitative and qualitative assessment of air leakage paths through reductive sealing

A full characterization of a building air leakage is labour intensive. As results of laboratory and mock-up experimentation rarely portray in situ conditions, the assessment of real case studies bring added value. Still, the results of experimentation of the latter face more challenges than the former. In this work a full quantitative and qualitative assessment of air leakage paths is performed, using a light steel framing (LSF) modular building with structural insulated panels (SIPs) as case study. Blower-door measurements undergo for a sealing campaign of eleven steps, a technique often described as reductive sealing. Additionally, smoke tracer measurements were carried out to visually identify the air leakage locations. The application of three regression methods resulted in different uncertainty estimates. Less than 7% of the total air leakage was not attributed to one of the considered types of air leakage paths. Assessing less impacting leakage paths first and placing similar types of air leakage paths in a consecutive sealing order seems to be the most correct strategy when using the reductive sealing technique. On average, at a reference pressure difference of 4 Pa, the sealing step uncertainty averaged, 9.9%, 18.8%, and 27.5%, depending on the method used for regression of the blower door test results. Despite the highest calculated uncertainty, literature shows that the application of the method leading to it, Weighted Line of Organic Correlation (WLOC), provides the results in closer agreement with the observed uncertainty of measurements.

Evaluating Patterns of Building Envelope Air Leakage with Infrared Thermography

The next-generation performance-based building energy codes are focusing on minimizing building envelope air leakage. The quantification of air leakage in buildings is typically performed with a blower door test. However, this test does not provide information about the locations of air leakage. The aim of this study is to demonstrate a method involving qualitative and quantitative components that can be used to characterize locations of air leakage with infrared thermography. Since air leakage can have a significant impact on building energy consumption in cold climates, like in Canada, this approach can quickly inform where air barrier discontinuities occurred during construction or where to selectively target air sealing efforts in existing buildings. The observations from this study are presented, based on a thermographic image analysis during a depressurized blower door test at various pressures, in an attempt to quantify the relative rates of air leakage. The results from the investigation showed that infrared thermography (IRT) was able to discern locations and infer relative ratios of air leakage. The qualitative analysis showed that areas of air leakage are more evident under higher pressure difference. The quantitative approach showed that a minimum of 25 Pa pressure difference was required to detect the air leakage in the vicinity of the window frame, as the surface temperature decreased rapidly (almost 60% of the indoor surface/outdoor air temperature difference) at this pressure. A temperature index was defined to prioritize the areas of air leakage for retrofitting purposes. Furthermore, a thermal image subtraction method was used to determine the characteristics of the cracks based on thermal patterns. Finally, the practical implication of this study, for building developers, home inspectors, property mangers, and homeowners, is the early detection of air leakage for both existing and newly constructed buildings which could result in energy and cost savings.

Correlation between air and sound propagation to determine air permeability of buildings for single/double wood pane windows

Building air leakage is a very important criterion on which one building could be differentiated from another one. It can lead to a huge impact on several important parameters inside a building, like energy consumption or indoor air quality. There are several possibilities for its determination, and it could be highlighted three major categories: experimental determinations, predicting models or simulations programs. As the experimental approach is difficult to be conducted being weather dependent or time consuming and the predicting models could lead to errors up to 100%, in this paper we aim to present a novel experimental method for determining the air permeability of a building, by measuring the sound pressure level difference between outdoor-indoor of the analyzed façade. An experimental campaign was conducted using the Blower Door method and an acoustic approach determining the impact of the window’s type on the airtightness of a façade. In extension, the correlation between the two transfer phenomena was highlighted throughout a mathematical model. Multiple acoustical parameters that could influence the air leakage determinations were analyzed. The importance of the reverberation time of the analyzed chamber in the acoustical transfer phenomenon was determined and a practical nomogram was developed.

An investigation of alternative methods for determining envelope airtightness from suite-based testing in multi-unit residential buildings

Blower door testing is commonly used to characterize exterior façade air leakage in buildings. This characterization is needed to improve the accuracy of energy models and certify building performance. Performing these tests in large buildings requires air flow rates that are sometimes impractical to achieve using available equipment, which necessitates testing in individual zones within those buildings. However, when performing these tests in individual zones, the conventional whole-suite tests are unable to isolate the required envelope flow characteristics and pressure neutralization tests are, in most cases, too logistically difficult to perform, which necessitates an investigation into alternative methods. In this study, two methods developed for use in row housing were adapted to a high-rise multi-unit residential building (MURB) context in which the test suite is surrounded by adjacent suites: The Love and Passmore method, and the Lstiburek method. The efficacy of these adapted techniques was assessed in a single suite located in a high-rise MURB that followed typical North American construction habits. To carry out these assessments, a combination of field data and calibrated CONTAM simulations are used. For the case study building, the Love and Passmore method exhibits exterior boundary characterization errors of 108%, and is inappropriate for this characterization in high-rise MURBs. Alternatively, the Lstiburek method exhibits an exterior boundary characterization error of 0.2%, but additional analysis showed the Lstiburek method exhibits greater sensitivity to measurement noise than the pressure neutralization method. As a result of this increased noise sensitivity, and because of the similar labour and equipment requirements, it is therefore also not recommended as a replacement for the pressure neutralization method. It is important to note that buildings constructed using different details and techniques may exhibit different results, which is a limitation of this study. Details related to these tests, including a discussion of potential shortcomings and strengths, are presented in this paper.

Assessment of wind impact on building air leakage measurements using a model scale experiment

Nowadays, many countries include requirements for building airtightness in their current national regulations or energy-efficiency programs, mainly for concern about reducing building energy consumption due to air leakage. Moreover, more and more countries impose a mandatory justification with an air leakage measurement at building commissioning. Therefore, the uncertainty of the measurements results has become a key concern in several countries over the past year. More specifically, the influence of wind speed has been identified as one of the major sources of error on the measurement result. The goal of this paper is to present the experimental facility we design and built to improve the uncertainty estimates and the measurement protocol based on model scale experiments in controlled laboratory conditions. We first present the similarity criteria we identified for our model scale experiment. Secondly, we present the experimental design. Finally, we characterize the wind speed inside the wind tunnel and we present the preliminary results regarding the reproduction of fan pressurization tests on the model for different leakage distributions.

Towards a methodological approach to builder specific, preconstruction airtightness estimates for light-framed, detached, low-rise residential buildings in Canada

Building air leakage has been shown to predominate at wall transitions rather than through the field of the building enclosure. Controlling air leakage forms an important part of the reduction of annual buildings energy use, as well as its contribution to green house gas emissions. Adequate airtightness estimation methods have thus become an important tool for designers in the construction industry as they adapt to stricter government mandated energy consumption targets. An empirically based design of experiments was devised to quantify the impact of air leakage through a floor-to-wall detail typical of light framed residential homes. A very strong laboratory-based model explained up to 88% of the air leakage through the floor-to-wall joint (R = 0.95, p « 0.001). The resulting estimation was then combined with a whole building, preconstruction airtightness multiple linear regression forecasting model. The results demonstrated an approach to estimating preconstruction airtightness in light framed, detached homes.

Modeling air leakage in buildings caused by the cyclic variation of the atmospheric pressure

This article considers a new type of air infiltration through building envelopes caused by the barometric pressure variation. This process is independent from wind action or stack effect. A new building–atmosphere differential equation of air exchange is established. Based on the solution of the differential equation of air exchange, we propose the notion of pressure equilibration time [Formula: see text] that characterizes the dynamic response of the building. Furthermore, experimental climatic data were processed using Fourier analysis methods in order to build an identification model based on the regular harmonics of external pressure oscillation. The barometric pressure reconstructed in its parameterized form was introduced in the differential equation of air exchange as a term that models the dynamics of the external action. The analytic solution of the differential equation of air exchange demonstrates that the indoor–outdoor pressure difference is insignificant at less than 10−3 Pa for any harmonic of the external pressure variation. At the same time, it is concluded that the airtightness of the envelope has little influence on the process, as the indoor–outdoor pressure equilibration is almost instantaneous in a continuous regime of variation. The described mechanism of air infiltration explains the alternation of infiltration and exfiltration of air in buildings. For this, a mass balance of air exchange for the specific ranges of time is performed. We prove that the barometric pressure variation has an effect that accounts for 3.19% of the total quantity of air exchanged. The advances provided by this paper constitute a useful instrument for further studies concerning the stack effect in thermal dynamic conditions. Practical application: The paper proposes a novel methodology of determining the air exchange building–environment by considering a new component of infiltration and its cyclic variation: the barometric pressure. A new mechanism of natural air infiltration is determined and modeled and it should be added to the existing ones: wind action and stack effect. A complete methodology of analysis and extraction of the cyclic processes hidden in an envelope of stochastic variations is defined and applied with the support of signal processing techniques and spectral analysis. The refinement of the mathematical instrument was able to distinguish through a deterministic approach an influence of 3.19% of the new barometric component. Furthermore, with few adaptations, the methodology constructed in this study can be applied for investigation of the stack effect by considering the cyclic variation of the atmospheric temperature. Currently, the stack effect is analyzed only for average conditions of temperature, a simplistic approach that suggests a large potential for further improvement.

Building air leakage analysis for individual apartments in North China

There is little known on the airtightness performance of apartment building in China. The present study intends to investigate the airtightness performance of twelve individual apartments from four buildings in China's cold area using the blower door method. The air leakage of two building components of each of the three individual apartments from the 4# building was further investigated by a series of blower door tests. The normality test was performed to the test results, and the correlation coefficients between the air leakage and possible influence factors were analyzed.Test results show that the air change rate of the tested individual apartments at 50Pa changes from 1.14 h−1 to 2.44 h−1 with an average of 1.77 h−1. The check valves at the inlets of the discharge flue and exhaust airway were tested to be leakier than the outer windows and doors in the three measured apartments from the 4# building. Results of statistical analysis show that the data was significantly drawn from a normally distributed population at the 0.05 significance level, and the envelope area and the joint length of the opening part of the windows and doors were identified as the main factors that influence the air leakage of the tested apartments at the 0.05 significance level.

Leakage Reductions for Large Building Air Sealing

This paper presents results from whole building air leakage tests used to document the leakage reduction due to envelope sealing and assess the accuracy of contractor’s estimates of the impact of their sealing. The measurements also compare the differences in envelope leakage reductions determined from depressurization versus pressurization tests and determine mechanical system leakage.The eight buildings were constructed between 1936 and 2007 with floor areas that ranged from 1100 to 22900 m2. The buildings were relatively tight with normalized air leakages that ranged from 2.66 to 7.41 m3/h·m2 at a 75 Pa pressure difference. Six of the buildings were air sealed with work that focused on spray foam sealing of accessible wall/roof joints and upgrades of exterior door weatherstripping. The sealing reduced air leakage from 6 to 17% with a median of 9%. The measured leakage area reduction was only 4% to 24% of the contractor bid estimates of leakage they would seal. Post-inspections indicate that the lower measured reductions were not due to incomplete air sealing, but an inability of the contractor to estimate the amount of leakage they would seal.There was consistently higher leakage under pressurization than depressurization. The ratio of pressurization to depressurization tightness for the pre and post sealing measurements varied from 1.12 to 1.31 with an average value of 1.21. The mechanical system leakage ranged from 0.57 to 3.78 m3/h·m2 and increased the envelope leakage by 17% to 103%. This suggests that mechanical system air leakage can have a significant effect on building air leakage when the systems are off.

Airtightness in New and Retrofitted U.S. Army Buildings

The Engineer Research and Development Center, Construction Engineering Research Laboratory (ERDC-CERL) recently developed design/construction strategies that improve the energy efficiency, reduce the potential for mould, and improve indoor air quality in newly constructed buildings and buildings undergoing major renovations. ERDC-CERL performed building envelope leakage tests on Army facilities to test their general integrity and the effect of increased airtightness on building energy consumption. Results were used to develop airtightness criteria and performance requirements for new construction and major renovation projects, which have been included in Army design/construction strategies.Since 2009, the U.S. Army Corps of Engineers (USACE) has implemented an airtightness requirement in all new construction and building enclosure renovation projects. Engineering and Construction Bulletin (ECB) 2012–16 set levels of airtightness for building enclosures at the material, assembly, and system level. ECB 2012–16 requires whole building air leakage tests to be conducted at completion of construction to verify the constructed air barrier system’s performance. The current Air Leakage Test Protocol for Building Envelopes developed by ERDC-CERL, the Air Barrier Association of America (ABAA), and other industrial partners was published in May 2012.This paper presents the results of airtightness tests before and after the new requirements were established, updated results for air leakage tests of more than 285 newly constructed and renovated large buildings, and a performance analysis of the design and construction process, air barrier materials, building use, and construction types. These data may support future decisions regarding airtightness levels to be adopted for commercial buildings.

The Changing Requirements of Airtightness in the US for Commercial Buildings - The Airtightness of Mid and High-Rise Non-Residential Buildings

Concern over the airtightness of commercial buildings in North America goes back to the mid nineteen sixties, and with increasing concern in the mid-seventies, primarily due to the energy crisis, but also due to building performance, comfort and durability issues. The Model Canadian National Building Code was the first to adopt airtightness requirements for air barriers in 1985 and quantify it in 1995. In 2001 Massachusetts became the first state in the US to adopt a quantified airtightness requirement for air barrier materials and criteria for their design and construction in commercial and high-rise residential buildings. Many Standards and guides followed suit with airtightness requirements, including ASHRAE 90.1 2010 and IECC 2012, making airtightness mandatory in all commercial buildings built to those Standards and Codes. The US Army Corps of Engineers instituted airtightness testing requirements for all its new and renovated buildings in 2009. It requires that a whole building air leakage test be performed at completion of construction to verify performance of the constructed air barrier system. The Air Leakage Test Protocol for Building Envelopes was developed by the USACE Engineer Research and Development Center (ERDC) together with the Air Barrier Association of America (ABAA). In the meantime, ASHRAE decided that there was a lack of scientifically gathered and reported data on modern mid- and high-rise non-residential buildings built since the year 2000. It instituted a research study, 1478 RP, to measure and report air leakage rates for existing mid- and high-rise buildings, to develop a protocol for testing large buildings and to analyze the results with respect to design and construction parameters.

Ventilation and IAQ in Homes Receiving Energy Efficiency Retrofits

Residential energy efficiency programs in the United States have become increasingly aware of the need to consider the indoor air quality impacts of the energy-based measures that are implemented. This has resulted in a shift from referencing outdated ventilation standards to incorporating ASHRAE Standard 62.2. Because this shift has resulted in substantial concern from program implementers regarding the cost of increased ventilation requirements, research on any benefits of this change is warranted. This presentation provides preliminary data from such a study. This study, which is still underway, implements the older ventilation standard in half of the homes and the current standard in the other half. In all homes, building air leakage reductions are measured before and after retrofit, along with indoor concentrations of a number of common contaminants, including carbon monoxide, carbon dioxide, formaldehyde, total VOCs, radon, and humidity. Existing ventilation is characterized, and additional ventilation to meet the applicable ventilation standard is documented. In addition, health surveys are administered to the occupants before retrofit and a minimum of 6 months after retrofit. This presentation will discuss changes in contaminant concentrations from before to after retrofit, corrected for outdoor weather factors. These changes will be evaluated separately by which of the two ventilation standards was used. Additionally, the total ventilation rates for the two groups will be presented, and the contaminant concentrations will be analyzed based on total ventilation rate, including natural and mechanical sources. Results of the health surveys will not be presented because at this time the sample size of fully completed houses is too small to draw any preliminary conclusions. Because the study is still underway the data presented should not be considered as representing the final conclusions of the study.

A methodology for 3-D multiphysics CFD simulation of air leakage in building envelopes

Air leaks into a building through various openings and cracks in the building envelope. This leakage affects indoor air quality, human comfort and, primarily, building energy consumption. Several experimental studies have estimated this energy impact to exceed 40% of the heating and cooling costs in buildings. Current methods for evaluating air leakage range from simple air change methods to multizone coupled methods. These vary between being overly simplified to complex sets of equations that utilize hard-to-obtain, often assumed, factors and coefficients. Some CFD simulations have also been attempted. They only consider a small portion of 2-D wall sections with a single predefined air flow path. A modeling methodology is developed in this work that represents a roadmap for performing full 3-D envelope multiphysics hygrothermal simulations for air leakage in buildings. The methodology realistically depicts the various cracks common in an envelope in terms of shape, location, and quantity. It also accounts for the true multiphysics nature of the problem and for various hourly weather variables. The higher accuracy expected with this methodology allows for a more accurate calculation of air leakage heat loading necessary for an efficient building energy design, and for various green and sustainable building design applications.

Infiltration as ventilation: Weather-induced dilution

The purpose of outdoor air ventilation is to dilute or remove indoor contaminants to which occupants are exposed. It can be provided by mechanical or natural means. In most homes, especially older homes, weather-driven infiltration provides the dominant fraction of the total ventilation. As we seek to provide good indoor air quality at minimum energy cost, it is important to neither over-ventilate nor under-ventilate. Thus, it becomes critically important to evaluate correctly the contribution that infiltration makes to the total outdoor air ventilation rate. Because weather-driven infiltration is dependent on building air leakage and weather-induced pressure differences, a given amount of air leakage will provide different amounts of infiltration. Varying rates of infiltration will provide different levels of contaminant dilution and, hence, effective ventilation. This article derives these interactions and then calculates the impact of weather-driven infiltration for different climates. A new “N-factor” is introduced to provide a convenient method for calculating the ventilation contribution of infiltration for over 1000 locations across North America. The results of this work could be used in indoor air quality standards (specifically ASHRAE 62.2) to account for the contribution of weather-driven infiltration toward the dilution of indoor pollutants.

Energy Efficiency Manual

Review: Energy Efficiency Manual By Donald R. Wulfinghoff Reviewed by Irwin Weintraub Brooklyn College Library, USA Wulfinghoff, Donald R. Energy Efficiency Manual. Wheaton, MD: Energy Institute Press, 1999. 1536 pp. ISBN 0-9657926-7-6. US$199.95 In today’s fast paced world where we spend a good part of each day in buildings at work and play, it is important to plan building energy systems that meet our needs for heating, cooling, air flow, and lighting successfully and efficiently. The Energy Efficiency Manual offers up-to-date and practical solutions for energy planning applicable to building environments in one comprehensive volume. Wulfinghoff presents the information you need to plan, design, and construct efficient energy systems in homes, businesses, institutions, factories, farms, and other buildings. This easy-to-read, heavily illustrated work will be used over and over again by architects, engineers, contractors, code officers, environmental advocates, students, and homeowners who are dedicated to producing energy activities that save resources, are cost effective, reliable, and function at maximum efficiency. Nontechnical language is used throughout and terms are explained and illustrated when appropriate. Thus, the volume will appeal to a wide audience of users who are involved in building maintenance and those who just want to read it and learn more about energy conservation concepts. The Manual is arranged in two parts. Part I, Energy Measures, presents 400 specific energy efficiency improvements and cost saving activities. The measures are arranged under 10 sections covering boiler plants, chiller plants, service water systems, air handling systems, air conditioning systems, building air leakage, building insulation, control and use of sunlight, artificial lighting, and independent components such as motors and pumps. Since many energy projects serve several parts of a building or facility, readers will find practical solutions to all their energy efficiency questions in this section. I chose some entries at random and was impressed with the wide coverage of nearly all aspects of energy design. There are measures for efficient operation of low load heating systems; managing refrigerants in cooling equipment; reducing energy consumption of water pumps; regulating outside air intake and building pressurization; improving the efficiency of heating with radiators and convectors; reducing air leakage through windows and window frames; insulating roofs to prevent heat loss during cold weather; using daylight to save energy in open buildings; spatial layout of fixtures and wiring to provide efficient lighting; and eliminating excess output in constant flow fans. Each measure gives an explanation of