Development of a Tool for Analyzing the Sustainability of Residential Buildings in Ohio

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1 SOFTWARE REVIEWS Development of a Tool for Analyzing the Sustainability of Residential Buildings in Ohio Abhilash Vijayan and Ashok Kumar Dept. of Civil Engineering, The University of Toledo, 2801 W. Bancroft St., Toledo, OH 43606; abhilash.vijayan@eng.utoledo.edu (for correspondence) Published online 8 September 2005 in Wiley InterScience ( DOI /ep INTRODUCTION The building industry is one of the biggest consumers in terms of natural resources and one of the biggest producers of pollution thereafter, which has always been a cause for concern. Various constituents of the building industry together use one third of all the energy and two thirds of all electricity consumed in the United States (U.S.). According to the U.S. Green Building Council (USGBC), buildings in the U.S. account for 36% of total energy use and 65% of electricity consumption; 30% of raw materials use; 30% of waste output, which is 136 million tons annually; and 12% of potable water consumption [1]. Furthermore, buildings are a major source of the pollution that causes urban air quality problems, and the pollutants that contribute to climate change. Buildings account for 49% of sulfur dioxide emissions, 25% of nitrous oxide emissions, and 10% of the particulate emissions, all of which damage urban air quality. Buildings also produce 35% of the nation s carbon dioxide emissions, the main green house gas [2]. Unhealthy indoor air is found in 30% of the new and renovated buildings worldwide. Typical buildings consume more of our resources than necessary, negatively impact the environment, and generate a large amount of waste. The growing population and technological advancements have added additional burdens on the resources and a point has come when the available resources need to be preserved and conserved for future generations. With the growing demand and construction, it becomes imperative to have methods to analyze both the performance and the influence of buildings and to provide accurate assessments to improve the living quality American Institute of Chemical Engineers This has led to changes in the way the design, construction, and operation of structures are approached by the building industry and owners and, subsequently, the move toward environmental performance and the birth of Sustainable or Green Buildings. Sustainable Buildings incorporate the concepts and principles of energy efficiency, water conservation, recycled-content materials, waste reduction, building longevity, healthy structures, and the integration of environmental concerns and green construction, thereby striking a balance between social, economic, and environmental performance. A number of tools are available to tie in the principles of sustainability for both new and existing buildings [3], although the high costs associated with these tools make them less usable by the public (see the comparison in Table 1). Although the available tools analyze the individual areas of the building and give recommendations, none of these tools can analyze the overall sustainability of the buildings and provide a comparative evaluation of the benefits of using sustainable options. None of the existing tools gives credit to the health, living conditions, and sustainable attitude of the occupants. The purpose of this paper is to present the development of a simple user-friendly occupant comfort and building assessment tool that helps to analyze and assess a building from the twin perspectives of sustainability and comfort. This tool aims at creating awareness on the advantages of sustainable construction and or remodeling, and educating people about environmental issues, possible solutions, and opportunities for reducing environmental impacts, and help people recognize the opportunity to lead an energy-efficient, pollution free, sustainable life. 238 October 2005 Environmental Progress (Vol.24, No.3)

2 Table 1. Sustainable Building (SB) vs. other sustainability tools. Parameter LEED BASIX ENVEST SB tool Indoor environment quality Energy efficiency Water conservation Appliances Insulation Fenestration Occupant health Occupant comfort Occupant behavior Site selection Alternative forms of energy Qualitative HVAC Qualitative Building materials Qualitative Radon User controlled User-friendliness N.A. Visual interpretation of results Cost Free DEVELOPMENT OF THE TOOL The steps involved in the development of the tool and analysis for the assessment of a building include: 1. Sustainable Building Concept: Proper study and thorough knowledge on the principles of sustainable or green buildings with insight into common problems arising from unhealthy, unsustainable conditions. 2. Significant Elements/Factors: Identifying the most important factors that need to be considered for evaluating a building and obtaining the relevant information and data. 3. Qualitative Questionnaire: Building a comprehensive list of questions and a corresponding scoring method for the qualitative analysis of a building from the dual perspectives of sustainability and comfort. 4. Tool Development: Development of tool using data available to output results in the terms of cost savings, resource savings, and pollution prevention in tables, reports, graphs, and Sustainable Building (SB) Score. 5. Tool Application: Application of the tool to residential buildings for validation and analysis purposes to demonstrate the proper functioning of the tool. 6. Result Interpretation: Identifying and establishing the basis for interpretation of the results from the tool. Microsoft Excel was chosen as the platform for the development of the tool mainly because of its easy accessibility, extensive computational features, and its user friendliness. The tool was designed to incorporate both quantitative and qualitative approaches of building analysis. The quantitative part of the tool analyzes a building with respect to the energy and resources consumed and the annual cost incurred. Every unit in the household consuming energy or water was compared with recommendations and criteria for efficient fixtures, which are given by Department of Energy Federal Energy Management Program (DOE FEMP) [4] and Energy Star [5]. The tool also compares the annual cost incurred by applying the user-selected options and compares the potential annual savings by using the recommended and best available options in the market. The qualitative part contains questionnaires, the answers to which portray the comfort, living conditions, and attitude of the occupants. Figure 1 shows approaches used in the tool and the different elements under the quantitative approach. Details on the tool development and analysis are given by Vijayan [6]. QUANTITATIVE ANALYSIS Energy This tool analyzes the household energy consumption that results from lights and appliances such as washers, refrigerators, and dishwashers and provides a comparison of potential energy and dollar savings by adopting better, sustainable options. Illumination is a major application of electrical energy used in an average household. The most common means of illumination used in the American subcontinent is by the use of incandescent bulbs. These bulbs are highly energy inefficient, have a short lifespan, and require frequent replacement. The most sustainable option is to replace these bulbs with more efficient compact fluorescent lights (CFLs). The criteria for selecting a CFL were based on DOE FEMP [4] recommendations for efficient lighting (Table 2) based on the necessary light output. Once the type of the bulb used, the number of fittings, and the wattage of each bulb are selected, the worksheet pulls out information about the necessary lumens required to replace the chosen type of bulb and computes the total energy consumption of the user s units and the sustainable options (Figure 2). This Environmental Progress (Vol.24, No.3) October

3 Figure 1. Methodology. Table 2. Efficiency recommendation for lights. To replace incandescent bulb rated at Necessary light output (lumens) Typical CFL replacement wattage Recommended CFL lumens per watt (lpw) Bare bulbs 60 watts 900 or more watts 60 lpw or more worksheet also computes the potential savings and the self-payback period of the sustainable options. Water Water usage is directed by the appliances and fixtures used in the house. This includes fixtures in bathroom, such as faucets, showerheads, urinals, and toilets, and other water-consuming appliances used in the house, such as clothes washers and dishwashers. Most of the time, the water flow from any water-consuming fixture is more than what is required. Selecting the appropriate fixture for the job can help regulate the needed flow. DOE FEMP [4] has set recommendations and criteria for energy- and water-efficient fixtures and an example is shown in Table 3. In the User Selected column (Figure 3), the flow rate of the fixture in gallons per minute/flush and the water use characteristics of the family including the number of people in the family, usage per day, and duration of use are entered by the user. The total usage days is assumed to be 365, but can be altered by the user depending on usage pattern. Water-heating cost for all the faucets and showers is also calculated based on the type of heating. Assuming a water-heating requirement for 6 months, the annual energy used to heat the water is calculated for both the user s fixture and the sustainable options. If the cost of the unit for the DOE-recommended faucet is higher, then the worksheet calculates the annual potential saving and the amount of Figure 2. Screenshot of the Lighting worksheet. 240 October 2005 Environmental Progress (Vol.24, No.3)

4 Table 3. Efficiency recommendation for faucets. Product type Recommended flow rate Best available flow rate Faucet 2.0 gallons per minute or less 1.5 gallons per minute 0.25 gallons per cycle (self-closing) Figure 3. Screenshot of the Faucet worksheet. time required to pay back the additional cost of the unit. Appliances Appliances are major consumers of energy and water, accounting for almost 20% of a typical household s energy usage. Better selection and thoughtful operation of these equipments can lead to greater comfort with minimizing cost. Appropriate selection is a major step toward achieving increased efficiency. Appliances considered for analysis were clothes washer and dryers, dishwashers, and refrigerators. The user is required to select the type of the unit, depending on whether it is Energy Star certified. If the unit is certified, then the user can select the unit from the drop-down list given. All the associated specifications of the unit are pulled out from the database. If the unit is not certified, then the user is required to input the kwh rating and frequency of usage. For clothes washers (Figure 4), the user is also required to input the washer volume and water factor to compute the water consumption. Based on these data, the model computes the annual resource (energy and water) consumptions for every appliance. The model also computes the heating cost for warm wash/cold spin cycle for the clothes washer. DOE FEMP has laid out minimum recommendations for energy and water use. These recommendations are based on volume for washers and refrigerators, and energy factor and electricity rating for dishwashers. The entire list of Energy Star approved appliances was obtained from their website, and sorted to find the unit that had the least energy rating and resource consumption in every category. The annual savings in the three categories (water, electricity, and gas) over the user s model for the recommended and best models are calculated. Building Envelope The building energy envelope was analyzed for adequacy of insulation and quality of window material that is responsible for the most energy leakage in a household. Insulation also acts as a sound absorber or barrier, keeping noise levels down. Insulation plays a very important role in restricting the energy flow to the outside of the building. Insulation is rated in terms of thermal resistance, called the R-value, which indicates the resistance to heat flow. The higher the R-value, the greater the insulating effectiveness. The R-value of thermal insulation depends on the type of material, its thickness, and density. The user is required to identify the location from the drop-down menu and indicate the thickness of the insulating material used. The worksheet pulls out information regarding the R-value of the selected material. The total available R-value is calculated and is compared with the total recommended R-value for the corresponding point of application. The ratio of the available insulation to recommended insulation is computed to analyze the percentage increase of insulation required to make the house energy efficient. The user can identify the locations where the Environmental Progress (Vol.24, No.3) October

5 Figure 4. Screenshot of the Washer worksheet. Figure 5. Window analysis section of the tool. Table 4. Emission factors. Pollutant Carbon dioxide Sulfur dioxide Nitrogen oxides Emission factor 1.8 lb/kwh 10.4 g/kwh 3.5 g/kwh insulation is below par from the results and can take measures to improve them. Selection of windows plays a very important role in reducing energy loss, thereby providing a covered building envelope. Energy consumption of a house can be substantially reduced if the heat losses through windows can be reduced. This worksheet gives an overview of how the windows in a residential building are performing (Figure 5). The user has to select the region in which the house is located. The state of Ohio is divided into Northern (mostly heating) and Central (heating and cooling) regions. The user is required to select from the worksheet the characteristics of the window installed in the house including glass type and thickness, glazing type, and coatings. The tool automatically pulls out the information on the U-factor, solar heat gain coefficient (SHGC), and visible transmittance (VT) of the selected window glass and glazing. This value is compared with the recommended value given for the corresponding region in the state of Ohio. The worksheet examines the adequacy of the U-factor and SHGC values and the user is advised to make amends with windows. The total score is a function of U- factor, SHGC, and VT of the user s windows. 242 October 2005 Environmental Progress (Vol.24, No.3)

6 Table 5. Computation of SB score. Contribution to SBS Sustainable Building Score User Best options Maximum Total Insulation Score % 10.00% 10.00% 10% Total Window Score 87.50% 8.75% 10.00% 10% Total Gas Energy Score 48.72% 4.87% 7.50% 10% Total Water Score 51.93% 7.79% 10.85% 15% Total Electricity Score 67.88% 10.18% 15.16% 15% Total Qualitative Score 97.89% 39.16% 39.16% 40% SB Score 80.75% 92.67% By changing to ideal living conditions, the SB Score can be increased to 93.51% Pollution Prevention Pollution is a by-product in the process of energy creation. For every unit of energy production, a proportionate amount of pollutants are added to the environment. Reducing the consumption of energy results in reduction in energy production, thereby reducing the pollution created. By using sustainable units and measures in everyday life, the total consumption of resources also diminishes. Table 4 gives the amount of pollutant produced per kwh of electricity generated. The tool uses these emission factors for carbon dioxide, sulfur dioxide, and the oxides of nitrogen obtained from the U.S. Environmental Protection Agency to compute the total emission of these pollutants and indicates the pollution prevention attained by adopting better sustainable options. QUALITATIVE ANALYSIS The qualitative section of the tool was developed to assess the presence of hazards in the living space, which inhibits the comfort of the occupants. A building s performance can be evaluated by the performance of its occupants. The indoor and outdoor environment plays a very important role in the productivity and comfort of the individual living in the building. It is important to identify the hazards within the space that we live and understand the risks associated with them. The qualitative section of the tool was developed to assess the presence of such hazards in the living space. The procedure for doing the qualitative analysis is: Identification of common sources that cause negative flow of energy Analyzing the presence of such hazards in the living area Evaluating the risk associated with the hazard Informing the occupants and suggesting measures to mitigate the problem The questionnaire contains questions that investigate household living conditions, such as temperature, humidity, dust, and illumination, and identifies common indoor hazards such as chemicals, building-related illnesses (BRI), and mold. The user is required to input the most appropriate response to the questions. The responses are analyzed and scores are given for the occupant comfort and building sustainability. The questionnaire is made up of 95 comprehensive questions that deal with the different aspects of the building. For each response, the user is given one point if the selected response is sustainable, or else is awarded no points. COMPUTATION OF SUSTAINABLE BUILDING SCORE The total SB score is a function of all the sections given in Figure 1. The SB score is computed as follows: Total Insulation score is the ratio of the available insulation to the total recommended insulation. Total Window score is calculated by assuming the recommended features of the window to be 50% sustainable. The window score, then, is the sum of recommended and total excess value of SHGC, U- factor, and VT available. Total gas, water, and electricity scores are calculated by assuming the recommended level to be 50% sustainable and any excess over this level is subtracted from 50%. Total Qualitative part constitutes 40% of the SB score. This is the percentage qualitative score achieved out of the maximum attainable. The graphs and charts give a visual interpretation of the results and help to identify the most sustainable options. Table 5 shows the weightage factor given to each section, and also shows a sample of the calculation performed. CASE STUDY The tool was used to assess a Health House of the American Lung Association for the purpose of illustration. The design criteria for this building were obtained from the American Lung Association (ALA) website [7]. The house is certified to provide a healthy and productive living environment. The analysis not only helped in establishing the validity of the tool, it also gave an opportunity to indicate the effect of occupant behavior and attitude on the sustainability of a building. The analysis showed that by following the design criteria set for constructing a Health House, the building required a considerably smaller amount of resources to operate. When the energy consumption was compared with the recommended level (Table 6), the building used a far lower amount of electricity Environmental Progress (Vol.24, No.3) October

7 Table 6. Total potential savings in resources. Total potential savings in resources Electricity (kwh) Gas (Therm) Water (Gallon) Best Consumption Recommended Best option Consumption Recommended option Consumption Recommended Best option Over 1 year Over 10 years For n number of houses, in one year Consumption Recommended Total potential savings in dollars Electricity Gas Water Best option Consumption Recommended Best option Consumption Recommended Over 1 year $ $ 9.18 $ $ $ 0.41 $ 8.33 $ $ 3.59 $ Over 10 years $ $ $ $ $ 4.05 $ $1, $ $ For n number of houses, in one year $2, $ $ $1, $20.27 $ $9, $ $1, Assuming cost Electricity ($/kwh) 0.06 Gas ($/therm) 0.6 Best option Water ($/1000gallon) October 2005 Environmental Progress (Vol.24, No.3)

8 Figure 6. Graph of excess consumption. Figure 7. Graph of annual expenditure. and water. The total expected expenditure by using the recommended level was $123 higher than the user selection over a year. The total excess consumption graph (Figure 6) has a negative spike in excess consumption, indicating that the building was highly energy efficient. The annual expenditure graph (Figure 7) showed that, although the building energy consumption was lower than the recommended level, there was still room for lowering the cost by selecting the best sustainable options in the market. The building received a 97.89% score in qualitative analysis and 80.75% in the overall sustainability scoring (Table 5 and Figure 8). This evaluation clearly showed that the sustainability of a building is not only affected by the resource consumption and equipment used, it is also considerably dependent on the occupant behavior. This indicates that purchasing the best quality pays off in the long run. The total pollution generated was also considerably lower than the recommended model (Figure 9). CONCLUSION AND FUTURE SCOPE From the literature, it is certain that no simple, userfriendly comprehensive tool exists to determine the Environmental Progress (Vol.24, No.3) October

9 Figure 8. Graph of qualitative and overall SBS. Figure 9. Graph of pollutant emissions arising from energy consumption (CO 2 ). sustainability of a building. An evaluation tool for building analyses, which gives the user an opportunity to assess the living space, was developed. The tool can be downloaded from This tool provides an easy and reliable way of estimating the building sustainability. It is possible that one may assign a different SB score to a building depending on the importance one gives to a particular element. This can be accounted for by changing the percentages in the final SB score section. This tool takes a formidable leap in providing the user with the opportunity to assess the user s living space and make amends to enjoy a better living standard. This tool can further be developed to establish a relation between sustainability and occupant productivity and performance. Incorporation of sustainable forms of energy and comparison of the performance of building by changing to an alternative energy form is another aspect that can improve the horizons of this research. With further research, 246 October 2005 Environmental Progress (Vol.24, No.3)

10 the tool can be applied to analyze subdivisions, offices, and industrial spaces. LITERATURE CITED 1. U.S. Green Building Council. (2005). usgbc.org/displaypage.aspx?categoryid 1, July. 2. U.S. Department of Energy (USDOE), Smart Communities Network. (2005). doe.gov/buildings/gbintro.shtml, July. 3. Vijayan, A., & Kumar, A. (2005). A review of tools to assess the sustainability in building construction, Environmental Progress, 24, USDOE, Federal Energy Management Program. (2005). eep_eerecommendations.cfm, July. 5. Energy Star. (2005). July. 6. Vijayan, A. (2004). Analysis of sustainability of a residential building in Ohio, MS Thesis, Toledo, OH: University of Toledo. 7. American Lung Association, Health House Builder Guidelines.(2005). build/04hhbuilderguidelines.pdf, July. Environmental Progress (Vol.24, No.3) October