COMPARATIVE ANALYSIS OF FENESTRATION SYSTEMS: A LIFE CYCLE ENERGY BASED APPROACH

Abstract

India is experiencing an unmatched construction boom and it is one of the important factor of Indian economy and development. However, it is also a major consumer of nonrenewable energy resources, which are mainly required for the production of building materials and their transportation to the site of construction. Since the late 1960's Life Cycle Assessment (LCA) has become an increasingly important tool for engineers, technologists, scientists, designers, managers and environmentalists alike. LCA (Life cycle assessment) assesses the effects which products, processes and activities have on local, regional or global energy consumption, adopting a holistic, or whole life approach to design methodologies. LCA is a tool that allows building specialists to understand the energy use, and payback period associated with all life cycle phases of the building: extraction, manufacturing, construction, operation, and demolition, thereby analyzing the best environment friendly materials, products and equipment for the building construction. To reduce the environmental impacts of buildings, green building initiatives, including certification schemes and eco-labeling, have emerged and grown in acceptance. Recently, efforts have been made to incorporate LCA results into green building certification and rating systems (Trusty and Horst 2002, US Green Building Council 2007). Life cycle energy is an approach of LCA in which all energy inputs to a building are accounted for. It is estimated by summing up the energy incurred for construction (initial embodied), operation, maintenance (recurring embodied) and finally demolition of the building at the end of its life. According to the literature review, generally the life cycle energy data indicates that the total embodied energy amounts to nearly a quarter of the operational energy over the lifetime considered. A building is a unique and complex system comprising of different components. Windows are one of the important elements of a commercial building and can account for 30 to 40 percent of a building's exposed surface (Recio, et al., 2005). The study completed by (Prajapati & Nayak, 2006) presented results from various cities of Indian climate zones revealed that maximum cooling load on an annual basis, is due to windows (52.9%-64.7%) followed by conduction through walls which had (26.5%-36.4%) impact on cooling load. Windows have changed more rapidly than almost any other building component in the past two decades. They perform multiple functions in a building envelope, by providing outdoor view, circulate air, acting as an interface to transmit light. While windows are available in lv different designs and sizes, their main material components include the insulated glazed unit with or without inert gas infill, frame and sash. Today the obsession for glass is increasing tremendously. Because of the increased glazed area in commercial buildings energy use increases, irrespective of glass type, climate or orientation of the building. But numerous advances in technology like: use of double or triple glazing, low e-coating and use of inert gases like argon in the air gap improve performance. New windows are rated based on their energy performance during the operational phase only while neglecting the environmental impacts caused by the raw material extraction, manufacture, maintenance and disposal of window assemblies. Till today there are no studies which justify the effect of manufacturing of materials for improved performance during operational phase of the building in India. In Indian context, the guidelines for fenestration largely focus on WWR, thermal and visual properties of glass and frame to optimize operational energy consumption. However, the role of embodied energy of the materials used in the building is totally neglected. To do a comprehensive research on impact of fenestration design on LCE, within the context of Indian building codes (ECBC in this case), thorough literature review of previous studies has been carried out. Heat flows through the glazing system in all the three possible ways, i.e. Conduction, Convection and Radiation. All these three mechanism of heat transfer works together in a real situation when any window assembly is being used. To collectively portray the overall energy performance of the window, the following are responsible for energy consumption of a building: Materials used for construction (glass plus the walling and roofing material), area covered by the window, orientation of the building, whether the glass is fixed or operable, no. of sides on which opening is provided, aspect ratio of the building, shading devices employed, nature of appliances and equipment's being used (air conditioner, Xerox machine, vending machine, fans, power saver tube lights etc.), climate of city/town where the building is located (Salazar & Sowlati, 2008). For this study, the floor area has been limited to 1200 m2 which is a typical office floor area in Delhi as per- Building ener, benchmarking study undertaken by the USA ID Eco- III prqfecr, New Delhi. Two aspect ratios 1: 1 and 2:3 are taken into account for this study as these are the most common aspect ratios which fits for most commercial building types. In some of the office buildings the core is at the center because of which all four sides of the building are available for openings, while in some cases there might be a possibility of

three, two or one side opening in the wall. So, all the above mentioned scenarios are kept in mind while designing the cases for the building. All possible orientations within one, two, three or four side openings are taken into account. ECBC recommends WWR up to 60%, but for this study WWR 10, 30, 40, 60, 80 (%) are considered so as to justify the recommendations of ECBC as well as to also take into account the prevailing scenario in the construction industry. Ten commonly available VI glass types and three frame types are used to design the cases. The combination of the above mentioned parameters resulted in 4500 cases as shown in the figure mentioned above. Present study is aimed to compare different Fenestration systems for application in a Commercial building based upon their Life Cycle Energy Assessment to arrive at best practices and to highlight improvements which are necessary to lessen its LCE, thereby - guiding the users towards an appropriate Aspect ratio, WWR. Orientation, Frame, and glazing solutions- having minimal thermal losses and electrical demands, at the same time focusing on the embodied energy of the building. The window parameter combinations selected and calculations presented are based upon the commercial office environment. It is highlighted, however, that the methodology developed is applicable to any building type. The result from this research would help in creating work environments which are efficient, productive and comfortable through glazing solutions that have a fine balance of design critena. In this study, the embodied energy and demolition energy was calculated by investigating the chronological records and by the data gathered from the field, industry standards and guidelines. To calculate the Operational Energy 4500 simulations tests were performed using Design Builder with Energy Plus engine to generate data for Annual energy consumption for typical commercial office space in New Delhi which falls in the composite climate. The Base case model is chosen from the previous study carried out by the author on comparative analysis of wall assemblies (Singh & Agrawal, 2016). In the previous study the model was simulated by using the materials and configurations of an existing typical commercial building and to verify the annual load, electricity bills of this building were used, which validated the results obtained by the software. This verified model was used for present study in which 4500 cases were designed based upon the variations of the above discussed parameters. The implications of varying aspect ratio, window-to-wall ratio, orientation, glazing distribution, glazing and frame materials on the overall energy consumption for a building was computed to acquire the LCE result. It was observed from the results that the design of window systems has a large impact upon LCA results generated, thermal performance properties influence energy consumption patterns throughout a lifetime of use, while appropriate use of materials, window positioning, orientation and size have a knock-on effect on lighting control functions and air conditioning demands Data handling is an important part of this thesis as it is crucial to analyse and present the result for 4500 cases. Various methods were adopted for analysis. Firstly, regression analysis was carried out which calculates the impact of each parameter of fenestration design on the overall Life cycle energy. In this analysis it was found that frame is the least significant parameter and does not impact the Life cycle energy while WWR had the maximum significance followed by WWR distribution, Glass type and then Aspect ratio. Though aspect ratio had less significance as compared to other parameters still it was way more than frame types. To justif' the significance in the regression analysis, another parallel analysis called Meritbased analysis was done in which best 150 and worst 150 cases were analysed, arranged in ascending order of their Life cycle energies. It was found from the results that the lighting and cooling load played an important role in the varying result of the analysis. WWR 30- 40% is the most recommended among the other variables, 40 % is recommended when the openings are on three sides while 60% was recommended when the openings are on two sides. While analysing glazing material it was found that (Trp LoE (e2=e5=1) Cir 3mm/I 2mm Air) and (Dbl Or 6mm! 12mm Arg) was recommended when the overall WWR of the building is in the range of 30-40%. Frames were found to be the most varying parameter in the top 150 list as it had least significance, no trend was found for the frame type. In the top 150 cases Aspect ratio 2:3 was found only 6 times that to at a very low rank. Top 146 cases for fenestration systems had aspect ratio of 1:1, which clearly signifies the effectiveness of aspect ratio on the analysis. To simplify the results and their presentation, micro-level analysis was carried out, in which separate spreadsheets were created according to the orientations and aspect ratios. In a single table all the Life cycle energy results were arranged according to the glass type and frame type. Base case was simulated with 0% WWR having no windows, the results of this simulation for aspect ratio 1:1 and 2:3 was used to find the percentage difference for all the life cycle energy of various parameters. Best and worst cases for a particular scenario like for e.g.: if we need to find which glazing is better in 30% WWR having openings on NW, then this sheet tells clearly the best suited glass type for the scenario. Conclusions for all the spreadsheet are mentioned after every sheet. Through the above findings the ECBC recommendations are justified that 30-40% WWR is the most effective scenario. While some major findings included that the uniformly distributed windows on all the four sides will respond to better LCE. Frame types barely had impact on the LCE, although 1.JPVC was found to be most efficient. VLT and U-value

plays a vital role in the cooling and lighting load. For WWR 10%, single clear was found to be more effective as single clear has high VLT the lighting loads were reduced while in other cases it altered the results. Various trends were found for different opening orientations which are elaborated in detail in the study. Table showing almost equivalent cases is also created to give important clues or alternatives for optimal distribution of openings on different orientations and their respective aspect ratio, WWR, glass type and - frame type. KPI dashboards in excel was also created to prepare and interactive medium for users to find their best conceivable solutions for their instances just by a single click without going through the charts and graphs. The observations and results stress the need to reanalyze local building regulations, which are currently leading to inefficient energy consumption as they fail to indicate the efficient materials, window sizes and orientation especially for commercial air-conditioned buildings.