1. EXECUTIVE SUMMARYDue to tremendous increase inpopulation globally over the years, the need for the sustainable housing developmentis gaining significance. The residential units are the major source of energyconsumption.
Due to advancement in technologies in building constructiontechniques over the years there is potential to save the energy loss. Lifecycle assessment is well accomplished technique that has been employed tocalculate the primary energy uses and associated environmental impacts during differentstages of the building such as: embodied stage, maintenance stage anddemolition stage. In this study the life cycle assessment of two residentialunits; home of today and home of tomorrow is performed. Home of today isbasically equipped with the conventional construction materials being used inresidential construction industry whereas home of tomorrow is equipped theenvironmental friendly construction materials. These two different alternativesof residential units in Kelowna (BC, Canada) with a 50-year lifespan have beenevaluated and comparison is carried out for the primary energy, embodiedenergy, demolition energy consumption and associated environmental impacts.Estimation of operational energy and LCA are performed using HOT 2000 softwareand Athena Impact estimator software respectively. The study results revealedthat over the life span of the buildings, the relationship between the energyuse and the environmental impacts are identical. Home of tomorrow is found tobe the best alternative in terms of embodied energy use and embodiedenvironmental impacts.
Sensitivity analysis has also been carried out to studythe influence of building service lifespan over 50, 75, and 100 years on therelative significance of embodied energy and total life cycle energy. 2. INTRODUCTIONThe human demands in growing urban environment,including residential housing, water and food supply, health care facilities,efficient transport, and disposal of domestic waste are dependent on theconstruction industry. All these facilities, significantly utilizes theresources and energy, and leads to adverse environmental impacts, such as generationof greenhouse gases leading to climatic changes, generation of wastewater,emissions and solid waste 1.
Since, residential buildings holds the majorshare of entire land use serving the largest number of consumers are the majorcontributors to the environmental impacts. In the United States, building industryaccounts for 39% of the total primary energy use, 38% of carbon equivalentemissions, and 40% of all raw material use annually; the statistics in Canadaare almost the same 2. Such consequences has increased the need ofsustainable housing development 3. The environmental aspects are increasinglymore significant in sustainability.
Therefore, environmental assessment ofbuilding is a right approach to attain the goal of sustainability. In general,Life-Cycle Assessment (LCA) technique is employed in building industry toquantify and evaluate the environmental aspects during its whole life time thatis from cradle to grave including the extraction of raw materials,construction, utilization, end of life, and beyond building life 4. Many LCAstudies have been conducted in building sector, various studies mainly focusedon residential buildings. For example, 5 presented the method to calculatethe energy use during the life cycle of a building and in the same year studiedthe life cycle of three single unit dwellings in Sweden. Reference 4 studiedthe LCA for three bedroom semidetached house in Scotland. This study is focusedon five construction materials and their embodied energy, and associatedGreenhouse gas (GHG) emissions. Reference 6 compared the high and low-densityresidential buildings in Toronto (ON, Canada) for their energy use andassociated GHG emissions.
Two functional units are selected for this study:living area (m2) and number of people in a house (per capita basis) and it isdemonstrated that the choice of functional unit is vastly relevant for fullunderstanding of urban density effects. The study found that, low-densitysuburban development consumes 2.0-2.5 times more energy and GHG intensive thanHigh-density urban development on per capita basis. Reference 7 studied thetwo-storey single family residential building located in Vancouver, Canada.This study focused on construction materials, and manufacturing and operationphases of a building. This study also shows that operational phase contributeshigh environmental impacts. Reference 8 proposed the ‘energy-based’ LCAframework and compared the single-family and multi-family residential buildingsin four Canadian provinces.
Nevertheless, this study was not intended to selectthe better sustainable building; instead this study offered a sustainabilityassessment tool by providing quantitative and transparent results for informeddecision-making. In conclusion, existing literature on the LCA of buildingfocuses primarily on the energy use and greenhouse gas emissions of small tomid-size houses. However, neither the full life cycle (cradle to grave) norfull range of impact categories that generally included in LCA is considered.The purpose of this study is to contribute towards a better understanding ofthe full LCA impacts of residential buildings in Canada by focusing on home oftoday and home of tomorrow.
The main objective of this study is to evaluate andcompare the primary energy use and the potential environmental impacts (EI)associated with the alternatives for residential buildings by using theconcepts of LCA. This study considered whole life cycle phases of buildingswith 50 years lifespan. In order to attain the main objective, the followingsub objectives have to be fulfilled:? Analyzing the operational energy ofthe building by performing energy simulation ?Identifying the best housing type consuming very less energy and contributingto the least environmental ? Perform the sensitivity analysis forfour types of houses over 50, 75, and 100 year lifespanThe following sections represents thepresent and comparison of the life cycle energy use and EI of each type of thehouse. It is anticipated that the results of this study would be beneficial fora wide range of stakeholders, including planners, engineers, developers, and policymakers.
3. METHOD STATEMENTThe methodology is represented in thissection for the present study. The approach to carry out the analysis for theenergy consumption and environmental impacts is described belowLifeCycle Analysis (LCA)To obtain the specified results theLife Cycle assessment methodology is selected in case of this study.
As thereare number of methods available to calculate the environmental impacts butthese methods have certain shortcomings. But LCA is well defined approach andis restricted strictly to the use of ISO 140-43 standards9–12. Themodelling for the LCA is done in Athena Impact Estimator (Athena IE) forbuildings 13. According to ISO 14040, there are four LCA analytical stages:1. Goal and scope definition for LCA2. Determine the LCI for materials andtheir corresponding environmental impacts3. Generating impact assessment datausing the LCI reports4.
Results interpretationThe first stage of the LCA is to definethe scope and boundaries of the system. The goal of the study is to evaluatethe life cycle energy use and EI of typical types of houses in Canada and toscrutinize whether the obtained results are significantly skewed by the type ofhouse. These results are then used to evaluate the overall energy use andimpacts from the Canadian housing sector with the aim of identifying the bestalternative.
The functional unit is considered as 1m2 of floor area of a houseover its lifetime. A 50 year lifespan was assumed for this study, which iscommonly used by researchers in LCA study of building. Also, this allows for asignificant time period for repair, and replacement of building materials. The briefdescription of each type of house is summarized in section B. The framework forsystem boundaries and outputs of this LCA study are shown in Fig.
1. Fig. 1: LCA system boundaries andoutputsAs can be seen, the system boundariescan be divided into three distinct phases, i.e. the pre-occupancy, theoccupancy, and the post occupancy. The outputs comprises of the total primaryenergy use and the EI for all phases.
The stage two of LCA study is life cycleinventory (LCI), starts with making a process tree or a flow-chart classifying theevents in a building’s life-cycle which are to be considered in the LCA, plustheir interrelations. This procedure is followed by data collection, wherequantitative and qualitative data for all inflows and outflows, such as rawmaterials, energy, ancillary products, land use and emissions are gathered. Thenext step in LCI is to calculate the amount of energy used and emissions of thestudied system in relation to its functional unit 10, 14. In this study,the Athena IE software is used to assess the material and energy inputs and outputs.
The stage three of LCA study is life cycle impact assessment (LCIA), whichcalculates the potential EI and estimates the energy used in the studied systemor process. The detailed LCIA results are presented in results and discussionsection. Finally, the last stage of LCA study is interpretation, which is aniterative process present during all phases of the study.
The findings of theLCI and LCIA are combined here in order to achieve the recommendations andconclusions for the study.In this study, two types of residentialbuildings in Kelowna (BC, Canada) are used as a case study to demonstrate themechanism of this research method. This home is built to minimum coderequirements. Thishome of today is built to minimum code requirements.Equipment and construction is of a standard nature, in orderto give a baseline comparison to the Home of Tomorrow:• HVAC: 92 % efficient 60,000 btu natural gas furnace c/w single stage pscblower c/w 14.5 seer 3 ton AC.• Nu Air non dedicated HRV system.• Fireplace: heat & glo DV3732SBI direct vent gas fireplace.
• Plumbing: standard fixtures. 60 gal elect HWT.• Windows: vinyl double glazed windows c/w 180 low E.• Insulation: R-22 batt walls, R-40 blown in ceilings, 2 lb Sprayed joist ends.• Lighting: Incandecent• Appliances: StandardThe Home of Tomorrow is built to higher energysaving standards:• HVAC: 5 series – ground source heat pump c/w ECMvariable speed blower• Zoned ducting (1 @basement/1 @ main)• Solar panels: CSUN Quasar 260 – connected to a Fortis net meter• Life Breath RNC155 dedicated HRV system• GE Geospring Pro heat pump water heater• Fireplace: Marquis 46? Skyline 2 ZRB46NE gas direct vent• Plumbing: water saving toilets and faucets• Windows: vinyl triple glazed windows c/w double 366 low E• 12 inch Insulated Concrete Form (ICF) foundation walls at entire basementlevel• QuikTherm 2? styrofoam wall system, c/w R14 batt insulation on the main floor• R-20 batted and R-50 blown in ceilings (total R-70), 2 lb Urethane Spray atjoist ends• Lighting – LED• Appliances: induction range, double ovens (clients can use the smaller oventhe majority of the time and save power), 5 door fridge (allowing the client toaccess smaller cavities resulting in less temperature fluctuations due to coldair loss), heat pump dryer (brand new technology resulting in significant gainsin efficiency. These dryers are also condensing units and do not requireoutside vent) • Energy Star rated hood fan with LED lighting and ultra-quiet blower• Energy efficient dishwasher• Energy management and climate control system by Honeywell B.
Athena Impact Estimator forBuildingsAthena Sustainable Materials Institute,a non-profit organization based in Ontario, Canada developed the ATHENA® ImpactEstimator for Buildings. The Institute’s mission is to promote sustainabilityin the built environment through the use of LCA in North America. Notably, itis the only software tool presently available in North American context. TheAthena IE was developed as a support tool to aid in the decision making processat the conceptual design stage. The software provides a cradle-to-grave LCA fora building and individual assembles. This software generates the bill ofmaterials based on the given inputs, this can be compared with expectedoutcome, and in case of any discrepancies the material quantities can beadjusted using ‘additional materials’ input feature.
The Athena IE takes intoaccount any or all of the following building characteristics and life-cyclefactors to measure the impact in each of the metrics: Material manufacturing,including resource extraction and recycled content, transportation, On-siteconstruction, regional variation in energy use, transportation and otherfactors, type of building and lifespan, maintenance and renovation effects, endof life management. C. Calculating Embodied Energy Use andEnvironmental Impacts Calculatingthe environmental damage caused by houses over its life cycle is a challengingtask. Embodied energy is the energy used during the construction stage of abuilding, it includes the energy incurred at the time of erection/constructionof materials, as well as the renovation of building components 16. Accordingto 17, LCI involves the collection of data and modeling to estimate the totalamounts of emissions, waste, energy used, and materials used throughout thelife cycle of a building 18.
Although specific techniques are available tomanually conduct LCI, various computer software tools develop din the recentpast have superseded these techniques. Calculating the energy use andenvironmental impacts at each stage of the house including raw materialsextraction, manufacturing of building materials, construction, maintenance, end-of-lifemanagement, transportation during all of these stages is computationally intense.The HOT 2000 software is used for calculating the embodied energy.
The methodevaluates different categories of environmental impacts, including,acidification, eutrophication, smog potential, fossil fuel consumption, global warming,human health particulate, non-renewable energy, and ozone depletion. Each housein this study is separately modeled as precisely as possible using the gatheredinputs. Athena IE generated the detailed bill of quantities for each house.Unfortunately, the embodied effects associated with the electrical, HVAC, andplumbing services in a building cannot be calculated using Athena IE. Hence,these embodied effects have not been considered in this study. The Athena IEcan evaluate only the embodied energy, and currently there is no option forevaluating the operational energy of a building. Yet, it consists of acalculator that transforms the estimated operational energy into primary energyover a building’s life cycle.
However, this estimation of operational energyuse must be calculated using additional building energy simulation softwaretool.Table 2: Home of Today Table 3: Home of Tomorrow D. Calculating Operational Energy Use and Environmental ImpactsDuring occupancy in a building,operational energy is required for space heating, space cooling, lighting,domestic hot water, and equipment; however, it varies significantly based onthe level of comfort, climatic conditions and the operating schedules 16.Currently, various computer applications are available to calculate theoperational energy of a building. For this study, Athena Building ImpactEstimator software is selected for the purpose.
In general, energy can beclassified in to two major types, primary and secondary energy. As mentionedearlier, in this study, the Athena IE for buildings evaluates embodied energy interms of primary energy and the HOT 2000 evaluates the secondary energy. Theestimated secondary energy (i.e. embodied or site energy) and energy mix (i.e. electricity,natural gas, geothermal, etc.) have been used as the inputs to Athena IE tocalculate the resulting total primary energy use and total environmentalimpacts.
2. Later, the obtained annual energy use values are entered inAthena IE to get the total operating energy and environmental impacts. Table 4 : LCA Measure by Assembly Group Table 4: LCA Measure by Assembly Groups(A to C)Table 5 : Comparison of Total PrimaryEnergy by Life Cycle Stage Table 6: Green Globes LCA MeasuresComparison Report Cradle to Grave E. Calculating Total Life Cycle Energy Use and EnvironmentalImpacts Thetwo major outputs of this study are the total life cycle energy consumption andthe total life cycle environmental impacts. The total life cycle energyconsumption in million joules (MJ) of each house is the sum of total embodiedenergy and the total operational energy over the lifespan of 50 years. In thisstudy, total embodied energy, total operational energy, and total life cycleenergy are presented in terms of primary energy consumption. The total lifecycle EI is also estimated similar to total energy use.
The total life cycle EIof each house is the sum of total embodied EI and the total operational EI over50 years of lifespan. 4. RESULTS AND DISCUSSIONIn this section, the results of acomprehensive LCA study of two types of residential buildings in BC, Canada arepresented. The presentation of results is divided into theFollowing categories: total embodiedenergy and environmental impacts, total operating energy and embodied impacts.
a. Total Embodied Energy Use and Environmental Impacts: A breakdown of total embodied energyfor two types of buildings for a service life of 50 years. The results aredivided into the relevant building life stages:product, construction process, use ormaintenance, end of life, and beyond building life. The total embodied energyof buildings of home of tomorrow is less than home of today.
In terms of thetotal embodied EI, the relationship between the EI and the embodied energy aremuch the same. The foundation and walls for all the building types are responsiblefor maximum embodied EI. 6.
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