Designing a Low-Carbon Building via LCB Method 3 . 0 , Case Study : An Educational Building in Tehran

Air pollution and its damage have caused growth of concerns in human societies in the last decades. Nowadays, environmental issues are being discussed more than ever and sometimes it leads to solutions and methods to improve current situations. One of the methods is introduced in 2009 as Low-Carbon Building (LCB) Method. This method considers reduction of emissions in building during its whole lifetime. In this study, an educational building is designed with the purpose of considerable reduction in greenhouse gas (GHG) emissions. This building is investigated in different stages and eventually, the amount of carbon emissions in the building's lifetime is estimated by LCB Method 3.0 which is built on Publicly Available Specification (PAS) 2050. After estimation, it is determined that the project building, according to low-carbon buildings classification, can be ranked in Class C (good). This study also discusses effective strategies which lead to low-carbon buildings.


INTRODUCTION
Human society and the environment interact with each other.Human impacts on the environment refer to the impacts of human activities on biophysical environments, biodiversity and other resources (Han, 2012).Those activities (such as burning fossil fuels and deforestation) are responsible for the release of considerable amount of greenhouse gas (GHG) in the atmosphere which has the property of trapping solar heat.Climate model projections indicate that global surface temperature will likely rise 1.1°C to 6.4°C during the 21st century.This elevation in temperature causes "changes" to the average weather of regions or the earth as a whole "climate change" (Fabre, 2009).The built environment is one clear example of GHG emissions, so buildings produce considerable impact on the environment (United Nations Environment Programme, 2009).For instance, in the Tehran region, due to the very high energy consumption, carbon dioxide (CO 2 ) emissions are also very high, with the residential and commercial buildings making up the largest share of 41% by 2008 (Nasrollahi, 2013).Therefore, the idea of low-carbon buildings could be a solution to reduce the excessive GHG emissions in Tehran.
Low-carbon building is a building which has been engineered to release significantly less GHG than a regular building over its lifetime (Ambapkar, 2015).Life Cycle Assessment (LCA) tools are needed in order to calculate GHG emissions from buildings.Between available tools, Low-Carbon Building (LCB) Method is used in this study.Further, this study introduces the concept of "low-carbon" buildings and LCB Method.Therefore, this paper is focused on following issues: 1. Estimating buildings lifetime GHG emissions and emissions reduction performance.
2. Low-carbon buildings design strategies and criteria which should be employed to reduce GHG emissions.
These issues are discussed and investigated with a case study and estimations are based on a LCB Method 3.0 (third edition).

LIFE CYCLE ASSESSMENT (LCA)
LCA is a technique to assess environmental impacts associated with all stages of a product's life (from raw material extraction through material processing, manufacture, distribution, use, repair and maintenance, disposal or recycling) (Sanders and Wood, 2014).In recent years, LCA software tools have become increasingly important.Today a large number of LCA programs are available.The foremost -and for the potential user also often prohibitive -property of a software tool is the price.The price of an LCA software tool can vary between several thousand euros and free of charge.Some tools offer a wider range of features than others.Some are focused on a specific field of LCA, e.g.LCA in waste management (Unger, Beigl and Wassermann, 2004).
Different groups of LCA software users can be distinguished.The first group includes scientists and researchers.The users in this group make high demands on LCA software tools: they need a flexible software tool that enables them to model "common" often-modelled scenarios as well as scenarios that diverge from the standard.Also the tool should support modelling of complex process chains.Industry, on the other hand, uses LCA software to improve its environmental performance, for process optimisation and product development.The users want "ready to-use" software, where many of the specifications are already pre-set with only a few parameters needing to be determined.Also decision makers use LCA to compare different solution options and hence also LCA software tools.Decision makers generally want an easy-to-understand presentation of the results in terms of which option is the best (Unger, Beigl and Wassermann, 2004).
This study is focused on a building industry.Table 1 includes some of existing building industry LCA tools.LCB Method is chosen among these tools.LCB Method is free, simple, relatively accurate (Fabre, 2009) and supports full LCA (Wang, Wu and Zhang, 2016).This tool is built and promoted for architects, engineers, construction managers, owners, or anyone interested in low carbon buildings across the design and construction industry.It is built to handle all building types, as well as, residential, commercial, industrial, interior design and infrastructure project types (Simonen et al., 2012).

THE CONCEPT OF LOW-CARBON BUIDLINGS
Low carbon content building is one of the techniques of sustainable development in which attempt is made for reducing emissions by using low carbon emission materials and low carbon emission techniques (Landage, 2013).A building emits GHG during its whole lifetime, therefore engineering a low-carbon building is a progress that concerns all stages of the building life.

Low-Carbon Building Classification
The LCB Method 2009 proposes LCB classification as illustrated in Figure 1.

Key Definitions
1. Baseline building: the building which would most likely has been constructed if no particular GHG emissions reduction strategies had been considered (Fabre, 2009).
2. Project building: the building which is designed by project team with GHG emissions reduction strategies (Fabre, 2009).

LOW-CARBON BUILDINGS: A STEP BY STEP APPROACH LCB Method (First Edition, 2009)
The LCB Method recommends the step by step approach (see Figure 2) for achieving the desired emissions reduction performance.
The project team should focus on phases 1 to 3 of the process as a priority (Fabre, 2009).Since estimation for the case study is based on the third edition of LCB Method, here only the most significant factors of the first edition are introduced.

Phase 2 from the first edition: Reduce energy consumption
After construction, a building has an "operational life" of approximately 50 years.GHG are emitted as a consequence of the energy used by the building for lighting, artificial heating and cooling, etc.Most of the time, this energy is generated by the burning of fossil fuels such as coal, oil, gas, etc. (Fabre, 2009).There are consequently three ways to reduce the emissions of a building during operation: 1. To install energy-efficient systems.
2. To produce on-site or purchase renewable energy, in particular clean electricity.
3. To use passive solar building strategies in order to reduce energy consumption.
Moreover, it should be mentioned that medium to heavyweight construction is likely to provide more potential for achieving higher levels of indoor comfort and reduced lifecycle CO 2 emissions (Hacker et al., 2008).

Phase 3 from the first edition: Produce clean electricity on-site
Renewable energy sources (such as wind, sunlight, biomass.)can provide part of the energy, to in theory all the energy of a building.If embodied emissions are excluded, the electricity produced from renewable energy is considered to be emissions free, and the associated emission factor is: (Fabre, 2009).

LCB Method 3.0 (Third Edition, 2011)
The life cycle GHG emissions/removals of the project building shall be estimated by the step-by-step approach as shown in Figure 3. Step 1: Pre-assessment Estimate the contribution of each material to the life cycle emissions of the building prior to the detailed assessment by doing the pre-assessment.The pre-assessment is intended to identify the sources of emissions that shall be included in the assessment (Fabre, 2012).This step can be estimated by www.shapedearth.com.

Step 2: Construction emissions
The construction sector is the largest global consumer of materials (Giesekam et al., 2016) and over half the embodied carbon in construction is associated with the consumption of materials (Giesekam et al., 2014).Generally, GHG are emitted during five phases in construction (see Figure 4).Emissions associated with the building construction are calculated as shown in Equations 1, 2 and 3 (Fabre, 2012).

Example for wall's material
Wall's material for the project building is considered to be light expanded clay aggregate (LECA) blocks and for a baseline building is clay brick.
LECA block for the project building: Results show that construction emissions for walls from LECA blocks is about 73% lesser than clay bricks.

Step 3: Deconstruction emissions
During deconstruction, materials constituting the building become waste.There are three main waste treatment methods: (1) disposal in landfills, (2) incineration and (3) recycling (Fabre, 2009).GHG are emitted during three phases in deconstruction (see Figure 5).Emissions associated with the building deconstruction are calculated as shown in Equations 4, 5 and 6.
Eq. 4 Step 4: Renovation emissions The use phase of the building spans from the end of its construction to its deconstruction.The emissions anticipated to occur during this phase are the emissions associated with the replacement of the materials constituting the building (Fabre, 2012).GHG are emitted during several phases in building renovation (see Figure 6).Emissions associated with the building renovation are calculated as shown in Equations 7 and 8 (Fabre, 2012).Step 5: Carbon storage Carbon storage may arise when materials containing biogenic carbon (e.g., wood) or materials having the ability to take up atmospheric carbon over their life cycle (e.g., cement) are used on the project (Fabre, 2012).Equation 9illustrates how to calculated carbon storage (Fabre, 2012).
Eq. 9 Step 6: Whole life emissions Total emissions of the building are calculated as illustrated in Equation 10 (Fabre, 2012).
Emissions from site activities (site work) and site land use change for construction, deconstruction and renovation should be estimated as below.Estimation of the emissions from construction site work and land use change as shown in Table 2 and Table 3  The emissions from deconstruction site work are estimated as indicated in Equation 11 while for the emissions from renovation site work, the estimation is as indicated in Equation 12 (Fabre, 2012).

CASE STUDY
Air pollution and its consequences (such as economic pollution) have caused irreparable damage especially in industrial cities of Iran, like Tehran (Karimzadegan et al., 2008).energy consumption per capita in domestic and commercial sector is 1.9 times more than the global average also using renewable energy sources are lesser than global average (Iran's Energy Balance 2012 [2013]).Therefore, it seems a method which can focus on both energy and GHG emissions issues are vital.Project site is located in Jashnvareh Blvd, sixth zone of district four, Tehran.four has the second highest number of industrial services unites in Tehran city.This could help to reduce materials transport emissions.The site is located near to taxi station, bus stop and subway station which provides easy access to the site.

Estimating Building Lifetime GHG Emissions by LCB Method Version 3.0
Step 1: Pre-assessment On this stage, emissions are estimated in www.shapedearth.com(Fabre, 2011) and some data like emission factors are available from www.lcbmethod.com/appendix(Fabre, 2014).
The construction industry requires the extraction of vast quantities of materials and this, in turn, results in the consumption of energy resources and the release of deleterious pollutant emissions to the biosphere (Hammond and Jones, 2008).To minimise emissions, it is essential to device technologies to produce building materials and products with minimum amount of energy expenditure (Reddy, 2009).Therefore, selecting materials with lower embodied carbon such as stabilised mud blocks, compacted fly ash blocks, rammed earth walls and blended cements can be used in low-carbon projects.This study is tried to use technology and materials which are common and available for construction in Iran in order to verify that lowcarbon buildings could be built by common materials and technologies.Table 4 shows materials consist in the project building.
Total emissions for the project building are estimated about 55,567 kgCO 2 e.Table 5 shows materials consist in a baseline building with a total emission for a baseline building is estimated about 89,568 kgCO 2 e.On the other notes, Tables 6 to 10 are required in the next steps (Step 2 to 5) for more accurate estimations and actual distances mostly used for this project.Step 2: Construction emission Construction emissions for the baseline and the project buildings are calculated as shown in Table 11.Note: If the vehicle is empty on its return, multiply its emission factor by 1.8.

Step 4: Renovation emissions
Renovation emissions for the baseline and the project buildings are calculated as shown in Table 13.Step 5: Carbon storage Carbon storage for the baseline and the project buildings are calculated as shown in Table 14.Some actions which are used in the project building to reduce emissions are: using recyclable materials, minimise site land use change, use earth material of the site (rammed earth), using durable materials and reducing transport distance by using local materials.

CONCLUSION
Overall, the amount of emissions from pre-assessment step for the project building is 38% lesser than a baseline building.Results of the detailed assessment (step 2 to 5) justify the pre-assessment estimation, and illustrate that the project building emission is 40.8% lesser than baseline building.Therefore, according to low-carbon buildings classifications, the project building can be ranked in Class C (good).
Estimations indicate that the construction phase has the highest amount of emissions compared to other phases.As can be seen by estimations, some of the effective factors to reduce emissions are building structure and materials transportation.Some effective ways to reduce emissions from buildings are: APPENDIX This is a list of the abbreviated terms used throughout the article and the definitions:

Figure 4 .
Figure 4. Emissions of GHG during Construction Phase

Figure 6 .
Figure 6.Emissions of GHG during Renovation Phase

Table 1 .
LCA Tools in Building Industry

Table 2 .
. Default Emission Factors for Construction Site Work Source: Fabre (2012) Note: GFA = Gross Floor Area

Table 3 .
Default Emission Factors for Site Land Use Change

Land Use Change Emission Factor kgCO 2 e/m 2
Land use change may occur on-site as a consequence of the construction activities.Multiply the surface area of the disturbed land by the appropriate emission factor from the table (+ve if loss of biomass; -ve if gain of biomass). Note:

Table 4 .
The Project Building Materials and Materials Data

Table 5 .
A Baseline Building Materials and Materials Data

Table 6 .
Default Emission Factor of the Vehicle Used for Materials Transportation

Table 8 .
Default Transportation Emissions of Each Material from Gate (Factory) to Site

Table 9 .
Default Emission Factor of Materials in Landfill and in Incinerator

Table 10 .
Default Transportation Distance of Materials Sent to Landfill, Incinerator and Recycling Plant Source:Fabre (2009)

Table 11 .
Construction Emissions for the Baseline and the Project Buildings

kgCO 2 e) Material Result (kgCO 2 e)
Deconstruction emissions for the baseline and the project buildings are calculated as shown in Table12.

Table 12 .
Deconstruction Emissions for the Baseline and the Project Building

Table 13 .
Renovation Emissions for the Baseline and the Project Building

Table 14 .
Carbon Storage for the Baseline and the Project Building

Project Building Emissions (kgCO 2 e) Baseline Building Emissions (kgCO 2 e) Emission Reduction Performance LCB Classification
trans mat, i Distance gate-site for material i Cradle-to-gate emissions of material i E trans mat, i Transport emissions of material i from gate to site E trans waste, i Transport emissions of material i from site to grave E waste, i Waste treatment emissions of material i EF inc, i Emission factor of material i in incinerator EF land, i Emission factor of material i in landfill EF mat, i Cradle-to-gate emission factor of material i EF trans mat, i Emission factor of the vehicle used to transport material i to site EF trans waste Emission factor of the vehicle used to transport waste to disposal K conc = 0.01; K wood = 1.56 K conc is the atmospheric carbon, expressed in kgCO 2 e, taken up by 1 kg concrete over a 100-year period.K wood is the carbon content, expressed in kgCO 2 e, of 1 kg wood (wet weight).