The 3th International [avnir] LCA Conference on Life Cycle Assessment.

Transcription

1 The 3th International [avnir] LCA Conference on Life Cycle Assessment. November 4-5, 2013, Lille, France Paper ID: 236 Dr. Ali Taileb Assistant Professor, Centennial College, School of Engineering Technology and Applied Science, Toronto, Canada Dr. Hamoud Dekkiche Associate Professor, Canadian University Dubai, School of Architecture and Interior Design, Dubai, U.A.E.

2 LIFE-CYCLE ASSESMENT OF LEED GOLD BUILDING WITH ALTERNATIVE EXTERNAL WALLS: THE CASE OF BROOKSIDE PUBLIC SCHOOL IN TORONTO, CANADA

3 Question Is a LEED certified building a green building? 3

4 Leadership In Energy & Environmental Design (LEED) rating system does not take into consideration the Life Cycle Assessment LCA of materials This study shows: if LCA is integrated to LEED rating system a considerable improvement can be reached

5 Life cycle assessment, LCA, LEED, building envelope Abstract This study analyses how different building envelope solutions and building materials affect the results of the environmental assessment of a whole building over the building's life cycle of 60 years. 3 options are examined and compared to the existing base case. 1 st Option: replacing the existing cladding from steel to wood cedar. 2 nd Option: replacing the existing aluminum frame with a wood frame. 3 rd Option: replacing both sidings and the window frames.

6 Life cycle assessment, LCA, LEED, building envelope Abstract By changing metal siding to cedar wood siding the embodied energy of the building can be reduced by 5%. By changing aluminum window frame to wood, the building can achieve a lower embodied energy and a reduction by 44%. Environmental impact assessment of LEED buildings is discussed, further research topic is suggested; for example: How to integrate LCA into green building rating system.

7 Introduction Environmental impact + Energy consumption of buildings as a major target for improvement. Many environmental policies have adapted or changed in order to ensure buildings are designed efficiently, and in the most environmental way possible. o Traditionally, Local materials with low energy costs as well as low environmental impact were used. o Nowadays, Global materials such as cement, aluminum, concrete and PVC are being used. Environmental assessment has became a popular research area. Buildings are complex = Systems + Sub-systems The life cycle of a building includes all the materials and processes that make the building. Therefore, when implementing the LCA of a whole building, it s important to understand the relationship between different components of the building.. 7

8 o A brick building should include: o Each of these components has a distinctive life cycle. o Kotaji states: When parts of a building and construction are studied, their functional equivalence within the final B/C is essential [1] 8

9 Environmental impact assessment LCA is a tool used to analyse the environmental burden of products at all stages in their life cycle: from the extraction of resources, through production and used until it is disposed of, reused or recycled. This cycle follows materials from the cradle to the grave. The total system of unit processes involved in the life cycle of a product is called product system The only legitimate basis on which to compare alternative materials, components and services The life cycle of buildings is more complex than that of other products in that it involves the aggregate effects of a host of life cycles of their constituent materials, components, assemblies and systems The ISO (1997) defines LCA as a technique for assessing the potential environmental aspects associated with a product (or service) by compiling an inventory of relevant inputs and outputs, evaluating the potential environmental impacts associated with these inputs and outputs, and interpreting the results of the inventory and impact phases in relation to the objectives of the study 9

10 LCA of Buildings and Building Components In many cases, LCA practitioners tend to work at the level of individual materials and products, while users of LCA data are concerned with the whole building performances. This represents a challenge and a limitation of the LCA, the challenge is understanding the impact of a specific component on the environment and how it translates into areas of concern, such as environmental impact. Prediction of the life cycle of building components is difficult, as stated by Kotaji, Schuurmans & Edwards, 2003: o Building components in buildings have long lifetimes, often more than 50 years. During this lifetime, a building can withstand many significant changes, at times theses changes are more important than the original construction. A building's uniqueness lies in the particular choice of the material that composes the building. Therefore proper design and material selection are critical in order to minimize their impacts on the environment. To reduce the impact of building components on the environment Kotaji suggests that standardisation of whole buildings can help reduce their impact on the environment. Architects and designers, during the design process of a building take into account the environmental factors as well as other factors such as the technicality of the material, its functionality, aesthetic and cost. It is the role of the architect to integrate all these factors in the most optimal way, in order to achieve the required performance of the building. Proper choice of building materials by designers and architects has direct implications on the building as well as the environment. Thus, when architects and designers aim for minimal environmental impact, the materials must be chosen selectively. 10

11 Aim of the study to analyse how different building envelope materials can affect the results of the environmental assessment of a whole building. Environmental assessment of a LEED gold building (The Brookside Public School) was calculated for this study with a life cycle assessment (LCA) based tool ATHENA Environmental Impact Estimator (EIE) Software Version 4.0. ATHENA allows an in-depth view to the three-storey public school, a building that reached LEED gold status in The following steps were taken, o Review of architectural drawings, o Data collection & input to excel sheet tables o Simulation o Analysis. The work undertaken provided a LCA of the Brookside public school and all the building materials were quantified through AutoCAD detailed drawings. 11

12 Brookside Public School located in the northeast part of Scarborough. opened its doors in September 2007 to over 600 students. achieved "LEED Gold" the TDSB's (Toronto District School Board) most sustainable school. To attain this level, all aspects of interior and exterior design and construction adhered to strict LEED rating system requirements 12

13 Brookside Public School a. Wall System Legend The following illustration shows the location of different wall systems that are related to the solar orientation. Metal decking (clad) system is located towards the south while the brick wall system is oriented towards the North 13

14 Brookside Public School a. Wall System The typical exterior wall consists of: o o o o 190mm concrete block wall, 89mm poly-isocyanurate insulation, 161mm air space a structural bracing and a 90mm block. The cladding wall system is composed of metal siding that is installed over an 89mm rigid insulation. The Grow wall is composed of: o a 20x75 Architectural wire mesh on a 152 galvanized metal z- girts fastened to the total area Grow walls are mainly placed on the southwest elevation. On the Northern side of the building, the wall system has: o o o o a higher thermal mass for energy storage and composed of a 90mm brick masonry veneer, an air space, an 89mm layer of insulation (poly-isocyanurate) and a 240mm concrete block. The other concrete block wall is composed of: o a 190mm block a 89mm insulation a vapour barrier, a structural bracing and a 90mm concrete block. 14

15 The Grow wall 15

16 Brookside Public School b. Windows and Framing Systems 3 types of windows Type A: thermally broken aluminum framed windows. Type B: thermally broken aluminum framed curtain wall system consisting of double glazed sealed insulating panes. Type TWA: translucent wall assembly with thermally broken aluminum system. The glazed units have a 25 mm air space, with a combination of operable and fixed units. 16

17 Environmental Impacts Assessment Environment assessment of a LEED gold School was calculated for this study with a building environmental assessment tool ATHENA Environmental Impact Estimator (EIE) software Version 4.0. The predicted life of the building was 60 years. The EIE uses the following main criteria for presenting the results: o Energy consumption by assembly group (MJ) o Weighted Resource by Life Cycle Stages ( Kg) o Global warming potential (Kg ) o Eutrophication (index ) o Smog potential (index) o Acidication (index ) 17

18 Environmental Impacts Assessment Analysis: Athena Modeling: Comparison of Primary Energy Consumption by Assembly Groups The existing building is composed of metal siding. The total energy consumption for the walls is MJ and the roofs represent MJ. The first option represents the replacement of the metal cladding with cedar wood siding the analysis shows a lower energy consumption of the walls MJ which represents a saving of 32 %. The second option is replacing only aluminum windows by wooden window the total energy consumption is MJ, which represent an overall energy saving of only 4%. The biggest impact is noticed on the third option, replacing the metal siding and the window frame has per consequence energy saving of 35%. Figure 1- Comparison of Primary Energy Consumption by Assembly Groups 18

19 Environmental Impacts Assessment Analysis: Athena Modeling: Comparison of Global Warming Potential by Assembly Groups Figure 2 summarizes the global warming impact of each assembly type. In the base case the global warming impact represents a value of kg CO2 eq. 1 st. option (wood siding) represent a decrease of 31% ( kg CO2 eq). 2 nd. option by replacing only wood windows the global impact increased by 1% ( kg CO2 eq). 3 rd. option shows a reduction by 23% ( kg CO2 eq). Figure 2- Comparison of Global Warming Potential by Assembly Groups 19

20 Environmental Impacts Assessment Analysis: Athena Modeling: Energy Consumption Summary Measure Chart by Life Cycle Stages From the chart, the energy requirement for maintenance of the building with metal siding and wood siding is the same ( MJ). Nevertheless, there is a 2% increase of energy required for maintenance with wood windows ( MJ). This can be interpreted from the fact that when the building age, it will require more energy to replace and maintain wood windows. Figure 3- Energy Consumption Summary Measure Chart by Life Cycle Stages 20

21 Operating and Embodied Energy A reduction of 5 % on the total embodied energy is achieved just by changing to cedar wood siding and 17 % reduction by changing to wood windows and importantly, by 44% by changing both to wood siding and wood windows. Building options Embodied (MJ) Percentage reduction Base case With wood siding (area 6601 m 2 ) % Wood windows only % Wood siding & window frame % Table 1- Embodied Energy for building options 21

22 Conclusion The overall embodied energy of the building MJ by changing the metal siding to wood the embodied energy of the building can be reduced by 5% Furthermore the analysis has also shown by changing aluminum window frame to wood the building was able to achieve a lower embodied energy and a reduction by 44% ( MJ) of the total embodied energy. 22

23 Discussion: Integrating Life Cycle Assessment (LCA) into green building rating system

24 Thank you! 24