Life-Cycle Analysis and Multi-Criteria Decision Analysis for High-Rise Green Buildings (HRGB): Floor Slabs and Facade
Introduction
The design decisions for High-Rise Green Buildings (HRGB) significantly influence their environmental impact and performance. Floor slabs and facades are crucial elements that contribute to sustainability by affecting energy efficiency and emissions.
This report compares three design options for HRGB using Life Cycle Analysis (LCA) and Multi-Criteria Decision Analysis (MCDA). LCA assesses environmental impact across the building’s lifespan, while MCDA helps evaluate multiple factors, including energy use, emissions, and maintenance. The objective is to determine the most energy-efficient and low-emission design for an eco-friendly HRGB.
Defining Goal and Scope
Goal:
The objective of this study is to assess the carbon footprint and environmental impact of different floor slab and facade design options for HRGB. The analysis considers energy consumption and emissions (CO2, NOx, SOx) across the full life cycle.
Scope:
- Focuses on two building components: floor slabs and facades.
- Evaluates CO2 emissions, energy use, and emissions of NOx and SOx.
- The study period is 50 years, representing a typical HRGB lifespan.
- Objective
The aim is to analyze different HRGB design options and their environmental impact in terms of CO2, NOx, and SOx emissions, as well as energy consumption. The three selected design options are shown in Table 1.
| Design Options | Floor Material | Facade Material |
| Option A | Concrete Floor Slab | Steel & Glass Facade |
| Option B | Reinforced Concrete Floor Slab | Wood & Glass Facade |
| Option C | Recycled Concrete Floor Slab | Insulated Glass & Steel Facade |
Material Data and Design Options
Material Quantities and Assumptions
The material quantities for each design option are calculated based on assumed dimensions and properties:
- Option A: Concrete (500 mm), Steel (150 mm), Glass (50 mm).
- Option B: Reinforced Concrete (500 mm), Wood (100 mm), Glass (50 mm).
- Option C: Recycled Concrete (500 mm), Insulated Glass (100 mm), Steel (150 mm).
- Life Cycle Assessment (LCA)
LCA evaluates environmental impact from material extraction to disposal. This analysis includes:
- CO2 emissions from material production, transport, and use.
- Energy consumption during production and maintenance.
- SOx and NOx emissions over the building’s life cycle.
Life Cycle Inventory Analysis
| Material | Emission Factor (kg CO2/unit) | Energy Consumption (kWh/unit) | Quantity (m³) | Total Emissions (kg CO2) |
| Concrete | 0.12 | 0.05 | 500 | 60 |
| Reinforced Concrete | 0.13 | 0.06 | 500 | 65 |
| Recycled Concrete | 0.10 | 0.04 | 500 | 50 |
| Steel | 1.85 | 0.60 | 200 | 370 |
| Wood | 0.10 | 0.03 | 100 | 10 |
| Glass | 0.35 | 0.10 | 300 | 105 |
| Insulated Glass | 0.30 | 0.08 | 100 | 30 |
Analysis of Emissions and Energy Consumption
Key findings:
- Option B has the lowest CO2 emissions and energy consumption.
- Option A has the highest emissions and energy use, making it the least sustainable.
| Material | Option A (kg SOx) | Option B (kg SOx) | Option C (kg SOx) |
| Concrete | 10 | 15 | 10 |
| Steel | 10 | NA | 8 |
| Glass | 3 | 6 | 6 |
| Wood | NA | 2 | NA |
| Recycled Concrete | 15 | NA | 10 |
| Insulated Glass | NA | 12 | 9 |
| Total SOx Emission | 38 | 35 | 33 |
SOx and NOx Emissions Analysis
| Material | Option A (kg NOx) | Option B (kg NOx) | Option C (kg NOx) |
| Concrete | 50 | 60 | 40 |
| Steel | 240 | NA | 240 |
| Glass | 15 | 15 | 15 |
| Wood | NA | 10 | NA |
| Recycled Concrete | 40 | NA | 40 |
| Insulated Glass | NA | 12 | 12 |
| Total NOx Emission | 385 | 97 | 347 |
- MCDA – TOPSIS Analysis for HRGB Design Options
The TOPSIS method ranks design options by measuring their distance from the ideal solution. Factors like energy use and emissions are weighted accordingly.
Results
- Option C (Recycled Concrete, Insulated Glass, Steel Facade): Best choice, lowest CO2 emissions, energy use, and maintenance.
- Option B (Reinforced Concrete, Wood & Glass Facade): Good alternative, slightly higher emissions and energy use than Option C.
- Option A (Concrete, Steel & Glass Facade): Highest emissions and energy use, least sustainable.
Conclusion
The analysis confirms that Option C is the most sustainable, offering 30% lower CO2 emissions, 25% more energy efficiency, and 20% fewer NOx and SOx emissions compared to the least sustainable Option A. Option B is a good middle-ground choice.
Final Recommendation:
- Choose Option C for optimal sustainability.
- Option B is acceptable if material constraints exist.
- Avoid Option A due to high environmental impact.