1. Embodied Energy Analysis of a Pre-cast Building System
SECM/15/162
D.M.K.W. Dissanayake
C. Jayasinghe
University of Moratuwa

2. Content Background Life Cycle Analysis
Embodied Energy of Building Components
Methodology
Energy consumption at production of building materials (Ep)
Energy in transportation of building materials (Et)
Energy at construction stage of the building (Ec)
Results of Embodied Energy Analysis
Conclusion

3. Background
Buildings consume more than 40% of global energy and contributes about 33% of greenhouse gas emissions
In European building sector, residential buildings represent about 63% of total energy consumption and 77% of total CO2 emissions (Li et al. 2013)
Residential Buildings: 1/3 of building construction in Sri Lanka
92% of occupied housing units, of the country are collectively single storied or two storied
58% of the houses are constructed with brick walls and 33.8% are constructed with blocks
Find alternative building systems
Environmental restrictions
Depletion of resources
Cost of labour
Depletion of natural resources to acquire -clay, sand, gravel
Clay
Sand
Metal
Cement
Steel

4. What level of sustainability can be achieved, with pre-cast concrete?
Precast concrete products have become a natural choice of achieving sustainability in buildings, since they incorporate holistic design, efficient use of material and minimize the construction waste and site disturbance.
What level of sustainability can be achieved, with pre-cast concrete?

5. Life cycle Analysis
Is a established method, used to quantitatively evaluate the environmental impacts of a product
ISO14040:2006 (Environmental Management - Life cycle Assessment - Principles and Framework)
So, it is useful to evaluate the LCA of established precast systems in Sri Lanka to understand the actual benefits of them over other building construction methods

6. System Boundary for LCA of a building
MATERIALS
CONSTRUCTION
OPERATION AND MAINTAINANCE
TRANSPORTATION
DEMOLITION
Embodied Energy Analysis
Raw materials and Equipment from ICE database and Work Measurements

7. Embodied Energy of Building Components
Embodied energy is the energy consumed by all of the processes associated with the production of a product, from the mining and processing of natural resources to manufacturing, transport and product delivery.
Three main methods of Analysis
Process Based Analysis
Input- Output Analysis (Economic I-O analysis)
Hybrid Analysis
Depends on,
System boundary of the analysis
Geographical location of the study
Transport distances and methods
Technology of the manufacturing process
Method of embodied energy analysis
Embodied energy is the ‘upstream’ or ‘front-end component of the life cycle analysis
When the product is a building---- product delivery is the padinchi wena awasthawa

8. Details of the precast building system
Precast pre-stressed beams (150mm×350mm) / columns (200mm×200mm)
Structure
In-situ isolated pad footings with precast pre-stressed tie beams
Foundation
Ground floor: 50mm G20 screed and 1st floor with precast pre-stressed slab panels (thickness 65mm×1m×4m)
Floors
Building System
Specific Characteristics
Windows
Timber flamed single glass windows
Doors
Timber and plastic (PVC)
Roof
Timber truss and asbestos sheets
Ceiling
Steel grid, 68% recycled content ceiling tiles (600mm×600mm)
Flooring
Ceramic Tiles
Both interior and exterior walls out of EPS panels (100mm×600mm×2400mm)
Walls

9. Scope of study Ec Et Ep EET
A house with identical architectural house plan, built at the same location is assumed for the two building systems. Ec Et Ep
EET
EET= Total embodied energy
Ep= Energy consumption at production of building materials
Et= Energy in transportation of building materials
Ec= Energy at construction stage of the building

10. Methodology
Prepare the inventory of materials used (using BOQ of the building)
Calculate the embodied energy of these materials
3 data sources were used, Sri Lankan data, Indian data , Inventory of Carbon and Energy (ICE database- prepared by University of Bath )
The embodied energy of electrical work and wiring of the house has been eliminated
Conduct Work studies and interviews with industry related people to collect data at the construction stage
Only equipment intensive activities are considered not labour intensive activities, Fuel usage data for different vehicles used in plants and sites
Convert electricity usage, fuel consumption at each activity into energy figures (MJ)
Calculate the total embodied energy for the building

11. Case Study: Two storey residential building
Location of the Site: Kandana
Floor Area: 325 sq. meters
Five bed room house
Initial construction:
Concrete framed structure with masonry walls( burnt clay bricks)
Foundation with pad footings combined random rubble

12. Energy consumption at production of building materials (Ep)
BOQ of the conventional in-situ house  obtain the amount of the building materials
Excavation and earth work, ceiling, roof, floor finishes, waterproofing, doors/windows remains same for both systems
Material quantities  structural elements such as beams, columns, slabs and wall panel are estimated individually

13. Embodied energy of metal
Data from Finite Lanka (Pvt) Ltd

14. Main construction materials and their energy density
Energy Intensities (MJ/kg)
Source
Aggregate
0.11 SL
River Sand
0.08
Aluminium
155
ICE
Cement
4.9
Cement Motar
2.55
Ceramic tiles 12
Sanitary products 20
Bricks
2.3
Wood
10.8
IND
Plywood 15
Steel
35.1
Materials
Energy Intensities (MJ/kg)
Source
Stainless steel
56.7
ICE
Brass 62
Asbestos
7.4
PVC
105
IND
Glass 15
Paints 70
Putty
5.3
Primer
144
Lime
5.63
EPS 36 EU
SL: Sri Lanka, IND: India, ICE: Inventory of Carbon & Energy V1.6a

15. Energy in transportation of building materials (Et)
Occur at different stages of manufacturing of products
The fuel consumption data and the transportation distances or waiting/idle times at different activities with those machinery related to this building construction were studied.
Transportation distances of several construction materials
Material
Transportation Distance (km)
to construction site
to redimix plant
to precast yard
Cement
200
180
Sand
100
Aggregate 50
Steel 30 -
EPS
Fly ash
Bricks 40
Plywood
130
Wood

16. Energy at construction stage of the building (Ec)
Energy usage at construction stage is minimal
i.e. most of the work is labour intensive and machinery usage is minimized
Frequently Used Machinery  concrete mixer, grinders, bar-cutters, arc-welding plant, electrical drill, etc
Record time duration of each machinery in use and its wattage or fuel consumption.

17. Work Measurements Results of Work Measurements.xlsx
Several site visits were arranged to the casting yard at Ekala and some construction sites
Work studies were done to quantify Labour, Machinery and Energy involvement at different construction stages
Collected data is then used to quantify the embodied energy of materials and products
Results of Work Measurements.xlsx
Vehicle Efficiencies and usage.xlsx
The biggest obstacle for this study is the lack of data availability in Sri Lanka
So,

18. Some photos from site visits5 6 1 2 4 7 3

19. Results of Embodied Energy Analysis
Embodied energy calculation for the conventional in-situ building
Embodied energy calculation for the pre-cast building
On site construction activity
Embodied Energy (GJ)
Excavation and earthwork
2.80
Total in-situ concrete
138.13
Total formwork items
89.20
Total Reinforcement
86.25
Masonry Works
231.13
Floor finishes with ceramic tiles
78.41
Wall finishes (plastering and painting)
280.36
Ceiling construction
128.80
Metal Work
5.63
Roof construction
39.48
Windows/ Doors
49.65
Plumbing & sanitary work
101.49
Total embodied energy of the house
On site construction activity
Embodied Energy (GJ)
Excavation and earthwork
2.80
Total in-situ concrete (10% from in-situ)
13.81
Total formwork items
0.50
Total Reinforcement (5% from in-situ)
4.31
Masonry Works
0.10
Floor finishes with ceramic tiles
78.41
Wall Finishes (painting 50% less)
116.14
Precast concrete elements
453.97
Ceiling construction
128.80
Metal Work
5.63
Roof construction
39.48
Windows/ Doors
49.65
Plumbing & sanitary work
101.49
Total embodied energy of the house
995.10
19% Reduction

20. Results of Embodied Energy Analysis
Results of embodied energy analysis for conventional in-situ building
Results of embodied energy analysis for pre-cast
building

21. Conclusion
Comparative analysis of embodied energy of a conventional in-situ building system and a precast building system, using process-based analysis was done.
Energy consumption at production, transportation and construction stages were considered
Total embodied energy of the precast building system (3.06 GJ/m2) is 19% less than the conventional building (3.8 GJ/m2)
Further studies on the production process of EPS wall panels and construction stage the energy usage of the building, will help to improve the accuracy of the results.

22. Thank you