Assessment of the Impacts of Industrialized and Conventional Wall Systems on Energy Consumption and Carbon Footprint

Mahmoud Shakouri Hassanabadi1, Mohammad Mahdi Tahmasebi 2, Seyed Saeed Banihashemi 3+,

Mohsen Bakhtiari Boroojeni 4, Mohsen Torabi5

1,2,3,4,5 University Teknologi Malaysia

Abstract. Issues of sustainability have been duly highlighted in the Construction Industry. Energy efficiency, environmental and ecological impacts of construction are among the most important factors in the quest for sustainable development. To cope with these issues, Malaysian construction industry has been urged to use more innovative construction techniques like IBS and BIM. The main objective of this work is to evaluate the direct impacts of IBS wall components such as sandwich panels on sustainability through BIM software and determining the rate of energy consumption and carbon foot print in accordance with the implemented changes in a residential building designed on the IBS basis. The case study is a 325 m2 residential bungalow which is built in two levels and located in Kuala Lumpur. The simulation is carried out by using ArchiCad 14 software which is one of the pioneers in BIM and its new sustainability plug-in integrated into this software known as Grafosoft EcoDesigner. It is observed that the IBS practice has no significant impact on saving energy and reducing CO2 footprint. In general, this conclusion is drawn that IBS technology doesn’t play a prominent role in energy efficiency. However, its contribution to promote sustainability may fall in other categories. Keywords: sustainability, energy consumption, carbon footprint, IBS, sandwich panel.

1. Introduction The term sustainable has recently gained popularity in Malaysian construction industry Master Plan

(2005 – 2015) as a crucial priority for the Malaysian construction industry [1]. The Malaysian Green Building Index (GBI) has been developed recently by Association of Consulting Engineers Malaysia (ACEM) and Pertubuhan Arkitek Malaysia (PAM) in order for enhancing sustainability in the built environment.

Energy consumption is the main responsible for emissions of greenhouse worldwide. It is estimated that the construction sector accounts for about 35% of greenhouse gas emissions [2]. The International Energy Agency predicts that the global energy demand will increase by more than 50% by 2030 if policies remain unchanged and more than 60% of this increase respects to developing countries. This will lead to a 52% increase in emissions of carbon dioxide (CO2), the main greenhouse gas [3].

With the growth in construction activities, it has become imperative that design tools to be provided, can give insights into the sustainability of a building at an early design stage itself, and helps the design team incorporate the sustainable solutions in a building very early in the design process.

This paper aims at evaluating the efficiency of various types of IBS wall components with regard to energy consumption and drawing an analogy between them and the conventional type.

2. Literature Review The minimum negative influence to an environment and built is attained through practicing sustainable

construction. As a result, properly using natural resources and controlling construction waste increase the environmental quality, decrease energy consumption resulting saving limited resources.

+ Seyed Saeed Banihashemi. Tel.: + (60177248796). E-mail address: (sbnseyed2@live.utm.my).

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In line with the growing global trend in applying sustainability, Malaysia introduced its national sustainability assessment tool in 2010. Green Building Index (GBI) is Malaysia’s industry recognized green rating tool for building to promote sustainability in the built environment. It is specifically developed for tropical climate, environmental and developmental context [4]. The major objectives of GBI include Energy Efficiency, Indoor Environmental Quality, Sustainable Site Planning & Management, Material and Resources, Water Efficiency and Innovation in which energy efficiency and material and resources comprise 32% of total marks in residential buildings in scale of 100. This shows the significance of modifying the conventional building construction and use of materials to enhance the efficiency in the building envelope.

To cope with these challenges, Malaysian construction industry has been called for incorporating innovative construction technique and to switch from traditional to modern techniques like Industrialized Building System (IBS) construction. IBS is defined as a construction technique in which components are manufactured in a controlled environment (on or offsite), transported, positioned and assembled in a jobsite with minimal additional site works [5]. It is claimed that IBS has a potential usage to promote sustainability from the controlled production environment, minimize waste generation, usage of energy efficient building materials and promote effective logistics [1].

One of the areas that IBS has shown a great merit is the construction of prefabricated wall panels or sandwich panels. A sandwich structured composite is a special class of composite materials that is fabricated by attaching two thin but stiff skins to a lightweight but thick core. The core material is normally low strength material, but its higher thickness provides the sandwich composite with high bending stiffness with overall low density. Open and closed cell structured foams like polyvinylchloride, polyurethane, polyethylene or polystyrene foams, balsa wood, syntactic foams and honeycombs are commonly used core materials. Open and closed cell metal foam can also be used as core materials. Laminates of glass or carbon fiber reinforced thermoplastics or mainly thermoses polymers (unsaturated polyesters, epoxies...) are widely used as skin materials. Sheet metal is also used as skin material in some cases. The core is bonded to the skins with an adhesive [6].

The strength of the composite material is largely dependent on two factors: • The outer skins: If the sandwich is supported on both sides, and then stressed by means of a

force in the middle of the beam, then the bending moment will introduce shear forces in the material. The shear forces results in the bottom skin being in tension and the top skin being in compression. The core material spaces these two skins apart. The thicker the core material, the stronger the composite. This principle works in much the same way as an I-beam does.

• The interface between the core and the skin: Because the shear stresses in the composite material changes rapidly between the core and the skin, the adhesive layer also sees some degree of shear force. If the adhesive bond between the two layers is too weak, the most probable result will be delamination [7].

3. Research Methodology The case study is a double storey bungalow located in Kuala Lumpur. It is modeled in Archicad 14 with

conventional materials. The next step is to determine the types of alternative for the exterior skin of the building. Among the available IBS wall components, five typical sandwich panels are to be chosen for simulation. The simulation is carried out by Graphisoft Ecodesigner which is a new integrated sustainability assessment tool in Archicad. EcoDesigner uses the same simulation kernel as the VIP Energy product, which is validated by EN-15265, IEA-BESTEST and StruSoft-BESTEST.

Table 1 shows the list of components used and their specifications. Energy efficiency is solely studied dependent on the types of material available in the market [8]. It is hypothesized that material used in the external shell has a direct impact on the energy loss and carbon emission in the building.

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Table 1: Components’ specification

4. Analysis and Discussion The simulation results indicate the annual energy consumption and carbon footprint. With reference

to table 1 and 3, it can be inferred that firstly, in addition to being the most efficient in terms of energy efficiency and CO2 emission, SP3 is the only IBS wall that does not include any concrete in its composition, providing that elimination of concrete will be likely to diminish the amount of CO2 emission in a building. Secondly, U-value which is a measure of the rate of heat loss through a material for SP3 amounted to 0.37 which ensures the least transition rate for the wall.

As depicted in table 2, a significant amount of consumed energy is generated by electricity. This is because of the hot and humid climatic condition of the region which necessitates the use of mechanical cooling systems such as air conditioning throughout the year.

Due to two layers of insulation used in the structure of SP 3, this panel has proven to be less thermal conductive and consequently maintains the inside temperature for a longer time resulting in reduction of energy consumption by 0.9%. According to figure 1, an average using sandwich panels as the exterior skin of the building saves almost 2521 kWh of energy which stands for 0.86% of reduction in annual electricity consumption.

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Table 2. Annual energy consumption for different types of sandwich panels

As it can be seen in table 3, the amount of carbon footprint and annual energy consumption are respectively 1057 kg CO2/year and 40175 kW/hr. In terms of energy efficiency among IBS components, the third type of sandwich panel (SP3) is the most efficient by consuming 37294 kW/h energy and sp5 is ranked as the least efficient due to less impact on energy consumption. On the other hand, all IBS wall components offer relatively better energy efficiency as compared to conventional walls. Along with energy efficiency, application of IBS leads to a slightly reduction in carbon emission. Similarly, among IBS walls, SP3 has the least rate in carbon emission, while SP5 emits the most amount of CO2 per year.

Fig 1. Simulation results

Table 3. Summary of annual Carbon footprint and energy Consumption

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Fig 2. Summary of simulation for different types of sandwich panels

5. Conclusion Designing a building entails considering a plethora of factors. In this competitive market, being able to

make quick decisions and choosing the best option is considered as an advantage. With respect to project appraisal and the impact of sustainable criteria such as the energy consumption and carbon footprint on the design, BIM can aid the AEC group to collect the vital information from the model to analyze and select the most beneficial alternative in the early stages of the design.

This paper aims at the evaluation of modern wall panels which are common in industrial building systems and drawing an analogy between them and the conventional wall system regarding to their impacts on energy consumption and environmental issues such as carbon footprint.

Regardless of slight variation in energy efficiency and CO2 footprint between IBS and conventional walls (figure 2), it is witnessed that the IBS practice has no significant impact on saving energy and reducing CO2 footprint. In general, this conclusion is drawn that IBS technology doesn’t play a cons piques role in energy efficiency. However, its contribution to promote sustainability may fall in other categories.

6. References [1] http://www.cream.com.my

[2] EC. Environment face sheet; energy for sustainable development. European Commission, 2006.

[3] Nelson, Andrew J., Rakau, Oliver. Green Buildings - A niche becomes mainstream. Dutch Bank Research, 2010.

[4] Shing Chyi ChuaCorresponding and Tick Hui Oha. Green progress and prospect in Malaysia. Renewable and Sustainable Energy Reviews 15

[5] IBS Roadmap (2003-2010). Construction Industry Development Board (CIDB) Malaysia. December 2006, Kuala Lumpur.

[6] J.Flanagan. The Realm of Building Possibilities Created by MCM and Insulated Metal Panels. Metal construction news 2007, 28 (10).

[7] Gere, James M. Mechanics of Materials. Thomson Brooks/Cole, 2004.

[8] http://www.concretethinker.com/energymodels/Residential-Energy-Model-Overview.aspx

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