Identification of parameters for embodied energy measurement: A literature review

Abstract

The building construction industry consumes a large amount of resources and energy and, owing to current global population growth trends, this situation is projected to deteriorate in the near future. Buildings consume approximately 40 percent of total global energy: during the construction phase in the form of embodied energy and during the operation phase as operating energy. Embodied energy is expended in the processes of building material production (mining and manufacture), on-site delivery, construction and assembly on-site, renovation and final demolition. Recent studies have considered the significance of embodied energy inherent in building materials, with a specific focus on this fraction of sequestered energy. Current interpretations of embodied energy are quite unclear and vary greatly, and embodied energy databases suffer from problems of variation and incomparability. Furthermore, there is no reliable template, standard or protocol regarding embodied energy computations that could address these problems in embodied energy inventories. This paper focuses on the analysis of existing literature in order to identify differing parameters so that development of a consistent and comparable database can be facilitated.

Introduction

The construction industry, along with its support industries, is one of the largest exploiters of natural resources, both renewable and non-renewable, that is adversely altering the environment of the earth [1], [2], [3], [4], [5], [6]. It depletes two-fifths of global raw stone, gravel, and sand and one-fourth of virgin wood, and consumes 40 percent of total energy and 16 percent of water annually [3], [7], [8], [9], [10]. Fig. 1 shows the percentage share of building's energy consumption over the span of eight years and its anticipated growth trends by the end of 2030. The anticipated growth in global population from 6.5 billion in 2005 to approximately 9.0 billion in 2035 [11] indicates the grave situation of material and energy consumption as a result of the anticipated increase in construction activities. The construction sector, in particular, is one of the largest consumers of commercial energy in the form of electricity or heat by directly burning fossil fuels [1]. Urge-Vorsatz and Novikova [8] assert that, during 2004, buildings alone depleted nearly 37 percent of the world's energy and this figure is anticipated to reach 42 percent by 2030. Construction activities not only consume energy, but also cause environmental pollution and emission of greenhouse gases, which lead to climate change. Therefore, it is urgent to review, as well as modify, current construction practices such as design and engineering methods, construction techniques and manufacturing technology to tame energy consumption.

The total life cycle energy of a building includes both embodied energy and operating energy [7], [12]:

• Embodied energy (EE): sequestered in building materials during all processes of production, on-site construction, and final demolition and disposal; and

• Operating energy (OE): expended in maintaining the inside environment through processes such as heating and cooling, lighting and operating appliances.

Until recently, only operating energy was considered, owing to its larger share in the total life cycle energy. However, due to the advent of energy efficient equipment and appliances, along with more advanced and effective insulation materials, the potential for curbing operating energy has increased and as a result, the current emphasis has shifted to include embodied energy in building materials [7], [12], [13], [14], [15], [16]. Ding [7] suggests that the production of building components off-site accounts for 75 percent of the total energy embedded in buildings [1] and this share of energy is gradually increasing as a result of the increased use of high energy intensive materials [9], [13]. Thus, there is a genuine demand to calibrate the performance of buildings in terms of both embodied and operating energy in order to reduce energy consumption [9], [17]. At a macro-level, proper accountability of embodied and operating energies will contribute to data and information needed to create an energy economy that accounts for indirect and direct contributions.

Langston and Langston [9] suggest that, while measuring operating energy is easy and less complicated, determining embodied energy is more complex and time consuming. Furthermore, there is currently no generally accepted method available to compute embodied energy accurately and consistently [12], [18] and as a result, wide variations in measurement figures are inevitable, owing to various factors [7], [9], [12], [18], [19].