A building is a complex product of different components of variable materials, structural importance, functional life, exposure constraints, and damage mechanisms. Each component of a building has a typical functional requirement and it should perform as per the prescribed function in its service life. Life cycle assessment (LCA) studies that have been conducted, to date, consider the service life of building and building components between 30 and 70 years with a most commonly used value of 50 years (
Table 1). However, the real picture is quite contradictory to these assumptions as the service life of buildings varies with materials, operation and maintenance and the surrounding environment [
1,
2]. This discrepancy may lead to inaccuracy of LCA analyses, and material and energy balance. Any building needs regular maintenance and replacement of its non-structural components to keep the building in performing conditions. In second half of the 20th century, a considerable number of buildings were constructed that need annual inspections and maintenance, influencing the national economy and competitive position of the construction industry [
3]. The maintenance and replacement intervals of existing buildings need to be optimized to achieve environmental, social and economic benefits. For new constructions, the estimated intervals of maintenance and replacements should be planned as concisely and wisely as possible. The integration of knowledge of building component durability and its structural and functional performance into building LCA could help conduct a realistic assessment of the environmental performance of building components [
4]. Due to the uncertainty associated with the use of assumed service life of a building, as well as the unavailability of service life data of building components, LCA studies have not frequently addressed the real energy consumed during maintenance and replacement activities. However, this energy (hereafter, named replacement energy) may be as much as 7% to 110% of the initial embodied energy, if the service life of building materials is not properly implemented in the design phase of a building [
4,
5,
6,
7]. The building life span, whether short or long, has discretionary effects on a building’s environmental performance. Short service life of buildings results in excessive solid waste, embodied energy and subsequent greenhouse gas (GHG) emissions during pre-use stage (extraction of material to construction). Long service life of buildings increases replacement of building components, resulting in an increase of replacement energy and prolonged use stage, increasing operational energy and GHG emissions [
1]. These two constraints need to be taken into account during material selection by considering the service life of the whole building, as well as its components, and is essential to achieve environmental performance while fulfilling social and economic objectives.
According to ISO 15686-1, “Service life is the period of time after construction, in which a building and its parts meet or exceed the acceptable minimum requirements of performance established” [
26]. The service life of building components largely depends on the materials’ properties, damage mechanisms, environment and quality of design, and work execution. This study aims to estimate the service life of buildings and building components and expected replacement intervals of non-structural components, and to assess the impact of this service life on life cycle environmental performance of buildings.
1.1. Service Life Estimation
Service life (SL) estimation of buildings is quite a complicated process that involves intensive data analysis as there is no proto-type in buildings. Each building is unique in its composition, material specification and architectural and structural design. Therefore, the SL estimation cannot be generalized and needs to be carried out on a component to component basis. Construction materials have different properties and damage mechanisms and behave differently in different climates. User requirements, degradation agents, and building performance against these agents are important factors to consider for service life planning [
27]. The state-of-the-art report on performance-based methods on service life prediction states that “Prediction of durability is subject to many variables and cannot be an exact science” [
28]. Therefore, efforts should be made to achieve the most likely estimate by considering the most reliable data sources.
SL prediction methods should be generalized, easy to apply to a variety of materials, user friendly and give clear boundary limitations [
29]. SL was first studied by Legget and Hutcheon in 1958. However, SL estimation has been under the limelight since the 1990s by different standard institutes. The Guidelines for Service Life Planning were first published by the Architectural Institute of Japan (AIJ) in 1989 followed by British Standard Institute (BSI) in 1992 and Canadian Standards Association (CSA) in 1995. International standard organizations (ISO) published ISO 15686-1, Building and constructed assets—Service Life Planning—Part 1 in 2000 [
30]. A series of publications on ISO 15686 were published afterwards, covering different aspects and procedures of service life predictions.
Service life can be estimated by deterministic, engineering and probabilistic methods. The probabilistic method is the research approach considering degradation probability of a building during a prescribed time. The deterministic method is a simple approach utilizing factors influencing the degradation of a building under certain conditions. The factor method, described in standard, ISO 15686-2 [
31], is the well-known deterministic approach. Engineering methods lie somewhere in between deterministic and probabilistic methods. Engineering methods are easy, and use the time-based degradation mechanism for interpretation [
32]. SL estimation needs a wide range of data from different sources and under different conditions. These information resources may be existing building data, information collected by surveys, manufacturer data, service life modelling, insurance companies and real estate data, and expert opinion [
33]. The engineering approach depends on structural properties of materials, loading conditions, chemical composition, and damage mechanisms in a buildings’ life time. However, there is a huge variety of chemical compositions in materials, degradation in different environments, and variable human influences, to treat all materials just the same. Accelerated life tests carried out on building components to predict SL give reasonably accurate results. It is still a big challenge to depict the realistic conditions for life tests. In addition, the accelerated tests are quite expensive. There are also some other approaches to predict SL by considering service life models and obsolescence factors [
1,
34]. This method can be used for existing buildings or to be built buildings with the same material. This method requires empirical data that cannot be collected for innovative materials. Acquiring data for service life models and time constraint can pose a challenge for the SL prediction approach.
The factor method is the deterministic method that uses seven factors to predict the service life behavior of the building in different climatic conditions and geographic locations. The factor method uses reference service life (RSL) of a building component as a baseline and seven factors to modify the RSL to estimated service life (ESL). The service life estimation is different from service life prediction in the sense that the first is meant for particular conditions, and the second is recorded performance over a prescribed time or referenced SL [
30,
35]. The factor method helps to estimate service life of building and building components using Equation (1) [
30].
where,
ESL = Estimated service life of building components
RSL = Reference service life of building components
Factor A = Quality of components including manufacturing, storage, transport and protective coating etc.
Factor B = Design level including incorporation, sheltering by rest of structure and surrounding buildings
Factor C = Work execution level, site management, workmanship level, weather condition during work
Factor D = Indoor environment conditions, humidity, ventilation, and condensation etc.
Factor E = Outdoor environment, microenvironmental conditions, weathering factors, building elevation etc.
Factor F = In-use conditions, mechanical impact, wear and tear, category user etc.
Factor G = Maintenance level, quality and frequency.
The method incorporates the material behavior, human involvement and degradation mechanism to interpret the ESL. The factor method is flexible, and it considers the combined effect of different deteriorating factors. The method needs judgement of factors as protective or deteriorating and requires fair and definite limitations on factors to avoid complexity [
36]. Reliable data is required for the RSL and factors for each building component. The availability of data and reliability of data sources play an important role in SL estimation. The data sources may be manufacturers of building products, test laboratories, government agencies reports, existing studies etc., [
37]. The most challenging issue in SL estimation is how to use effectively the available data to predict the SL of a structure that is to be built. In this study, the service life was estimated for most likely values (±5 years) using the factor method.
1.2. Environmental Life Cycle Assessment
The environmental life cycle assessment (ELCA), frequently known as life cycle assessment is a comprehensive tool to assess the environmental impacts of a product or system or service, in pre-use, use, and post-use stages [
38]. The ELCA was studied for the first time in the 1960s and up until the 1970s, it was used only to compare the packaging options of consumer goods. In 1969, the Midwest Research Institute conducted a study on LCA for a Coca Cola Company for different types of beverage containers [
39]. The studies in this period revolved around policy making and enterprises with a focus on solid wastes, energy consumption, and air pollutant impacts. In the 1990s, SETAC, conducted various workshops and published the first code of practice for life cycle assessment in 1993 [
40]. Afterwards, the international standards organization (ISO), was involved actively and published generalized procedures and methods for LCA in ISO 14040-44 in 1997–2000 [
38].
In the construction sector, ELCA was first applied in 1980s by Bekker to study the environmental implications of the use of renewable resources in buildings [
41]. ELCA was used in buildings to assess the environmental impacts of construction materials and is a credible solution to compare material sustainability [
42,
43,
44,
45]. Now, the ELCA covers a wide range of areas from building materials (i.e., bricks, cement etc.) to urban planning [
46]. The life cycle stages that are usually considered from life cycle assessment of buildings and building components include pre-construction, construction, use and end of life stages. Environmental product declarations (EPDs) involved the use of LCA to estimate environmental impacts for environmental declaration purposes for certification purposes [
47]. ELCA helps to improve the performance of building in its entire life span by first identifying hotspots and then by applying mitigation strategies [
47,
48]. However, the system boundaries, functional units and scope definition are unique for each building LCA study, resulting in variation in results among studies [
49,
50,
51].
Environmental performance of buildings is also defined as a quantified relationship between occupant’s comfort level and environmental impacts [
52,
53,
54]. Embodied and operational impacts are usually two main categories of environmental impacts. Embodied impacts are static and further divided into pre-use embodied impacts and replacement embodied impacts [
6]. Pre-use embodied impacts are the impacts due to extraction, manufacturing and construction of buildings and replacement embodied impacts are a result of renovations, replacements and maintenance in the active service life of buildings. The operational or use stage impacts are dynamic in nature and occur in the service life of building [
55,
56]. Better building performance can be achieved by considering factors including material selection, construction techniques, cost factors, and cleaner production strategies (CPS).
Whilst Australia accounts for only 0.32% of the world’s population, its per capita GHG emission is extremely high compared to countries with similar economies (UK, Mexico, South Korea) i.e., 26 tonnes GHG emissions per capita per year as opposed to 13 tonnes per capita GHG emissions for South Korea, 10 tonnes per capita GHG emissions for UK and 20.3 tonnes per capita GHG emissions for Canada [
57]. Australia is the second driest continent after Antarctica [
58]. The annual rainfall is highly variable and central Australia is mostly arid with only 6% arable land in coastal areas [
59]. Water is the most precious commodity and its scarcity is covered by desalination of sea water [
60,
61,
62]. Water mapping in the construction industry helped to identify need for reducing the life cycle water demand/footprint of buildings by using renewable resources. In addition, Australia’s per capita waste generation is 2.6 tonnes per year as compared to 0.706 tonne per capita per year for US, out of which 0.8 tonnes per capita per year is construction and demolition waste [
63]. Therefore, these two issues are inevitable for assessment of the environmental impacts of building and construction industry at the planning stage of buildings using an ELCA to discern strategies to avoid these environmental consequences. This study thus considered these impact categories, including cumulative energy demand, GHG emissions, water consumption and land use to assess the environmental performance of buildings.