ABSTRACT
The building sector is one of the largest consumers of natural resources and energy in the world. Design strategies to improve the energy efficiency can be a solution to decrease impacts of a building. To evaluate the correct way to choose design strategies in buildings, they should be analysed with a multidisciplinary approach based on sustainable development. The method presented herein is based on a system of indicators that allows performing a comprehensive evaluation of alternative design solutions. Through the Life Cycle Assessment, Life Cycle Cost Analysis, indoor comfort conditions, future effects of climate change and the Multi Criteria Decision Making (COPRAS) it is possible to choose the most sustainable design strategies in buildings. A multi-family social building, located in Milan, north of Italy, was evaluated based on a 100-year lifespan. Six design solutions with different structure and envelopes of the building were evaluated. The results have shown that the design solution with the highest sustainable behaviour degree is the reinforced concrete frame with rectified bricks (100%), followed by reinforced concrete frame with cellular concrete blocks (75,4%) and by X-Lam and wood fiber (20,79%), compared to the actual design building. This research pointed out the need of using a multicriterial method to assure the right selection of design strategies for obtaining more sustainable buildings.
Keywords
Sustainable buildings; Life cycle assessment; MCDM; Energy efficiency.
INTRODUCTION
The building construction sector is considered one of the largest consumers of natural resources and energy. Buildings consume 30‒40% of all primary energy and natural resources over their lifespan (construction, operation, maintenance and demolition) and respond for 30% of the emission of greenhouse gases in the world [1,2]. An appropriate choice of design strategies reduces the energy demand of buildings [3-5]. Often, researches focus on the reduction of energy consumption during the operational phase of buildings [6, 7]. The increase of energy efficiency in the buildings' sector is reducing the energy consumption during the operational phase. But, the improvements to design a more energy efficient building require more materials and, consequently, the environmental impact of the building in its construction, maintenance and demolition phases is greatly increased [8-13]. Therefore, studies have addressed a more holistic approach, which covers from the production process of materials involved in the construction all the way to the demolition and recycling phases. Through a methodology based on sustainable design of buildings, it is possible to reduce their environmental impact and improve the quality of life of the inhabitants. In recent years different methods have been developed. One of these is the Life cycle assessment (LCA) use to analyse the environmental impacts attributable to the life cycle of products and services [14]. Through LCA is possible to analyse different environmental impact categories arising from the construction, use, maintenance and demolition of the buildings. Recent studies show different approaches to apply the LCA in buildings. Stazi et al. [15] studied 70 Italian residential buildings, of which five case studies were monitored and one case underwent an in-depth environmental evaluation. The authors used the Global Warming Potential, Ozone Layer Depletion Potential and the Acidification Potential to analyse the building using the LCA method. Motuziene et al. [11] analysed the life cycle of a single-family house in Lithuania considering three impact categories: Primary Energy Demand, Global Warming Potential and Ozone Layer Depletion. The goal of the study was to improve the energy efficiency of buildings, given the impact on the environment in the life cycle. Atmaca and Atmaca [16] studied the life cycle of two different residential buildings in Turkey through two impact categories: the Primary Energy Demand and the Carbon Dioxide Emissions. These studies show a different form to analyse the buildings through the LCA method. The selection of the impact categories, like as the analyse of the final results, are evaluate in an arbitrary manner. The impact categories more used were the Global Warming Potential followed by the Energy Demand [11, 15, 16]. This is because the energy efficiency aspect is the most relevant parameter for the researchers, when evaluate buildings through a LCA. Often, the LCA method is associated with the Life-Cycle Cost Analysis (LCCA) to evaluate the cost of the building in the life cycle [17-19]. Studies on LCCA have been developed to analyse the best constructive choice in buildings and evaluate which phase presents the highest cost [17-19]. Often, the use of the methods LCA and LCCA in buildings does not help the decision-making [11, 20, 21]. For this reason, Multi Criteria Decision Making (MCDM) frequently appears like a complementary tool to LCA or LCCA [11, 21]. There are many ways to apply different multi-criteria analysis methods. One of the most used is the analytic hierarchy process (AHP). Proposed for the first time by Saaty [22] as a multi-criteria decision-making tool, which attempts to determine weighting factors for the criteria under consideration through pairwise comparisons. The MCDM is a great tool to analyse different parameters in the same case study, however, its application in the LCA is not common. Through the MCDM, LCA and LCCA, Motuziene et al. [11] analysed three different types of envelopes in a single family-house in Lithuania. The results show that the MCDM method is an important tool to analyse different parameter in buildings. To analyse and choose the correct design solutions in buildings is of paramount importance bases its one decision not only in one parameter. The aim of this study is to propose a method for the selection the design solution, that combines adaptive thermal comfort, LCA, LCC and MCDA methods, and to illustrate its performance in a multi-family social building located in Milan considering the effect of climate change in buildings. The presented approach is based on a complex system of criteria that enables comprehensive evaluation of the alternative design strategies. The proposed method can be applied for different types of buildings at different locations.
METHOD
The method used the three pillars of the sustainable development to evaluate the design strategies in buildings. The four parameters analysed are: the comfort hours, the primary energy demand in the life cycle, the carbon dioxide emissions in the life cycle and the cost in the life cycle. The method is the combination of LCA, LCCA, indoor comfort conditions, future effects of climate change and MCDM to analyse the design strategies in buildings (Fig. 1).