life cycle cost analysis of different walling materials with an environmental approach:
Climate change, environmental concerns, and economic problems pose challenges to the construction sector in Iran, which must provide affordable solutions while addressing environmental issues. Hence, natural earthen building materials are critically needed to reduce energy-intensive and costly construction practices dramatically. The purpose of this paper is to provide a framework for comparing life cycle assessments (LCA) and life cycle costs (LCC), for load-bearing walls of a single-family affordable housing unit in a desert part of Iran, Ardakan City.
To do so, both LCA and LCC for the unit were performed, considering a cradle-to-site perspective. For this purpose, 22 load-bearing wall systems are assessed, including 18 stabilized and unstabilized earthen construction techniques, such as adobe, rammed earth (RE), and compressed earth block (CEB), in addition to four conventional wall assemblies of fired brick (FB), autoclaved aerated concrete block (AAC), ceramic block (CB), and concrete masonry unit (CMU). As well as assessing the environmental impact and life cycle costs associated with the life cycle of each wall, the optimal assembly of the wall is also examined.
Results show that unstabilized earthen walling alternatives have significantly lower environmental impacts than conventional materials. Conclusions Sensitivity analysis indicates that by utilizing local materials to the maximum extent possible, impacts can be further minimized. Considering the results, transportation may even account for a greater proportion of EI than wall components.
Housing, as one of the basic needs of everyone, presents a particularly challenging situation in emerging economies. The UN reports that worldwide, the population may reach 9.6 billion by 2050, which will naturally increase housing demand. In this context, the building sector contributes 39% of CO2 emissions related to energy, leading to global warming (Nejat et al. 2015). Therefore, urbanization and construction exacerbate the pressure on the environment, by consuming finite resources, releasing greenhouse gases (GHG), generating energy, and generating waste (Pomponiet al. 2017).
In recent years, Iran’s population has grown rapidly, particularly in urban areas. In light of this, Iran’s government faces a considerable challenge in providing low-cost housing units for a large population. Observing the massive growth of new constructions in economies in transition, some researchers have shown that if nothing is done, greenhouse gas emissions from buildings will be more than double over the next few decades (Nematchoua et al. 2020), and on the other hand, Iran ranks first in the Middle East is among the seven most carbon-emitting countries in the world (GCP 2021).
Because Iran is following the global trend of increasing residential demand, there is an urgent need for affordable and low-carbon strategies to be integrated into new housing construction (MOE 2022; MRUD 2022).
Meanwhile, Iran’s regulations have been developed focusing on operational energy reduction while ignoring embodied carbon emission, which means due to increased energy efficiency policies, buildings are expected to become more efficient during their operation stage, thereby increasing embodied carbon (Pomponi et al. 2017).
To address this issue of carbon intensity in the embodied stage, it is important to select materials and construction systems that have the least impact on the environment. (Cabeza et al. 2014). Generally, Iran’s residential built environment exhibits two main types of construction: contemporary and traditional. In the former, construction and building technologies follow conventional construction trends; which uses highly processed, industrially produced materials (e.g., concrete, aluminum, steel, glass), resulting in natural resource depletion (Bribián et al. 2011; Fernandes et al. 2014).
However, in the latter, earthen building techniques and earth-based materials are used, as Iran has a rich history in earthen architecture. Earthen materials have been shown to have significant environmental benefits, although few studies have examined the impacts of earthen construction techniques on the environment within the country.