Life cycle assessment was used to evaluate the environmental
impacts of the twenty proposed transitional shelter design options.
This assessment method was developed to quantify the material
use, energy use, and environmental impact associated with specific
products, services, and technologies. LCA is described and standardized
in ISO1440 [34] and consists of four steps: the definitions
of goal and scope, the development of life cycle inventories, an
impact assessment, and interpretation [35]. Over the past few decades
since its development, LCA has been established as the main
method for quantitatively assessing the environmental impacts of
goods and processes throughout their life spans. LCA models assume
causeeeffect relationships between the environment and
human activities and highlight their impacts and consequences
[16]. The term “environmental impact” is used in LCA to refer to the
effects of the studied system on the environment. These impacts
depend directly on the evaluation method used during the impact
assessment step. For this research project, the IMPACT 2002þ [36]
evaluation method was used for the impact assessment. This
method models the cause-effect chain up to the end point or
damage point. This type of evaluation method is known as damageoriented
and is very useful in assessments that have a global
context. In this method, four categories are considered: human
health as assessed by the disability-adjusted life year (DALY);
ecosystem quality as assessed by the potentially disappeared fraction
(PDF) over a certain area and during a certain period per kg of
emitted substance (PDF.m2. yr); climate change as assessed by the
global warming potential as described by the Intergovernmental
Panel on Climate Change [37] (IPCC) in terms of kg CO2 equivalents;
and resources as assessed by the energy demand in mega joules
(MJ). The results are normalized for the respective impact categories
using the following factors, which represent the yearly
emissions of one European citizen: 0.0071 DALY, 13,700 PDF. m2. yr,
9950 kg CO2, and 152,000 MJ [36]. This allows the results to be
expressed in a single unit of points easing the processing of the
results but makes them sensitive to the normalization factor. The
values used on the normalization process can be considered as a
good proxy for calculation on a global scale. As a final step, the
results for the four impact categories are summed, considering an
equal contribution from each impact category to the total result,
and presented as a single score [36].