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Article

A Systematic Approach to Developing Sustainable Post-Disaster Shelters in the Southern Region of the United States

by
Alka Khadka
1,
Soojin Yoon
2,*,
Richard G. Walker
3,
Amy King Lewis
2 and
Yeonjin Bae
4
1
Intertek-PSI, 1137 S Jupiter Rd, Garland, TX 75042, USA
2
Division of Engineering Technology, Oklahoma State University, 511 Engineering North, Stillwater, OK 74078, USA
3
College of Civil and Environment Engineering, Oklahoma State University, 511 Engineering North, Stillwater, OK 74078, USA
4
Building Technologies Research and Integration Center (BTRIC), Oak Ridge National Laboratory, 1 Bethel Valley Rd, Oak Ridge, TN 37830, USA
*
Author to whom correspondence should be addressed.
Buildings 2024, 14(8), 2536; https://doi.org/10.3390/buildings14082536
Submission received: 19 April 2024 / Revised: 1 July 2024 / Accepted: 30 July 2024 / Published: 17 August 2024
(This article belongs to the Special Issue Advanced Building Technologies for Energy Savings and Decarbonization)
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Abstract

:
This study aims to propose a sustainable shelter design involving energy savings, less environmental impact, and rapid construction. The structural design of the shelter is based on 3D-printing technology. Sustainability assessments, including life cycle analysis (LCA), life cycle energy assessment (LCEA), and energy justice of the designed shelter, were conducted to prove the sustainable shelter design. The outcomes of this study for several scenarios will not only allow decision-makers to design permanent shelters with maximized utilization of limited resources but also help local communities strengthen their ability to recover with minimal outside assistance post-disaster. Furthermore, residents can utilize the sustainable shelter to maintain critical functions, including business continuity and local business in emergencies.

1. Introduction

Natural hazards result in an average of 45,000 deaths yearly [1]. The 2004 Sumatra tsunami caused between 200,000 and 310,000 deaths, while Hurricane Katrina, which struck the US Gulf Coast in August 2005, resulted in the deaths of 1833 people and caused property damage valued at USD 81 billion [2]. Moreover, Hurricane Katrina damaged 200,000 homes in New Orleans, of which 41,000 were rental homes for low-income families [3]. The impacts of such disasters extend to housing instability, especially among low-income families who face significant challenges in coping with the aftermath [4]. Disaster shelters play a crucial role in providing temporary accommodation, but existing solutions often lack adequate space, protection, and amenities. Additionally, currently provided temporary shelters are made of nylon, polyester wool, and fiber-reinforced mylar, which are unsustainable in terms of cost and environmental impact [5,6]. Therefore, addressing the shelter needs of disaster-affected populations requires a coordinated and comprehensive approach involving pre-disaster planning, immediate response, and long-term rehabilitation efforts [7].
The primary purpose of this study is to propose a sustainable permanent shelter design involving energy savings, reduced environmental impact, rapid construction, and cost-effectiveness, which will contribute to the resilience of local communities and positively affect business continuity post-disaster. This study considers the availability of energy to power a 3D printer onsite and adequate road conditions for transporting heavy precast modules to create alternative solutions post-disaster. The proposed methodology consists of five steps: (1) structural design, (2) construction method, (3) scenario development, (4) sustainability assessments, and (5) decision-making for the shelter design. The structural design of the shelter is developed with disaster-resistant construction materials and a shape that enhances resilience. Three-dimensional printing (3DP) printing technology is rapidly being applied in the construction field. Due to its quick construction and design flexibility, the market value of concrete 3D printing was expected to reach USD 56.4 million by 2021 [8]. Three-dimensional printing technology is utilized for the rapid construction method of the shelter. The sustainability assessment includes a life cycle assessment (LCA), life cycle energy assessment (LCEA), and energy justice assessment. Various scenarios are created based on onsite 3DP, insulation types, and HVAC (Heating, Ventilation, and Air Conditioning) systems. Therefore, the proposed shelter design scenario would provide a permanent shelter design pre- and post-disaster for resilience, promoting sustainability in terms of the environment, energy consumption, and the economy. The designed shelter also offers commercial uses, which can uplift the economic conditions of the local community after the transition of the victims to their habitat.

2. Background and Related Studies

2.1. Current Research in Sustainability

In the construction sector, there is a growing recognition that sustainable development must address the goals of environmental quality, well-being, and social justice. To assess and promote sustainability in building practices, Building Industry Reporting and Design for Sustainability (BIRDS) has introduced a new measurement system [9]. This system encompasses three essential components: environmental performance (assessed through LCA), energy performance (evaluated through LCEA), and economic performance (analyzed using life cycle cost analysis—LCCA). Current research in the construction sector demonstrates a significant focus on utilizing LCA, LCEA, and LCCA for studying building and infrastructure projects.
Ashworth et al. [10] stated that LCA and LCCA assist stakeholders in making well-informed decisions during the early design phase of buildings and infrastructure. In addition, they discussed the promising benefits of integrating life cycle tools with Building Information Modeling. Researchers have utilized this integration to compare different solutions and select sustainable options that prioritize both environmental well-being and user well-being. Choosing a method for decision-making can greatly increase the effectiveness and implementation of a project, such as the many methods shown by [11]. Similarly, LCA and LCCA were applied in the study to evaluate the use of phase change materials (PCMs) in office buildings considering environmental and economic performance. The results revealed that while the overall environmental impact was reduced, the cost of the construction stage increased significantly [12]. Vasishta et al. [13] aimed to understand the environmental impacts and costs over the complete life cycle for precast and cast-in-place building systems and found that precast building systems have lower life cycle environmental impacts and life cycle costs compared to cast-in-place building systems. Liang et al. [14] conducted LCA and LCCA to compare a mass timber building and a concrete building to contribute more information to building developers and policy makers. The study concluded that the mass timber building has less environmental impact than concrete construction. The authors of [15] compared the eco-efficiency of 3D printing technology to conventional construction methods using LCA and LCCA techniques, and the results revealed that 3D-printed buildings are environmentally favorable, and the cost of construction is reduced by 78%.
Utama and Gheewala [16] performed LCEA to determine the energy consumption of buildings considering envelope materials. They showed that double-wall envelopes have almost two times less energy consumption than single-wall envelopes in the long run. Similarly, ref. [17] compared the embodied energy and operational energy of concrete- and steel-framed structures using the LCEA method. The results show that concrete has the highest influence on embodied energy for concrete-framed structures, while beams represent the largest component of embodied energy for steel-framed structures, with no significant differences in operational energy between the two structures. An integrated assessment (LCA, LCEA, and LCCA) was performed to compare the environmental impacts, energy use, and economics of a green roof against a built-up roof. The environmental impact analysis indicates that the built-up roof has 3 times more environmental emissions, 2.5 times more energy, and 50% higher costs than the green roof over the building life span when considering the material acquisition life stage, use stage, and maintenance stage. The authors of [18,19] found that LCA, LCCA, and LCEA are mostly carried out for advanced building designs but rarely in traditional buildings.

2.2. Shelter for Disaster Relief

Emergency shelters provide natural disaster victims with safety, security, support, and their own place to cope with the destruction during disaster recovery [20]. Table 1 outlines the current state of emergency shelters that are provided to refugees and disaster survivors.
As shown in Table 1, WeatherHyde was designed by Parsoon Kumar to solve homelessness targeted at people in Southeast Asia. This temporary shelter can be ready in 15 min and is made of nylon, polyester wool, and fiber-reinforced mylar. The total area of the shelter is 2.69 m2 and costs USD 199 [21]. Better Shelter [22], constructed with polyolefin panels and galvanized steel, along with high-density polyethylene fibers, costs USD 1260. The construction duration is about 4–6 h, and its total area is 17.47 m2 [22]. The temporary shelter Hexyurt (2011) is the modern adaptation of a Yurt (a tent used by nomads for a hundred years), and its design is less susceptible to the winds. It varies in size from 3.8 to 25.64 m2, can be built in 4 h, and costs approximately USD 229.71. The materials used are cloth, wood, plastic, Polyiso insulation, OSB, sandwich panels, and cardboard [23]. The Emergency Smart POD (2015) is constructed of all metal with a steel frame covered in aluminum, making it the most durable and permanent option. This comes with the fastest erection time of 20 min and the largest area, but it is also the most expensive at USD 195K–USD 485K. The MTS DOMO System [25] offers similar features to the Hexyurt with a Yurt dome-like structure but offers a slightly more durable design with higher-grade materials, with the biggest difference being its lack of insulation. This also comes with a faster erection time of just 25 min but also a much higher cost of USD 4625. Though the current temporary shelters provided are fast to construct, they lack space, protection, sanitation, and reusability after people move back to their homes.

2.3. The 3D Printing of Structures

One of the emerging technologies in the construction sector is 3D printing. Along with rapid construction, 3D printing involves less waste production due to construction and design flexibility [8]. Specifically, there has been a significant expansion of concrete 3D printing, with a projected value of USD 56.4 million in 2021 due to the increasing number of innovative construction projects being planned [8]. Table 2 showcases notable examples of concrete 3D-printed buildings from around the world. One such example is the WinSun ten 3D-printed house, which was unveiled in 2014. These houses were constructed using offsite 3D printing, and each took just one hour to print. With an area of 18.58 m2, the cost of these houses amounted to USD 4800 [26]. Another noteworthy project is the onsite 3D-printed home by SQ4D, located in New York. This home, with an area of 12.91 m2, was printed in just two days and is currently available for sale at USD 3 million [27]. The 3D-printed community by ICON and Lennar, with homes costing over USD 470K and measuring around 148 m2, exemplifies strong and energy-efficient construction. From Table 2, it becomes evident that 3D printing requires less time for the printing process, whereas offsite 3D printing offers the advantage of lower construction costs.

3. Methodology

This research proposes an optimal design of a shelter considering sustainability with five steps, as shown in Figure 1. The first step is (1) structural design, focusing on disaster-resistant shelters with modular features to facilitate multipurpose usage. Next, step (2) is the construction method employing concrete 3D printing, a rapid and efficient method during an emergency, and step (3) is scenario development, with six options based on the insulation and HVAC system used. Then, step (4) is evaluating sustainability in the six proposed scenarios by conducting LCA, LCEA, and energy justice assessment. Depending on the results of the sustainability assessment, this step will provide an optimal decision for the shelter design.

3.1. Step 1: Structural Design

The objective of step 1 is to provide a structural design of a permanent shelter by considering key performance criteria: (1) disaster resistance, (2) multipurpose functionality of the unit, and (3) unit modularization. To achieve this, we have conducted a comprehensive literature review focusing on exemplary buildings that have withstood disasters and analyzed their construction materials.
One such remarkable building is Alma Hall, which is made of concrete, brick, wood, and metal structural beams and withstood the Johnstown Flood (1889). It was built in 1884 and is capable of housing 264 people [33]. Another notable example is the UST Main Building, known as the first EQ resistance building in Asia, which was built in 1927 and faced major earthquakes in 1937, 1968, 1970, and 1990. The construction materials of the building are concrete, bricks, wood, metals, and aggregates [34]. Similarly, the Sand Palace built in 2017 survived the powerful Hurricane Michael that occurred in the year 2018. The construction materials for the building are concrete, rebar, and steel cables [35]. It can be observed that concrete as the construction or structural element in the above buildings is the major cause of disaster resistance. Furthermore, we can learn valuable insights from the East Pagoda at Yakushiji Temple in Japan, which was built 1300 years ago and has endured various earthquakes. It is believed that its central core pillar is the major reason behind its resistance to earthquakes. During an earthquake, the central core pillar acts as a vibration suppression element [36]. This vibration suppression absorbs and minimizes ground vibrations. When the shelter shakes during an earthquake, the overall shaking is countervailed and minimized by the core that shakes out of sync within the building [36].

3.2. Step 2: Construction Method

Three-dimensional printing has been a big buzz in the construction sector over the past decade. Like every method, 3D printing has its own pros and cons. Its benefits are fast construction, design flexibility, reduced human error, and waste reduction, whereas the disadvantages are high cost and a lack of qualified labor [8]. Different types of 3D printers are available for sale in the market [37]. Table 3 lists the 3D printers that are available for sale in the market and their features.
ICON Vulcan II can build within the dimensions ∞ × 11.1 m × 3.2 m and has a printing speed range of 12–25 cm per second [38]. Similarly, COBOD BOD2 constructs the structure in gantry style with a speed limit of 1 m per second. It can print dimensions up to 14.62 m × 50.52 m × 8.14 m [39]. All of the 3D printing systems shown in the table use gantry-style printing. A gantry in 3D printing is the frame structure that supports the printer while moving along the X/Y-axis as the printer head moves around to print the part on the build platform [41]. A gantry-type printer can print both large and small buildings. The hopper in a gantry-type printer increases the possibility of controlling the material flow for non-continuous printing. Gantry printers are mobile and can be used for onsite as well as offsite printing [41]. A sulfur concrete mix is considered for this study. The component materials of the mix are silica sand, gravel, sulfur, air, and polypropylene, and their content by volume is 44%, 34%, 20%, 1%, and 1%, respectively. The mix yields a comprehensive strength of 40 MPa without the addition of polypropylene fibers. The addition of fibers to the mix is assumed to increase the comprehensive strength and create a self-reinforced printable mix [16,42,43,44].

3.3. Step 3: Scenario for Shelter Design

Insulation and HVAC systems play a significant role in the energy consumption of the house [45]. Scenarios for the design of a shelter were developed considering insulation types and HVAC systems. The insulation types are an air cavity and expanded polylactic acid (E-PLA); the HVAC systems are Packaged Terminal Heat Pump (PTHP), Rooftop Unit (RTU), and variable refrigerant flow (VRF) systems. Figure 2 shows that six different scenarios are derived from the insulation types and HVAC systems. In scenario A-PTHP, the exterior wall has air cavity insulation, and the HVAC system is a PTHP. Similarly, in E-PTHP, the exterior wall uses E-PLA insulation, with the HVAC system being a PTHP.
In building techniques, the thermal transmittance value can be improved by incorporating air gaps or layers of insulation between the components of building elements. The use of 3D printing technology offers designers the flexibility to create printing layouts with air cavities that meet both thermal and structural requirements. The arrangement of these cavities significantly affects the thermal transmittance value of hollow concrete blocks, as it involves the simultaneous occurrence of conduction, convection, and radiation heat transfer processes. By utilizing different cavity configurations, it is possible to reduce thermal transmittance by approximately 20% [46]
In situations where the desired thermal transmittance values cannot be achieved through the configuration of air cavities, it is recommended to utilize cavity-filling materials instead of adding additional insulation layers. These cavities can be filled with insulation materials possessing specific thermal properties, which aid in achieving the target U-value. In the conducted study, hollow brick activities were tested with three different filling materials: dry sand, polystyrene, and polyurethane. The introduction of these fillings resulted in a significant reduction in thermal transmittance. In particular, the sand filling led to a reduction of 54.3%, while polystyrene and polyurethane fillings achieved a reduction of 80.4% [47]. One promising alternative to expanded polystyrene is expanded polylactic acid (E-PLA), which is characterized by a low density, sustainability, and an environmentally friendly nature. E-PLA exhibits thermal properties like expanded polystyrene and can be effectively used as a replacement in various applications [48]. Regarding the material properties, E-PLA has a density of 30 kg/m3, a thermal conductivity of 0.03 W/m·K, and a specific heat of 1.483 J/g·K. Meanwhile, the air cavity has an ideal gas density, a thermal conductivity of 0.0242 W/m·K, a specific heat of 1.00643 J/g·K, and a viscosity of 1.7894 × 10−5 kg/m·s. The material properties of the air cavity and E-PLA are sourced from [42].

HVAC System Options

The HVAC system plays a crucial role in maintaining a comfortable indoor environment for buildings. Selecting the appropriate HVAC system is important for achieving optimal energy efficiency, occupant comfort, and indoor air quality [45]. Among the various options available, the three suitable HVAC systems for this shelter design are the Packaged Terminal Heat Pump (PTHP), Rooftop Unit (RTU), and VRF systems. The choice of an HVAC system depends on factors like the building size, occupancy level, geographical location, and climate zone. Figure 3 provides an overview of the specifications, advantages, and disadvantages of PTHP, RTU, and VRF systems. An appropriate HVAC system is selected with the careful consideration of these factors to operate the building comfortably.

3.4. Step 4: Sustainability Assessment

3.4.1. Life Cycle Energy Analysis (LCEA)

Life cycle energy assessment (LCEA) is an approach to the identification and quantification of all energy input to a building in its life cycle. Buildings consume energy directly or indirectly in all phases of their life cycle from start to end (i.e., cradle to grave); hence, they are analyzed from the life cycle point of view [18]. The system boundaries of LCEA include the energy use in three phases of the building life cycle; these are the manufacturing phase, operation phase, and demolition phase, which can be seen in Figure 4 [30,52]. The manufacturing phase encompasses the production and transportation of the building materials to the site, the installation or construction of new buildings, and the renovation of existing buildings. The operation phase includes all of the activities that occur during the use of the buildings throughout their life span. The demolition phase consists of the destruction of existing buildings and the transportation of the demolished materials to the landfill or recycling plants.
The corresponding energy required in these three phases is embodied energy, operational energy, and demolition energy. Embodied energy is related to the energy required for the extraction of raw materials, the production of construction materials from raw materials, the transportation of these materials to the construction site, and the construction and renovation of the building. Operational energy is the energy required to operate the building comfortably for the occupants over its life span and includes the energy consumed by HVAC and appliances. Demolition energy is the energy required to demolish and transport the dismantled materials.

3.4.2. Life Cycle Assessment (LCA)

A technique for assessing environmental aspects and potential environmental impacts associated with the development of a product and its potential impact throughout its life from the cradle to the grave, including raw material acquisition, processing, manufacturing, use, and finally, disposal, is called life cycle assessment (LCA) [53]. The framework of LCA consists of four phases, i.e., (1) goal and scope definition; (2) life cycle inventory analysis; (3) life cycle impact assessment; and (4) life cycle interpretation. The goal and scope define the objectives, system boundaries, and functional units for the study. Life cycle inventory (LCI) analysis deals with the collection of the data, the selection of the data source for the assessment, and the compilation of inputs and outputs of each stage of the life cycle. Impact assessment aims to determine the contribution of each selected material to the environment. The impact can be measured using different impact categories. The last step is the interpretation of the observed results through an impact assessment and the determination of better alternatives if the results are negative [53].

3.4.3. Energy Justice

Energy justice serves as a conceptual framework for promoting the fair distribution of benefits and costs for energy services and facilitating impartial decision-making in the energy sector [53]. Fetanat et al. [54] and Sovacool and Dworkin [55] evaluate energy justice using four criteria: availability and affordability, rights, social aspects, and environmental issues. Availability emphasizes the provision of sufficient energy services of high quality to all individuals. Affordability, on the other hand, advocates for equitable access to energy as cheap as possible, especially to disadvantaged groups, so that there will be no issues with energy needs. Rights include intragenerational equity, due process, and intergenerational equity. Intragenerational equity focuses on the right of all people to fairly access energy services, whereas intergenerational equity centers on the right of future generations to enjoy a good life undisturbed by our energy activities. Due process relates to energy activities performed with respect to due process and human rights. Social aspects have three sub-criteria: resistance, transparency and accountability, and intersectionality. The social aspects criterion evaluates the resistance of a scenario to challenges, the transparency and accountability in providing information and making decisions, and the attention given to the diverse social groups and vulnerable sections of society in the decision-making process. Sustainability and Responsibility are two sub-criteria of environmental issues. This criterion examines the effects on existing energy sources and addresses concerns related to water and soil pollution, toxic emissions, climate change, and global warming. It concerns understanding the impact of a scenario on the maintenance of alternative energy sources and evaluates its potential consequences on environmental pollution, emissions, and long-term climate patterns [54,55]. Much of this decision-making needs to ensure balance, and to maintain the most objective balance of needs, the use of decision-making methods can also be utilized in complex situations [56].

4. Outcomes

4.1. Structural Design

4.1.1. Disaster-Resistant

In support of our literature review, we have recognized the pivotal role of concrete as a construction material and central core pillar for disaster-resistant structures. Therefore, in our shelter design, we have chosen to incorporate concrete as a construction material and concrete central core pillar to resist potential disasters. In designing the structure, particular attention was paid to the literature review and what has shown the best performance in various locations and conditions in search of the most universal design. The proposed design was created by this team and based on a mixture of existing structures and current shelter designs to offer the best design for optimal performance and constructability in any location. Autodesk Revit 2023 was used for the comprehensive design of the shelter, which is illustrated in Figure 5. Its dimensions include a height of 2.4 m and nearly equal lengths and breadths of approximately 19.8 m. The 3D-printed exterior wall has a width of 50.8 in, while partition walls measure 10 cm each. The depicted shelter is configured to accommodate four suites, each comprising a kitchen space (KS), living space (LS), two bedrooms (BDs), a restroom equipped with a washer and dryer, and a storage room (S). The shelter’s shape resembles an octagon for a more stable configuration to resist disasters.

4.1.2. Multipurpose

The proposed designed shelter can be used for both commercial and residential purposes. Figure 5 showcases its residential functionality. In a commercial context, the shelter can be utilized as a medical facility, collaborative workspace, and storage area. This adaptability to multiple purposes and the reusability of the proposed shelter design provide an opportunity for the local community to improve their economic conditions once the affected individuals return to their homes. The ability to repurpose also contributes to long-term sustainability as shelters can continue to serve the evolving needs of the community, ensuring their ongoing usefulness beyond the initial emergency phase. Multipurpose disaster shelters offer a comprehensive solution that addresses immediate needs while supporting long-term recovery and development in disaster-affected areas.

4.1.3. Unit Modularization

Figure 6 showcases the modular nature of the designed shelter, highlighting its expandability, stackability, and accessibility. This modularity offers several significant advantages in disaster scenarios. First, the ability of the shelter to expand and adjust its size allows for efficient space utilization. In situations where space is limited, this feature ensures that a large number of victims can be accommodated within a confined area and that housing solutions are provided for a greater number of individuals. Second, the stackable design of the shelter enables the vertical utilization of space, where multiple units can be stacked on top of each other without compromising safety and stability. This vertical expansion maximizes the use of available land and further increases the capacity of the shelter to accommodate more victims. The shelter’s accessibility features play a crucial role in ensuring the safety, security, and well-being of its occupants by considering easy and equal access to occupants. Moreover, the convenient modularization of the shelter facilitates its rapid multiplication and deployment. The standardized components and assembly methods enable the quick replication of shelter units to meet the immediate needs of the affected population. The modularity not only optimizes space utilization but also promotes safety, security, and a homey atmosphere for individuals experiencing emotional and mental distress due to a disaster.

4.2. Construction Method

The designed shelter is constructed utilizing the COBOD BOD2 3D printer. The printer operates by adding layers of prepared mortar through a nozzle. The 3D printer is supported by software COBOD Slice converts 3D models from any CAD/ BIM software for printing preparation. The printer operates on 3 A, 400 V three-phase power. Each printed layer has a width of 7.6 cm and a height of 3 cm [39]. Figure 7 provides details of the printer’s configuration for the exterior walls, including the cavity walls and a side view of the printed walls.
For printing the exterior walls of the shelter, the speed is set to 63 cm per second, allowing the walls to be printed in approximately 7.34 h for 1 unit. Table 4 and Table 5 present the sulfur concrete mix quantities of each material and properties of the 3D-printed exterior walls, respectively, which were determined based on the literature review for a unit. Furthermore, it is noted that the transportation of construction materials from suppliers to the site covers a distance of 1000 km.

4.3. Sustainability Assessment

4.3.1. LCEA for Shelter Design

The embodied energy of construction materials, from production to the site, was calculated using the available embodied energy coefficients from various studies. These coefficients, measured in megajoules per kilogram (MJ/kg), were multiplied by the respective material quantities of the sulfur concrete mix to determine the embodied energy of each material in megajoules (MJ). The specific values can be found in Table 6. Upon analysis, it is observed that the embodied energy for material production required for the exterior air cavity wall is approximately 16,368.68 MJ. In contrast, the exterior wall with E-PLA insulation has a higher total embodied energy of approximately 75,926.36 MJ because it also includes the energy required for the production of E-PLA. The energy required for the construction of the designed shelter was specifically calculated for the printing of the exterior wall. The total energy consumption for this process was found to be 338 MJ. These calculations were performed considering the power required to operate the COBOD BOD2 for a duration of 7.34 h.
Figure 8 illustrates the embodied energy required for printing the exterior walls of one unit of the shelter. The x-axis and y-axis represent the types of walls and the energy required in megajoules (MJ), respectively. The embodied energy for the production of air cavity wall materials is 16,707.12 MJ, whereas the embodied energy for the E-PLA-insulated wall is 76,264.8 MJ. The figure reveals a significant difference in the energy required for the production, transportation, and construction of insulated walls; it is almost seven times higher for E-PLA walls than for air cavity walls, and the major reason behind this difference is the energy required for the production of the E-PLA material.
Openstudio®, along with Sketchup Pro 2021, was used to determine the operational energy of the shelter. Lighting, building occupancy, the HVAC system, and relevant equipment are considered for the operation state of the shelter. A few considerations are made for the energy analysis in Openstudio®. The building type of the single-unit shelter is considered a large hotel, the 90.1-2010 template is used, and ASHRAE 169-2006-3A (Stillwater, OK, USA) is the climate zone [59]. The surface type, different space types (highlighted by like colors in Figure 9b), and thermal zones (highlighted by different colors to show separation but share no relation to Figure 9c) considered for a single unit can be seen in Figure 9. Similarly, in accordance with Bae et al. [60], occupancy schedules, along with lighting and equipment schedules, are set up for operational energy use analysis.
Table 7 represents the annual energy consumption for the operation of the 3D-printed shelter, considering various HVAC systems and wall insulation types. Six different scenarios have been created, and the operational energy is predicted in gigajoules (GJ). The source energy is then compared to ensure a fair assessment across different energy sources. All of the scenarios use electricity as the energy source, but A-RTU and E-RTU use natural gas for heating along with electricity for cooling. A-RTU has a source energy of 368.52 GJ (electricity) and 92.65 MJ (natural gas); similarly, E-RTU’s source energy is 344.25 GJ (electricity) and 74.66 GJ (natural gas). From the table, it can be concluded that the source energy required for insulated walls with E-PLA and the PTHP system is less than in other scenarios, whereas air cavity walls with a VRF system require the most energy. The best alternative to E-PTHP seems to be either air cavity walls with a PTHP system or insulated walls with a VRF system.
Figure 10 illustrates the total energy required in all three phases of the 3D-printed shelter, i.e., production and transportation, construction, and operation, for different scenarios. The x-axis in the figure shows the different scenarios formed depending on the types of walls and HVAC system, whereas the y-axis represents the total energy required in gigajoules. From the figure, it is clear that E-RTU requires the most energy when considering all three phases. Although the operational energy required for E-PTHP is low during the operation state, the total energy required for A-PTHP is the lowest among all scenarios. Considering the total energy, the air cavity wall is better than the insulated wall with every HVAC system due to the energy required for the production of insulated walls.

4.3.2. LCA for Shelter Design

The goal of this study is to determine the environmental impacts of designed shelters. Figure 11 shows the system boundaries of the examined systems, including material production, the transportation of materials and equipment, construction, operation, and maintenance. The end-of-life phase is excluded from the study due to the lack of available data. The input data related to the shelter were gathered from the literature review and Ecoinvent database.
The technical data include the quantities of materials, transportation, and energy consumption for construction and operation. The environmental impacts of the designed shelter were estimated using TRACI 2.0. The method represents the impacts of a global representative and addresses nine impact categories: ozone depletion (kgCFC-11eq), global warming potential (kgCO2eq), smog (kgO3eq), acidification (kgSO2eq), eutrophication (kgNeq), fossil fuel depletion (MJ Surplus), carcinogenic effects (CTUh), non-carcinogenic effects (CTUh), respiratory effects (kgPM2.5eq), and ecotoxicity (CTUe) [61]. The software SimaPro (SimaPro PhD) was used to evaluate the environmental impacts associated with the 3D-printed shelter. Figure 12 shows the environmental impacts caused by the production and transportation of construction materials and the construction of 3D-printed exterior walls onsite. Ten different categories of environmental impacts were measured based on the quantities provided, and these categories can be found on the x-axis of the figure. The y-axis represents the normalized value in percentage for the two different types of walls. The figure shows that insulated walls have higher environmental impacts compared to air cavity walls. Insulated walls seem to have 50% higher environmental impacts compared to air cavity walls, except for acidification, respiratory effects, and fossil fuel depletion. This suggests that E-PLA has less impact on these categories compared to others.
The environmental impacts of the operation phase of different scenarios can be seen in Table 8. From the table, it can be concluded that the source energy required for insulated walls with E-PLA and a PTHP system is less than in other scenarios, whereas air cavity walls with a VRF system require the most energy. The best alternative to E-PTHP, which has the lowest operational energy, is an air cavity wall with a PTHP system (37.33 greater GJ) or an insulated wall with a VRF system (41.47 greater GJ) to improve operational energy consumption.
To calculate the overall environmental impacts of each scenario, the environmental impacts of each phase were identified and then aggregated. Figure 13 presents the total environmental impacts of each scenario for three different phases of the considered shelter unit. The figure clearly illustrates that the E-RTU scenario exhibits lower environmental impacts compared to the others, except for ozone depletion, global warming, and fossil fuel depletion. And, this suggests that the operational energy is more significant than that used for production and construction. Notably, the E-RTU and A-RTU scenarios have similar impacts in terms of eutrophication, but E-RTU outperforms the other scenarios in all other impact categories, demonstrating its superior environmental performance.

4.3.3. Energy Justice

In order to identify more favorable options in light of energy justice, the scenarios were carefully analyzed. The analysis employed the linguistic energy justice theory and utilized the Analytical Network Process (ANP) methodology. Figure 14 visually presents the ANP layout, which serves as a framework for evaluating and determining the best scenario in terms of energy justice. Within this framework, the energy justice decision-making theory classifies the criteria, sub-criteria, and scenarios into different levels. Specifically, the criteria are categorized as level 2, the sub-criteria as level 3, and the scenarios as level 4. LCEA and LCA are also taken into consideration as independent variables in decision-making. These variables play a significant role in the analysis, providing valuable insights into the energy justice implications associated with each alternative.
Table 9 shows the supermatrix derived from the eigenvector of criteria and independent variable. The initial eigenvector was constructed by comparing criteria with each other based on the goal. Subsequently, a comparison was made between criteria and independent variables, and vice versa. The supermatrix was column-stochastic and was raised to a sufficiently large power until convergence occurred [55]. Given the irreducible supermatrix, it is raised to the power 2K + 1 and converges if k tends to infinity [62]. In the current study, convergence was stable at W12. Table 10 shows the final weights of the criteria.
Table 10 illustrates the process of determining the final weights of sub-criteria by evaluating each sub-criterion in relation to its respective criterion. This involves multiplying the eigenvectors obtained from the comparison with the final weights of the criteria. The table also displays the limiting values, which represent the final weights of the criteria. Additionally, it presents the relative weights of the sub-criteria derived from the comparison and the resulting final weights of the sub-criteria.
Table 11 presents the eigenvector, which is obtained by comparing each alternative or scenario according to sub-criteria and the final outcome. The final outcome is determined by multiplying the scenario’s eigenvector with the final weights of the sub-criteria. The results indicate that the value for the E-RTU scenario is significantly higher (0.3690) than the others, suggesting that it is the most favorable scenario in terms of energy justice.

4.4. Decision-Making for Shelter Design

From the findings of the three analyses, a decision-making table, Table 12, has been created. Table 12 incorporates the results of LCEA, including various environmental impacts, such as carcinogenic effects, global warming, and smog from LCA, as well as the outcomes of the energy justice assessment. The second column is for LCEA, which is obtained based on the embodied energy required for insulation and operational energy. For instance, LCEA (426.144) for A-PTHP shows a total operational energy of 409.85 GJ and an embodied energy of 16,707 MJ for air cavity insulation. The third–fifth columns are generated based on the environmental impact required for the production of materials, transportation, and the construction of the 3D-printed exterior walls from Figure 12 and the operation of the shelter from Table 8.
As can be seen in Table 12, the LCA result of A-PTHP for carcinogenic impacts is 0.004285. This value is the sum of 0.004201 from the environmental impacts of operation and 0.000081 from the environmental impacts of production, transportation, and the construction of the 3D-printed exterior wall shelter. According to the LCEA results, scenario A-PTHP requires 426.144 GJ less total energy than other scenarios across all three phases. On the other hand, when considering LCA, scenario E-RTU is preferred due to its lower impact values in all categories, except for smog. Furthermore, in terms of energy justice, scenario E-RTU outperforms the other scenarios with a higher value of 0.3690, indicating greater fairness and equity in energy distribution. Therefore, there is no single ideal scenario, but if we prioritize LCA and energy justice, scenario E-RTU is the preferred choice for constructing the shelter. However, if the focus is solely on LCEA, scenario A-PTHP would be the recommended option.

5. Conclusions

To address the issues related to existing disaster shelters, this study proposes a permanent shelter design that incorporates rapid construction technology and focuses on reducing environmental impacts and energy consumption and offering multipurpose functionality. The designed shelter features an octagonal shape, utilizes concrete as the primary construction material, and incorporates a central core pillar. Its multipurpose nature allows for variable uses, such as housing, a medical center, a collaborative space, or a storage area during and after a disaster. Onsite 3D printing technology is adopted for the exterior walls, enabling a quick response to resilience demands. Various scenarios were created considering different combinations of cavity filling for the exterior walls and HVAC systems. Six scenarios were formed considering insulation options (air cavity or E-PLA) and HVAC systems (PTHP, RTU, or VRF). Sustainability assessments were conducted using life cycle analysis (LCA), life cycle energy assessment (LCEA), and energy justice assessment. According to the results of these assessments, scenario E-RTU (exterior wall with E-PLA insulation and RTU HVAC system) emerges as the best choice in terms of LCA and energy justice. However, if the decision is based solely on LCEA, scenario A-PTHP (air cavity with PTHP system) is the most favorable. It is important to note that these results may vary depending on different building types, sizes, and climate zones.
This study’s outcomes have provided a shelter design considering sustainability that will allow decision-makers and stakeholders to perform a systematic decision-making process, which will ensure maximum utilization of limited resources to reach out to a larger number of people post-disaster. The proposed methodology will help local communities to uplift the economic conditions through business continuity after people move back to their own homes. In addition, the developed sustainability assessments can be applied in public buildings, including public libraries, universities, government buildings, etc.
For further studies, analysis can also include 3D-printed roofs or floors for sustainability assessments. Having focused on the southern region of the United States, this study is meant to act as a guide through the process of determining the optimal shelter design for a needed area. Adding life cycle cost analysis as one of the sustainability measurement techniques would be beneficial for some stakeholders, as cost plays a major role in decision-making. Sensitivity analysis can be performed based on different transportation distances of construction materials and equipment, construction materials, and construction methods (onsite/offsite), which would give a more concise scenario.

6. Limitations and Future Work

This study focuses on the sustainable design of shelters post-disaster in the southern region of the United States. However, its applicability to other parts of the United States is limited due to differences in weather, building materials, and LCA and energy justice criteria. Therefore, it is noted that a generalized approach is needed in future work. Additionally, sensitivity analysis will be conducted in future work to understand the impacts of different assumptions made in the calculations.
Furthermore, it is necessary to consider a power supply and energy management system in the sustainability assessment. A building may be well designed, but if it requires excessive amounts of energy for its use, it can become problematic. In many emergency situations, it is not possible to have enough energy to power air conditioning. Therefore, the system should be versatile and capable of accommodating less energy-intensive air-conditioning systems or, in some cases, functioning without them. Future research will integrate plant engineering to ensure that the design is truly reliable and applicable in various contexts.

Author Contributions

A.K.: Formal Analysis, Investigation, Writing-original draft, S.Y.: Methodology, Supervision, Project administration, and validation, R.G.W.: Designing, Writing, Review/Editing, Y.B.: Resources, Software, Writing-review & editing, A.K.L.: Review/Editing, Conceptualization and Supervision. All authors have read and agreed to the published version of the manuscript.

Funding

This work was partially funded by field work proposal CEBT105 under DOE BTO activity no. BT0302000 and BT0305000.

Data Availability Statement

The raw data supporting the conclusions of this article will be made available by the authors on request.

Acknowledgments

This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (https://www.energy.gov/doe-public-access-plan (accessed on 18 June 2024).

Conflicts of Interest

Author Alka Khadka was employed by the company Intertek-PSI. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Figure 1. Research methodology.
Figure 1. Research methodology.
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Figure 2. Scenario tree.
Figure 2. Scenario tree.
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Figure 3. Types of HVAC systems. a [49], b [50], c [51].
Figure 3. Types of HVAC systems. a [49], b [50], c [51].
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Figure 4. Framework of LCEA.
Figure 4. Framework of LCEA.
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Figure 5. Proposed floor plan and elevation of designed shelter (Revit 2023).
Figure 5. Proposed floor plan and elevation of designed shelter (Revit 2023).
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Figure 6. Modularity of designed shelter.
Figure 6. Modularity of designed shelter.
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Figure 7. Configuration of 3D-printed exterior walls.
Figure 7. Configuration of 3D-printed exterior walls.
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Figure 8. Embodied energy for air-cavity- and E-PLA-filled 3D-printed walls.
Figure 8. Embodied energy for air-cavity- and E-PLA-filled 3D-printed walls.
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Figure 9. Rendered images (a) by surface type, (b) by space type, and (c) by thermal zone.
Figure 9. Rendered images (a) by surface type, (b) by space type, and (c) by thermal zone.
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Figure 10. Total energy for different scenarios.
Figure 10. Total energy for different scenarios.
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Figure 11. System boundaries of LCA.
Figure 11. System boundaries of LCA.
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Figure 12. Environmental impacts of production, transportation, and construction of 3D-printed exterior wall.
Figure 12. Environmental impacts of production, transportation, and construction of 3D-printed exterior wall.
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Figure 13. Environmental impacts of production, transportation, construction, and operation of 3D-printed exterior walls.
Figure 13. Environmental impacts of production, transportation, construction, and operation of 3D-printed exterior walls.
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Figure 14. ANP Layout for energy justice assessment.
Figure 14. ANP Layout for energy justice assessment.
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Table 1. Current disaster relief shelters.
Table 1. Current disaster relief shelters.
AuthorsShelter NameMaterial UsedCostConstruction DurationTotal Area
[21]WeatherHyde, 2013Nylon, polyester wool, fiber-reinforced mylarUSD 19915 min2.69 m2
[22]Better Shelter, 2015Polyolefin panels and galvanized steel, woven high-density polyethylene fibersUSD 12604–6 h17.47 m2
[23]Hexyurt, 2011Cloth, wood, plastic, Polyiso insulation, OSB, sandwich panels, cardboardUSD 229.714 h3.8–25.64 m2
[24]Emergency Smart Pod, 2015Aluminum panels and steel frameUSD 195K–USD 485K20 min36.98 m2
[25]MTS DOMO Systems, 2014Aluminum, polyester PVC tarpaulin, cottonUSD 462525 min23.4 m2
Table 2. Three-dimensional-printed houses.
Table 2. Three-dimensional-printed houses.
AuthorsBuilding NamePrinted
Onsite/Offsite		Construction CostPrinting DurationsTotal Area
[26]WinSun ten 3D-printed houseOffsiteUSD 48001 Day18.58 m2
[28]Dubai 3D-printed Commercial BuildingOffsiteUSD 140K17 Days22.48 m2
[29]Belgium onsite 3D-printed houseOnsite-3 Weeks8.36 m2
[30]SQ4D 3D-printed houseOnsiteUSD 299.99K2 Days12.91 m2
[31]Netherland 3D-printed houseOffsiteUSD 946/month2 Days8.73 m2
[32]East 17 Street ResidenciesOnsiteUSD 450K and above7 Days/home8.36–17.19 m2
Table 3. Specifications of 3D printers.
Table 3. Specifications of 3D printers.
AuthorsSystem NamePrint Speed (cm/s)Print Dimensions (L × W × H) (m)Type
[38]ICON Vulcan II12.7–25.4∞ × 11.1 × 3.2Gantry
[39]COBOD BOD2Up to 100∞ × 14.6 × 14.6Gantry
[40]Total Kustom StroyBot 6.2 A1–24.910 × 15 × 5.8Gantry
Table 4. Properties of 3D-printed wall [2].
Table 4. Properties of 3D-printed wall [2].
Wall TypeDensity (kg/m3)Thermal Conductivity (W/m.K)U-Value (W/m2.K)Specific Heat (J/g.K)
Air Cavity1254.240.41141.870.803
E-PLA1254.240.1210.550.803
Table 5. Inventory for construction of 3D-printed exterior wall of one unit.
Table 5. Inventory for construction of 3D-printed exterior wall of one unit.
DimensionVariable
3D-printed external wall a17.197 m3
Silica sand9235.4 kg
Gravel9237.15 kg
Sulfur3784 kg
Polypropylene160.82 kg
Insulation E-PLA a,b509.037 kg
Energy c94.011 kWh
Transportation1000
a [42], b [57], c [39].
Table 6. Embodied energy coefficients of materials used for construction of shelter.
Table 6. Embodied energy coefficients of materials used for construction of shelter.
MaterialEmbodied Energy Coefficient (MJ/kg)Thermal Conductivity (W/m.K)Specific Heat (J/g.K)
Silica sand0.039 a9235.4360.18
Gravel0.16 b9237.151477.94
Sulfur1.12 c37844238.08
Polypropylene fiber64 a160.8210,292.48
Insulation (EPLA)117 a509.0459,557.68
a [58], b [11], c [31].
Table 7. Operational energy for different scenarios.
Table 7. Operational energy for different scenarios.
ScenarioOperational Energy (GJ)
A-PTHP409.85
E-PTHP372.52
A-RTU461.17
E-RTU418.91
A-VRF454.38
E-VRF413.99
Table 8. Environmental impacts of operation of 3D-printed shelter for different scenarios.
Table 8. Environmental impacts of operation of 3D-printed shelter for different scenarios.
Impact CategoriesA-PTHPE-PTHPA-RTUE-RTUA-VRFE-VRF
Ozone depletion (kgCFC-11eq)0.0039340.0035760.0041430.0037920.0043620.003974
Carcinogenic effects (CTUh)0.0042010.0038190.0038290.0035710.0046580.004244
Non-carcinogenic effects (CTUh)0.0139130.0126460.0126220.0117760.0154250.014054
Respiratory effects (kgPM2.5eq)118.7023107.8907107.3047100.1644131.5993119.9014
Eutrophication (kgNeq)332.9282302.6044299.9802280.1439369.1007336.2912
Acidification (kgSO2eq)155.8035141.6126146.0823135.693172.7314157.3773
Smog (kgO3eq)1570.311427.2831496.7771387.3191740.9241586.172
Fossil fuel depletion (MJ surplus)59,960.354,498.9969,752.9363,126.7766,474.9560,565.97
Global warming (kgCO2eq)56,700.1851,535.8156,964.5352,445.3762,860.6257,272.92
Ecotoxicity (CTUe)567,314.1515,641.9514,214.1479,821.7628,952.5573,044.7
Table 9. Supermatrix.
Table 9. Supermatrix.
TypeScope2ARIGSCLAEILCEALCA
Scope0000000
2A0.51200000.8450.155
RIG0.08100000.1670.833
SCLA0.07200000.7600.240
EI0.33500000.1110.889
LCEA00.5300.1050.0500.31500
LCA00.0460.1050.1590.60200
Table 10. Final weights of sub-criteria.
Table 10. Final weights of sub-criteria.
Sub-CriterionFinal Weight of CriterionRelative Weight of Sub-CriterionFinal Weight of Sub-Criterion
AVA0.220.5000.110
AFF0.5000.110
INTERE0.1610.1060.017
DP0.6340.102
INTRAE0.2600.042
RES0.121.3570.163
T&A0.2510.030
INTERS0.7430.089
SUS0.4990.5000.250
RES0.5000.250
Table 11. Comparison of alternatives and findings of ANP.
Table 11. Comparison of alternatives and findings of ANP.
TypeAVAAFFINTEREDPINTRAEREST&AINTRESSUSRESResult
A-PTHP0.09230.27000.20230.27520.09320.16670.16670.09430.09430.10150.1639
E-PTHP0.13480.42160.44440.34310.15540.16670.16670.17530.17530.16560.2383
A-RTU0.24940.08250.10440.12910.28460.16670.16670.25870.24000.25120.2412
E-RTU0.44350.14600.15370.16460.39260.16670.16670.38640.42840.37980.3690
A-VRF0.02820.02670.03570.03010.02850.16670.16670.03240.03100.03440.0623
E-VRF0.05170.05340.05950.05800.04570.16670.16670.05370.05370.06740.0875
Table 12. Decision-making based on sustainability assessment for scenarios.
Table 12. Decision-making based on sustainability assessment for scenarios.
ScenarioSustainability Assessment
LCEALCAEnergy Justice
CarcinogenicGlobal WarmingSmog
A-PTHP426.1440.00428558,110.51681.9770.1639
E-PTHP448.3720.00402454,492.451633.4180.2383
A-RTU477.4640.00391358,374.851608.4440.2412
E-RTU494.7620.00377655,402.021593.4530.3690
A-VRF470.6740.004741638,410.51852.5910.0623
E-VRF489.8420.004449611,222.31792.3070.0875
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Khadka, A.; Yoon, S.; Walker, R.G.; Lewis, A.K.; Bae, Y. A Systematic Approach to Developing Sustainable Post-Disaster Shelters in the Southern Region of the United States. Buildings 2024, 14, 2536. https://doi.org/10.3390/buildings14082536

AMA Style

Khadka A, Yoon S, Walker RG, Lewis AK, Bae Y. A Systematic Approach to Developing Sustainable Post-Disaster Shelters in the Southern Region of the United States. Buildings. 2024; 14(8):2536. https://doi.org/10.3390/buildings14082536

Chicago/Turabian Style

Khadka, Alka, Soojin Yoon, Richard G. Walker, Amy King Lewis, and Yeonjin Bae. 2024. "A Systematic Approach to Developing Sustainable Post-Disaster Shelters in the Southern Region of the United States" Buildings 14, no. 8: 2536. https://doi.org/10.3390/buildings14082536

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