K Oviya et al 2023
Abstract. The current trends in the construction sector are responsible for majority of the CO2 emissions in India. The sustainable methods to reduce the CO2 emissions should include not just recycling but also upcycling the materials, for instance – shipping containers. Despite the industry’s best efforts to minimize waste generation, millions of shipping containers end up as scrap materials, every year. This phenomenon can be changed effectively by reusing the scrap materials as alternate building materials. The trend of reusing the shipping containers as building materials is at its peak in Western countries, while in India, it is still in a nascent stage. The aim of the current research paper is to evaluate and assess the thermal performance of upcycled shipping containers as a building material in warm humid climatic condition.
- Introduction
The construction sector in India accounts for an approximate of 38% of the country’s total yearly CO2 emissions. The products or industrial processes of the four energy-intensive building materials such as cement, bricks, lime, glass, and others contribute to 80% of the CO2 emissions from the construction sector. This can be lessened by reusing the construction materials. [1]
Cargotecture corresponds to the use of ISO-certified shipping containers, also known as cargo containers, for the construction of fully-operational buildings, commercial spaces and housing. Cargo containers have an active life of 8-10 years, when used for shipping purposes. However, it has a lengthy technical life and if properly maintained, it has the potential to last another 15-20 years [2] [3].
Refurbishing the existing containers reduces the need to extract and process new raw materials. Further, the used containers are also kept out of the waste stream, thus making the construction sector, a highly sustainable one. [4]
The aim of the current research paper is to evaluate and assess the thermal performance of upcycled shipping containers as a building material in warm humid climatic condition.
This research includes a review of literature about the strengths and weaknesses of the shipping containers as a building material; it also compares and evaluates the thermal performance of uninsulated container buildings with base case conventional building and the insulated container building through Opaque simulation method. The results were obtained by comparing and assessing the thermal performance and cost of various insulating materials for a container building. The study outcomes greatly help the architects to reuse the shipping containers as a sustainable alternative building material in warm humid regions.
Based on their proportions, the shipping containers are categorized as either regular or high cube containers. The High Cube (HC) shipping containers are best suited for building construction since the space between the ceiling and the roof is sufficient for ductwork and a clear ceiling of 2.4m is provided. [5]
The shipping containers offer enormous potential as a habitable space including constructability, structural performance and building services. [6]. The current research paper examines the energyefficient and cost-effective insulating materials for shipping container buildings in warm humid climate.
Table -1.
Table 1 depicts an overview of the Strengths, Weaknesses, Opportunities and Threats of employing the shipping containers as building materials.
Shipping containers are relatively thin, uninsulated, and acoustically inferior boxes in which thermal comfort remainss a primary concern. Heat is a key issue, when adopting the shipping containers as housing since steel has a high thermal conductivity. In such case, the shipping containers require thermal insulation and a ventilation system to maintain a suitable indoor environment in high temperature and high humidity climates. [16] [3]
- Methodology
The study methodology contains the following steps; listing out the cost and thermal performance of various building and insulation materials used in the construction industry; a conventional 40 ft. (12.2m x 2.43m) brick building and a 40 ft. (12.2m x 2.43m) container building were designed as the base case and alternative case respectively, including various insulation materials to the setup; then, the thermal performance of the container steel along with insulation materials and conventional building materials was assessed and compared; a cost analysis was carried out to establish the cost-effectiveness of container building in comparison with the conventional brick building; the results were obtained by utilizing an opaque tool to evaluate the thermal performance and cost of the chosen insulating materials for a container building in a warm humid region.
In this study, 21 building models were considered. The models 1-5 correspond to base case buildings with conventional building materials, Model 6 is an un-insulated 40 ft. shipping container and the models 7-21 are insulated shipping container buildings.
Table 2 displays various types of insulation materials and its cost (per square meter), thickness (mm)
and thermal conductivity (W/m.k) values.
Table 3 shows different types of conventional building materials along with its cost (per square piece), number of pieces required (per square meter) and its thermal conductivity (W/m.k) value.
- Comparative analysis
3.1. Material specification
Table 4. Detailed material specifications for base case and the alternative case
Table 4 illustrates different material layers of the selected walls and roofs for the 21 models that are
inclusive of the base model and the alternate cases.
3.2. Base case – Sample conventional building
Figures 1 and 2 depict the floor plan and section of a 40-foot-long base case brick building (12.2m x 2.43m) resepctively, which includes a bedroom, a living space, a kitchen and a bathroom.
3.3. Alternate case – Sample container building
Figures 3 and 4 depict the floor plan and section of a 40-foot container building (12.2m x 2.43m) respectively, which includes a bedroom, a living space, a kitchen and a bathroom.
3.4. Analyses of the thermal performance and cost of wall and roof materials using OPAQUE tool [21]
Opaque tool was used in this research to evaluate the thermal performance of the chosen base and the alternative cases. The thermal properties of the material such as k-value, density, specific heat capacity, thickness and the location of the building were fed into the tool for analysis and comparison.
Based on the chosen climate, this tool assumes the rest of the parameters such as the surface temperature, absorptivity and reflectance to determine the U-value, Time Lag, and Decrement Factor by generating the details of a wall or roof section and plotting the temperature drop using a Heat Flow graph.
Table 5 illustrates the U-value, heat gain/loss, time lag and the cost of 21 cases in which the highperforming materials are highlighted for each parameter.
- Result and Discussion
4.1. Comparison of efficiency of the wall material
Figure 5. Comparison of the performance between base case and the alternate case wall materials
4.1.1. Discussion. The shipping container building case, with polyisocyanurate (Polyiso) insulation,
achieved the least U-value for a wall – 0.2 W/m²K, followed by polyurethane (PU) sandwich panels
with a U-value of 0.3 W/m²K, Open-cell spray polyurethane foam and Open-cell polyurethane foam
with its U-values being 0.38 W/m²K. However, neither polyiso nor PU sandwich panel was found to be
cost-effective.
Editors Note : Here’s what this means in plain English:
Polyisocyanurate (Polyiso) insulation gave the best thermal performance for the container wall, with a very low U-value of 0.2 W/m²K—this means it resists heat transfer very well.
Next best was the PU sandwich panel, with a U-value of 0.3 W/m²K.
Open-cell spray polyurethane foam and open-cell polyurethane foam also performed well, with U-values of 0.38 W/m²K.
However:
Despite Polyiso and PU sandwich panels having better insulation performance, they were not considered cost-effective—meaning they were too expensive for the level of benefit they provided compared to other options like open-cell spray foam, which was cheaper but still very efficient.
The open-cell spray polyurethane foam and the closed-cell spray polyurethane foam had a maximum
time lag of 12 hrs and 11 hrs respectively.
The open-cell spray polyurethane foam and the damp-spray cellulose insulation achieved a low heat
gain/loss of 4.2 Wh/sq.m. However, the damp-spray cellulose insulation was expensive than the opencell spray polyurethane foam insulation.
Table 6 compares the thermal performance of open-cell spray polyurethane foam with open-cell
polyurethane foam.
4.1.2. Inference. Figure 7 shows that the open-cell spray polyurethane foam had the least heat gain/loss
(4.2 Wh/sq.m) and was found to be the most cost-effective one (₹ 70,146) of all the insulating materials
evaluated, with a U-value of 0.384 W/m²K and a maximum time lag of 12 hours.
4.2. Comparison of the efficiency of roof materials
Figure 6. Comparison of the performance between base case and the alternate case roof materials
4.2.1. Discussion. The shipping container building, with polyisocyanurate (Polyiso) insulation,
achieved the least U-value – 0.19 W/m²K for its roof, followed by the green roof with a U-value of 0.2
W/m²K. However, neither polyiso nor green roof was found to be cost-effective.
While, Strawbale (₹ 27,548), cork insulation (₹ 28,916) and open-cell spray polyurethane foam (₹
30,284) were found to be less expensive. But, the cork insulation yielded the least time lag of 1 hour
followed by Strawbale insulation time lag being 6 hours.
Table 7 compares the thermal performance of open-cell spray polyurethane foam with Strawbale
insulation.
Editors Note:
Straw bale insulation performed moderately well in the study. It had a U-value of 0.47 W/m²K for walls and 0.46 W/m²K for roofs—meaning it provides decent thermal resistance, but not as high-performing as materials like open-cell spray polyurethane foam (U-value 0.384 for walls). Its time lag was 6 hours, helping delay heat flow through the structure. The main advantage of straw bale is its low cost—₹27,548 for the roof setup—making it a budget-friendly and natural insulation option. However, it is bulkier and may not be as space-efficient or moisture-resistant as high-performance spray foams.
4.2.2. Inference. Figure 8 depicts that the open-cell spray polyurethane foam achieved the least U-value – 0.334 W/m²K, maximum time lag – 12 hours, minimum heat gain/loss – 4.1 Wh/sq.m, and better costefficiency (₹ 30,284), of all the insulating materials evaluated.
Conclusion
Shipping containers have been recommended as potential building materials to address various housing issues in temperate and cold regions. However, due to lack of awareness and social acceptance among people, the use of cargo containers as buildings is limited in warm and humid climate conditions.
In this study, the authors found that the open-cell spray polyurethane foam wall outperformed the traditional brick wall by 83% in U-Value, 81% in heat gain/loss and 18.2% in cost. Further, the opencell spray polyurethane foam roof outperformed the traditional RCC roof by 88% in U-Value, 88.3% in heat gain/loss and 20.7% in cost.
In this study, the authors found that the open-cell spray polyurethane foam wall outperformed the traditional brick wall by 83% in U-Value, 81% in heat gain/loss and 18.2% in cost. Further, the opencell spray polyurethane foam roof outperformed the traditional RCC roof by 88% in U-Value, 88.3% in heat gain/loss and 20.7% in cost
The study outcomes infer that if adequate insulating materials are incorporated in a shipping container building in a warm humid climate, it may be both thermally comfortable as well as costeffective. So, it is important to create an awareness among the public that low-cost container buildings are not inferior to conventional brick and concrete structures. In the future, further research should beconducted on the structural stability and life cycle evaluation of the shipping container buildings
References
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Acknowledgments
I’d want to express my heartfelt gratitude to Ar. Shobana and Ar. Sheetal Amraotkar (Associate Professors – Department of Sustainable Architecture, Sathyabama Institute of Science and Technology, Chennai) for their insightful advice and encouragement throughout the research process.
ICDIMSE-2022
IOP Conf. Series: Earth and Environmental Science 1210 (2023) 012008
IOP Publishing
doi:10.1088/1755-1315/1210/1/012008
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