Experimental Investigation of Phase Change Material and Thermal Insulation Integrated Building Envelopes for Energy-Efficient Buildings in Hot Climates

Abstract

The building sector accounts for a substantial share of global energy consumption, particularly due to heating, ventilation, and air-conditioning (HVAC) systems. In hot and tropical climates, excessive cooling demand significantly increases operational energy use and greenhouse gas emissions. This study experimentally investigates the thermal performance of building envelopes integrated with Phase Change Materials (PCMs) and thermal insulation as passive energy-saving strategies. A comparative analysis was conducted among three roof configurations: a conventional roof system, a PCM-integrated roof, and a hybrid PCM-insulation roof system. An organic paraffin-based PCM with a melting temperature range of 26-28 °C was incorporated into the roof assembly along with expanded polystyrene (EPS) insulation. Temperature monitoring was performed under real climatic conditions using calibrated digital sensors and a multi-channel data acquisition system. The results demonstrated that PCM integration reduced indoor peak temperature by 2.9 °C and increased thermal lag from 0.6 h to 2.1 h. The combined PCM-insulation system further reduced indoor peak temperature by 5.0 °C and enhanced thermal lag up to 3.4 h compared with the conventional roof system. The hybrid system also reduced indoor temperature fluctuation and prolonged indoor thermal comfort duration. The findings confirm that integrating PCMs with thermal insulation can significantly improve thermal inertia, reduce cooling demand, and enhance indoor comfort in hot climates. The study highlights the applicability of PCM-insulation systems for sustainable building design and energy-efficient retrofitting of existing and heritage buildings.

Introduction

Rapid urbanization, population growth, and higher living standards have significantly increased global energy demand. Buildings account for about 40% of global energy consumption, with a large portion used for heating, ventilation, and air conditioning (HVAC). In hot climates such as India, rising temperatures have increased the demand for cooling, leading to higher energy use and environmental impacts.

To reduce reliance on energy-intensive cooling systems, passive thermal regulation strategies are gaining importance. Traditional insulation materials reduce heat transfer but are less effective against changing thermal loads. Phase Change Materials (PCMs) offer an advanced solution because they can absorb and release large amounts of heat during phase transitions, helping stabilize indoor temperatures. Combining PCMs with insulation materials can improve thermal performance and reduce cooling energy requirements.

Objective

The study aimed to experimentally evaluate the effectiveness of integrating PCM and thermal insulation in building roof systems under hot tropical climatic conditions. The goal was to reduce indoor temperature fluctuations and improve passive thermal comfort.

Methodology

Three roof configurations were tested under real outdoor conditions:

1. Conventional roof system
2. PCM-integrated roof system
3. PCM + insulation hybrid roof system

Materials Used

• Organic Paraffin PCM
  • Melting temperature: 26–28°C
  • Latent heat: 180–200 kJ/kg
  • High thermal energy storage capacity
• Expanded Polystyrene (EPS) Insulation
  • Thermal conductivity: 0.035 W/m·K
  • Thickness: 40 mm
  • Effective thermal insulation material

Temperature sensors recorded data every 10 minutes, and thermal comfort was assessed using Predicted Mean Vote (PMV) and Predicted Percentage Dissatisfied (PPD) indices.

Results

1. Conventional Roof Performance

The conventional roof showed poor thermal resistance:

• Peak indoor temperature: 36.8°C
• Thermal lag: 0.6 hours
• Indoor temperature fluctuation: 9.4°C

This indicated rapid heat transfer from the outdoor environment into the building.

2. PCM-Integrated Roof Performance

The PCM roof significantly improved indoor thermal conditions:

• Peak indoor temperature reduced to 33.9°C
• Temperature reduction: 2.9°C
• Thermal lag increased to 2.1 hours
• Indoor temperature fluctuation reduced to 6.2°C

The PCM absorbed excess solar heat during the day and released it later, delaying heat transfer and improving thermal stability.

3. PCM-Insulation Hybrid Roof Performance

The combined PCM-insulation system delivered the best results:

• Insulation reduced continuous heat transfer.
• PCM managed fluctuating thermal loads through latent heat storage.
• The combination provided greater thermal inertia, better temperature regulation, and enhanced indoor comfort compared to either system alone.

Conclusion

This study experimentally evaluated the thermal performance of PCM-integrated and PCM-insulation hybrid roof systems under hot climatic conditions. The findings demonstrate that PCM integration significantly improves thermal inertia and reduces indoor peak temperature. The combined PCM-insulation system achieved the best overall thermal performance by simultaneously reducing heat transfer and regulating transient thermal loads. The hybrid system reduced indoor peak temperature by up to 5 °C and increased thermal lag to 3.4 h compared with conventional roof systems. These improvements can substantially reduce cooling energy demand and improve occupant thermal comfort. The study confirms that PCM-insulation systems represent an effective passive cooling strategy for sustainable buildings, particularly in tropical climates and energy-efficient retrofitting applications.

References

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Copyright

Copyright © 2026 Amit Gupta, Sanjay Kumar Sharma, Amit Goyal. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.