Extended Abstract
Aims:
The growing energy use in the building sector and its contribution to greenhouse gas emissions have highlighted the need for building materials with improved thermal performance. Phase Change Materials (PCMs), due to their ability to store and release latent heat within a relatively stable temperature range, are considered a passive approach for reducing indoor temperature fluctuations, moderating heating and cooling loads, and improving thermal comfort. However, their direct application in building materials is associated with leakage, reduced mechanical properties, incompatibility with the material matrix, low thermal conductivity, and challenges related to long-term durability.
Accordingly, this study aims to conduct a scoping review of methods for integrating PCMs into building materials, with particular emphasis on encapsulation. It seeks to classify and compare integration approaches in terms of thermal performance, leakage control, mechanical properties, durability, applicability, and scalability, identify key research gaps, and provide an operational basis for selecting appropriate methods according to thermal, mechanical, economic, and climatic priorities.
Materials & Methods:
A scoping review was conducted to systematically map research on PCM integration into building materials. The review followed the Arksey and O’Malley framework, with ScR-PRISMA principles and JBI guidance applied to improve transparency in searching, screening, data extraction, and reporting. The research questions addressed PCM types and characteristics, integration methods, and building applications.
A systematic search was conducted in Scopus and Web of Science for studies published between 2019 and 2025, with an update on April 30, 2026. Search terms covered PCMs, organic and inorganic PCMs, building and construction materials, building envelopes, walls, roofs, floors, façades, panels, encapsulation, microencapsulation, macroencapsulation, impregnation, direct incorporation, and shape-stabilized PCMs. Of 72 initial records, eight duplicates were removed, leaving 64 for title and abstract screening. Following inclusion and exclusion criteria and full-text assessment, 35 studies were selected for final analysis. The review focused mainly on English-language studies indexed in Scopus and Web of Science because Persian-language literature on PCM integration was limited. Data were extracted on study characteristics, PCM type, integration method, building material or component, application, thermal performance, leakage control, mechanical consequences, durability, applicability, and research gaps. Integration methods were classified into direct incorporation, impregnation, encapsulation, and shape-stabilized composites.
Findings:
The reviewed studies mainly addressed three interconnected areas: thermal performance of building envelopes; effects of PCM incorporation on the mechanical properties and durability of concrete, mortar, gypsum, and related materials; and integration strategies for leakage control and thermal-cycle stability. Among the 35 selected studies, 24 (68.6%) investigated encapsulation, microencapsulation, or macroencapsulation, while 12 (34.3%) examined direct incorporation, impregnation, or shape-stabilized approaches. Because some studies addressed more than one method, the frequencies exceed the number of selected studies.
Direct incorporation and impregnation are simple and economical but present greater risks of leakage and reduced mechanical performance and durability without an effective protective barrier. They are therefore more suitable for specific non-structural applications or limited PCM contents. Encapsulation reduces direct contact between PCM and the host matrix through a protective shell. Microencapsulation provides relatively uniform PCM distribution and a high surface-to-volume ratio, making it suitable for mortar, gypsum, concrete, and wall panels. However, shell type and strength, capsule size and morphology, PCM content, manufacturing process, and matrix compatibility can affect performance. Increasing PCM content may improve thermal storage while reducing compressive strength and density.
Macroencapsulation enables larger PCM quantities and is particularly applicable to prefabricated components and multilayer envelope systems. Its performance depends on capsule geometry, heat-transfer paths, contact surface, and PCM location. Poorly designed systems may cause incomplete charging and discharging during daily thermal cycles. Shape-stabilized composites can reduce leakage and maintain PCM in the supporting structure during the liquid phase, although excessive supporting material may reduce effective latent heat storage capacity.
Building envelopes were the most frequently studied application, appearing in 19 studies (54.3%), while concrete, mortar, gypsum, and related materials appeared in 10 (28.6%). Regarding research design, 26 studies (74.3%) were reviews or analytical studies, 5 (14.3%) provided experimental evidence, and 4 (11.4%) used simulation or case-study approaches.
Conclusion:
PCMs can improve the thermal performance of building materials and envelopes by increasing latent thermal energy storage, reducing indoor temperature fluctuations, and supporting thermal comfort. However, effectiveness depends substantially on the integration method and cannot be assessed solely by thermal storage capacity.
Direct incorporation and impregnation offer simplicity and cost-effectiveness but involve greater risks of leakage, mechanical degradation, and durability problems. Microencapsulation and macroencapsulation provide more effective leakage control and improve PCM stability and compatibility, although they involve higher manufacturing costs, greater shell-design complexity, and potential reductions in compressive strength. Macroencapsulation is particularly appropriate for larger PCM quantities and component-level applications, while shape-stabilized composites provide another viable approach for improving leakage resistance and durability, although excessive supporting material may reduce effective latent heat storage capacity.
Selection of an integration method should consider the interaction among PCM type, phase-change temperature, building material, climatic conditions, mechanical requirements, and long-term durability. Encapsulation is among the most promising approaches, but it cannot be considered universally superior. Key research gaps include limited real-building and field-scale studies, insufficient long-term and thermal-cycle durability data, lack of standardized evaluation criteria, limited direct comparisons among integration methods, and inadequate integrated economic and environmental assessments. This study, by classifying integration methods and identifying key research gaps, provides an operational framework for selecting appropriate methods based on thermal, mechanical, economic, and climatic priorities, helping reduce the gap between research and industrial application.