The most significant threat that mankind faces in the 21th century is global warming. Buildings, which account for 40% of global energy consumption and greenhouse gas emissions, play a pivotal role in global warming. Estimates show that their destructive impact will grow by 1.8% per year through 2050, which indicates that future consumption and emissions will be worse than today. Therefore, the impact of cooling systems cannot be ignored, as they, along with ventilation and heating systems, account for 60% of the energy consumed in buildings. Passive cooling techniques are a promising alternative to conventional cooling systems. Of the various passive cooling strategies, thermal energy storage by means of latent heat is an efficient way to increase the thermal inertia of building envelopes, which would reduce temperature fluctuations, leading to the improved thermal comfort of occupants. Phase change materials (PCMs) with high density for thermal energy storage can be efficiently employed to this purpose. This paper reviews recent studies of the application of PCMs for passive cooling in buildings. From the literature, a comprehensive list of different organic, inorganic and eutectic PCMs appropriate for passive cooling in buildings are reviewed. Full-scale testing and numerical modeling were found to be the most popular investigative methods used for experimental and theoretical analysis of PCMs. The combination of these two methods can provide a detailed and valid technique for PCM investigations. Finally, incorporating PCMs into building walls with macro encapsulation was also a dominant interest in previous studies.

A review on phase change material (PCM) for sustainable passive cooling in building envelopes

The energy consumption of a building is strongly dependent on the characteristics of its envelope. The thermal performance of external walls represents a key factor to increase the energy efficiency of the construction sector and to reduce greenhouse gases emissions. Thermal insulation is undoubtedly one of the best ways to reduce the energy consumption due to both winter heating and summer cooling. Insulation materials play an important role in this scenario since the selection of the correct material, its thickness and its position, allow to obtain good indoor thermal comfort conditions and adequate energy savings. Thermal properties are extremely important, but they are not the only ones to be considered when designing a building envelope: sound insulation, resistance to fire, water vapor permeability and impact on the environment and on human health need to be carefully assessed too. The purpose of the paper is to provide a review of the main commercialized insulation materials (conventional, alternative and advanced) for the building sector through a holistic and multidisciplinary approach, considering thermal properties, acoustic properties, reaction to fire and water vapor resistance; environmental issues were also taken into account by means of Life Cycle Assessment approach. A comparative analysis was performed, considering also unconventional insulation materials that are not yet present in the market. Finally a case study was conducted evaluating both thermal transmittance and dynamic thermal properties of one lightweight and three heavyweight walls, with different types of insulating materials and ways of installation (external, internal or cavity insulation).

Insulation materials for the building sector: A review and comparative analysis

Phase change materials (PCM) for cooling applications in buildings: A review

Phase Change Materials and Products for Building Applications: A State-of-the-Art Review and Future Research Opportunities

Shape-stabilized phase change materials based on porous supports for thermal energy storage applications

Vacuum insulation panel products: A state-of-the-art review and future research pathways

Low-emissivity materials for building applications: A state-of-the-art review and future research perspectives

Vacuum insulation panels (VIP) represent a state-of-the-art high-performance thermal insulation solution. The pristine non-aged centre-of-panel thermal conductivity value for a VIP can be as low as 0.002–0.004 W/(mK) depending on the core material. Normally, declared average values accounting for thermal bridge effects and ageing during e.g. 25 years are to be given, typical an effective thermal conductivity value between 0.007 and 0.008 W/(mK) for VIPs with fumed silica cores. VIPs enable highly insulated solutions for building applications, both for the construction of new buildings and for the renovation of existing buildings, and may hence be a measure to reduce the energy usage in buildings without having to employ very thick building envelopes. This study gives a state-of-the-art review of VIP products found available on the market today and explores some of the future research possibilities for these products. The application of nanotechnology is regarded as a promising pathway for achieving and improving both vacuum and non-vacuum based high-performance thermal insulation materials. During the last years, VIPs have been utilized with success for building applications in increasing numbers, where one of the main driving forces is the increased focus on e.g. passive houses, zero energy buildings and zero emission buildings. Thus, VIPs are now in the early market stages as a building product. The implementation of VIPs in various building constructions has lead to an increased interest in the utilization of this product, both in new and refurbished constructions. Even though there is not enough data to conclude the effect over a lifetime of a building yet, the immediate result in decreased energy usage can be seen. However, the challenges of guaranteeing a set of lifetime expectancy, along with high costs, are some of the major reasons why VIPs are met with a certain scepticism in the building industry. Aiming to give better quality assurance for the users, make further advances in VIP envelope technologies and the development of VIP core materials, along with a further cost reduction, represent crucial aspects for VIPs to become a competing thermal insulation solution for buildings.

Simen Edsjø Kalnæs

Papers

Phase Change Materials and Products for Building Applications: A State-of-the-Art Review and Future Research Opportunities

Vacuum insulation panel products: A state-of-the-art review and future research pathways

Low-emissivity materials for building applications: A state-of-the-art review and future research perspectives

Nanotech Based Vacuum Insulation Panels for Building Applications