Assessment of buildings' dynamic thermal insulation technologies-A review

Towards the achievement of nZEB and the enormous effort for mitigating climate change effects, new sustainable construction strategies are continuously introduced and adopted in the building sector. Thermal insulation is considered a fundamental strategy before moving to more complex ones. Over the past 50 years, thermal insulation is mainly conceived and implemented through the steady-state heat transfer simplification, making its contribution easy to predict and control with high confidence. While historically, the concept of 'dynamic thermal insulation', or otherwise, variable thermal insulation is mainly found in warm regions, numerous recent studies show that there is a continuously growing interest in implementing it into buildings to counterbalance the few disadvantages of intense thermal insulation or to allow buildings adapting to the varying seasonal climate conditions. This interest is depicted in numerous published studies, supporting that thermal insulation can have a more beneficial and complex contribution than the steady-state assumption allows and that it can provide great potential for improving a building's energy efficiency by advancing and optimizing the envelope's thermal insulation according to the actual needs of the building on a year-round basis. In this review study, an effort to organize and classify the advances in the field is attempted, aiming at defining the complexity, the limits, the applicability and the barriers of all systems and techniques. Challenges regarding their wide utilization in the construction industry are highlighted, along with suggestions for future research. As the study shows, a few of the many approaches to dynamic thermal insulation can be simple and effective, while others show greater potential. What is more evident thought, is that further research is needed before their implementation can become practical.