The Urban Heat Island (UHI), a consequence of urban development, leads to elevated temperatures within cities compared to their rural counterparts. This phenomenon results from factors such as urban designs, anthropogenic heat emissions, and materials that absorb and retain solar radiation in the built environment. Materials commonly used in cities, like concrete, asphalt, and stone, capture solar energy and subsequently emit it as heat into the surroundings. Consequently, this phenomenon amplifies summertime cooling energy demands in buildings. To mitigate the UHI impacts, various mitigation strategies have emerged that include but are not limited to using higher solar reflectivity materials, known as “cool materials”, and increasing vegetation and greenery in urban areas. Cool materials have high reflectivity and emissivity, effectively reflecting solar radiation while emitting absorbed heat through radiative cooling. Increasing the solar reflectivity of building envelope materials is a promising sustainable solution to lessen the UHI effects. This state-of-the-art review summarizes the UHI causes and effects, states the mitigation strategies, describes the cool building envelope materials, explains the solar reflectivity index measurements, indicates the building and micro-climate simulations, highlights the performance evaluation of using cool building envelope materials, points out the research gaps, and proposes future research opportunities.

Extreme low temperatures, heavy snowfall, ice accumulation, limited daylight, and increased energy consumption in cold climates present significant challenges but also offer opportunities for improving building efficiency. Advanced materials and technologies in climate-responsive envelopes can enhance sustainability, reduce carbon footprints and operational costs, and improve thermal comfort under these environmental conditions. This literature review combines theoretical aspects of building performance in cold climates with a summary of current and critical applications in building envelope design, identifying research gaps and proposing future research directions. It has been shown that various BIPV systems require further climate-based studies to optimize solar energy yield. For example, integrating PV layers and PCM within DSFs can reduce cooling loads, but more research is needed on PCM transition temperatures and ventilation strategies in cold climates. A notable research gap exists in building-integrated vegetative systems, particularly regarding soil thickness, irrigation, hygrothermal performance, and snow accumulation. Despite excellent winter performance in buildings incorporating CLT components, they face increased cooling energy consumption and potential overheating in summer. Additionally, the high initial moisture content in CLT raises the risk of mold growth, especially when covered with vapor-tight layers. The design examples in this paper emphasize the need for further investigation to achieve sustainable, low-carbon, energy-efficient envelope designs for cold climates.

This study investigates the impact of high-performance polyvinylidene fluoride-co-hexafluoropropylene (P(VDF-HFP)HP), a reflective material, on the energy performance and Indoor Thermal Autonomy (ITA) of a primary school building in Montreal under historical and future climate scenarios. Energy simulations, conducted using Rhino-Grasshopper, analyze heating and cooling demands for an ANSI/ASHRAE/IES Standard 90.1 school prototype designed according to the 8th edition of the National Building Code of Canada (NBC), reflecting construction practices the 1980’s. The results reveal that reflective materials slightly increase heating demand due to reduced passive solar heat gains during winter but significantly lower cooling demand by minimizing solar heat absorption. In a heating-dominated climate like Montreal, this trade-off leads to a net reduction in total energy use under future climate scenarios. As the warming climate lessens heating requirements, the substantial decrease in cooling demand contributes to overall energy savings. Reflective materials thus prove particularly advantageous in warmer future climates, where the cooling energy savings outweigh the heating penalty, improving overall building energy performance. In addition, reflective materials enhance ITA, albeit marginally, with a maximum increase of 3%, improving indoor comfort under both historical and future climate conditions. These findings highlight the potential of passive building envelope enhancements to contribute to energy efficiency and climate resilience. By promoting sustainable solutions, reflective materials align with the United Nations Sustainable Development Goal 13 (Climate Action).