Impact of Incorporating NIR Reflective Pigments in Finishing Coatings of ETICS

Abstract

Near-infrared (NIR) reflective materials are being developed for mitigating building cooling needs. Their use contributes to broadening the range of colours, responding to the urban aesthetic demand without compromising the building performance. Despite the increase in NIR reflective pigments investigation, there is still a knowledge gap in their applicability, impact, and durability in multilayer finishing coatings of External Thermal Insulation Composite Systems (ETICS). Hence, the main goal of this work consists of evaluating the impact of incorporating NIR reflective pigments (NRP) in the solar reflectance of the surface layer of ETICS, without affecting the colour perception, as well as their influence on the colour durability and surface temperature. As such, colour, solar reflectance, and surface temperature were monitored for 2 years in dark-coloured specimens of ETICS, with and without NRP and a primer layer. It was confirmed that the main contribution of NRP is the increase of solar reflectance and, consequently, the decrease in surface temperature, especially for high exterior temperatures (around 30 ºC). Moreover, these pigments highly increase the NIR reflectance without affecting the visible colour. In addition, they contribute to maintaining the colour characteristics. The application of primer increased the surface temperature, especially for higher exterior temperatures. However, it contributes to a lower colour difference and solar reflectance variation, which is an important achievement for durability purposes.

NIR reflective Paints as an Alternative for Sustainable Façade Renovation

“…The studied control samples have a colour difference superior to 3, and this difference is attributed to the lightness variation. The described results were similar to the found by Alonso et al [24] and Ramos et al [7], indicating that paint refurbishment changes the optical properties of existing systems, keeping the emissivity and increasing the reflectance on the black system but reducing the grey, as expected due to the colour change.…”

“…The gain was 67% in samples with the original black system using the regulation layer (BCW vs. BSW), while in the grey system, the improvement was 123% without the regulation layer (GCG vs. GSG). The reflectance modification due to NIR reflectance was also verified in [7,16]. Figure 4a and Figure 4b present the reflectance spectral behaviour of the system after paint, respectively, for the UV-Vis and NIR regions.…”

“…The colour of the finishing coat of ETICS can impact the durability of the system [5] since it contributes to the protection against weathering but can cause thermal shock leading to cracking and the loss of hygrothermal performance. To prevent thermal stress, the European Association for the External Thermal Insulation Composite Systems (EAE) [6] recommends that the finishing coat should have a solar absorption under 70% and the surface temperature should not go above 80º C. But coatings with dark colours like brown, grey, and black could present around 80% and 95% solar absorption, as demonstrated by Ramos et al [7].…”

Cool Surface Strategies with an Emphasis on the Materials Dimension: A Review

“…On the other hand, the development of new compositions of reflective pigments continues to increase, reaching more potential evaluations. In addition to the high reflectivity, the research field has also been evaluating the functional and long-term performances against surface contamination [69], thermal insulation [70,71], and the synthesis methods in terms of the energy and raw material costs, which were directed for the sol-gel method and rare-earth compounds [72][73][74][75][76][77].…”

The Application of Silica-Based Aerogel Board on the Fire Resistance and Thermal Insulation Performance Enhancement of Existing External Wall System Retrofit

“…Currently, applying the thermal barrier coating on the outer surface of the wall or roof is a common solution to enhance the heat insulation performance of a building in the regions with a subtropical or tropical climate [5,7,8]. Alternatively, thermal insulation the interaction of external factors such as typhoons, earthquakes and dramatic temperature changes, problems such as falling and defects of tiles will affect the buildings' appearance and even endanger the safety of the people.…”