Improved methodology for the characterization of thermochromic coatings for adaptive façades

Recent simulation studies conclude that the use of thermochromic (TC) materials at facade coatings has strong potential to reduce the energy demand of the building and the urban heat island effect. However, an improved methodology for the characterization of TC materials is necessary to obtain realistic simulations and to validate the simulated thermal behavior through affordable tests. In this context, the detailed variation of the optical performance of a TC mortar is characterized in this work under dynamic conditions, both for increasing and decreasing temperatures. The specific solar reflectance is determined for each temperature within the transition range with a resolution of 1 °C. The key factor is to couple the time for each measurement and the rate of temperature variation of the material. Furthermore, an affordable setup is defined to quantify the effect of the TC mortar on the surface temperature of facades compared to conventional coatings. The configuration adequately reproduces the relative orientation of facade coatings with respect to solar radiation. In addition, it ensures comparable exposure to solar radiation on all surfaces under analysis. Outdoor tests are carried out during three periods that represent the autumn, winter and summer climates in Madrid (Spain) and the experimental results are consistent with previous energy simulations. The methodology proposed in this work will be useful for the characterization of TC materials with greater durability currently under development. It will allow for more precise energy simulations and quantitative estimates of the effect of TC façade cladding on the sustainability of buildings.