Abstract
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.
Highlights
Reduction of energy demand in buildings and mitigation of envi ronmental impact of cities are two of the main social, economic and environmental challenges nowadays
– To define the continuous variation of the TC material solar response when temperature varies along the transition range
The methodology is applied to the characterization of a TC mortar (TCM) developed by the authors for application as façade coating
Summary
Reduction of energy demand in buildings and mitigation of envi ronmental impact of cities are two of the main social, economic and environmental challenges nowadays. Substantial progress to achieve these two challenges may be provided by properly managing the optical response to solar radiation of the materials implemented in building envelopes For this reason, important research efforts have been devoted in the last decades to the development of building materials with specific solar response. Thermochromic (TC) smart materials, able to adapt their solar optical response depending on the temperature, are more suitable to manage solar radiation in locations with significant variations of ambient temperature This functionality has been mostly developed for TC glazing based on vanadium (IV) oxide thin films and nanoparticles (Cui et al, 2018). This transition temperature may be lowered by adequate elemental doping down to values close to usual envelope temperatures in buildings (Faucheu et al, 2019)
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