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With the recent discoveries and engineering solutions emerging in nanomaterials and nanostructures, independent band modulation of solar radiation on building envelopes, including glazing systems, has become increasingly viable as a potential means of improving building energy savings and indoor visual comfort. However, when it comes to the prediction of these new materials’ potential energy performance in buildings, most studies utilize a simple solar irradiance (e.g., global horizontal solar irradiance, direct beam solar irradiance) or a rough estimation of solar infrared (e.g., 50% solar irradiance) as input, which may cause significant errors. Consequently, there is a pressing need for reliable performance estimations of the solar infrared control and response at the building’s scale. To assess this, we need a solar spectral irradiance model, or at least a wideband (visible or infrared) solar irradiance model, as input. To develop this new type of model, one needs to understand the modeling-related key elements, including available solar spectral irradiance datasets, data collection methods, and modeling techniques. As such, this paper reviews the current major measurement methods and tools used in collecting solar spectral irradiance data with a focus on the solar infrared region, identifies the available related resources and datasets that particularly encompass the solar spectral irradiance data with a sufficient wavelength range, and studies existing solar irradiation modeling techniques for building simulations. These investigations will then form the background and backbone for a study scheme of solar infrared radiation modeling and indicate future research paths and opportunities.

Windows not only mediate thermal transfer, light transmission, noise control, and natural ventilation but also serve as an architectural element affecting a structure’s aesthetics and appearance. Since the glazed window was first developed in Egypt in 100 AD, the thermal and optical performance of windows have been primary concerns for architects, engineers, and researchers. Today, windows are of special note because of their relationship to building sustainability and energy-efficient design. According to recent National Fenestration Rating Council reports, due to the relatively lower thermal insulation among all building envelope components, windows are normally responsible for 25–30% of the total heating, ventilation, and air conditioning energy use. This non-neglectable use of energy has motivated researchers to investigate various energy-efficient technologies and design solutions. Windows gain and lose heat through conduction, convection, and radiation. These properties can be measured and rated according to the following energy performance characteristics: insulating value, heat gain from solar radiation, and air infiltration rate. Conversely, the optical properties of windows determine their interaction with light and indoor occupants. The visible transmittance (corresponding to the fraction of impinging visible solar radiation transmitted) and haze value (meaning the clarity of the window) must both be taken into account. Most technology modulating the optical properties of windows also affects their thermal properties. Thus, the process of designing and engineering building windows is uniquely complex, involving both thermal and optical behaviors that affect building energy use, occupant comfort, and architectural aesthetics.

Thin films made of metallic nanoparticles can exhibit strong photothermal effects (PPE) on near-infrared light irradiation, paving a way for new designs of spectrally selective building windows for solar infrared modulation that operates without the need to compensate for visible transmittance. More importantly, the surface plasmon-induced light-to-heat conversion creates strong localized heating effects with a much smaller fraction resulting in the heating of the substrate. Incorporating such nanoscale PPE into the design of complex building fenestrations, this research conducted a comprehensive analysis to better understand the PPE-induced heating effect and conductive, convective, and radiative heat exchanges between windowpane surfaces and the surrounding indoor and outdoor environments. The authors first developed and then validated a numerical analysis method to incorporate spectral features, solar spectral irradiance, and nanoscale PPE. Subsequently, using the established numerical method, two-dimensional windowpane temperature profiles and solar heat gains were yielded under different boundary conditions. To understand the energy performance of windows with solar near-infrared-dependent PPE, a series of parametric energy simulations was employed. The results show the photothermal coating can be used as a new energy-efficient retrofit technology for single-pane windows, with heating energy saving 16.2–20.8%, which performs similar to the double pane windows. Notably, these energy savings were not achieved by increasing the thermal insulation via additional layers or insulating materials, but rather by the spectrally selective design of glazing materials and utilization of solar near-infrared energy. This work presents the energy saving mechanism on an architectural scale due to the nanoscale surface plasmon-induced photothermal effect and associated heat gain coefficient enhancement. It also poses a fundamental reference for the future integration of this novel nanoscale phenomenon into the building envelope systems.