Infrared radiation transfer through semitransparent windows supporting absorbing droplets

•First infrared transmittance and reflectance data for droplet-covered glass windows.•The droplet contact angle varied from 26 to 76o and surface area coverage up to 60%.•In most cases, the droplets reduce the transmittance due to absorption and/or back-scattering.•Measurements agree well with predictions from Monte Carlo ray-tracing simulations.•Solar transmittance of water droplet-covered glass windows can decrease significantly.