This paper presents a novel and facile approach for synthesizing silica/polymer hollow microspheres (SPHMs) and their application as highly effective thermal insulation fillers in UV-cured coatings. The SPHMs were synthesized without the need for templates, offering an eco-friendly and energy-efficient production method. These SPHMs exhibit uniform particle sizes (average 450 nm) and hollow cavities (around 200 nm), featuring a silica shell layer, leading to a maximum reduction of 66.5% in thermal conductivity. Comparative studies against commercially available hollow glass microspheres (HGMs) reveal that SPHMs demonstrate superior thermal insulation performance and lower thermal conductivity. Moreover, SPHMs can be evenly dispersed in UV-cured resins at concentrations of up to 7.5 wt %, significantly enhancing the thermal insulation capabilities of the coatings while preserving their fundamental properties. Experimental results conducted on house models underscore the exceptional thermal insulation potential of SPHMs. In comparison to pure resin coatings, SPHMs induce a remarkable temperature reduction of 14.5 °C, surpassing the performance of HGMs with a temperature decrease of 7.5 °C. This study introduces a novel and straightforward synthesis method for SPHMs and highlights their outstanding potential as thermal insulation fillers in UV-cured coatings. The environmentally friendly synthesis process, combined with their low thermal conductivity and remarkable thermal insulation performance, positions SPHMs as a valuable candidate filler for the coating industry. They hold the promise of contributing to energy-efficient building solutions and advancing the field of thermal insulation coatings with their exceptional properties.