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Radiant floor heating system combined with hydrate salt phase change materials (PCMs) can obtain energy savings along with improving thermal comfort. However, the inappropriate phase change temperature and the leakage of PCM limit its further applications. Here, sodium acetate trihydrate (SAT)-potassium chloride (KCl)-urea composite phase change material (CPCM) was composited with fumed silica (SiO2) to prepare shape-stabilized CPCM (SSCPCM) with adjustable phase change temperature for use in floor radiant heating. The effects of the mass fraction of SiO2 on phase change properties, and shape-stabilized ability of SSCPCM were emphatically studied. Besides, the morphology, porous structure analysis and chemical compatibility and related thermal properties of SSCPCM were discussed detailedly. The results manifested that SiO2 could not only regulate the melting temperature of SAT-KCl-urea CPCM, but also stabilize CPCM into its porous structure with large surface area and high porosity. Meanwhile, SSCPCM with 30 wt% SiO2 exhibited a good shape stability, and melted at 40.85 °C with high latent heat of 132.6 J/g, low supercooling degree of 0.29 °C as well as good thermal stability and thermal reliability. The result comparison of two test rooms confirmed that phase change floor radiant heating system can effectively increase the duration of indoor thermal comfort. All good thermal properties of SSCPCM make it prospective potential in radiant floor heating system for building energy efficiency. © 2023 Elsevier Ltd