Multiscale hygro‑radiative performance of innovative lime mortars for heritage building conservation

Heritage buildings require sustainable retrofit solutions that enhance hygrothermal behaviour without compromising material compatibility or long‑term conservation. To address this challenge, this study employs a multi‑scale experimental and numerical framework to investigate the performance of three innovative lime mortars engineered for low solar absorptance and reduced thermal conductivity. The diatomaceous‑earth mortars are characterised in the laboratory to quantify their hygrothermal and optical properties, and these results are integrated into component‑level and zone‑scale simulations calibrated with in‑situ measurements from a historic public building in Morón de la Frontera (Seville, Spain). Six lime‑mortar retrofit layer configurations are assessed against a conventional dolomitic‑sand lime mortar to compare moisture and thermal performance under Mediterranean climatic conditions. Results show that external application of the diatomaceous mortars prevents moisture accumulation, enhances drying capacity, and increases wall thermal resistance by approximately 8% for most of the year. Indoor comfort responses are season‑dependent, with moderate improvements in summer and mid‑season but slight reductions in winter due to lower solar gains. Dual interior–exterior applications perform worst, likely due to restricted night‑time heat dissipation. Overall, this work provides one of the first multi‑scale evaluations of reflective, heritage‑compatible mortars, demonstrating both their potential and their limitations for energy‑aware conservation strategies.