Long-term performance of glass fiber Vacuum Insulation Panels exposed to severe operating conditions in buildings

Vacuum insulation panels (VIPs) provide an effective solution for retrofitting building envelopes, particularly when space for conventional insulation is limited. However, certain conditions can accelerate the ageing of VIPs. Roofs, in particular, represent the largest exposed area to outdoor thermal stresses (rain, solar radiation, temperature fluctuations). This study examines the long-term thermal performance of glass-fiber VIPs in building applications, with a focus on attic space conversions and energy retrofits. Specifically, glass fiber VIPs incorporating integrated getter technology were investigated. These panels, which offer lower thermal conductivity than traditional fumed silica VIPs, can extend service life by adsorbing permeated gases. A full-scale roof test room was used to monitor the long-term performance of these panels under natural exposure conditions over four years, assessing their thermal and hygrothermal behavior over the time. The primary objectives of the study were to evaluate the improvements of the thermal performance achievable by retrofitting an attic space with glass-fiber VIPs. Analyses were extended to cover both summer and winter period and were aimed at: analysing the risk of hygrothermal stress on the panels, validating models for the prediction of their service life, with real-world data, and detecting possible changes in thermal conductivity over time due to ageing. The results showed that the VIP-retrofitted roof significantly reduced heat losses in winter and enhanced thermal insulation in summer, keeping thermal conductivity below 2.7 mW/mK after four years of real life usage. The monitored boundary conditions—temperature and humidity at the panel surfaces — revealed that VIPs were exposed to severe operational conditions. Despite this fact, the observed values remained within acceptable limits, ensuring long-term service life without rapid degradation. The data from this study are significant for validating ageing prediction models and improving the knowledge about the use of glass fiber VIPs in real building envelope applications. In conclusion, glass fiber VIPs offer significant potential for improving the thermal efficiency of roof attics, providing a durable and effective solution for energy retrofits. The data gathered from four years of exposure to severe environmental conditions will be instrumental in validating ageing prediction models, that can be extensively used for demonstrating the conditions under which glass-fibers VIPs can guarantee an acceptable service life and supporting their adoption in sustainable building practices.