Assessment of the visual, thermal and energy performance of static vs thermochromic double-glazing under different European climates

Highly glazed buildings are typically responsible for significant solar heat gains/losses and, consequently, considerable cooling and heating energy needs throughout the year. Thermochromic glazing is an innovative passive technology, which autonomously and reversibly modifies its thermal and optical properties when direct sunlight heats it, potentially improving both energy efficiency and comfort. However, there is scarce evidence about the global performance of this glazing when installed in commercial buildings. Therefore, this study aims at assessing the annual visual, thermal and energy performance of a thermochromic glazing (12 + 12 + 6 mm) against a conventional clear glazing (6 + 12 + 4 mm) with and without a reflective solar control film installed in an existing office room, considering different European climates. To this aim, a building simulation model calibrated with experimental data obtained on a previous study was used. The results showed that in respect of the percentage of working hours with useful illuminance levels the thermochromic glazing (80%–88%) is better than the conventional clear glazing (64%–74%). However, the glazing with the reflective solar control film is more effective in reducing potential glare. Regarding the thermal performance assessment, under free-float conditions (no mechanical heating/cooling), the thermochromic glazing shows a better performance (20%–48% working hours within comfort conditions) when compared to conventional glazing (1%–42%). The results also show significant total energy savings (climate control and artificial lighting) in the case of the thermochromic glazing, particularly in the hot climate of Lisbon (50%). • Comfort and energy performance of thermochromic versus conventional static glazing. • Building simulation model of an office room calibrated with experimental data. • Up to 88% of working hours with useful illuminance with thermochromic glass. • Up to 48% of working hours within thermal comfort with thermochromic glass. • Up to 50% of energy savings with thermochromic glass when compared with clear glass.