In the centre of Sofia, the HARMONIA residential tower introduces a façade approach defined less by surface expression and more by controlled environmental response. The 16-storey volume is conceived as a calibrated envelope where glass selection directly shapes comfort, light quality, and the building’s external reading.
The façade system is based on a combination of SunGuard™ SN 70S in triple insulating glass units and SunGuard HD Silver Grey 32, supplied by Guardian Glass. Rather than treating glazing as a uniform skin, the composition uses two distinct optical behaviours to manage performance. The SN 70S units prioritise daylight optimisation while moderating solar gain, allowing deeper penetration of natural light without destabilising internal thermal conditions. This is particularly relevant in multi-storey residential layouts where consistent comfort across varied orientations becomes a design constraint.
In contrast, the HD Silver Grey 32 layer introduces a denser, more controlled reflectivity. It sharpens the façade’s depth and reduces visual noise, allowing the elevation to read as a continuous, composed surface rather than a fragmented grid of openings. The interplay between transmission and reflection creates subtle shifts across the façade, where the building’s appearance changes with sky conditions, time of day, and viewing angle.
The execution of this envelope required tight coordination between ARTEKS ENGINEERING as architect, Staklopaket TA as fabricator, and Arte Facade Design Ltd. responsible for glazing installation and façade delivery. Each party contributed to translating performance specifications into precise fabrication tolerances and on-site alignment. 
Rather than relying on ornamentation, HARMONIA builds its architectural identity through material calibration. The façade operates as a responsive layer, mediating climate, shaping interior experience, and defining the building’s urban presence through measured optical effects rather than overt visual gestures.
Photography © Stefan Shterev
Source: Guardian Glass with additional information added by Glass Balkan
