Maximising the amount of light entering deep into a room and minimising glare hotspots has always been a gauge of the success of a humane living and working environment. However, it has always been deceptively difficult to do well. Serraglaze, a company fronted by venture capital firm Redbus, automotive designers and building technologists, believes that it has come up with the answer.
With conventional glazing, the sunlight which enters a room is restricted by its angle of incidence and the size of the window opening. Even though secondary light (that is, light bouncing off reflective surfaces) will improve the general level of illumination, it is the rays directly entering which are the most significant. Usually, light will fall within just a few metres of a window, (depending on sun elevation and proximity of adjacent structures), creating unacceptable glare at the front and inadequate light levels at the rear.
By manufacturing a glass with minuscule air pockets in the middle, primary source light can be bent further into the room.Although only in prototype stage at the moment, early results look promising.
The system comprises a film, sandwiched between two layers of glass to form a laminated finished product, which has the same toughness and safety properties as other laminates. The film layer itself is the secret. It is made up of two opposing saw-tooth faced films, which are adhered so that only one pair of unbonded, non-contact surfaces remain (see sketch). These gaps in the film - 0.3 mm deep, a few microns thick and the full width of the pane - occur at 4mm horizontal centres. The proximity of these voids ensures that a significant percentage of light striking the glass undergoes total internal reflection; effectively bending the light upwards with no need for silvering the glass.
Tested on a scale model of a darkly furnished office (light behaves the same way regardless of scale), light levels were improved by 70 per cent at the rear of the room and glare reduced by 30 per cent at the front. The resultant 'evening out' of light across the room means that discomfort will be reduced and visibility enhanced.However, unless viewed directly perpendicular to the glass surface, the glass appears slightly tinted and vision through the glass is distorted as light is bent away from the eye, until visual cut-off at about 45degrees to the normal.
Those sitting near a Serraglaze window will not be able to see clearly up or down and the manufacturer is considering a number of options to correct this, including locating the laminate in top panes only, or by angling the unit.
Additional work needs to be done on the psychological effects of the visual distortion, as well as reducing the incidence of light flares across the striations of the sandwiched film.
However, the possibilities for substituting Category 2 blinds, enhancing north-facing windows (using vertically aligned films) or glare-reducing/light-enhancing brises-soleil are just some of the exciting avenues yet to be explored.
Serraglaze's system comprises a film sandwiched between two layers of glass.
Minuscule air pockets in the middle of the glass enable the primary source light to be bent further into the room