| Primary value | 1/10 of floor area (≈ 10%) |
| Applies to | Bedrooms · Living rooms · Kitchens (separate) · Study rooms |
| Measured as | Total glazed window area as a ratio of the room carpet area. Rooms with two external walls may have windows on either side to meet the ratio. |
| Source | NBC 2016 — Part 8, Section 1 📚 Cross-referenced |
10% glazing is the minimum that delivers usable daylight to the depth of an Indian room. Below this, occupants must use electric lighting throughout the day, defeating the climate-responsive design that NBC encourages.
Most modern apartments provide 12–15% glazing in habitable rooms. Premium and passive-solar designs go to 20%+.