Denied delights of daylight in density: Optimizing building codes to achieve maximum daylight in apartments of Dhaka, Bangladesh

Abstract

Daylight-inclusive building codes are difficult to establish for rapidly developing dense urban centers in the global south. Obstruction Angle (OA) has long been used as a precursor in daylight-inclusive building codes. However, such codes are more suitable for higher latitude cities with low-rise developments but less effective in low latitude dense cities such as Dhaka. Existing research established Unobstructed Vision Area (UVA) as a critical daylight precursor for dense urban developments. This study further established Canyon Wall Porosity (CWP) as another critical daylight precursor and detailed a CWP calculation method. Via OA, UVA, and CWP, this study examined existing Dhaka building codes against optimal values for setbacks, building height limit, Floor Area Ratio (FAR) and Maximum Ground Coverage (MGC). The findings revealed: (a) 63° OA is critical for Dhaka, and it should be used to set setbacks distances and building height limits (b) front setbacks could be narrower as streets assist in sustaining 63° OA, but rear-setbacks should be significantly wider (c) MGC should be lower to achieve high CWP for adequate daylight. These findings, especially the introduction of CWP for daylight inclusivity, could be a catalyst for solar legislation in other mega-urban centers on similar latitudes.