Abstract:
Globally, over one-third of total energy is consumed by the residential building sector (IEA, 2013). In
Bangladesh, more than 40% of electricity is consumed in the domestic sector by air-conditioning (AC)
and fans for comfort cooling (JICA, 2015). Windows, the drivers of natural ventilation, if designed and
adopted properly can offset energy guzzling AC devices, while providing thermal comfort. During the
design phase, sizing windows against room area and wall area have a considerable effect on achieving
thermally acceptable indoor air temperature for occupants. This simulation based study analyzes the
impact of varied window-to-floor area-ratio (WFR) and window-to-wall area-ratio (WWR), on
bedroom air temperature in residential apartments, thereby providing possible design options for such
spaces, to offset energy consumption, while keeping air temperature within a comfortable limit.
Initially, a base-case bedroom simulation model was formulated by conducting a random questionnaire
survey and case study analysis of high-rise apartment buildings of the upper middle income group of
Dhaka along with a comprehensive literature review on comfortable air temperature in such rooms.
Simulation was done in Ecotect Analysis and WinAir to figure out indoor air temperature and air
movement pattern respectively for the base case, as well for varied WFR and WWR. Simulation
outcomes were validated, by comparing with measured values from a pilot survey conducted inside a
bedroom of the topmost floor of an existing high-rise residential building. Comparative analysis was
used to predict the best possible WFR and WWR configurations for obtaining a comfortable air
temperature within this space. The result reveals that WWR, ranging from 20% to 30%, is preferable
for inducing lower indoor air temperature in the south west corner rooms of naturally ventilated
buildings.
