Upcycled construction materials to reduce dwelling overheating in tropical climates: The bottle house

Component testing indicates that overheating in tropical buildings could be reduced using walls built from upcycled sand-filled plastic bottles, which also reduces building costs and prevents waste from polluting the environment. It is not yet known, however, how these bottle-composite walls influence thermal comfort in dwellings in-situ. This study presents the world's first in-situ measurement of indoor temperature in a “bottle house” which is compared to four other traditional dwellings, two with mud walls and two with sandcrete walls, over a 76-day monitoring period between April and June 2019. Aside from the wall and ceiling construction, the dwellings were otherwise similar in design and located in the same settlement in Abuja, Nigeria. The results showed that on average the bottle house was 2.4 °C cooler than the hottest mud dwelling and 1.8 °C cooler than the hottest sandcrete dwelling. Overheating, determined using the adaptive thermal comfort criteria, occurred in all five dwellings but was lowest in the bottle house. On the day with the highest maximum outdoor temperature (38.2 °C), the bottle house was the coolest dwelling during night time sleeping hours and was 3.4 °C cooler than the hottest mud dwelling during daytime waking hours, although 2.0 °C warmer than the coolest house, which had sandcrete walls. Thus, bottle-composite walls could be a suitable low-cost construction method which contributes to reducing overheating in tropical climates but require additional heat mitigation measures to reduce indoor temperatures to comfortable levels on the hottest days.