A year-assessment of the suitability of a green façade to improve thermal performance of an affordable housing

Abstract

The urban green infrastructure has been increasingly used for sustainable design and resilient cities. Despite its many benefits, such as aesthetic enhancement, improvement of the physical and mental health of residents, especially for vulnerable youth and elderly people, or creating opportunities for social cohesion and climate regulation, green infrastructure has not been used in low-income housing in subtropical Brazil, where the temperature can reach over 40 °C along the summer. This study evaluated a full-scale, low-cost green façade over a year to assess its effect on the thermal performance of an eco-friendly affordable housing located in humid subtropical climate. Aiming to be eco-friendly and keep its cost low, the house was built with materials such as unplastered hollow soil-cement bricks, not having very good thermal performance. The Wisteria floribunda, a deciduous vine, was used in the green façade installed on a west-facing wall, adjacent to a bare wall, which was also evaluated enabling to establish the thermal difference between the shaded wall and the bare wall. In the winter, the shaded and bare walls' amplitudes were remarkably close, due to leaf shedding, a desirable feature to improve temperatures within the house. The benefits of the green façade were clearer during spring and summer when the external surface temperature of the shaded wall was reduced by up to 9 °C compared to the bare wall, and its thermal amplitude varied by 8.4 °C, while the amplitude of the bare wall was more than double this value. The plant layer diminished the heat flux through the external wall by up to 22.3 W/m2 during the summer, and 8 W/m2 during the winter. These results show the potential of a low-cost green façade to improve the thermal comfort of green affordable housing projects.