This study evaluates the performance of three low-income passive housing designs at
providing thermal comfort for their inhabitants in temperate tropical rural Tanzania. Severe climatic
conditions in these upland regions include large daily oscillations in air temperature (14°C-36°C)
and high levels of solar radiation, causing overheating which affects inhabitant health and
wellbeing. Inadequate shelter in these difficult climatic conditions is a widespread problem with 71%
of Tanzanians living in rural areas, of which 28% of are below the national poverty line. Over the
last 10 years an increasing number of houses are using modern building materials (brick or concrete
walls and iron roof) rather than traditional vernacular design (mud-pole walls and thatch roof). Three
designs were chosen to describe this transition. The performances of the three houses were
simulated across a study year using IES and then compared against five chosen criteria to assess
thermal comfort. Detailed analyses of critical times of day and specific areas of the building
envelope were used to identify critical areas of design. The traditional house overheated
significantly less often with smaller diurnal indoor temperature swings than the modern houses (due
to its higher roof insulation and wall thermal mass). It also experienced uncomfortably low
temperatures least often but maintained higher temperatures for longer during hot evenings. The
modern houses outperformed the traditional house in ventilation gains with constant heat rejection
throughout the day and night. The traditional house’s open structure resulted in high daytime
ventilation gains and night-time heat rejection. Consideration of the position and internal gains of
each room was found to be an important design factor. Across the study year the traditional design
provided greater thermal comfort. However, as durability and social pressures are important factors
in the choice of building materials, the design of modern materials that can mimic and improve on
traditional material performance is critical to improving the health of inhabitants.