Thermal Comfort in a Hot-Humid Climate Through Passive Cooling in Low-Income Residential Buildings in Abuja, Nigeria

The research investigates the thermal performance of residential buildings in Abuja, Nigeria during the dry and rainy seasons. A field study was conducted to understand the real and preferred conditions of thermal comfort in low-income residential buildings, which represent the largest single housing sector. Knowing the temperatures people are experiencing in their houses and the limits that residents can tolerate is a first step to proffer passive solutions to reduce discomfort and energy demand and then satisfy the energy demand passively. During the survey, 222 people responded to a post occupancy questionnaire and for the ten selected case study dwellings, a comfort survey questionnaire was used. Physical measurements were taken simultaneously during the comfort survey in both air-conditioned and naturally ventilated residential buildings. The ASHRAE and air flow sensation scales were chosen as voting scales. This survey further looked at possible barriers to the implementation of more sustainable approaches that would enhance passive solutions in Nigeria, since the conventional means of cooling in this hot-humid climate is becoming expensive and less satisfactory.

The results from the study showed that during the dry season monitoring period, the average and maximum temperatures in the air-conditioned case studies were 32°C and 34°C; and 31°C and 36°C for the naturally ventilated buildings. This compares with the external average and maximum air temperatures of 31°C and more than 40°C. Dynamic simulation modelling was used to reveal the sensitivity of the cooling loads to various thermal interventions (e.g. insulation and shading) in the case study buildings. The optimum passive cooling intervention (involving roof and wall insulation and shading) proved to be effective in reducing the indoor maximum temperatures by more than 5°C for naturally ventilated cases and the cooling load. This translates to a monthly cost saving in the air-conditioned model of N8,110 (£16.97) which is significant compared to the Nigerian National Minimum Wage of N18,000 (£37.66).

This study makes a significant contribution to understanding the real and ideal thermal conditions occupants experience in low and middle income residential buildings in Abuja and demonstrates the effectiveness of passive interventions in reducing indoor temperatures and cooling loads.