Measuring ventilation in different typologies of rural Gambian houses: a pilot experimental study.

BACKGROUND

African houses are frequently too hot and uncomfortable to use a bed net at night. Indoor thermal comfort is often evaluated by measuring temperature and humidity, ignoring ventilation. This study explored ways to measure ventilation in single-roomed rural Gambian houses during the malaria transmission season and evaluated building designs that could increase airflow at night and help keep the occupants comfortable.

METHODS

Two identical mud-walled houses were constructed with a metal roof, three doors and closed eaves. Experiment 1 compared five methods for measuring ventilation in a building: (1) using a blower door, (2) increasing carbon dioxide (CO) levels indoors using an artificial source of CO and then measuring the rate of gas decay, (3) using a similar approach with a natural source of CO, (4) measuring the rise of CO when people enter a building and (5) using hot-wire anemometers. Experiment 2 used CO data loggers to compare ventilation in a reference metal-roofed house with closed eaves and badly-fitting doors with a similar house with (1) thatched roof and open eaves, (2) eaves tubes, (3) screened doors and (4) screened doors and windows.

RESULTS

In experiment 1, CO data loggers placed indoors in two identical houses showed similar changes in airflow (p > 0.05) for all three methods recording either decreasing or increasing CO. Blower doors were unable to measure airflow in houses with open eaves or screened windows and the anemometers broke down under field conditions. In experiment 2, open eaves in thatched houses, screened doors alone, and screened doors and windows increased indoor ventilation compared to the reference metal-roofed house with closed eaves and badly fitting doors (p < 0.05). Eaves tubes did not increase ventilation in comparison to the reference house.

CONCLUSION

CO data loggers proved to be a simple and efficient method for measuring ventilation in rural houses at night. Ventilation of metal-roofed houses can be improved by adding two screened doors and windows on opposite walls. Improved ventilation will result in increased thermal comfort making it more likely that people will sleep under a bed net.