It can be observed from the table above that, in this study, the main weaknesses in terms of the prototypes’ thermal performance are issues of: high maximum ambient air temperature values during the hot season, with variation depending on the building, and low minimum ambient air temperature values during the coldest period of the winter This indicates a possible direct relationship to external air ambient air temperatures without much modulation, especially in the cooler periods. Different materials appeared to behave in very different ways with regards to their capability to absorb and release the heat. The two corrugated sheet metal roofs (Types A & B) appear to absorb heat at the very highest rate, whilst the golpata leaf roof (Type C) seems to absorb heat at the lowest rate. Clay tile roof performance (Type D) is in between the golpata leaf roof and the corrugated sheet metal. With regards to the walls, the bamboo mat walls actually appear to a better material for allowing the living space to breathe and avoiding the overheating of the houses during the hot season, as we could observe comparing the thermal performance of both corrugated sheet metal roof prototypes A and B. During the hot season, the golpata leaf roof (Type C) records the lowest maximum ambient air temperature values and its ambient air temperature stays above the comfort range for the shortest period of time during the day. On the basis of these observations, the thermal performance of the golpata leaf roof appears to be better than the other prototype houses. During the winter, there seem to be no 20
considerable differences in minimum ambient air temperatures between the four prototype houses. In fact, the houses have been designed to maximise air flow in order to answer the need for ventilation during the hot months of the year, and therefore fail to keep the living zone warm during the winter nights, with ambient air temperatures dropping below the comfort range of 17 ËšC, sometimes reaching minimum values of 13-14ËšC for up to 8 hours overnight. However, the colder internal ambient air temperatures at night were for a period of approximately 2-3 weeks, whereas the warmer season lasts for approximately 8 months a year, in which case one could conclude that overheating may be more of an issue than being too cool. This does not however preclude good design that can do both, and further investigation into the inclusion of thermal mass and/or other materials in housing would be beneficial, to understand how winter performance could be improved. This may also have beneficial consequences for overheating in summer.
Research limitations The main limitation of this study is due to the absence of external ambient air temperature data from the weather station. This made it impossible to compare internal ambient air temperature data from the monitored houses to local external ambient air temperatures, in order to assess with more precision their level of performance (eg ability to modulate external temperatures). Further limitations come from the positioning of the data loggers inside the houses. The data loggers were placed very close to the surface of walls and roofs. They therefore may not have reflected exactly the internal ambient air temperatures perceived by the occupants. They may have been affected either by proximity to metal components of the buildings such as sheet metal walls, wood, each with different