Low-cost housing is a major issue in a developing country like India. In a region located close to the equator, such as  Deep South India, warm discomfort that occurs during the day time could become a problem unless houses are planned  with careful consideration. The main drawback in the existing modern low-cost housing is that it is not congenial to live and work in tropical climate. Because of thermal discomfort, the occupants spend most of the time living and sleeping outdoors. For preliminary investigation on thermal performance, housing units at three different locations in the deep south were selected. The parameters that affect thermal comfort were measured for different configurations at an interval of three hours round the clock in a day in alternate months from January to December of 2006. Accounting the observations, the value of Tropical Summer Index (Sharma andAli-1986) was determined and compared with that of the comfort temperature provision (Nicol.F.etal 1994). The result lie well beyond the level of comfort and the present research confirms the prevalence of thermal discomfort in all these housing units. The study highlighted that these units failed to provide thermal comfort mainly through lack of ventilation. This paper also presents a set of rules so that designers can easily include such rules at the stage of house-planning to bring down the parameters to comfort level.

Key words: Tropical Summer Index, Low-cost Housing, Dry BulbTemperature, Relative Humidity