Housing marginalized communities in resilient homes is an important aspect of building a climate-resilient population. In this study, the daily temperatures in a semi-permanent home in a densely populated slum have been compared to those in the homes in a consciously designed in situ slum rehabilitation project built using vernacular technologies. On monitoring the indoor and outdoor temperatures over nine months under both conditions, results clearly indicated that the permanent homes are significantly cooler than the semi-permanent homes or slums by an average of 10%−15% due to the higher thermal mass, insulation, and ventilation. The temperatures are also more stable, with lesser variation between seasons. The paper demonstrates that through minimal additional investments and good design prioritizing thermal comfort and ventilation, low-cost slum rehabilitation projects could lead to a healthier and more productive society. Such field investigation studies support robust modeling and design of rehabilitation homes.