Performance evaluation of humidity controlled decentralized ventilation systems in social housing in Chile

More than 70% of the dwellings in Chile were built before 2000, when the use of thermal insulation in the roofs of residential buildings became mandatory. This explains why less than 2% of dwellings are considered energy efficient. Social housing is no exception. Several studies have shown poor thermal performance of the envelope of social housing throughout the country, with low levels of thermal comfort and indoor air quality that affect the health of its occupants. Retrofitting programs for social housing launched by the government in recent years have implemented more rigorous thermal standards, along with the installation of humidity controlled decentralized mechanical exhaust ventilation systems. However, it is not known whether such ventilation system can effectively guarantee air quality in homes.  
This study evaluated the indoor air quality and ventilation heat losses of a typical social house in Chile equipped with a humidity-controlled ventilation system using the airflow and pollutant transport calculation software CONTAM. It was shown that such a system does not at all guarantee the indoor air quality, especially in the bedrooms during the night hours. Several alternative ventilation systems and strategies were identified and evaluated. Two of them showed good performance in terms of indoor air quality while limiting ventilation heat losses, for the moderate and high occupancy profiles considered in this study. They include demand-based ventilation using CO2 concentration detection. The first system is based on the extended cascade ventilation principle, while the second includes the addition of an exhaust system specific to bedrooms. They reduce the ventilation heat losses by about 32% and 37% on average, respectively, compared to a continuously operating ventilation system, while ensuring an equivalent level of indoor air quality.  
By proposing better solutions than those currently used in social housing, this study will contribute to the development of public policies aimed at improving the comfort and health of social housing occupants while limiting the dwelling’s energy use.