In the south states of Brazil the buildings of social interest do not have any kind of heating possibility. Although it is hot in the most part of the country, in the winter there are some regions in south with negative temperatures. The costs of the energy and technology for heating are expensive. This makes with those who doesn't have financial conditions do not have thermal quality in the winter, because in this cases there are not any kind of heating systems in the buildings. For this reason, it has been developed, in the Architecture Department of Passo Fundo University, Brazil, a new natural heater to be used in building with social interest. The objective of this work is to create equipments with low costs. The equipment uses solar radiation to heat internal spaces in the buildings, and uses solar energy to reduce the costs of the artificial acclimatization in the internal spaces. When the temperature is lower than 18 ºC, the system will be used. The equipment is composed by a metal structure with 1.00×0, 60×0, 30 meters, with glasses and an external protection for the hot seasons of the year. Inside the prototype, there are black rocks which receive solar radiation and heat both air and the wall. There are windows in the wall that control the heated airflow entrance. The prototype has already been made. The tests will start next June. The paper presents the project of the natural heater and the first results of the verification in loco.