System for heating a building, wherein the system comprises: a building; a first inlet pipe located at a ceiling of the building; a first outlet pipe comprising a first part connected to the first inlet pipe and a second part connected to a first air membrane; a water container to which the first air membrane is connected; a first fan connected to the first inlet pipe or the first outlet pipe, wherein the first fan is arranged to, in operation, draw solar heated air through the first inlet pipe and blow the solar heated air through the first air membrane into the water container for forming micro-air bubbles of solar heated air in the water container; a second outlet pipe comprising a first part connected to an upper part of the water container for receiving heated air from the water container and a second part located at, or in a room in the building for supplying the heated air from the water container into the room; characterized in that comprising: a second inlet pipe comprising a first part located in the building and a second part connected to a second air membrane which is connected to the water container; and a second fan connected to the second inlet pipe, wherein the second fan is arranged to, in operation, draw air from the building through the first part and blow the air through the second air membrane into the water container for forming micro-air bubbles of air from the building in the water container. a building; a first inlet pipe located at a ceiling of the building; a first outlet pipe comprising a first part connected to the first inlet pipe and a second part connected to a first air membrane; a water container to which the first air membrane is connected; a first fan connected to the first inlet pipe or the first outlet pipe, wherein the first fan is arranged to, in operation, draw solar heated air through the first inlet pipe and blow the solar heated air through the first air membrane into the water container for forming micro-air bubbles of solar heated air in the water container; a second outlet pipe comprising a first part connected to an upper part of the water container for receiving heated air from the water container and a second part located at, or in a room in the building for supplying the heated air from the water container into the room; characterized in that comprising: a second inlet pipe comprising a first part located in the building and a second part connected to a second air membrane which is connected to the water container; and a second fan connected to the second inlet pipe, wherein the second fan is arranged to, in operation, draw air from the building through the first part and blow the air through the second air membrane into the water container for forming micro-air bubbles of air from the building in the water container. a second inlet pipe comprising a first part located in the building and a second part connected to a second air membrane which is connected to the water container; and a second fan connected to the second inlet pipe, wherein the second fan is arranged to, in operation, draw air from the building through the first part and blow the air through the second air membrane into the water container for forming micro-air bubbles of air from the building in the water container.