Abstract: A light absorbing unit for heating at least one liquid medium by solar energy includes a transparent surface layer including a channel configuration inside of which liquid medium can be streamed for heating. A light absorbing device is configured to contain the channel configuration. The light absorbing unit is configured to constitute an integrated part in a roof construction. The transparent surface layer includes roofing tiles transparently arranged to be supported by means of a batten. The batten is arranged to constitute a part of the light absorbing unit in the roof construction. The batten is arranged to be applied in the roof construction with the light absorbing unit. The batten is arranged to be supported along a long side of the light absorbing unit extending substantially horizontally in the roof construction.