The invention relates to a facade or roof element that is to be mounted on a building and comprises an exterior wall, an interior wall (10), and a latent heat accumulator (14) that is disposed between the exterior and the interior wall (10). The exterior wall is designed as transparent thermal insulation (TWD), while a fluid duct (26) is disposed in the latent heat accumulator. In order to design a facade or roof element in which heat can be quickly transferred between the fluid duct and the latent heat accumulator, the latent heat accumulator comprises at least one thermally conductive, open-cell light building board (24) within which a storage medium (28), preferably a phase change material (PCM), is retained, and the light building board (24) is in thermal contact with the fluid duct (26).