Scattered along these roads are many grass-roofed houses. Houses have been built like this for more than a thousand years, protecting from rain and thermal insulation.
A sod roof or turf roof is a traditional Scandinavian type of green roof covered with sod on top of several layers of birch bark on gently sloping wooden roof boards.
Until the late 19th century, it was the most common roof on rural log houses in Norway and large parts of the rest of Scandinavia.
By the way, there is much evidence that green roofs help reduce the flow of heat into and out of the surfaces they cover. The is also evidence that the benefit is much greater in the summertime because the reflectivity of the leaves of the plants and the evaporation rates are maximized in the summer.