Increasing thermal protection with use of green roof

Abstract

The use of green roof is a great choice in case of climate change mitigation and reduction of urban heat islands. Positive aspects of green roofs during winter or the whole year round balance are often overlooked. The surface of highly insulated flat roof is overcooled during the night by the long wave sky radiation. This radiative cooling increases the thermal losses that are reduced by the existence of additional layers. The green roof composition layers also have their thermal resistance, which is not usually included within the calculation of thermal resistance using the EN ISO 6946. The presence of snow on the roof can also increase the resistance. This paper analyzes the measurement results of various experimental green roof fragments in Central Europe.

Experimental Analysis of the Influence of Seasonality on the Temperature Regime of Extensive Roofs in Central Europe

“…The surface temperatures of the vegetation layer compositions were around 0 °C. Similar results were measured in paper [31], when the surface temperature remained at 0 °C on a snowy day. From the 22nd to the 23rd, when snow melting occurred, a significant drop in surface temperature was seen for the reference roof; however, the vegetation layer compositions continued to maintain a stable surface temperature.…”

“…A significant difference occurred between the comparisons of the green roof and the reference roof-a roof without a vegetation layer. The paper [31] again points out the temperature difference between the roof variants with a vegetation layer and without a vegetation layer. The daily temperature amplitude at the waterproofing in the snow-free period was 37 • C for the reference roof, while only 0.4 • C for the green roof.…”

“…In winter, on the other hand, the focus has been on reducing the sub-cooling of the individual layers in the structure's composition [31,32]. In particular, temperature progression at the waterproofing level has been observed.…”