Cool roofs and the influence on the energy consumption under Danish conditions

Experience from countries in warm climates has shown that the color of the roofing material has a significant effect on the energy consumption of the building. Especially changing from black to white roofing material provides reduction in energy consumption. The investigated roofs have been with a moderate amount of thermal insulation.
The Danish Roofing Advisory Board in Denmark has conducted an analysis of the effects of roofing color on buildings energy consumption under Danish conditions i.e. with a colder climate and with a larger amount of thermal insulation.
An experiment was performed in order to study the effects of the roofing color on the temperature distribution in a roof structure. The studied roof specimens were flat roofs covered with roofing felt in different colors. Temperatures have been measured in the roofing felt as well as in the middle and the bottom of the structure. The paper informs of the experiments and the achieved results.
In the analysis consideration was taken to the insulation type as previous investigations have shown an effect from the heat capacity of the insulation material.
On the basis of the experiments and the analysis it is concluded that there are no significant advantages of using white roofing felt instead of dark under Danish conditions in common buildings with active heating and passive cooling. Quite to the contrary it appears that dark roofing felts have significant advantages over white roofing felts. The results are discussed in the paper.
It should be mentioned that white roofing materials might be beneficial for poorly insulated buildings with high internal heat loads. In this case the white roofing might contribute to a reduced cooling. Also buildings with constant cooling demands or cold-storage plants etc. may benefit from white roofing instead of dark. It is discussed under which circumstances light colored roofing is beneficial.