Implication of plant selection for building insulation

Green infrastructure can increase sustainability of urban environments and improve the wellbeing of urban inhabitants by offering invaluable ecosystem services. In terms of thermal effects, if integrated in the building architecture, plants will increase insulation. This can be beneficial especially in summer but in some cases also in winter. However, little information is available on how different plants could be easily integrated onto the building's envelop, comparing their potential for this annual 'temperature regulation' service. Based on experimental work over two years (2012-2013) in Reading (UK), we explored the implications of plant selection on both summer and winter insulating properties, however, in this paper we discuss results related to the winter period only. We compared substrate temperatures below succulent plant canopies, usually used as green roof coverage, with alternative non succulent plant canopies and bare substrate covering purpose-built model roofs (1.5x1.5x0.1 m). We measured substrate temperature at 10 and 60 mm depth and canopy attributes (LAI and canopy height). Results suggest that over winter all plants will generally provide similar insulating effects, regardless of their attributes. On warm winter days (i.e. days with maximum air temperature >10 degrees C) plants may reduce insulation, compared to bare substrate. However, on very cold days and nights (i.e., days with maximum air temperature <3 degrees C or nights with minimum air temperature <0 degrees C), or in periods when the surface is covered by snow, some plants (e.g., Stachys and Sedum) may provide better insulation than bare substrate.