What is a biosolar roof? Simple - it's a green roof with solar panels. I wish I'd known about biosolar roofs when we built our house; instead, we have a really nice green roof area and a smaller flat roof with solar panels on. We should have combined the two. There are many benefits to green roofs, which I've written about before. They range from the obvious - their aesthetic appeal and the biodiversity they bring - to the more obscure. Their insulating properties are excellent and they protect the roofing membrane from getting photo degraded, extending its life. Urban planners are particularly excited about them as a way of controlling water run off and lowering temperatures in city centres. Combining green roofs with solar panels gives you further benefits. Most obviously, solar is the coming renewable technology and will soon become an efficient way of generating electricity without subsidy, even this far north.* Our panels here worry me because they're pretty exposed, and would be much better anchored by several tonnes of green roof substrate. It also turns out that mounting them on green roofs reduces their operating temperature and increases efficency. Like ground mounted panels, solar panels on flat roofs offer the potential for a tremendous variety of micro-habitats. Rainfall and light varies according to the position of the panel. At its leading edge there is water running off its face and sun. Underneath the panel it's relatively dark and dry. It's almost like a synthetic woodland, which lends itself to establishing a tremendous variety of plants. If these plants are native that will mean a tremendous variety of invertebrates. My interest in biosolar roofs was piqued at a conference in London hosted by the indefatigable Dusty Gedge, doyen of green roofs, to whom my thanks for the use of this photo. His partner Gary Grant has suggested a species list for biosolar roof plants, which we've used as the basis for the plug plants for biosolar roofs selection on our website. *Given the current regulatory environment, the only biosolar roofs being installed at the moment in the UK are sadly by those folk who already have solar, or by companies looking to brush up their CSR (Corporate Social Responsibility) credentials.