It is always great to see new ways of doing things. The World Green Roof Congress in Copenhagen last week offered a chance to see Scandinavian styles of green roofing, ranging from large impressive projects in Sweden to tricky and challenging roofs in Copenhagen city centre.
For me there were two great revelations in the course of the week that changed the way I think about green roofing. The first was two separate attempts by American green roof experts to formulate the holy grail of green roofing – the cost benefit analysis.
Because of the many variables of different green roofs and the diverse drivers and functions, this has always been difficult. The dependence on local incentive schemes by local authorities and water companies promoting reduction of surface water runoff has usually been considered the main financial motivator, followed by the desire to lengthen roof lifespan and in particular cases the energy savings from temperature regulation.
Now the picture has changed rather dramatically. While water is still a big driver it has been overtaken by another that was rather surprising: amenity. The increase in productivity of staff who were able to view a green roof was so great, and the reduction in number of sick days so marked that the financial payback was on average twice that of the water management incentives.
This has big implications for the quality, aesthetic and location of green roofs. Clearly any company with a roof overlooked by its own staff has great motivation to make sure they have a healthy, lush looking space.
However the huge impetus is on local planners to incentivise those who are not lucky enough to view their own rooftop. How much happier and more productive a city is will have more long term payback for citizens and politicians than even the noble credits of air cleaning, water collection and biodiversity support. And in these tough economic times this is exactly the kind of productivity boost business needs.
I will save the second revelation for the next blog as it deserves a good explanation, and will change from the wider view of planning to the microscopic view of substrate organisms!