Retrofitting Historic Buildings - Westminster City Council

Technologies have evolved to enable planted roofs – both ‘brown’and ‘green’, ensuring they have an appropriate medium to grow inand the necessary support system. A well designed living roof willmake a significant contribution to conserve and enhancebiodiversity, creating green corridors. They also are beneficial inmanaging flood risk, as they attenuate rainwater, reducing thelikelihood of flooding from surface water runoff. There is also someevidence that they act to reduce overheating (and reduce the urbanheat island effect), reduce CO 2 emissions, absorb noise and trapair pollutants.An intensive roof, which can bear the weight of people walking onit, will require a greater load bearing capacity, and this will be lessachievable on historic buildings.Costs: The cost of a living roof will vary depending on the type ofroof and specification. The issue is considered in detail in the GLAtechnical report ‘Living Roofs and Walls: Technical Reportsupporting London Plan Policy’ 70When to do this: A living roof is worth considering even when thereare competing demands for roofspace, such as for solar panels.Solar PV can work very well with a living roof with the panels on aframe above a living roof. This has benefits of microclimate – theliving roof helps to cool the PV panels, which can have problems ifthey overheat, and the shade that the panels provide on the livingroof, create areas more hospitable to a wider range of biodiversity.For further information see:• www.livingroofs.org• Environment Agency Green Roof Toolkit:http://www.environmentagency.gov.uk/business/sectors/91967.aspxLivingRoofListedBuilding 71UnitCost(lower)Cost(Upper)Cost(average)SubsidiesFor £2400 £6000 £4200 -20m 253