A corporate roof that welcomes insects and birds while keeping the building cool has been unveiled in London.Law firm Eversheds has a sedum-covered roof with bird boxes and a view of St Paul's Cathedral.The company opted for the green roof as a way of taking responsibility for its environmental impact and a way of appealing to clients, for whom the environment is increasingly important.Gareth Griffiths, of Capita Symonds, the construction consultancy tasked with redeveloping the building, told the Independent. "It was a conscious decision to enhance the green credentials of the building because the consensus in the City is that we have to be responsible members of society."He added: "Offices are a significant contributor to carbon dioxide emissions because of their high energy consumption."The green roof, which according to architect Tony Pollintine is actually an ancient Viking building technique, helps keep the building cool. It also retains rain water so it doesn't just run off into drains, preventing overflows and flooding.