Prime Minister Mark Carney announced the government’s intention Friday to launch an open competition for bids to renovate the historic home, which has been vacant for 11 years. The announcement ended a big part of the decade-old mystery about the future of the prime minister’s official residence, which had been plagued by an array of problems: heating and cooling, outdated wiring, asbestos, water damage, mould, rats, and more practical problems such as insufficient space for offices and events.