The answer is: Nothing. The church has nothing to do with buildings. Though buildings may be used by the church, they are not required to be the church. Buildings may help the church accomplish its mission, but at the same time, the church must admit that buildings may hinder the mission as well.
One thing the church must not do, however, is treat buildings like holy sacred places where the true, spiritual stuff happens and everywhere else is secular and unspiritual. Nothing could be further from the truth.