No they don`t require load calculations yet.The only moron that put`s single pane windows is a broke person.I should add the city it`s in Taylor Mi.I have not done any work in.So I can`t say how the inspectors are as far as codes.Plus it`s a home owner pulled permit so city thinks home owner did job himself.They may cut some slack for that reason not sure was not there when inspection took place.