Building paper is that which has largely been replaced with Tyvek house wrap on vertical members and rubber ice dam guard and roofing felt underlayment on the roof. It's still "there" in concept, which is to provide an air barrier and block the wind coming straight though.
Ah right, forgot about Tyvek.
On the bright side you can knock off the price of the sash weights, and probably "building paper"
(unless that means they pay the price to have the blueprints signed off by an engineer).