The house came with some old yellow Batts in half the ceiling.
In early/mid 2004 I bought some R3.6 Batts (on special from Placemakers) and covered the roof.
Then I laid the old Batts on top of the first layer, but in the other direction (and over the rafters). Later I bought some used Batts from the local recycling yard to complete the second layer.
So now I should have at least R4 in the ceiling.