My circa 1880 Victorian has a walk-up attic. The floor in the space is tongue and groove and at some point a small amount of insulation has been blown into the floor. The roof is uninsulated. Unfortunately the heat is seeping throught the floor and on a very cold day it's very bearable in the unisulated attic as a result! It would be very difficult, time consuming and difficult to blow more insulation into the floor. I am wondering if I could/should install some hard board insulation on the floor, and cover it with plywood to protect it. My concern would be trapping the air/humidity between the second floor ceiling and the attic floor. At the moment it can breath very well. Or is there a better solution? Thanks.