Hardi has about 30% cellulose fiber in it and the rest is cement. Hardi shrinks after it is installed so you must keep it tight to the the next board and not leave expansion gaps on either side. It de ... read more
Christofer, There is a lot written about your particular condition. What I would do would be to install a spray polyurethane insulation (closed cell insulation) into the attic ceiling and down to and ... read more