We have repelaced our HVAC system, 97 % eff. in Cleveland, OH in August 2012. We live in a ranch style home with a basement. Our problem is a cold kitchen and 1/2 bath. Behind our kitchen is a large cavity, the area is the ceiling for the basement stairs. This area is 5' X 10' it is cold, my question is can I fill this area with insulation- blow in or use bat type?