Question by Megan: Is it OK to use “attic cat” blown insulation on an attic that’s already half-covered with roll-out insulation?
If half of my attic is properly insulated with roll out insulation with vapor barrier and the other half requires insulation, could I just blow “attic cat” insulation in the other half as long as I do not blow it on top of the insulation with the vapor barrier?
Answer by RobertB
First, the vapor barrier for insulation goes on the warm side of the insulation to prevent condensation on the cold side. For instance in the ceiling and walls the vapor barrier should be right in back of the drywall. If you allow the moisture from inside the home go to the cold side it may condense and give you problems.
That said you should be looking at insulation when you go into the attic. As long as the existing insulation is not crushed and still maintains its insulating value there is nothing wrong with blowing insulation on top of it to supplement it or with blowing insulation on an adjacent half to save money on heat and ac.
Recently I just saw a homeowner pull out all of the existing batt insulation and replace it with blown in insulation. It must have been a good salesman.
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