Blown in Attic insulation -to pack or not to pack?

I am putting a floor in my attic for storage. (3/4 OSB) Currently the attic floor has about 2 feet of blown in insulation. (about 1 foot above the joists) When I lay the floor in the attic should I pack down the insulation or should i jsut spread it evenly up to the joist so it is nice and loose and get rid of the rest. Not sure what is a more effective insulator.

 

If you pack or compress the insulation. you will severely reduce the insulating value.

If you throw away the rest, you will also reduce the insulating value.

Is the storage area that valuable to raise your heat & A/C costs?

Dick

 

Dick is right.

Neither option is feasible and could create a code violation if your reduce the insualting ability of the ceiling.

Your attic floor may not even be designed to carry the loads of a floor.

In your case the proper option is to not install the floor it seems.

 

Let me clarify. The joists in the attic are 2 x 10's and the attic is on the second floor- even with the other bedrooms. You actually walk into the attic off one of the bedrooms. I will still have 9 inches of insulation and I am pretty confident 2x10's can support a floor. I understand it will not be quite as efficient but I cant see how reducing the amount of insulation down to 9 inches would be code violation.

 

Whether or not your 2x10s can support a floor depends on their spacing, span, and edge connections. Why would a builder pay to provide that kind of structural strength to a space that is not expected to be used as living space?

9 inches of insulation is more than enough. Provided, of course, that you take the opportunity to clean it out and and air seal the ceiling plane first. This can be done either by caulking & taping at the ceiling line, or by spraying down an air barrier coat on the backside of the drywall. This will reduce your heat loss even at a low thickness of insulation, and will prevent winter condensation problems on the underside of your expensive new floor.