Floor An Attic That Is Already Insulated
A finished attic should be insulated much like the rest of the house with insulation in the walls and ceiling.
Floor an attic that is already insulated. In practical terms you can choose between mineral wool or insulation boards. To build a catwalk you would usually elevate a section of the framing perhaps with 2x6s installed at 90 degrees to the joists and you would install osb or plywood on top of the elevated framing. That means insulating the attic floor only not the walls and having vents in the roof. With a finished attic insulation must help keep the attic areas comfortable.
Use a zippered insulated tent to keep the enclosure draft free attic tent at 7 attic cover insulator 120. Or one could attach insulation to the underside of the floor if the wood and pier foundation is tall enough to get under the shed. That makes the surface of the spray foam cooler possibly even below the dew point. Removing the attic floor insulation will solve this problem.
So insulating the floor of the attic is not only the best solution but it is also the simplest and cheapest. Hiring a professional contractor to install loose fill insulation is the wisest choice in such cases. Add weatherstripping around the perimeter and a sweep to the door of a walk up attic. Affix rigid foam insulation to the attic side of the hatch or door.
If your attic has been finished with a floor insulating it becomes much more complicated. The attic floor which is the ceiling of the living space below often already is insulated. However if the shed is already built there could be two ways to insulate the floor. Attic hatch or door.
If it is and you plan to provide heating and cooling to the finished attic space you need to remove. Pull down stair or ladder. The attic is much warmer than outdoors in winter but significantly cooler than the living space if you leave the old insulation in the attic floor. One could remove the floor and add the insulation between the joists and then reattach the floor.
If you need regular access to your attic it makes sense to build a catwalk before you insulate the floor of your attic. But now the attic isn t vented to outdoors. If you do not use the attic much it is pointless heating this area.