1. Work from the perimeter of the attic toward the door or hatch so that you don't trample all over the insulation you just put in.
2. Always cover the tops of the ceiling joists to make sure the insulation is deep enough to reach your target R-value and to prevent thermal bridging, the heat loss that occurs through the wood framing.
3. Shower thoroughly after you're done for the day to remove fibers from your skin, and launder your work clothes after one wearing.
For loose fill
Fasten blocking around the hatch or door to allow the material to be installed around this area without escaping.
Make sure the fill's depth is uniform across the attic. To make it easy to eyeball how level the material is as you blow it in, screw depth guides to joists throughout the space.
To get the target R-value from the product you chose, use the number of bags your calculations showed that you needed to insulate your attic—never fewer. If you've reached your target depth but still have a few bags left over, keep adding the material at an even depth throughout the space until all the bags your calculations called for are empty.
To help the material achieve the right density as you install it, hold
the blower hose parallel to the floor and the floor joists. Blow in the fill between and over the joists rather than across them.
Always use unfaced batts, both when laying product for the first time and to prevent moisture from becoming trapped between new and old layers of insulation. You can buy them unfaced or simply remove the paper or foil backing.
Place a new layer of unfaced batts perpendicular to the old layer, to cover any gaps in the lower layer. Adjoining batts should be butted snugly together, but not tight enough to compress them.
Never lay heavier batts, such as cotton, over lighter ones, like fiberglass. You'll compress the lower layer and reduce its effectiveness.
Always cut batts to fit around obstructions and penetrations. Stuffing or cramming them around ducts, piping, and the like will compress the air-trapping pockets in the material, reducing its insulating properties.
Don't leave any gaps between batts and joists, obstructions, or abutting batts. Even narrow ones will let air escape. Instead, cut a thin strip of the insulation you're using to size.