In this video, This Old House general contractor Tom Silva demonstrates a cost-effective way to save energy.
1. Measure the depth of the existing blown-in insulation. If necessary, add more cellulose insulation.
2. Dump cellulose insulation into each joist bay and spread it evenly with a leaf rake. Be sure the insulation is slightly above the top edge of the joists.
3. Lay batts of un-faced, 9½-inch-thick fiberglass insulation perpendicularly across the joists.
4. Cut the batts of insulation to fit tightly together.
5. Continue to cover the attic with fiberglass batts, including any wood subfloor.
6. Build a storage-platform frame out of 2x10s.
7. Fill the interior of the platform frame with fiberglass insulation.
8. Cover the platform with 7/16-inch oriented-strand board (OSB) or plywood.
9. To create a walkway to the platform, cover the wood subfloor with pieces of 2-inch-thick polystyrene.