How to Install Fiberglass
- 1). Unroll the sheets of fiberglass and cut them to fit the spaces in between the ceiling/floor joists or wall studs. Cut the sheets so they are just slightly longer and wider than the open spaces, but not enough that they'll be compressed inside the spaces.
- 2). Adjust any fiberglass sheetsgoing into sections with obstructions. If a section has pipes or wires running through it, peel the fiberglass material of that sheet into two halves. For sections with things like live electrical boxes, cut the fiberglass pieces so they will fit around them.
- 3). Insert the fiberglass sheets into each section of the ceiling, floor or wall, making sure each piece lies completely flat within its section. If the sheets have foil or paper faces, these go on top. For sections with pipes/wires, insert the bottom half of the insulation you tore so it fits underneath the obstructions.
- 4). Fill in the remaining cracks where needed. In the sections with pipes, lay the top half of the torn insulation on the bottom part so it wraps over the wires or pipes. For sections with electrical boxes, stuff small pieces of fiberglass around the borders of the boxes to fill in the gaps.
- 5). Lay a vapor barrier over the fiberglass if the sheets don't have foil or paper barriers. Drape sheets of polyethylene over the fiberglass, making sure they overlap the fiberglass by about a foot, and staple them to the studs or joists. This prevents water vapor from entering the wall/ceiling.