Installing Attic Insulation
If you have an unheated, unfinished attic (without a floor; it's just joists and the ceiling from the room below) that you want to insulate, first check to see what you're working with. Although the attic needs ventilation, you want it coming from vents, not from gaps around wiring or chimneys. Before you add insulation, check for such gaps, and caulk around them to cut drafts and prevent insects, birds, and animals from entering through them.
If there's already some insulation in place between the ceiling joists, you'll need to choose unfaced insulation (some insulation batts come with a facing on one side that provides a vapor barrier). If there's faced insulation in place already, check that the vapor barrier is facing the right way (down, toward the heated house). If it's not, you'll need to flip it over so that the vapor barrier is installed correctly, or run a utility knife through it to break its seal.
If there's no insulation, either choose faced insulation (the facing goes toward the heated area, so against the attic floor) or install a vapor barrier (available in rolls of plastic from the home center) before laying the insulation in place. Lay the 6-millimeter plastic vapor barrier between the joists, adding a couple of staples at each end of the plastic to tack it while you're laying the insulation. Don't worry about stapling it down really thoroughly, because gravity and the weight of the insulation will hold it in place.
For the insulation itself, choose bags of loose-fill insulation that you can pour between and over the joists (a rake will help to spread loose-fill insulation evenly), or fiberglass batts.
Fiberglass batts just need to be unrolled into place. Don't pack them too tightly, as the air between their layers is an essential part of their insulating ability.
If you'll be laying insulation batts between the joists, measure the space between the joists so that you purchase the correct batt width. This will save you from having to cut the batts to fit between the joists and will help you avoid squeezing the batts too tightly between the joists (which will reduce their insulating ability).
Carry the bags of batt insulation up into the attic intact. Do not attempt to open them beforehand; they're tightly compressed, so they're much easier to handle when they're still closed. Open them one at a time, as needed, once they're in the attic.
To lay your insulation, work from the walls toward the center of the attic, and start at the spot furthest away from the attic hatch (like painting a room, you want to work your way toward the exit). Lay the batts in place by unrolling them between the joists, pressing them down without compressing them too tightly. If you lay one batt on one side of the attic and another batt on the other side, you'll likely have a space in the middle that you'll need to cut a batt to fit. Because you're working from the walls in, you'll be measuring and cutting in the area with the highest roof clearance, which should make things easier. To cut fiberglass insulation batts, compress the bat with a straightedge. Cut through the compressed material against the straightedge with a utility knife. Join the ends of batts by butting them up against each other firmly, so that there's no space between them.
Don't forget to weather-strip the attic hatch. Running a length of self-adhesive foam weather stripping around the top of the attic opening will create a good seal when the hatch is placed over the opening.
If you're laying insulation over the top of a layer of batts filling the joists, lay the new batts (which must not have a vapor barrier) perpendicular to the old ones. Insulation can be cut around cross bracing between joists, but remember to keep it 3 inches away from any source of heat, such as electrical fixtures (unless they're clearly rated IC, which means that insulation can be installed near them), or metal chimney flues. And remember not to block venting. If you're using loose-fill insulation, you can nail wooden frames together to fit around vents or heat-producing elements, to keep the insulation away from these items.
Increasing your attic insulation (while making sure that the attic is ventilated properly) can be very gratifying when you start noticing savings on your utility bills, particularly if you've started with an insulation value that's well below what's recommended for your area. You've now walked through your house interior, from the basement to the attic-skipping, however, two important elements: doors and windows. In Chapter 16, you'll find out how to solve the most common problems with doors and their hardware, from hinges to locks.