Blown in Insulation for an Old Home

Benefits

• Unlike fiberglass rolls or batts, blown-in insulation fills small cavities where you can’t reach with your hands. Better coverage means a more comfortable home, which is a challenge in drafty older houses. Properly installed, the fluffy material fills all empty spaces where heat could otherwise transfer through. Because it’s loose, there’s no cutting or trimming to make it fit. Factory-applied flame- and insect-retardants help insulation reduce the risk of fire spreading and insects taking up residence in the wood framework of the house. Blown-in insulation is often made from recycled materials such as old newspapers and even denim jeans. This adds an extra layer of eco-friendliness to the energy-conserving benefits.

Loose Insulation: Not Ideal for Every Wall

• Walls have numerous cavities, many of which have little or no insulation in an old house. Drafts waft across the room, but loose insulation isn’t always the answer; in fact, it can create bigger problems. Plaster walls with no insulation inside also have no vapor barrier to prevent humidity from wicking through. Drywall doesn’t guarantee that a vapor barrier exists. Damp, loose insulation encourages mold, attracts insects and becomes heavy, sagging to the bottom of the walls instead of filling the cavities. Installing a vapor barrier requires plaster or drywall removal to access the studs. A workable compromise for walls is weatherstripping for windows and sealing every gap around windows, doors and behind baseboards with expanding foam to keep out drafts.

Attics: The Best Place for Blown-in Insulation

• Of every space in an old house, attics return the highest reward in loose-insulation-related comfort and reduced energy bills. Blown-in insulation is ideal, as old insulation can stay in place with new, loose materials added on top. Where old insulation is dirty or compacted, which decreases efficiency, removing it exposes the joists for filling with new, loose materials. As with walls, the vapor barrier goes closest to the living space to prevent household humidity from wicking into the insulation. When filling empty attic floor cavities, the barrier sheeting goes into the cavities first and insulation goes on top. No barrier is necessary when old insulation is left in place.

Installation

• Loose insulation requires professional installation in most cases, whether in walls or attic floors. A long hose blows tufts of fibers out into the space, and the installer guides the hose to apply it evenly. The blower fluffs up insulation and lets it settle loosely into the cavities, which gives the highest level of protection against heat transfer. Homeowners can handle the materials without danger, but spreading it by hand is the least efficient method and doesn’t let it perform as well as it could. Where installing in walls is possible, the installer cuts holes through the siding near the top of the wall and blows insulation down into the cavities. This requires one hole per every cavity between wall studs, and holes are patched afterward.