Saturday, July 24, 2004
We recently had the pleasure of touring a major insulation manufacturing plant and acting as judges in a regional and national competition recognizing "America's Best Insulation Installer."
The competition, sponsored by Johns Manville and Insulate America, an industry trade group, honored insulation installation professionals with the neatest, most professional installation.
We came away with a deeper understanding of the importance that a quality insulation job plays in improving home comfort and the impact that it can have in controlling soaring utility costs. Most importantly, we learned that insulation can be of little value when not installed properly or in the right locations.
Many people tend to regard insulation as a building component that has value only during winter when home heating bills are high. In reality, insulation is important every day of the year.
Insulation resists the flow of heat. Heat is a form or energy. By reducing heat flow in a properly insulated building, less energy is used for winter heating and summer cooling.
Other benefits
There are other less obvious benefits that insulation provides, such as moisture control and sound control. A vapor-resistant membrane, commonly called a vapor barrier, attached to batt or roll insulation, or installed separately, decreases the possibility of moisture vapor condensing to water within a structure. This reduces the prospect of mold, mildew, rot and musty odors.
Insulation also reduces sound transmission. An insulated floor, wall or ceiling will have an improved sound transmission class compared with a similar building section with no insulation. As an example, 31/2 inches of fiberglass insulation in a wall can improve the STC from 4 to 11 points, depending upon construction details.
Though insulation is available in many styles and materials, fiberglass is the most widely used. Batts and rolls of varying widths are designed for installation between floor joist, wall studs and ceiling joist. Alternatively, loose fiberglass can be blown into attics or in existing wall cavities where it is impossible to install batts or roll material.
Key areas
The areas that should be insulated to provide the best bang for your energy buck include exterior walls, ceilings with cold spaces above, and floors with cold spaces below. The following are a few key areas that should not be overlooked:
UExterior walls between unheated garages and storage rooms, dormer walls, knee walls of finished attics, basement walls.
UDormer ceilings and sloped walls and ceilings of attic spaces finished as living quarters.
UFloors above vented crawl spaces, living space above garages or porches and over unheated basements. Cantilevered portions of floors (that extend outward beyond the foundation).
Insulation is available in varying thicknesses depending upon the required R-value. The thicker the material, the higher the R-value and the better the level of energy protection.
However, the mistake that many do-it-yourselfers make is to try to force thick material into a shallow cavity, assuming that it will be more efficient. For example, they will compress R-19 into 2-by-4 wall that is designed to accept a maximum thickness of R-15.
Compressing insulation diminishes its effectiveness and reduces its R-value.
Pay close attention to manufacturer material recommendations for specific cavity depths.
Techniques vary
Insulation techniques vary depending upon location in the structure and the size and type. In general, if you are installing batt or roll insulation with an integral vapor barrier, the barrier is installed in the wall, ceiling or floor framing cavity toward the warm-in-winter side.
Thus, ceiling insulation would be installed with the vapor barrier down, wall material toward the interior of the space and floor material with the vapor barrier up against the underside of the subfloor.
In hot, humid climates, vapor barriers can be installed facing the outside.
In cold climates, unfaced insulation is installed with a separate continuous plastic vapor barrier over the face of the interior side of the wall. This prevents condensation occurring due to extreme differences between interior and exterior temperature. Check local practices or building codes for what method will work best in your neck of the woods.
Stapling options
Faced insulation (material with an integral vapor barrier) is usually installed in one of two ways: face-stapled or inset-stapled.
The stapling flanges that extend over the sides of the insulation can be used for either stapling method. When face-stapling, the face material is flush with the face of the framing and the flanges extend over the face of the framing and overlap. The material is then stapled to the face of the framing. With inset-stapling, the flange is placed along the side of the framing material with the outside edge of the flange flush with the face of the stud. This method is usually preferred by the wall finish trades because it allows adhesive application of wall board.
Both methods provide acceptable performance.
When insulating a ceiling with batt or roll material, it may take more than one layer of material to achieve the desired R-value specified by the Department of Energy for your climate zone.
When such is the case, the material should be placed between the framing with the vapor barrier on the primary layer (closest to the ceiling) facing down. The second layer should consist of unfaced material run perpendicular to the first layer.
One common mistake when insulating an attic is to block soffit and eave ventilation. Ventilation works in harmony with insulation and must be preserved. Prefabricated baffle boards can be installed at the underside of the roof sheathing near eave and soffit vents to maintain a minimum of 1 inch of clearance for free air movement.
Other pro tips
Other insulation installation tips and tricks that we learned from the pros:
Insulate nonstandard-width framed spaces by cutting the insulation and facing about an inch wider than the space to be filled. This will provide a snug fit and the facing will be wide enough to staple.
Whether face- or inset-stapling, prevent gathering or buckling of the flange. This condition is referred to as "fishmouthing" and can reduce the effectiveness of the insulation.
Be sure to insulate all gaps, especially narrow cavities around windows, doors and at corners. Cut material to size and stuff it into the area. Where a vapor barrier is required, cover the warm-in-winter side of the narrow space with excess vapor barrier, duct tape or polyethylene film.
Repair rips or tears in the vapor barrier using duct tape or polyvinyl tape.
Where electrical wiring exits, split the insulation to prevent compaction.
Where plumbing pipes exist, insulate only the exterior (between the pipes and the cold side) to prevent the pipes from freezing.
A good insulation job is like money in the bank. It improves comfort and lowers your utility bill.
XFor more home improvement tips and information, visit www.onthehouse.com.
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