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Choosing Home Insulation

by Don Vandervort, © HomeTips

Are you spending too much on your monthly energy bills? If your home’s insulation isn’t up to snuff, you may well be. And there’s no better time to rectify the problem than during a remodel.


home insulation diagramAccording to the Department of Energy, 50% to 70% of the energy used in the average American home goes toward heating and cooling. If your attic, walls, or floors are under insulated, a large part of your costly, conditioned air may be making a beeline for the great outdoors.

Insulation retards heat in its natural quest to move from a warmer to a cooler space. In the winter, when warm room air exits through walls, rises up through the attic and roof, and flows down through the floor, insulation blocks—or at least slows—its departure. And in the summer, when warm outdoor air tries to force its way into your air-conditioned rooms, insulation holds the heat at bay.

By slowing heat movement, insulation not only saves energy but also reduces drafts, making a house more comfortable. Some types—foam in particular— seal out air infiltration, a major contributor to heat loss.

Just how well insulation resists heat flow is rated by an R-value. Insulation materials differ in the R-values they deliver per inch of thickness.

How Much Insulation Is Enough?

Houses built in the last few years may or may not have optimal levels of insulation, depending upon how much attention was given to energy conservation when they were built. But nearly all older homes, unless recently retrofitted with insulation, are likely to be lacking. The best way to find out whether or not your house has enough is to call your local utility company for information about getting an “energy audit.”

Recommended minimum R-values for homes vary by climate and may be affected by how a house is built and the type of heating used. Here are a few rules of thumb:

  • For mild climates, R-11 in the walls and floors and R-19 in ceilings below ventilated attics.
  • For moderate climates, R-19 in the walls and floors and R-30 in ceilings below ventilated attics.
  • For cold climates, R-19 in walls and under floors and R-38 to R-49 in ceilings below ventilated attics.

(For more specific recommendations by region, contact the Department of Energy for its Information Fact Sheet.)

Where Insulation Belongs

Insulation should be installed inside any barrier that’s located between heated and unheated spaces. In essence, it should form an envelope around a home’s living spaces. The attic is the most important place.

attic insulation diagramButtoning up an uninsulated attic can cut fuel bills by 30%. Bringing a minimally insulated attic up to optimum levels can yield comparable results, relative to the amount added. And, if an attic is unfinished, insulating is a relatively inexpensive project. If an attic is finished with walls and ceilings, insulation should be installed in the end and knee walls, the ceiling joists beyond the knee walls, and, if possible, between the rafters of the attic ceiling (however, ventilation between the rafters from eaves to ridge should not be blocked).

It’s also important for house walls to be insulated, but, in an older house, this doesn’t always pencil out. Insulating walls during construction, remodeling, or re-siding, before wall coverings are applied, is a breeze. But insulating them after the fact is an expensive and difficult proposition. If your home has uninsulated walls and is located in a cold climate, ask two or three insulation contractors for bids and then figure out how long it will take to pay for the cost at a savings of 16% to 20% of your fuel bill.

Insulating crawlspaces is also helpful—doing so can trim 5% to 15% off heating costs. If crawlspaces are reasonably accessible, insulating is a relatively affordable job. Outer walls and foundations in finished basements also should be insulated.

Types of Insulation

It’s easiest to consider the various insulation materials by major category (though there is some overlap): batts and blankets, loose-fill, blown-in, plastic foam, rigid boards, and reflective insulation. These categories are based primarily on the material’s form and method of installation.

Batts and blankets are the most familiar to homeowners (and the type most commonly installed by do-it-yourselfers). The main insulating material is mineral fiber—either fiberglass or rock wool fiber. Batts are sold as precut strips and blankets as continuous rolls. Both are sold in widths that match conventional wall-stud and ceiling-rafter spacings so they can be simply stapled into place. They are sold both with and without kraft or reflective foil/vapor-retarder facings. A vapor barrier is faced toward the warm-in- winter side; types without a barrier are used when adding to insulation.

The advantages of batts and blankets are that they’re readily available and relatively affordable. Having them installed in nonstandard stud or joist spacings requires a little extra labor as the material must first be cut to fit.

Loose-fill insulations, meant to be poured, stuffed, or blown in place, are made from several materials: glass and rock wool fibers, cellulosic fibers, and expanded vermiculite and perlite. Loose-fill fibers are made of the same spun minerals as batts and blankets, only they’re left loose or made into pellets. They’re commonly used in attics and walls.

Cellulosic insulation is made from recycled paper (mostly newspaper) and wood fibers that have been treated with a fire retardant. It’s used in both attics and walls.

Vermiculite is made from mica ore, and perlite comes from volcanic rock. Both are heated and expanded into a fluffy, noncombustible material that is used to insulate ceilings and some walls, mostly concrete block.

Loose-fill materials are sold in bags or bales and work well for insulating between ceiling joists in an accessible attic. To fill up wall cavities, pneumatic equipment is often necessary. Blown-in loose-fill insulation is loaded into a machine that then fluffs and blows it through a hose into the areas between ceiling joists or cavities between wall studs. The insulation itself may consist of cellulose, loose mineral fibers, fiber pellets, or fibers that are coated with an adhesive (the latter type being the most effective at sealing a cavity and the least prone to settle once inside a wall). When using loose-fill insulation in an attic, it’s usually necessary to have a vapor barrier (such as plastic sheeting) installed first.

Foamed or sprayed-in-place insulation (typically polyurethane) is installed by professionals who have special equipment for monitoring the mix and application. It provides very high R-values, doesn’t shrink or settle once in place, blocks drafts caused by air infiltration because it conforms to every nook and cranny, and offers a barrier to moisture. Sprayed-in-place types are designed for new construction and can be used in walls, beamed ceilings, and around the foundation’s perimeter. They are relatively expensive. (Do not be talked into using urea-formaldehyde foam-in-place insulation because of potentially dangerous vapor emissions.)

Rigid foam board insulations are made from a number of different materials: asphalt-impregnated fiberboard, polystyrene, polyurethane, and polyisocyanurate. These rigid panels are generally used in new construction (or re-siding and reroofing) where they may be installed as wall or roof sheathing, insulation beneath interior walls, or around foundations. Because they are classified as combustible, they cannot be left exposed indoors. The panels may have foil facings on one or both sides to reflect heat.

Reflective insulations, made from aluminum foil, are most effective in hot climates at blocking radiant heat. Effectiveness depends on whether the foil is simply a flat sheet, used to block heat transfer through roofs, or a barrier that has multiple layers separated by air spaces, appropriate for reducing heat gain through roofs, ceilings, walls, and floors.

Getting Insulation Installed

Before hiring a pro to insulate your home, get two or three bids. To compare apples with apples, be sure each bid clearly describes the material being used and specifies the R-values of the insulation to be installed in each area of the house. When the material arrives, bags should be labeled with R-value information; with loose-fill insulation, check to be sure the appropriate number of bags is installed.

Also talk with your contractor about both ventilation and moisture control. Ventilation is important to be sure your home’s air quality is maintained without unnecessary energy loss. And, in most climates, vapor barriers must be installed when you insulate to prevent vapor, naturally present in the air, from collecting inside insulated walls, ceilings, floors, and roofs. In most climates, a vapor retarder such as the foil facing on batts and blankets or, for loose-fill, 6-mil polyethylene plastic sheeting must be installed at the warm- in-winter side of the insulation. Walls that are filled with blown-in insulation can be coated with a low-permeability paint to repel vapor.

Last but not least, be sure all cracks and crevices that allow air infiltration are well sealed with caulking compound and weatherstripping. Doing so is key to capitalizing on the energy savings and comfort of your new insulation.

To get free recommendations for top-rated local contractors, call the most reliable and comprehensive referral service, HomeAdvisor, at 866-350-2983 (toll free).

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