How To Better Insulate Your House

The Attic

With a ruler, measure the depth of the attic insulation and note which type you have. You’ll most likely find fiberglass, either in blankets or as loose fill. If you have roll- or blanket-type insulation, pull up a piece and look at the backing, which should have the R-value printed on it. You may also find loose, brownish material known as vermiculite. Be careful, as vermiculite is sometimes contaminated with hazardous asbestos (call an insulation specialist if in doubt).

If the attic is a finished living area, you may need to remove a floorboard or cut a small hole in the floor to check the insulation between the ceiling joists. If the ceiling is finished, you may need to remove a ceiling light fixture to check for insulation. Be sure to turn off the power to this circuit beforehand.

Outer Walls

Now turn your attention to the outer walls of your living spaces. The easiest way to check insulation here is to remove the cover plates on a few electrical outlets or light switches located on outside walls in different parts of the house. First, turn off the circuit to the outlet or switch, and then peek into the wall cavity to look for insulation.

Using a wooden ruler, pencil or wood skewer, probe the wall cavity next to the outlet or light switch to see whether it’s insulated. If the probe passes through the cavity without resistance, there’s no insulation. If you run into some resistance, it’s insulated. Bear in mind, however, that electricians sometimes trim away insulation from electrical outlets and light switches for fire safety, so the absence of insulation near a light switch or electrical outlet may not mean the rest of the wall is uninsulated. You can also check for insulation by drilling a small hole in an out-of-the-way place, such as in a closet against an outside wall.

Floors, Crawl Spaces and Basements

If your home is built over a crawl space or an unheated basement, check the insulation under the floor from below. If you’re lucky, you’ll find insulation batts between the floor joists. Make sure there’s a vapor barrier (plastic or paper backing) on the fiberglass batts. If the spaces between the floor joists are not insulated, measure the depth of the joists so you know the thickness of the batts you need to purchase. Next, check the foundation insulation. Begin by looking at the exterior of the foundation wall for rigid foam that may have been applied to it. You may need to dig a little, but be careful — you don’t want to damage any insulation that may already be there. Chances are, you won’t find any.

Interior insulation is common in finished basements and is applied in the space between framing members attached to the foundation wall (behind the drywall or paneling). As mentioned earlier, you can remove a few electrical cover plates to check.

How to Better Insulate Your House

If parts of your home are uninsulated or underinsulated, you’ll need to determine how much insulation to add. Call your local building department to ask for recommendations. For attics, the current standard in most parts of the United States is about R-30 to R-38, which translates into 10 to 14 inches of insulation, depending on the material. Energy Star guidelines recommend insulating your attic to as much as R-60, depending on where you live. You can go to the Energy Star website and search “recommended levels of insulation” to check recommendations for your area.

The Attic

When insulating an attic, you can use fiberglass batts or blown-in insulation. For installing blown-in cellulose insulation (with an R-value of about 3.5 per inch), you can hire a professional or rent a blower from a local home improvement center. Using one of these is a relatively easy task. If you choose to lay fiberglass blankets over the existing insulation and the old insulation comes to the top of the ceiling joists, lay the new insulation perpendicular to the joists, covering them entirely. Another approach is to blow liquid foam insulation between the rafters (the framing members that support the roof deck). This is a job for a professional.

Walls

To insulate exterior walls, you can “fur out” the wall — that is, apply framing lumber to the inside of the walls to create spaces for adding insulation. Use 2-by-4s, 2-by-6s, or smaller furring strips, then install cellulose, fiberglass blankets or batts, or spray-in liquid foam insulation between the furring strips. After the insulation is in place, attach new drywall or paneling to the framing. This method can be used on all walls and is especially applicable to solid brick and concrete block walls. It’s also a job best handled by professionals.

If you’d like to use rigid foam insulation, you can attach the material directly to the wall, then secure new drywall over it. While effective, this technique makes rooms a bit smaller, as does the furring-out technique mentioned earlier. Base and ceiling moldings, as well as window and door trim, will also have to be removed and reinstalled.

If your walls are uninsulated, professional installers can blow cellulose insulation into the stud cavities through small holes drilled in the siding or the interior wall surface at the top and bottom of the walls. Another option is to spray liquid foam insulation into wall cavities through small holes drilled in the wall. I think this type of insulation does a better job of filling spaces than cellulose, especially in older homes with plaster-on-lath walls. Both of these are jobs that should be done by an experienced installer — one who can also patch up the holes when the job’s done.

While attics are relatively easy to insulate, walls can be quite difficult. If the space between framing members is already filled or partially filled with insulation, it is difficult to blow in additional loose-fill material. Your best option is to apply rigid foam insulation to the interior or exterior surface of the wall. On the outside, rigid foam insulation can be attached directly to existing siding. New siding can then be installed over the insulation. Of course, window and door openings will have to be extended (“retrimmed”) to adjust for the thicker wall. Insulating this way is a good idea if you’re planning to put new siding on your home anyway, but it’s a job best left to professionals.

Floors, Crawl Spaces and Basements

If your home’s floors lie over unconditioned space (such as a crawl space), and the floor is not insulated, it’s a good idea to add insulation. Do not insulate walls in a crawl space that is damp or is ventilated with outdoor air.

Batt insulation can be installed between the floor joists beneath the finished floor. To hold batts in place, use metal insulation supports. Use paper- or foil-backed batts under floors. The backing serves as a vapor (moisture) barrier. In cold climates (where moist air tends to move from the home’s interior to the outside), the vapor barrier side of the insulation batt should be against the floor to prevent moisture from the house from penetrating the insulation. In warm climates (where moist air tends to move from outside to inside), the vapor barrier should face down toward the basement or crawl space to prevent moisture in those areas from entering the insulation. After installing insulation batts in a crawl space, lay 6-mil polyethylene plastic sheeting over the dirt floor to reduce the amount of moisture entering the space and to help keep the insulation dry.

For uninsulated basements, it’s best to install insulation on the interior of the concrete foundation walls — as long as they are dry. Moisture creates a breeding ground for mold and mildew, so always fix moisture problems before you insulate. You can apply insulation to the inside of the basement’s foundation walls in much the same way as you would apply it to the inside of walls in the main living space, as described previously. (You don’t have to cover the insulation with drywall unless you’re planning to finish the basement.) You should also choose a type of insulation that’s impervious to moisture, such as liquid spray-on foam or rigid foam.

What to Watch Out For When Installing Insulation

Installing insulation can present challenges for beginners and even experienced do-it-yourselfers. Here are a few tips:

• When walking about in an unfinished attic, be careful to step only on the ceiling joists so you don’t fall through the ceiling. You can take some lightweight planks into the attic and lay them across the joists to create more places to step.
• When applying insulation, wear eye protection and a respirator or a high-quality dust mask. If working with fiberglass, wear a long-sleeved shirt, long pants and gloves to protect your skin. It’s worth it to do this, even if it makes you uncomfortably hot.
• Do not apply insulation over old or frayed wiring.
• Do not apply insulation against the flues from woodstoves, or against light fixtures (cans for recessed lights) that penetrate the ceiling, if the fixtures are not rated for insulation contact (most are not). Doing so could cause a fire.
• When insulating an attic, do not cover the soffit vents (openings on the undersides of the eaves) if you have them. This interferes with airflow and can lead to moisture problems.
• If you notice stains in ceilings, mold in insulation, or even rotting wood in your attic, this is an indication that the roof is leaking. Get it fixed before you insulate!
• When installing fiberglass insulation, don’t compress it, because this will lower its R-value. Also, be sure not to leave gaps between insulation and framing members.

Eco-Friendly Insulation Options

When insulating, I recommend the use of environment- and people-friendly products. Here are some to consider.

Cellulose is considered environmentally friendly because it’s made from recycled newspaper and wood fiber. For fiberglass, some products are made from recycled glass. Also, some fiberglass insulation batts are encapsulated to prevent workers from inhaling the fibers, and some manufacturers now use safer binders that replace the typical formaldehyde resin in fiberglass batt insulation.

For rigid foam, many of the insulation products are no longer made with ozone-depleting chemicals. However, be aware that some green builders have expressed concerns about the health effects of brominated flame retardants, which are usually added to polystyrene insulation.

Cool new products to consider include cotton batt insulation (made from waste from blue jean factories), wool insulation, and liquid foam insulation made from chemicals derived from soy.

What Will Adding Insulation Cost?

The cost of this project will depend on the levels of insulation you already have in your home, how much you need to add, and whether you do the job yourself or hire an installer. There are a couple of helpful websites with charts indicating how much R-value you need for the insulation in various parts of your home, based on your location and climate, and the type of heating and cooling system you have: U.S. Department of Energy’s Energy Efficiency and Renewable Energy website and the Energy Star website.

R-Value Cost Estimate: Installation of unfaced R-3 fiberglass floor and attic ceiling insulation. Includes supports and rafter vents for a 2,500-square-foot, two-story home.

Cost for materials only: $2,400 (as of 2010)
Contractor’s total, including materials, labor and markup: $5,500 (as of 2010)

Insulation options, cost per square foot installed (as of 2010):

Fiberglass
R-13: $0.84
R-19: $0.92
R-30: $1.42
R-38: $1.69

Cellulose
R-13: $0.58
R-19: $0.80
R-22: $1.04

Costs are national averages and do not include sales tax.

What Will You Save?

Insulation substantially increases energy efficiency. It is even more effective when coupled with weatherization. The U.S. Department of Energy suggests that, together, adding insulation and sealing air leaks can save you up to 30 percent on home energy bills. Actual cost savings will vary widely, however, depending on energy prices in your area and how leaky and underinsulated your home was to begin with. Also consider that with rising fuel costs, this project becomes an increasingly attractive investment.