The Best Insulation Types for Your Home

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Icynene foam insulation is blown in using water and contains no CFCs or formaldehyde once cured.
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Air Krete cementitious foam is a nontoxic insulation that’s sprayed into wall cavities.
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Formaldehyde-free Johns Manville MR-Faced Batts (fiberglass) are treated with a food-grade preservative to protect against mold growth.
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Johns Manville Spider is a formaldehyde-free, spray-in fiberglass insulation that contains some recycled-glass content. (For use in open walls only.)
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UltraTouch insulation, made from recycled natural cotton/denim fibers, doesn’t itch and can be installed without protective clothing.
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UltraTouch insulation, made from recycled natural cotton/denim fibers, doesn’t itch and can be installed without protective clothing.

Installing insulation is one of the most environmentally friendly things a homeowner can do. About 65 percent of U.S. houses are poorly insulated, a 2005 Harvard study estimates. Fortunately, you can cut heating and cooling bills by about 30 percent with proper insulation.

These days, insulation is made with everything from newspaper and sheep’s wool to cotton and chemical foams. Many are far more “green” than their predecessors-including formaldehyde-free and recycled-content insulation. Even fiberglass, that old standard, has improved environmentally.

When choosing insulation, most homeowners contemplate R-value, which measures resistance to heat flow. The higher the R-value, the better the insulation material is at reducing energy consumption. Another important consideration should be where the insulation will go. The attic is the easiest place to insulate and the most important in terms of saving money and energy. Sealing large air leaks is next, followed by insulating the basement.

A federal energy tax credit can help homeowners recoup their insulation investment if they complete the improvements by the end of 2007. A tax credit is actually a dollar-for-dollar reduction in taxes equal to 10 percent of the cost of insulation (up to $500). For more information see www.SimplyInsulate.com.

Fiberglass insulation: The pink stuff

The most common type of insulation, fiberglass is made with glass fibers that can break off and be inhaled, causing lung damage, especially to professional installers. Most of it contains phenol-formaldehyde, a substance the Environmental Protection Agency has pegged as a probable human carcinogen. Fortunately, manufacturers have developed ways to eliminate formaldehyde-used as a binder-and to create fiberglass insulation from 30 to 40 percent post-consumer recycled-glass content.

Foam insulation

Spray foam insulation is an effective insulator with an R-value that ranges from about 3.2 to 7 per inch. It starts as a liquid that’s sprayed or poured into a wall cavity and then expands to fill every nook and cranny. Some foams can be blown only into new walls; others are appropriate for retrofitting. It must be installed by professionals.

Foam insulation stops air leaks and can be used where other insulations can’t, such as in foundations. However, the presence of polyurethane, a plastic, means spray foam insulation isn’t all natural. Another problem has been that ozone-damaging chlorofluorocarbons (CFCs) were used historically as blowing and foaming agents.

A new, greener generation of vegetable-based spray foams uses small amounts of oils from soy, sugarcane, corn fructose and other botanical sources, plus a minimum of 5 percent recycled content. Vegetable-based foams are blown with water, carbon dioxide or hydrofluorocarbons (HFCs), which don’t damage the ozone layer.

The more environmentally sound versions are low density, meaning they also have a lower R-value, closer to the range of 3.2 to 4.5 per inch rather than the 6 or 7 R-values found in denser, more toxic varieties. Because they actually block air flow much more than other types, however, the R-value is only part of the reason to consider foam insulation. Another drawback is that during installation foam insulation outgases toxic chemicals. Once it cures, it becomes inert.

Another type of foam insulation, polyisocyanurate, is a rigid foam good for exterior retrofitting, often on roofs, with an R-value of 6 to 7.5 per inch. “Polyiso,” as it’s called, was formerly created with ozone-depleting HCFCs as blowing agents, but the new “green polyiso” uses hydrocarbons that don’t emit greenhouse gases.

Cementitious foam-a nonflammable, extremely stable insulation-is made of magnesium oxide derived from seawater. When dry, it’s inert and should have no impact on chemically sensitive people.

Cotton insulation

Cotton insulation is made from remnants that denim manufacturers and other textile plants otherwise would have thrown away. It’s sold either as loose fill or in batts, like fiberglass, but without chemical or respiratory irritants. Like other textile products, cotton insulation is treated with boric acid as a fire retardant, pest repellent and an antifungal agent. Unlike most pest repellents and antifungals, boric acid is fairly nontoxic.

Cellulose insulation

Cellulose insulation consists of 80 to 90 percent post-consumer recycled newsprint, cardboard and paperboard. It’s sometimes applied by making it into a wet newspaper mush and spraying it into open wall cavities; sometimes it’s shredded dry and used in attics as loose fill. Like cotton, cellulose insulation is often treated with boric acid.

Although cellulose insulation is earth friendly and benign, some chemically sensitive people are bothered by outgasing from the newsprint ink. Because it’s made of wood fiber, cellulose can absorb more moisture than most other types of insulation. If the wall insulation gets wet often or is unable to dry out, the boric acid could leach out and mold could grow.


When weighing insulation options, consider where you’re going to use it and how R-value might be affected, advises Joel Hirshberg, president of Green Building Supply in Fairfield, Iowa.

1. If insulation isn’t installed properly, most manufacturers won’t guarantee the promised R-value. That means savings you gain from doing it yourself could cost you in energy savings.

2. Loose insulation such as cellulose and blown-in cotton fibers can be dislodged by critters or can settle, reducing R-value.

3. Damp insulation won’t work as well as dry insulation. Some insulation, such as cellulose or cotton, holds moisture more than others, such as cementitious foam. “Vapor barriers” made of plastic or foil can help protect insulation from rain or snow. Vents can prevent moisture from getting trapped, but if there’s a significant leak and moisture-retaining insulation gets soaked, it may have to be replaced.

4. Foam insulations tend to hold their R-value very well for the first two years because the gases in the foam block airflow. Then the gases begin to escape, and the R-value drops. A foil radiant barrier can help overcome this.

5. Fiberglass loses up to 50 percent of its R-value at temperatures below -20°F. Homeowners in cold climates might want to chose cellulose; its efficacy actually increases at lower temperatures.

Insulation at a Glance

R-value is used to measure insulation’s resistance to heat flow. The higher the R-value, the better the insulation. The overall R-value is the insulation rating per inch of thickness multiplied by the number of inches installed. (R-value rating may vary by brand.) How much insulation you need depends on your climate. Check the U.S. Department of Energy’s website for recommendations on overall R-value in various parts of your home (attic, walls, basement).

Cotton Batts

• R-value: 3.4 per inch
• Uses at least 90 percent recycled materials
• Can be recycled or composted at the end of its life
• Can be installed by homeowner

• Can settle, losing R-value
• Cotton is a chemical-intensive crop
• Costs about twice as much as fiberglass batts
• Boron fire retardant could leach out if it gets wet repeatedly

Spray Foam Insulation

• R-value: 5.9 per inch
• Inert when dry
• Won’t sag or settle
• Prevents seepage
• Extremely durable

• Less than 10 percent recycled material
• Must be installed by a professional
• Relatively high cost
• High embodied energy
• Outgasses during installation

Polyiso Foam Insulation

• R-value: 7 per inch (9 with foil vapor/radiant barrier)
• Newer green versions use hydrocarbons instead of HCFCs
• Extremely durable
• Can be used for walls and roofs

• Is a petroleum product
• Should be installed professionally
• Generally higher cost
• Some imported products still made with HCFCs

Cementitious Foam

• R-value: 3.9 per inch
• No toxic emissions
• Does not shrink or settle
• Nonflammable
• Extremely durable
• Can be recycled or composted

• Generally higher cost
• Must be installed by a professional
• Crumbles easily, so care should be taken about dust

Cellulose Insulation

• R-value: 3.5 per inch
• Made of 75 percent post-consumer recycled paper
• Low embodied energy
• Excellent acoustical insulation
• Relatively low cost

• Can settle, losing R-value
• If gets wet repeatedly, boron can leach out
• Printer’s ink may affect chemically sensitive people
• Costs slightly more than fiberglass


Air Krete
cementitious foam

BioBased 501
soy-based polyurethane foam spray

cellulose insulation

Green Zone
resources for CFC-free polyiso

formaldehyde-free foam

cotton insulation

Johns Manville
formaldehyde-free fiberglass

cotton insulation

Published on Nov 1, 2006

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