Wall Insulation Installation Costs and Values

This wall insulation guide discusses the purposes, types and wall insulation costs associated with this home building or renovating project. Wall insulation is one of the two most important types of insulation, along with attic/ceiling insulation, in controlling energy costs for your

home. With heating and cooling accounting for 50 to 60 percent of a home’s energy use, you can see that having properly insulated walls is crucial.

Reasons to Insulate the Walls

Wall insulation is a critical for preventing heat loss through the cavity of a wall in cold weather or the penetration of heat from outside in warm weather. Framed walls are filled with insulation that forms a heat barrier between the sheathing on the outside of the house and the material that forms the finished walls, typically drywall.

Recommended Insulation Levels for Interior and Exterior Walls

This data is supplied by the US Department of Energy in order to give homeowners an understanding of the value of wall insulation in reducing energy use and lowering energy costs.

Zone 1: Hawaii, Guam, Puerto Rico, the Virgin Islands

• Recommendation: Install R-11 to R-18 in uninsulated walls. Gas heat or heat pumps requires less insulation; electric furnace heat requires more in order to maintain cost-effectiveness.

Zones 2 & 3: Florida and the Gulf Coast States, Texas, Georgia, the Carolinas, Arkansas, Southern Arizona, Southern California

• Recommendation: Install R-13 to R-18 in uninsulated walls. Gas heat or heat from a heat pump requires less insulation; electric furnace heat requires more in order to maintain cost-effectiveness.

Zone 4: Mid-Atlantic States, Tennessee, Kentucky, Missouri, Kansas, southern areas of Indiana, Illinois, Iowa, Nevada, coastal areas of northern California, Oregon and Washington

• Recommendation: Install R-13 to R-18 in uninsulated walls. Gas heat or heat from a heat pump requires less insulation; electric furnace heat requires more in order to maintain cost-effectiveness.

Zone 5 to 8: Everything north of Zone 4

• Recommendation: Install R-18 to R-28 in uninsulated walls. Gas heat or heat from a heat pump requires less insulation; electric furnace heat requires more in order to maintain cost-effectiveness.

Types of Insulation Used in Walls

There are more than ten types of insulation used in walls including straw, sheep’s wool and recycled plastic fiber made from milk jugs. However, in this section, we will look at the most common types of wall insulation. They account for more than 85% of the wall insulation used in homes today.

Fiberglass batt insulation remains the most popular choice of homeowners and contractors. It is energy efficient, easy to install and affordable. The insulation is made from fibers created by melting glass and spinning it. Depending on the density of the fiberglass, the batt will offer an R-value of R-11 to R-15 in 2×4 frame construction. In 2×6 framing, the R-value offered by thicker batts increases to about R-21.

Faced fiberglass batts have a vapor barrier applied to one side, and the barrier should be installed facing the interior of the home. It prevents moisture produced by cooking, laundry, bathrooms and breathing from entering the wall cavity where it may cause mold and rot to the framing materials. Unfaced fiberglass insulation is available too. Check with your insulation contractor for the best choice for your home.

Rock wool insulation, also known as mineral wool or stone wool, is similar to fiberglass in look and texture. It is manufactured using molten stone or slag that is spun into a wool-like material. It has roughly the same insulation value as high-density fiberglass batts. Rock wool insulation is quite green; manufacturers use an average of 75% post-industrial content. Like fiberglass, no chemicals are needed to boost its fire-retarding capabilities. Faced and unfaced batts are available.

Loose fill insulation, technically known as cellulose insulation, is typically made from recycled paper, mostly newsprint, which is reduced to very small pieces and made into fibers. The recycled content averages 80 to 85 percent. As far as R-value, it is comparable to high-density fiberglass and rock wool with an R-value of about 3.7 per inch of thickness. That equates to just over 12 in 2×4 construction and nearly 20 in 2×6 construction. Cellulose insulation must be chemically treated to resist burning.

One advantage of loose fill insulation is that it can be added to existing walls while batts cannot be. When using in this fashion, a layer of siding is removed. Three-inch holes are drilled into the sheathing of the home, and a filler tube is inserted through which the insulation is blown into the wall. The holes are plugged, and the siding is replaced.

In new construction applications, cellulose is usually dampened and then sprayed into wall cavities. Up to 72 hours may be required before drywall or other wall material can be installed over it. Dry cellulose can be installed in wall cavities in new construction if a netting is fixed to the studs and the cellulose insulation is placed behind it.

Wall Insulation Costs and Comparisons for Interior and Exterior Walls

Here’s a general comparison of wall insulation costs to give you an idea of what to expect on your project. For the best prices where you live, get estimates from at least three wall insulation contractors who know they are competing for your business.

Loose Fill Cellulose Insulation

Table 1: Prices shown for Loose Fill Insulation, divided down into Material per Sq. Foot and Labor per Sq. Foot:

Fiberglass Batt Insulation

Table 2: Prices shown for Batt Insulation, divided down into Material per Sq. Foot and Labor per Sq. Foot:

Rock Wool Insulation

Table 3: Prices shown for Rock Wool Insulation, divided down into Material per Sq. Foot and Labor per Sq. Foot:

Spray Foam Insulation

Table 4: Prices shown for Spray Foam Insulation, divided down into Material per Sq. Foot and Labor per Sq. Foot:

For all types of insulation, expect there to be additional costs of $25 to $50 per 1,000 square feet of insulated space for extra supplies.

To compare wall insulation costs in your area, it is recommended that you receive at least three written estimates from contractors. This will give you an opportunity to discuss which material is right for your application as well as learn more about each insulation company.

Factors Affecting the Cost of Wall Insulation

• Size of the Walls – Since the cost of wall insulation is calculated in sq. ft., you will note that the larger the wall the more the insulation will cost.
• The depth of the Cavity – The depth of the wall cavity will increase both the insulation r-value required to achieve the appropriate level of insulation, furthermore you will require more insulation to fill that gap. Therefore the cost increase is twofold.
• Location of the Wall – Different rooms, such as the basement vs a living room or a bedroom which require different levels of insulation as their r-value requirements will be different. On average the r-value of a basement is r-19 to r-20, whereas the r-value requirement for a standard living space, such as a bedroom or living room, will be lower at around r-13. Therefore the cost to insulate a basement wall will be $1.15 to $1.65, whereas the cost to insulate a wall in a living room or bedroom may only be $1.00 to $1.50 per sq. ft. Not a massive difference, but a noticable enough difference when you have 600-1000 sq.ft to insulate.
• Where You Live – Living in a colder climate increases the r-value of insulation required, where as if you live in a warmer climate and have shorter winters then you may not require an insulation with as high an r-value. We discuss the recommended levels of insulation for various zones earlier on in this article.

More Insulation Types & Locations