Compare Basement Insulation Installation Costs and Values

basement-insulationThis basement insulation guide discusses the reasons to insulate, how much insulation and what type, and the costs of insulating a basement.

Jump to: Insulation Levels | Types | Costs

Reasons to Insulate the Basement

There are two main reasons to insulate your basement. First, the insulation you add will make your home as a whole more energy efficient. The insulation will reduce heat loss through the foundation walls.

The second reason, and the main reason homeowners insulate their basements, is to make the space more comfortable for use. Finished basements almost always have insulated walls to retain heat.

When insulated, basements feel less damp too, and this is due to the installation of a moisture barrier, one of the most important steps when finishing any space that is below grade.

The moisture barrier should be next to the concrete to prevent moisture vapor from passing through the foundation and into the basement. One of the biggest mistakes homeowners and some contractors make is using faced insulation with a vapor barrier between the insulation and the drywall. That barrier will trap moisture in the insulation and cause mold and the rotting of the framing timbers.

See the section below on the Types of Insulation Used in Basements for proper ways to incorporate a vapor barrier into basement insulation.

Recommended Insulation Levels for Basements

Always check the building code in your area for insulation requirements. Insulation contractors you get estimates from should have the information too. However, here are recommended insulation values for basements from a national building association.

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

  • Recommendation: Install R-10 to R-12 on the interior of a basement or crawl space; Install R-4 to R-6 if you choose to add insulation to the exterior.

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

  • Recommendation: Install R-10 to R-12 on the interior of a basement or crawl space; Install R-4 to R-6 if you choose to add insulation to the exterior.

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-12 to R-14 on the interior of a basement or crawl space; Install R-4 to R-8 if you choose to add insulation to the exterior.

Zone 5 to 8: Everything north of Zone 4

Recommendation: Install R-12 to R-19 on the interior of a basement or crawl space; Install R-4 to R-10 if you choose to add insulation to the exterior.

Types of Insulation Used in Basements

There are three main types of insulation used in or on the exterior walls of basements. We’ll address them in the order of their popularity.

Before we do, however, it is essential to note that a vapor barrier must be installed against the concrete foundation. This can be done with the use of a spray-on rubberized barrier that does not provide insulation, rigid foam insulation or spray-on foam insulation. Using plastic sheeting as a vapor barrier is of limited value and is not recommended by basement and insulation contractors.

Without the vapor barrier, moisture will pass through the foundation wall. If you finish a basement with framed walls, that moisture will likely become trapped in the walls and cause mold and rot. One mistake to avoid is using faced insulation in framed basement walls. It will certainly trap moisture and cause problems with mold.

The best basement insulation material is rigid foam insulation, sometimes referred to as closed-cell foam board. It’s made by a range of manufacturers in several different widths. Rigid insulation can be adhered to either the exterior or interior wall, or both.

For the exterior, it is recommended that you use board at least one-half inch in depth. This will provide an R-value of about 3 (R-3.2). You’ll need 1.5 inches for roughly R-10.

Rigid foam board is the ideal basement insulation for the interior. It can be glued directly to the concrete to provide a vapor barrier and significant insulation value. Most contactors recommend using at least 1.5 inches in all climates. If it’s the only source of insulation, you may want to use more in colder climates. Basement insulation experts recommend caulking the seams with foam insulation in a can and then taping the seam to prevent the penetration of moist, cold air.

Spray foam insulation is slightly more expensive than rigid foam board, but works in the same way. It provides both insulation and a vapor barrier. The convenience of this type of insulation is that it does not have seems, so no extra caulking or taping is required.

Fiberglass insulation can also be used in framed basement walls, but it should never be the only source of insulation. If it is used by itself, it will trap moisture which will lead to mold and rot.

Instead, non-faced fiberglass insulation batts may be used in framed walls where at least 1 to 1.5 inches of rigid or spray foam insulation has been installed against the basement foundation walls. For example, some contractors will install the rigid board or spray foam against the foundation wall and then frame the finished wall on top of the foam insulation. In this scenario, filling the wall cavity with fiberglass insulation is a very effective option. It insulates well and is more cost-effective than foam board or spray insulation.

Basement Insulation Costs and Comparisons

Let’s compare the costs for rigid foam, spray foam and fiberglass while keeping in mind that fiberglass insulation, even unfaced fiberglass, should never be installed against concrete. The costs are given per square foot of material.

Rigid Foam Insulation

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

Insulation RatingMaterial per Sq. FootLabor per Sq. Foot
R-13  $0.90 to $1.60 $0.55 to $0.65
R-19  $1.10 to $1.30 $0.90 to $1.30
R-21$1.20 to $1.45$0.95 to $1.30

Spray Foam Insulation

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

Insulation RatingMaterial per Sq. FootLabor per Sq. Foot
R-13  $0.75 to $0.90  $0.80 to $0.95
R-19 $1.30 to $2.50 $0.75 to $1.00
R-21$1.40 to $2.70 $0.75 to $1.10

Fiberglass Batt

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

Insulation RatingMaterial per Sq. FootLabor per Sq. Foot
R-13 $0.30 to $0.40 $0.30 to $0.40
R-19 $0.50 to $0.75 $0.60 to $0.95
R-21 $0.55 to $0.85 $0.65 to $0.95

All these types of insulation have extra costs for materials and supplies. Expect to pay an additional $25 to $65 per 1,000 square feet of insulated surface.

In addition, it always makes sense to get at least three free estimates from local contractors to find the lowest basement insulation costs where you live.

Helpful Resources:

Check Out Contractor Rigid Insulation Costs

Get Foundation Information Tips from the US Oak Ridge National Laboratory

Learn about Basement Insulation Technology