Fiberglass Batt Insulation Guide and Cost

Fiberglass Batt Insulation

Fiberglass batt insulation remains very popular for use in wall applications. Cost ranges from about $1.00 per square foot for R-11 insulation in 2x4 construction to about $2.40 per square foot for R-21 in 2x6 and 2x8 construction.

There’s a lot more on the cost below. First, this fiberglass batt insulation buying guide explores this common home insulation type, faced vs. unfaced, where these types are used and other useful information.

When Was Fiberglass Batt Insulation Invented?

Very few people today cannot remember a time when one of the leading types of home insulation was not fiberglass. This is because it has been around since 1938 when it was first introduced by Owens Corning. What began as a laboratory accident a few years before, quickly became a popular product, and by the mid- 1940’s, building contractors began using it as a primary way to make homes and commercial buildings comfortable in any climate.

What Is Fiberglass Insulation?

Simply stated, fiberglass is made from silica sand, recycled glass and several other minerals and chemicals. It is spun into very fine strands and formed into various products; some are extremely hard and tough, others are very soft and fluffy. Fiberglass products used for insulation range from very firm to very light.

Fiberglass insulation can be found in rigid fiberglass panels, loose fiberglass for pouring or blowing, fiberglass rolls and fiberglass batts. Fiberglass insulation rolls are just like batts, except that they are purchased in long rolls and cut to length for insulation, given you flexibility. Each type of insulation has a place in the building and remodeling industry, and each type is best suited for particular applications. Loose fiberglass and roll fiberglass insulation are common options for attic insulation.

What Is a Fiberglass Batt?

Insulation Batts

A fiberglass batt is a pre-cut piece of insulation that is designed to fit in the space between the wall studs, ceiling or floor joists, or roof rafters of a building. They are made in different thicknesses and widths in order to fill these spaces completely, depending on the material that was used in construction – wood or metal frame. Some types are also made in low, medium or high density, which affects the R-value of the batt.

Did you Know? The R-value, “R” standing for “resistance,” is the fiberglass’s ability to stop or resist heat transfer. For all types of insulation, the thicker the material, the higher the R-value. A minimum of R-13 is recommended for the walls of residential construction. Up to R-21 is preferred in cold climates.

Because of the large variety of building materials available today, as well as the various styles of construction, manufacturers of fiberglass batts have responded with an amazing variety of product types and sizes. This will be shown at length later in this article.

What is Faced and Unfaced Insulation?

Faced Unfaced Batt

An unfaced fiberglass batt is one that has nothing added to any of its six sides. On the other hand, a faced fiberglass batt will have a material of either kraft paper, foil, or vinyl on one side. Depending on the material, it will provide a vapor barrier, a flame retardant surface or a light-reflecting face. A vapor barrier is especially important in colder climates because it will prevent moisture from the warm, inside air to travel into the wall space where it can condense. There are several reasons you don’t want this to happen.

First, wet insulation isn’t as effective as material that remains dry. Secondly, the moisture may lead to mold and mildew.

Many of the faced batts also have a flange – an extra piece of the facing about 1 inch wide – on each edge. When this flange is spread to the side to overlap the batt beside it, it will “lock” them together, rather than having each batt sitting alone in its space. This will make the finished surface more continuous with fewer gaps for water vapor and air leaks to pass through.

That flange is also used to secure the batt to wall or ceiling studs.

There’s a lot more information on the differences between faced and unfaced fiberglass batt insulation in our guide to Faced vs Unfaced Insulation.

Why Or Why Not Use Fiberglass Batts?

Here are the pros and cons of fiberglass batt insulation.

Why? Fiberglass batt pros:

They are inexpensive – one of the least expensive ways to insulate, especially in new construction or when adding insulation where the space is open.

They are easy to install. Using batts is intuitive; see the space, see the batt, fill the space with the batt. It’s (almost) that easy.

  • They are fire resistant.
  • They are made from recycled and renewable materials.
  • The R-value is known; several are available for many applications.
  • The R-value does not decrease with time (tho if improperly installed, they might slump in wall cavities over time).

Why Not? Cons of fiberglass batts:

  • Air gaps can rob you of the R-value if batts are not properly installed.
  • Lower R-value per inch of insulation than some other insulating materials.
  • If DIY installed, care must be taken to avoid inhaling fiberglass particles.

What Different Types and Sizes are Available (and where to use them)?

Among the major manufacturers of fiberglass batt insulation, one stands above the rest in its line of products. This is the original producer of fiberglass, Owens Corning. Knauf and Johns Manville also make a nice selection, though not as large as Owens Corning.

The following is the most extensive list of any major manufacturer – Owens Corning:

  • EcoTouch Insulation. This is their standard insulation for walls, ceilings and roofs.
  • EcoTouch Flame Spread 25 Insulation. This is a special insulation for ceilings and roofs that not only provides the insulating factor, but also is faced with a low flame spread vapor retarder. It is available in a reinforced foil laminate (FSK), or a light reflective white poly facing (PSK). The PSK facing helps improve interior lighting. Note that the designations FSK and PSK are used in the sizing chart below.
  • PROPINK FastBatt Insulation. This is a flexible, fiberglass insulation batt with a kraft facing with no flange. It is designed to “friction fit” between ceiling joists and roof rafters. No stapling is needed to hold the batt in place. The kraft paper facing provides a vapor retarder that is required in many areas.
  • QuietZone Batt is a fiberglass acoustic batt insulation. It is designed to absorb sound vibrations in the wall, floor and ceiling for noise control. It is available in either unfaced or kraft-faced. No R-values are listed by the manufacturer for this product, and according to Owens Corning, it isn’t usable to create an external thermal envelope for any structure.
  • Sonobatts Insulation is another specialty insulation. It is designed to provide additional thermal and acoustical control when used above suspended ceilings. It is available either unfaced or with asphalt-coated kraft facing on one side.
  • Sound Attenuation Batts are designed for use primarily in interior walls where sound control between rooms is desired. These special batts are composed of unfaced fiberglass insulation and can improve the noise level ratings between rooms by up to 10 decibels. They are sized for metal frame construction only.

Below is a table with the various types and sizes of fiberglass batts available and the type of construction with which they are designed to be used.

Note - All widths, lengths and thicknesses are in inches.

Type/ConstructionWidthsLengthsThicknessesR-Values
EcoTouch
Unfaced - Metal Framing16, 2448, 963.5, 5.5, 6.2513, 15 19, 21
Unfaced - Wood Framing11, 15 19.25 2393, 1053.5, 5.5 6.2511, 13, 15, 19, 21
Unfaced - Roof/Ceiling15, 16, 19.25 2324, 48, 966.25 - 12.019 - 38
Kraft faced - Metal Framing16, 2448, 963.5, 6.511, 13, 19
Kraft faced - Wood Framing11, 15 19.25 2393, 1053.5, 5.5 6.2511, 13, 15, 19, 21
Kraft faced - Roof/Ceiling11ÔÂ24ÈÕ48, 966.25 - 12.019 - 38
Foil faced - Metal Framing16, 24963.5, 5.5, 6.2511, 13, 19
Foil faced - Wood Framing11, 15 19.25 2393, 1053.5, 5.5 6.2511, 13, 15, 19, 21
Foil faced - Roof/Ceiling16, 2448, 966.25, 9.519, 30
EcoTouch Flame Spread 25
Metal Framing16, 24963.5, 6.25 (FSK)11, 13, 19 (FSK), 30, 38 (FSK/PSK)
Wood Framing15, 23936.2519
PROPINK FastBatt15, 15.593, 1053.5, 5.5, 6.2513, 15, 19, 21
QuietZone Batt
Kraft faced - Wood Framing15, 2393, 1053.5N/A
Unfaced - Wood Framing15, 16, 23.2593, 1053.5, 5.5N/A
Sonobatts24483.5, 6.25, 9.511, 13, 19, 30, 38
Sound Attenuation Batts16, 24962.5, 3.58, 11

This is an impressive array of types and sizes of fiberglass batt insulation that will fit every possible need for building construction. The builder or homeowner who wants to use fiberglass batts for insulation will surely be able to find a product to meet his requirements.

How Much Do Fiberglass Batts Cost?

There are two basic ways of estimating the cost of any type of insulation. One is by the cost per board foot of insulation. A board foot in construction terms is 1 square foot of surface 1 inch thick. Put another way, this is an area 12” x 12” x 1”. Obviously, insulation is normally applied more than 1 inch thick, but this gives one way to compare the different types of insulation available.

The second way to compare the cost of insulation is by R-value per inch. R-value is a measure of the ability of a material to resist the transfer of heat through itself. Since each type of insulating material has a somewhat different ability to do this, cost is often compared by this method.

Prices will vary from time to time and place to place, but here are some approximate costs for the most commonly used types of insulation. This is for the material only. Buying in bulk always costs less and accounts for some of the variation in costs.

Sample Project Costs and Factors

Here are common R-values for walls, foundations and ceilings plus the cost of faced and unfaced fiberglass batt insulation at each R-value. These are professionally installed prices. You’ll save roughly half if you DIY the installation.

 Unfaced/sq. ft.Faced/sq. ft.
R-13$.90 - $1.65$1.10 - $1.90
R-15$1.05 - $1.80$1.25 - $2.00
R-19$1.30 - $2.10$1.60 - $2.50
R-21$1.50 - $2.25$1.90 - $2.60
R-30$2.00 - $3.15$2.15 - $3.40
R-38$2.35 - $3.40$2.50 - $3.75

The cost factors include:

  • Pro vs DIY installation
  • Fiberglass thickness
  • Whether it is faced or unfaced
  • Access to the location
  • Difficulty – Ceilings and attics are harder to insulate than walls

Cost Comparison to Other Installation Type

There are several other types of insulation to consider for your residential or light-commercial insulation project.

  • Blown-In Fiberglass Insulation: $0.40 to $1.00 per board foot.
  • Fiberglass Batt Insulation: $0.24 to $1.20 per board foot.
  • Open-Cell Spray Foam Insulation: $0.44 to $0.80 per board foot.
  • Closed-Cell Spray Foam Insulation: $1.00 to $2.00 per board foot.

Conclusion

We are fortunate to have so many options when it comes to choosing the right kind of product for our insulation needs. Of all the types of insulation available, fiberglass batts provide the largest number of these options from which to choose. Widths, lengths, thicknesses, facings, densities – all of these add up to making fiberglass batts the most widely used insulation product in residential as well as commercial construction today.

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