Blown-In or Batt Insulation in Attic Spaces? – Georgia Roof

Blown-In or Batt Insulation in Attic Spaces?

attic insulation

The attic is one of the easiest places to add insulation to improve the comfort and energy efficiency of your home.  When insulating an attic space, many homeowners ask “which is better, blown-in or batt insulation”. The answer is that it depends. Here is some information about insulation for you to make the decision.

What is Fiberglass Insulation?

Fiberglass is a man-made material used in construction as insulation and soundproofing. It is made with melted glass spun out into very thin fibers. The microscopic glass fibers are captured then either left loose or pressed into a layered matrix for batts and rolls.

What is Cellulose Insulation?

Cellulose insulation is the oldest form of home insulation. It can be either a loose-fill or blown-in insulation and can be used in both new and existing homes. Typical places to use cellulose is in enclosed existing walls, open new walls, and unfinished attic floors. It is primarily made from recycled newsprint. These small particles form an insulation material that conforms to most spaces without disturbing the structure or finish.

Blown-In Insulation

Blown-in insulation is a common way to insulate your attic, crawl space or walls of your home. It can be done by a homeowner or by a roofing professional. Most home improvement stores can supply rental blower units, but many homeowners find the option of a hired installer easier due to the large size of the job. Blown-in insulation increases the comfort of your home by neutralizing humidity and drafts and usually brings the largest return on investment.

With blown-in insulation, you can expect an R-value of 2.2 to 2.7 per inch for fiberglass and between 3.2 and 3.8 per inch of cellulose.

Blown-in provides a seamless blanket over the boards of your attic. There’s no way for air to get through it, as compared to batt insulation. It’s also faster to install than batt or rolled insulation and costs less to install overall. One of the best advantages to installing this material is that it’s considered renewable. Other advantages to this material include:

  • Added longevity for the roof and shingles. A well-ventilated roof that includes an adequate layer of blown insulation can create a conditioned space in the attic. This conditioned space reduces the strain of heat on the sheathing that causes shingles to fail earlier.
  • Decrease in energy bills. Blown-in insulation can fill the crevices and cavities of attic space in ways that batting cannot. This creates a tight fit for little air gaps in the roof and eaves of the home, which saves a great deal of money by reducing the energy an air conditioner or furnace has to expend to heat or cool the home.
  • Vapor retarder and moisture barrier. Blown-in insulation that is installed correctly can reduce moisture infiltration. Maintaining the R-value keeps the house as warm as possible in the winter and cool in the summer. Adding an attic fan also helps to mitigate moisture that may infiltrate a vapor retarder near the insulation.

Batt insulation

The most common form of home insulation is “Batt and Roll” or “Blanket” insulation. It is typically stored in rolls, is generally made of fiberglass and is the least expensive way to insulate a home.

Batt insulation is precut sections of fiberglass or rock wool insulation. Designed for easy handling and use between framing, such as studs and joists. It is available either with or without paper or aluminum foil facing and can be used in floors, walls, attics and ceilings.

Batt and roll insulation is manufactured in various sizes for easy transport, and to make the installation easy for everybody from contractors to do-it-yourselfers. Insulation helps save energy by preventing heat transfer either into or out of your home (depending on the climate). But insulation is not effective at stopping air from infiltrating through gaps and cracks in the home’s exterior shell, or envelope. Therefore, for the insulation to be effective, you must seal air leaks before adding insulation.

The thermal performance or resistance to heat flow (R-factor) is not the same when comparing fiberglass batts to blown-in fiberglass. Batts offer a slight advantage. You can usually obtain an R-factor of 3.1 to 4.2 or slightly higher per inch of material with batts. The R-factor of blown-in fiberglass is usually 2.3 to 2.8 per inch of material.

Blown-In and Batt Combination

If you are re-insulating an attic space due to moisture, mold, or other contamination first install batt, and then blow in insulation on top of it.  You can also use batt insulation to insulate around attic access doors.

If you are upgrading your attic space, you can blow in insulation on top of your batt to achieve desired insulation values.

Current energy standards recommend the installation of a first layer of craft faced (moisture barrier) fiberglass batt be installed in your attic space. Blown in insulation is then applied over the batt level to fill any voids and gaps around joists and other structures, and to increase the level of insulation to recommended levels.

R Value

An “R” value is the level of heat flow resistance provided by the insulation material.  The higher the “R” value the greater the insulation performance.

Before the government set standards and recommendations, some contractors insulated with just a few inches of material. Today, the U.S. Department of Energy recommends certain levels of insulating material based on the area of the country in which you live. If your home heats up too fast once the sun comes out, then that’s a clear sign you need more layers of insulation. You can request that an HVAC professional measure the R-value of your current material which is the ability of the material to resist heat.

An “R” 60 value is the recommended level of insulation for maximum energy efficiency in most attics.

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