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   Blown-in insulation is a material made of fiberglass or cellulose that's blown into cavities in walls to fill in gaps in insulation. This insulation is ideal for attic spaces with nooks and crannies that are difficult to insulate with fiberglass batting due to their size and shape

What Is Blown-In Insulation?

   Blown-in insulation refers to the process of blowing insulation material (also known as loose fill) into walls and attics or around crevices using special equipment consisting of a tube or hose. Blown-in insulation materials can be made from cellulose, fiberglass fibers, or even styrofoam pellets. 

When a home is being constructed, thick, long strips of fiberglass insulation are placed between the wall studs and ceiling joists before the sheetrock is put up. Over time, this insulation can settle, creating small crevices that air can get through. This is a problem because it leads to heat loss. What’s more, re-installing these sheets isn't always feasible, not to mention the fact that certain areas like unfinished attics or obstructions in the room are difficult to install the long strips of fiberglass insulation around. 

That’s why it makes sense to install blown-in insulation to keep the heat from escaping. It also will improve the home’s R-value. 

Blown-In Insulation R-value 

   What is R-value? R-value refers to a grading system used to determine how effective an insulation product is. R-values are measured per inch of insulation thickness. The higher the R-value, the more insulated the product is. Check with Energy Star or your local home improvement store to determine the appropriate R-value for your geographic region.

The R-value of blow-in insulation depends on how much product you use. You could use a thin layer and get a low R-value that’s more appropriate for an attic in the South. Or you could use a layer that is several inches thick and applied on top of existing insulation to get a higher R-value ideal for an attic that deals with Midwest winters.  

Blown-In Insulation Advantages

  • Energy efficiency: Fitting insulation around small crevices not only locks in heat during the winter months, but also can prevent cool air from escaping in the summer so your HVAC and air conditioning unit don’t need to be running all day.

  • Fire resistance: Small crevices and spaces tend to fill with smoke in the event of a fire. By filling them in with insulation and creating an air-tight seal, fire protection is increased in your home. 

  • Ease of installation: Blown-in insulation is simply blown in with a hose and can typically be installed in a few hours. Installing rolls of fiberglass requires tearing into walls.

  • Insect and critter repellent: Some types of blown-in insulation are treated with borates, preventing a potential insect or critter infestation in your attic.

  • It pays for itself: While the upfront cost of blown-in insulation averages $1,500, the energy savings you will see pay for itself over time. Use our Blown-In Insulation Cost Guide to get more specific information on pricing per square foot for the different types available.

Blown-In Insulation Disadvantages

  • Professional installation is usually required: This project usually requires a professional considering you need to drill between studs, which can contain electrical wiring. However, this can be a DIY project in an unfinished attic with the proper tools and protective gear.

  • Weight: If too much loose fill is installed on an attic floor, it can cause the ceiling below to sag due to the weight. 

  • Messiness: Loose-fill insulation can be a messy job, requiring proper protective gear and the additional task of cleaning up.

  • Must be kept away from recessed lights: Even though blown-in insulation materials are fire-resistant, they can still become too hot and ignite if exposed to extreme heat over an extended period of time. Because the heat cannot dissipate, lightbulbs can also burn out easier if insulation is installed too close to recessed lights (also known as can lights or high hats). 

  • Noticeability: During installation, holes are drilled in the home’s exterior so the hose can blow the loose fill into the wall cavity. These holes are then filled in with a plug that matches the color of the exterior wall. While siding can be easily matched and looks discreet, the plug becomes more noticeable if you have brick, stone, or stucco. 

  • Not water-resistant: It’s important to install the loose fill in a dry area. Otherwise, water can wear at the R-value and can even lead to mold or mildew. Seal any gaps or cracks and address leaks or even ice dams that may let in water before installation so you get the best performance.

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