About Attic Insulation
Attic space is usually insulated by using one or a combination of three different types of insulation. Whichever ones you use depends on the particulars of your space, such as existing insulation, if any, or the type of access you have to install the insulation, among other factors. The three types are:
- Batts and Rolls Insulation–These are pre-sized lengths, or rolls of fiberglass “wool” often referred to as “blanket” insulation, designed to fit between framing studs, or in the case of an attic, the top floor ceiling joists. Batts are pre-cut and sized for particular uses, while rolls provide more material to work with and cover more space. Both can be cut to fit the exact dimensions needed. Rolls are ideal for most attic insulation projects.
- Loose Fill/Blown-in Insulation–This type of insulation is usually made of recycled paper or another source of cellulose and blown in place using a machine. It is ideal for cavities and spaces that are hard to reach. It can be installed over existing blanket insulation if need be.
- Polyurethane Spray Foam Insulation–This expanding foam is sprayed into place, and is great for filling small crevices and holes. It molds to surfaces and sets quickly. It is excellent at blocking moisture. It usually has a higher R-value than batts/rolls and blown-in insulation and forms an air barrier, often reducing the need for additional weatherizing, such as applying vapor barriers or sealing with caulk.
As with the rest of the insulation throughout your home, R-value is the important indicator of how well the insulation will perform, so take special note of it. Different regions need insulation with a higher R-value than others—the Northeast, compared to the Southwest, for example. For all regions though, insulation’s required R-value usually will be anywhere from R-30 to R-60. In most applications, a general benchmark for adequate insulation is around R-38. The R-value you need will also depend on whether you already have existing attic insulation or not. If you’re not sure about exactly what you need, ask a Hardwarian at your local True Value hardware store for advice.
A quick and easy way to see if you need more insulation is to take a trip to your attic and look at its “floor.” If your existing insulation doesn’t cover the joists completely, you probably should add insulation.
Before you add any insulation, stop and plan out your project. Determine where in the attic you need to add insulation and how much additional R-value you need from your new insulation, if you’re adding to existing insulation. To find out how much more R-value you need, examine your existing insulation. If you can determine its R-value, subtract it from, say, 38 (as in R-38), to determine how much more R-value you need. Next, decide on the type of insulation that best suits your needs. In most cases, adding blanket insulation is the most user-friendly type for a DIY-er. Lastly, calculate by square feet how much insulation you need to buy. Rolls and batts usually come in 16″ or 24″ widths to fit between joists. Either can be cut to fit in the space between joists, using a utility knife. The amount of insulation you buy will be determined by the length of the batts or rolls and how much attic space you need to insulate.
Blown-in insulation is fairly easy to install but requires specific equipment for the job. In most cases, it is added in new builds by contractors. As they have ready access to the required equipment to install it, consider hiring a professional if you want to add this type of insulation to your attic.
Remember to seal all air leaks throughout your home before adding insulation in your attic. This makes it easier to find any leaks in the attic and helps overall with your home’s efficiency. Polyurethane spray foam sealant is ideal for sealing air leaks and creating a vapor/moisture barrier.