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What Type of Insulation is Best for Your Attic?

what type insulation best

Adding insulation to your home can be a great way to save hundreds of dollars a year on your utility bill. However, there are several types of insulation, and many things to take into consideration. Some are more effective than others, some can easily be DIY projects, while others require hiring a professional. What type of insulation is right for you? Let’s take a look at the different types, their costs, effectiveness, and accessibility as a DIY project.

Batts and Blankets

The most common type of insulation, batts and blankets, are great for DIY projects. They usually come packaged in rolls and are easy to transport and carry. However, they can lose up to 50% of their effectiveness if they are improperly installed in difficult to reach places. Sometimes they come with a vapor barrier to help protect against moisture. The three most common types of batts and blankets are fiberglass, rockwool, and cotton.

Fiberglass batts have an R-value of 3-4 per inch, and they are widely available for about 30 cents per square foot. Unfortunately, fiberglass can be very irritating to the skin and lungs because it is made of fine glass fibers. Protective clothing and masks will be needed during installation. Another disadvantage to fiberglass is the batts can lose effectiveness due to compression.

For double the price, rockwool does not have the same disadvantages, is more fire resistant, and has an R-value of 4-5 per inch. The downside however, is that rockwool batts are harder to find, and they can harbor mold growth if they’re allowed to get damp.

The third option is the cotton batt, also known as “blue jeans”. These batts have an R-value of 3.5-4 per inch, and they cost around 90 cents per square foot. For this price, you get insulation material that is made of 85% recycled fiber and borate fire retardant material, which also acts as a repellent to certain insect pests. However, these batts are not widely available either.

Loose-Fill Insulation

Loose-fill insulation is great for filling hard to access nooks and crannies. It consists of strands of fiber which are blown into walls or attics using a special machine. Competent DIYers can tackle insulating an open attic on their own if they can rent an insulation blower from a tool rental store or a local home improvement center. But if the job is more complicated than an open attic, it’s best to hire a pro. Loose-fill insulation is available in either fiberglass or cellulose.

Loose-fill fiberglass costs around 30 cents per cubic foot, and it has an R-value of 2.2-2.7 per inch. It is very lightweight, which makes it perfect for attic applications above ½-inch drywall ceiling with framing every 24 inches. The problem is that it can lose over 50% of its effectiveness at very low temperatures unless blanket insulation is used in conjunction with the loose-fill fiberglass.

Loose-fill cellulose, on the other hand, is a much heavier type of insulation, which makes it very effective in low temperatures. This weight, however, makes it too heavy to use in attic installations, and it can settle over time, losing as much as 20% of its effectiveness. At a price of 31 cents per cubic foot, it’s best used in ceilings and walls.

Structural Insulated Panels

Structural insulated panels, or SIPs, are best used in new construction. SIPs are made of a foam core sandwiched between two structural facings, such as OSB (oriented strand board). They are usually 4×8 feet sheets that can cut an extra 12-14% off your energy bill. There are two types of SIPs: polystyrene SIPs and polyisocyanurate SIPs.

Polystyrene SIPs are lightweight. They must be treated with insecticide before use, otherwise insects and other pests will tunnel through them. Expanded polystyrene SIPs come with a price tag of roughly $6 for a 4×8 foot, 1-inch thick sheet, and have an R-value of 3.8/inch, while extruded SIPs can cost $15 for the same board size, and have an R-value of 5/inch.

Polyisocyanurate SIPs, on the other hand, have the highest R-value per inch of any type of insulation of its thickness. The value ranges between 5.6 and 7.7 per inch. They come with a built-in moisture barrier. The only disadvantage to these panels is the price tag at around $22 for a 1 inch-thick 4×8 feet sheet.

Spray Foam

Spray foam is a more expensive and more effective alternative to batt insulation. It comes with a higher R-value, and can also be used in place of caulking to seal the space. Spray foam is great for hard to reach gaps because it starts off as a liquid that expands, creating an insulation barrier. Once the foam has expanded and dried, any excess can be cut away. This makes spray foam an excellent choice for use in framing cavities. There are two types of spray foam: open-cell polyurethane and closed-cell polyurethane.

The open-cell polyurethane foam has an R-value of 3.5 to 3.6 per inch, with a price tag of $1-$1.20/square foot. DIYers can use this foam for small jobs such as insulating door frames. For bigger jobs such as roof, attic, floor, and wall insulation, you will need professional help and equipment. The major disadvantage of this type of foam is that it allows water vapor to pass through. You will need a moisture barrier as well.

The closed-cell polyurethane foam is more expensive at $1.75-$3/square foot. However, it comes with an R-value of 6-6.5/inch, and it stops moisture as well as air transfer. This type of foam requires professional installation. The manufacturing process to obtain this type of foam might have a higher negative environmental impact.

Which type of insulation is best for you?

Given that there are several options when it comes to insulation, which do you consider to be the best choice? You could go with cost saving DIY options, or you could hire professional help and go for top-shelf products. All choices, however, have their benefits and drawbacks.





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