Thinking about adding insulation to your attic? Great idea. The best, in fact. There is literally no other insulation project that has more impact when it comes to improving the comfort and energy efficiency of your home. If you’re just beginning the process of adding or replacing insulation throughout your house, the attic is the perfect place to start.
The first step of your project will be choosing an insulation type. When I think of insulation, what comes to mind is fiberglass blanket insulation, that fluffy pink stuff resembling cotton candy. Invented in the 1930s, this was the most popular type of home insulation well into the 1970s and is still widely used today. But, in addition to the pink stuff, there are several newer types of insulation worth considering.
Scientists have figured out how to make insulation out of other materials, including rock, slag, paper, sheep’s wool, cotton and more kinds of plastic than I can count or pronounce. They have also developed different forms of insulation. In addition to the “blanket” type, which the average homeowner can purchase at the home improvement store and install without any special tools or expertise, there are now “higher-tech” options that do require a degree of machinery. These include loose fill (small pieces of material) that must be blown in with a pneumatic hose and plastic foam that is sprayed in through a membrane using specialized equipment. For these latter two, hiring a professional installer is highly recommended.
All types of insulation have their pros and cons, including variations in cost, ease of installation, eco-friendliness and more. You can spend lots of time researching the different types before you make your choice. Information on the topic abounds on the internet. I personally am a passionate DIYer and the kind who likes to thoroughly understand what I’m delving into before I start spending my valuable money and time on it. One of my favorite resources for building knowledge is the U.S. Department of Energy website. If you’re like me, check out their quick, easy-to-read insulation primer before beginning your project. The DOE’s Building America program’s website is also a gold mine, though its target audience is professional builders, so there is a lot of information to weed through, much of it very technical.
If, on the other hand, you’re eager to get started and determined to do the project yourself, I recommend using blanket insulation (fiberglass or otherwise). It’s tried, true, less expensive than other options, and reasonably safe. (Some find fiberglass insulation irritating to their skin, eyes and/or throats. Wearing gloves, goggles and a mask will guard against this.) Blanket insulation can be purchased at your local home improvement retailer and installed using nothing but a putty knife, a utility knife and a tape measure. While easy to install, it has a reputation for being trickier than some other types — namely blown insulation — to “get right.”
Skeptics say the challenge is cutting and installing the material precisely enough to avoid the cracks and gaps that drastically reduce its effectiveness. But not everyone agrees this should deter DIYers. Many say that even the experienced can use this type of insulation successfully — as long as they’re careful. In fact, some say people insulating their own homes may do a better job with blanket insulation than some professional contractors, as taking the time to do the job right is what’s critical to making it work. If you do run into challenges, there are oodles of videos online you can use to educate yourself quickly in order to overcome them. Another great thing about blanket insulation is that it’s not only easy to install, but simple to remove. If you change your mind later, you can fairly quickly take it out and install a different material.
Once you’ve decided to use blanket insulation, it’s time to determine which particular product is the right one for your project. You’ve got a couple of choices to make. One, you will need to choose the material (fiberglass, mineral wool, cotton or sheep’s wool). And two, you will have to decide whether to use batts or rolls. Batts are pieces of blanket insulation that are pre-cut to manageable sizes (15-24 inches wide by 48 or 93 inches long), while rolls are strips of insulation similar to batts in width but much longer (25, 32 or 48 feet, for example).
The standard widths of both batts and rolls match the spacing found in the framework of almost any home (the typical width between studs and joists), making it a snap to lay a piece of blanket insulation right where you need it. I cannot stress enough how important it is to measure your space carefully and choose insulation sized to match it. Yes, blanket insulation can be cut, and cutting isn’t hard, but it’s not something you want to have to do if you can avoid it.
So, which is better, batts or rolled insulation? The answer depends on a number of factors, including the size and shape of the area you will insulate, any obstructions it contains, and your personal preferences. There is little to no price difference between batts and rolls, and both come in the same ranges of heat resistance values (or R-values). Though you may be anxious to get started, I urge you to spend a little time learning about the differences between the two in order to, hopefully, choose the right one for you. It will save you time and make the job a lot more fun in the long run.
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Attic Insulation Batts vs Rolls
Both batts and rolls have their advantages. Rolled insulation may take less time to install than batts if you have large areas to cover. On the other hand, if your attic is small, batts are easier to work within a cramped space. Even if your attic isn’t small, if you want to minimize the physicality of the job and prefer extra cutting to additional crouching, kneeling and stretching, batts are the way to go. Batts also tend to be better if you have odd-shaped or sized areas to cover, or obstructions to insulate around. This is because they’re smaller and less wieldy than rolls — and, therefore, easier to cut and manipulate.
Heat Resistance or R-Value
Some think the purpose of insulation is to keep cold out. In fact, it’s to keep heat in. The ability of insulation to block the flow of heat from one place to another is known as its thermal resistance value or “R-value.” The higher a material’s R-value, the more insulating power it has. An insulation product’s R-value depends on what it’s made of, its density and its thickness.
Blanket insulation — both batts and rolls — comes in a wide range of R-values. The one you need for your project depends on where you live. Refer to the International Energy Conservation Code (IECC) climate zones map to find your zone, then go to the DOE website to find the R-value recommended for your area. You may also be able to ask someone who works at your home improvement store. Most insulation products are labeled with an R-value. Be sure to keep in mind that in order to “live up to” its full R-value, insulation must be properly installed.
As mentioned before, blanket insulation can be made of any of a variety of substances, including the following.
Fiberglass has long been and still is the most prevalent type of blanket insulation. Its primary constituent, a thin glass fiber, was discovered accidentally at Corning Glass in the early 1930s. Trademarked as Fiberglas in 1936, it was rapidly incorporated into many products, including mass-produced insulation. It wasn’t long before other companies began manufacturing the glass fibers, competing for their share of the huge market for the product. To distinguish its insulation from others’, Owens-Corning began adding red dye, which turned the stuff pink. Fiberglass insulation, which is 40 to 60 percent glass, does not contain cancer-causing asbestos and is not hazardous to health in any way when used as directed. Chemicals are added to make it fire-resistant.
Mineral wool refers to a manufactured substance made from rock or slag, a byproduct of molten metal. Interestingly, the insulating properties of slag fibers were discovered in the late nineteenth century and used for this purpose before fiberglass insulation made its debut. Mineral wool insulation is becoming more popular — perhaps because consumers as a whole are growing more environmentally conscious, and it is made of 75 percent post-industrial recycled material. Unlike fiberglass, mineral wool is naturally fire-resistant.
Like mineral wool, cotton insulation is fairly new to the mass market. Today’s cotton insulation is approximately 85 percent recycled cotton fabric, including denim. It is available in batts, and costs about 15% to 20% more than fiberglass batt insulation. Cotton insulation is treated with borate, a naturally occurring mineral, to make it fire-resistant and repellant to insects and rodents.
Another eco-friendly alternative insulation material is sheep’s wool. It is touted for being naturally resistant to both moisture and fire, as well as good for the air. Proponents also like that it doesn’t irritate the skin as fiberglass can, making it easy to work with. Like cotton, it is treated with borate to repel pests, mold and fire.
Facing and Vapor Barriers
Both batt and rolled insulation come with and without “facing.” The purpose of facing, a covering attached to one side of the insulation, is to provide a vapor barrier that protects the material from moisture. When the heat rises in a home, moisture rises along with it. When the hot air finally meets the cold it seeks, moisture condenses and falls. If it falls into your insulation, you can end up with a mold problem. This is why experts recommend using insulation with a built-in vapor barrier (usually made of kraft paper) or covering your insulation with a polyethylene sheet after it is installed. Importantly, if you are adding to existing insulation in your attic, you must only use unfaced products.
Blanket insulation is hardy stuff — as long as it’s adequately protected from moisture. Assuming it doesn’t get wet or moldy, manufacturers claim the following lifespans for their products in both batt and roll form:
- Fiberglass — Up to 100 years
- Mineral wool — As long as the structure it’s installed in lasts
- Cotton — Up to 100 years
- Sheep’s wool — The duration of a typical home’s lifespan
Experts generally agree that, for the DIYer, blanket insulation, in either batts or rolls, is the least expensive insulation option. Cost comparisons differ, but the following is fairly representative:
- Blanket insulation (batt or rolled): $0.65 to $1.35 per square foot
- Blown-in insulation: $1 to $1.35 per square foot
- Spray foam:
- Open-cell: $0.45 to $0.65 per board foot (a board foot is a square foot multiplied by depth in inches)
- Closed-cell: $1 to $2 per board foot
Much to my surprise, I have decided that I prefer batts to rolls. Because I’m a “work smarter not harder” (some might say lazy) kind of person, I assumed rolls would involve less measuring and cutting and therefore be the best way to go for me. A third of the way through my project, I changed my mind. Here’s why. When it comes to covering the large, uniform space of an attic floor, it is only necessary to measure once and do some basic math to figure out the amount of insulation you need and what the dimensions of the pieces should be.
Because it’s highly unlikely any piece of rolled insulation will be the exact length you require, you are probably going to have to cut each piece at least once. If I’m going to have to cut something I’d rather it would be a batt, which I can manage with just my two hands, than a piece of rolled insulation. Insulation is big, floppy and physically awkward to deal with by nature, and, when it’s rolled, it’s even larger, heavier, and harder to control. So, from now on, I will choose batts. But that’s just me.