How to Insulate Your Attic

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Most of us rarely go up there and we don’t think about it much. More than likely you only think of it as extra space to put our old junk. But if you could find another place to put those future garage sale items, you have the opportunity to drastically reduce your energy bills. And this can save you big money every month.

The attic is an essential piece of your building envelope, the part of the home that separates the inside from the outside elements. As much as half of the energy you use in your home goes toward heating and cooling, and if you don’t have enough insulation in the attic you could lose thirty to forty percent of it. This inefficiency will cause your heating and air-conditioning system to work harder costing you a lot of extra money to keep you and your family comfortable.

Unfortunately, most of the homes standing today were not built with energy efficiency in mind. The attic insulation put in by most builders was the minimum they could get away with at that time, and is hardly adequate for today’s standards.

You don’t need an engineering degree to figure out whether or not you have enough insulation. The easiest way to tell is to simply poke your head into the attic. If you can see the floor joists of the attic you could benefit greatly from adding insulation.

Here is all of the science that you need to know: Insulation has something called an R-Value which is a rating on how well it resists heat flow. The higher the R-value the better it is at insulating. Each type of insulation material has a different thickness and density which is all factored into the R-Value. Many attics today are insulated with either fiberglass batts, which have an R-value of approximately 3.2 per inch, or blown-in loose cellulose which has an R-value of approximately 3.5 per inch. The math is simple, if you have five inches of fiberglass batt insulation then you have around an R-16.

The United States Department of Energy has created recommendations for the adequate level of attic insulation you’ll need based on the region of the country you live in. The R-values range from R38 to R49 in most of the country. You can click here to enter your zip code to see what R-value is best for your house.

In the average American home, adding insulation to the attic can take a novice do-it-yourselfer one day. If you can operate a utility knife you can do it. Plus, you’ll recoup your investment on the materials in just a few seasons.

The tricky part is getting all of those big bundles of insulation home. You may have to make more than one trip to the supplier or borrow a friend’s pickup truck. If your home improvement store or supplier offers home delivery, it’s likely worth the money to avoid the hassle of lugging bundles around yourself.

How much insulation you’ll need depends on the size of your attic and how high of an R-value you are trying to achieve. There will be a chart on the packaging explaining how much area that bundle will cover. Follow their chart based on your desired R-value and the square footage of your attic. What kind you need is a different matter.

Blown-in cellulose is recycled newsprint that has been fire treated and fiberglass batts are made of thin fibers of glass that trap the air. There are pros and cons to both methods. The cellulose is going to be a little cheaper and a bit more fun to put in, but you’ll need a friend’s help. For this method you’ll rent a machine for about twenty dollars a day which will blow the insulation into place. A hopper is placed outside and a long hose is run up into the attic. The person outside loads the hopper with the cellulose insulation and the person upstairs shoots it into the attic, to the desired thickness over the existing insulation. Fiberglass batts come in large rolls and are rolled out perpendicular to the floor joists over top of the existing insulation. It is cut by simply compressing it with a straight edge and scoring it with a utility knife. Regardless of the method you choose there are important things you should do to make sure the job is done right.

Air-sealing your home before insulating is extremely important. Once again, most existing homes were not built with energy efficiency in mind and therefore are probably not air-sealed appropriately. Small air leaks into an un-insulated attic are a major cause of heat loss. Any time something pokes a hole in the attic floor it should be air sealed with caulk or expanding spray foam which you can buy in a can. Look for wires that run up through interior walls and into the attic, those holes may seem small but they all add up to big air leakage. Recessed lighting, vent pipes and electrical boxes are also areas that should be sealed.

Keep insulation at least three inches away from heat-producing fixtures such as recessed lighting. Use wood or rigid foam boards between the floor joists to create blocking that will hold the insulation away from the fixture. Some fixtures are IC rated which means they can come in direct contact with the insulation. These will be clearly marked as “IC Rated.” If you don’t see that rating, stay three inches away.

Ventilation is a necessary part of a roof’s design. Adding insulation all the way out to the edges of the attic floor can clog up that natural venting, causing unintended problems for you down the road. Air baffles, also known as rafter vents, are long thin foam boards shaped like a wide square ‘U’. These baffles get stapled to the roof deck and provide an air passage so you can run your insulation all the way out to the top of the exterior wall. They only cost about two dollars a piece and are worth the investment.

One more important item to check for before insulating is sub-par electrical work. If you have an extremely old house with exposed wire connections or open junction boxes don’t bury them in the insulation. Consult an electrician to make any fixes and ensure that it is safe to cover that wiring.

With all the preparation out of the way it is time to insulate and start saving money.

Use a piece of wood to stand on as you work. Walking on the floor joists is like a high wire act without a net. I was helping my cousin insulate his attic and he slipped off a joist and put his entire leg through the ceiling of his baby’s room. We spent the rest of the day repairing the ceiling.

Start at the furthest away corner and work back to the attic access. You don’t want to have to climb over all the new insulation to get out. And, always wear a breathing mask, long sleeves, gloves, and eye protection.

This is the perfect time of year to add insulation to your attic. With the mild weather upon us you will not roast up in the attic as you work.

Jason Gurskis is a licensed home improvement contractor based in Mystic Island, New Jersey dedicated to making homes more comfortable, durable, and energy efficient.