Monday, November 19, 2007

Attic Insulation


You can cut heating bills dramatically by installation of insulation. And, the best part is that it is easy to do in most instances.

We bought a house in East Lansing, Michigan. It was built in 1943 at the same time that a building the size of a 3 car garage was built next to it. It was at the height of WWII when this home was built, and it must have been very hard to get the building materials for the home builder. The living area of the house is about 1,500 square feet.

It was heated by a coal fired furnace originally, but thankfully, after several furnace replacements it had an efficient natural gas furnace. We still dig up burnable size pieces of coal in the garden area. I don't exactly think we are living over a coal deposit. The owner also thoughtfully installed an indoor bathroom sometime in the postwar period.

Even though the furnace was efficient, the house was not in keeping the heat inside.
The furnace frequently turned on and off and heating dollars went out the ceiling.

Research shows that cooling and heating make up 50 to 70 percent of your total energy used in the average home. Unless you planned ahead when you built your home, adding insulation will probably reduce your utility bills. Adding insulation can save you enough money in a short time to pay for itself and save you money in the long run.



Razor Knife
Ladder (If needed to enter the attic access)
Carpenter's pencil or a Sharpie
Non- Halogen work light for poorly lit attics


Rolls of R 25 attic insulation


This kind of insulation comes in long, one piece shrink wrapped rolls and is used mostly in large open areas like attics and in new construction. Select the width of these blankets that are the same size of the spaces between the ceiling joists. The joists are usually 16 inches center to center where you will be unrolling the blankets in the attic. Sometimes you will find the spaces 24 inches center to center.
Insulate the attic to the level recommended for your climate. Owens Corning makes a dandy pink kraft faced insulation which comes in both widths that's ideal for the attic area. The facing acts as a vapor barrier and should be installed face down.
There are two very important things to remember when you walk around in your attic. As you measure or unroll the insulation blankets, be sure to walk on the joists only. At the least, if you set foot on the area between the joists, your foot will go through your ceiling and make a big hole. At the worst, you may find yourself falling through the ceiling. Just a little care will prevent either of these things from happening. Just look where you are walking.
The other thing to avoid are the roofing nails that may stick down into the area where you are working. Hitting a sharp nail point can really ruin your day.
Make sure you wear a minimum of an N 95 face mask to keep from breathing fiberglass fibers. Fiberglass fibers will also adhere to your clothing.
Here is how to estimate the amount of attic insulation needed for a 32 by 40 foot house. . Open the attic access or lower the stairs. If your attic area is not well lit, then plug in and take up an old fashioned shielded automotive work light with a regular 60 watt lamp bulb in it up there with you. You can temporarily tack in a 16 penny nail into a rafter to hang it from. Do not under any circumstances use a halogen light bulb, because these can cause a fire.
The insulation blanket rolls usually come in 26 feet lengths Count the number of spaces that there are between the joists in the attic. In an attic where the joists run perpendicular to a 32 foot wall, there are 8 spaces between the joists or 8 runs that need insulation rolls.
In this example you will need 8 full rolls to cover a 26 by 32 foot area. But the attic is an additional 8 feet longer than the 26 foot rolls, since the total length to be covered is 40 feet. You need an additional 8 feet in each space between a to joist center to center insulation run to complete it to a 39 foot run.
Since each roll is 26 feet long, each blanket roll can be cut into two 13 foot lengths to make up the difference to 40 feet in this example. This means that to get 8 of the 13 foot lengths, you need 4 additional blanket rolls to complete a 39 foot insulation run. One more roll is needed to complete the additional one foot to make the run 40 feet.
Use your tape measure to measure the length of extra insulation that you need on the insulation roll. Mark the correct length where you will cut on each side of the faced side of the insulation. Put a straight edge, such as a long metal yardstick on the marks where the insulation is to be cut and mark a line across the insulation with a carpenter's pencil or a sharpie. Press down on the yardstick next to where you carefully cut the insulation with a razor knife. Pressing down on the yardstick and insulation will compress the insulation and make it easier to cut.
Unroll each blanket with the kraft paper or plastic facing side down on the area you are filling. Add additional lengths as necessary. You do not need to staple or otherwise attach the insulation to the joists.
Cover the attic access panel or the fold down door with insulation too.
You may not need the extra roll to make the insulation run 40 feet long. A proper roof installation has proper ventilation. This means good soffit and rooftop ventilation. Don't cover up the soffit vents with insulation. You need airflow into the attic. So, don't insulate completely all the way to the side of the ceiling where the roof meets the joists. You have leave enough space so that the soffit vents are not covered. Also, do not allow the insulation runs at the wall edges to touch the roof. This will allow continued roof ventilation.
If the soffit vents are covered up, you will create lots of problems.

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