Insulating an Attic

Choosing the right insulation for a home can have dramatic effects on the costs associated with heating and cooling the home. The right insulation can save homeowners hundreds of dollars a year in heating and cooling costs. It can also minimize the wear and tear on the home’s heating and cooling unit. Before purchasing or installing insulation there are some insulation basics of which homeowners should be aware. This information can help homeowners ensure they choose the insulation that will be appropriate for their home and adequately meet their needs.

How Does Insulation Work?

There are three methods by which heat flows from warmer to cooler areas in the house. These three methods are: conduction, convection, and radiation. Conduction occurs when heat flows through a solid and delivers heat to the solid. In other words, conduction is the process by which a

warmer object transfers heat to a cooler object. Convection involves rising air. In the case of a home, convection is when hot air rises and cool air sinks. Radiation occurs when a warm object passes heat toward a cooler object. Sunlight is a form of radiation.

Attic InsulationThe purpose of insulation is to keep a home cooler in the summer months and warmer in the winter months. Insulation is designed to curtail the effects of the three aforementioned methods of heat transfer. Insulation accomplishes this task by minimizing the heat effects of convection, radiation, and conduction. Insulation can effectively slow the movement of heat from an area of the home that is hot to an area of the home that is cool. This is because the insulation absorbs heat and resists the flow of heat. The ability of an insulation to resist heat flow is known as its R-value.

What Types of Insulation are Available?

There are four basic types of insulation: loose fill, batts and blankets, spray foam, and rigid board. Loose fill insulation includes things such as cellulose fiber, fiberglass, and rock wool. In most cases, loose fill insulation has an R-value of 3 to 4 per inch of insulation. This type of insulation can be installed by using a dry-pack process, moist-spray method, or by a blowing technique.

Batt and blanket insulation is made from things such as fiberglass and rock wool. This type of insulation fits between the wood-framing structures of the house. This type of insulation can be purchased lengths of up to 8 feet and cut to desired lengths. The R-value of this insulation is approximately 3 per inch of thickness.

Rigid board is made from fiberglass or polystyrene. Its R-value is approximately R-4 to R-8 per inch. This type of insulation is suitable for flat roofs or a perimeter insulation.

Spray foam is comprised of a polymer and a foaming agent. This insulation will be sprayed into the attic space. It is ideal for homes that are irregular shapes, but it typically needs to be installed by a professional.

How Much Insulation Do You Need?

An insulation’s R-value designates its resistance to heat flow. The R-value required to effectively insulate the home will depend on the climate in which the home is located and the needs of the home. In most cases, it is recommended that most homes have an insulation level of at least R-38. In order to determine how much insulation a home needs, it will be necessary to measure the existing insulation in the home. Homeowners will also need to know the type of insulation in their home and the square footage of their attic.

Once the existing insulation has been measured, comparison charts can be used to determine how much insulation needs to be added. For example, if a home has 0” of loose fill fiberglass insulation homeowners will need to install 40 loose fill fiberglass bags of insulation per 1000 square feet to obtain a R-38 insulation level. If the home has 5” to 6” of loose fill fiberglass insulation a homeowner will need to install 22 bags of loose fill fiberglass per 1000 square feet to obtain a R-38 insulation level. Again, the amount of insulation a home needs will depend on the climate in which the house is located, the square footage of the attic, and how much existing insulation is in the home.

How Do You Install Attic Insulation?

Spray Foam
When installing attic insulation a homeowner will need to lay temporary flooring across the joists in the attic. This will provide a safer, easier working environment. Insulation should be installed from the edge of the attic toward the center. Make sure that the joist cavities are filled with insulation to the top. Once filled, place a layer of insulation perpendicular to the direction of the joists. Homeowners will want to ensure that the insulation covers the tops of the insulation covers to the tops of the exterior walls without blocking the eave vents. Homeowners need to ensure that the insulation is kept at least three inches from items such as recessed lighting fixtures, metal chimneys, and gas water heater flues.

What is the Best Attic Insulation?

The best type of insulation will be the one that meets the home’s R-value needs. Again, this will be based on climate and geographical location. The larger the insulation’s R-value, the heavier and thicker it will be. One of the best types of insulation for attics is the loose fill insulation installed using a spray method. If homeowners prefer to install the insulation themselves batts and blankets will be the next best option.

How Much Does Attic Insulation Cost?

Homeowners can expect to pay between $2,000 and $10,000 for a complete insulation job. However, the average cost that most homeowners can expect will range somewhere between $2,500 and $5,500.