Attic Insulation & Ventilation

With the exception of newer housing, almost every home can benefit from improving the insulation. Saving money on fuel costs is perhaps the best motivation for upgrading. There are usually some areas of the home where it makes financial sense to upgrade. In some older homes, certain types of upgrades do not make economical sense, such as insulating solid masonry exterior walls. Be sure to weigh the cost savings vs. the cost of improvement.

The thermal resistance of insulation is measured in R-values. The higher the number, the greater the resistance to heat transfer. Different types of insulation have different R-values per inch of thickness. The same type of insulation can have a different R-value depending on its form. For example, fiberglass has a higher R-value in batt form than it does in a loose form.

Types of Insulation:

• Fiberglass: Probably the most common insulation used, this material is made from threads of glass glued together with phenolic resins. It is available in batt form, loose form, and rigid board. It is resistant to moisture, mildew, fungus, and vermin. Fiberglass can cause irritation to eyes, skin and the respiratory system. R-Value is 2.9- 4.2 per inch.
• Cellulose Fiber: The low cost of this material makes it a very popular choice. Cellulose is made from shredded paper treated with chemicals to make it resistant to fire, moisture, and vermin. This gray material is typically blown into the attic. R-Value is 3.4-3.6 per inch.
• Mineral Wool: Mineral wool (or rock wool) is very similar to fiberglass in that it has good resistance to fire and rot. This type of insulation is made from mineral waste products. It is available in loose or batt form. R-Value is 3.0 to 3.2 per inch.
• UFFI: Urea-formaldehyde foam insulation was banned in the United States by the Consumer Product Safety Commission (CPSC) in 1982. Although the ban was overturned by a federal court, few homes have installed the product since 1982. New installations of UFFI is not advised due to potential health problems, but homes that are already insulated with UFFI should no longer have formaldehyde levels that present a significant health risk. The color and texture of UFFI varies but it can be distinguished from other foams by its frail, crumbly structure and powdery residue. Positive identification can only be made by laboratory testing.

Over the years there have been many types of material used for insulating and many new types are certain to be available in the future. The above mentioned are the most common materials found in homes.

• Having proper ventilation in your attic will help prevent damage to the structure, increase the life expectancy of the roofing, reduce energy use, and improve the living conditions below the attic.
• The two main reasons for attic ventilation are heat and humidity. In the summer the temperature in a poorly ventilated attic can reach 150 degrees! Excessive heat cannot only damage roofing materials, but it can make the living area under the attic uncomfortable and difficult to cool. Humidity will naturally drift upward to the attic from several sources including showers, clothes dryers, cooking, and even breathing. Excessive humidity can cause damage to the roof structure, insulation, and even interior surfaces
• The requirements for proper ventilation will vary depending on which part of the country you live in. The minimum recommendation is one square foot of free vent area for each 150 square feet of attic floor (if there is not a vapor barrier under the insulation). With a vapor barrier you need half the amount. In older homes these requirements are usually not met.
• Good ventilation will usually be provided with the use of, ridge or box vents at the top of the roof, and soffit venting under the eaves. Both the upper vents and the lower vents need to be installed and open for proper airflow through the attic.
• Building science has come a long way in understanding the importance of proper attic ventilation. Many new and different types of vents are now available to vent all types of roofs.