Fort Worth Roofing: Article About Roof Materials
When choosing what type of insulation to have the roofers install underneath a new roofing system, homeowners are faced with a variety of questions. From foam boards or sprayed in foam to loose fill and rolled types, the number of options may be confusing. When working with an experienced Fort Worth roofing company, property owners should keep in mind what each of the insulating material's R and K values are. These numbers are of considerable importance when it comes to determining a home's energy efficiency, interior comfort and utility costs.
An insulation's R value is usually labeled right on the manufacturer's packaging. For materials such as spray foam insulation that require application by professionals, they will have the information in written charts, graphs or brochures that can be provided to a homeowner upon request. This allows the homeowner to choose materials with the highest R value per inch for small spaces, such as roofs with a shallow slope. It also allows homeowners to compare the cost of materials to the level of thermal resistance that it provides.
While most people have heard of R values, the K value is less commonly recognized. A material's K value is a measure of its heat conductivity. To calculate the K value of a material, roofers divide its R value by its thickness.
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The resulting number is a measure of the BTUs, or British thermal units, transmitted per hour through one square foot of material that is one inch thick to make a change of temperature one degree Fahrenheit from one side of the material to the other. Some good insulators include wood, foam and cork. Poor insulators include glass and metal. The lower a material's K value, the better of an insulator it is. In most cases, the manufacturer will state the product's K value on the package. The K value of a material is the same no matter what its thickness, so a piece of glass that is just one eighth of an inch thick has the same K value as a piece that is two inches thick.
When a homeowner is trying to prevent heat from the sun from getting into a house through the roof or walls, R value is the most important measure. The home's total R value will include its interior drywall or sheet rock in addition to all the layers of wooden framing, insulation, underlay, vapor barrier, radiant barrier and siding, stucco, brick, shingles, tiles and other materials. The K value is only about the insulation.