First, the resistance to heat flow through radiation, conduction and convection in a building is measured in R-values. The higher a material's R-value, the greater its insulating power. R-values are marked or identified on batts and rolls of insulation, as well as on its packages. Colorful charts show the number of bags, thickness and weight needed per 1,000 square feet to achieve a certain R-value.

 

Johns Manville's ComfortTherm™ batts and rolls have R-values ranging from R-11 to R-25. ComfortTherm's installer-friendly features have rapidly become popular in both DIY and professional markets. The pre-cut, poly-wrapped batts place a barrier between the installer and the fiber glass. The batts install quickly while providing greater handling comfort with less dust and itch for cleaner, more comfortable and more professional installation. In addition, the poly facing and triple reinforced flanges are tougher and more tear-resistant than kraft-faced insulation. Easily stapled into position, these durable flanges also expedite installation.

 

The batts are made of long glass fibers bonded with thermosetting resin. Their wide R-value range is achieved by varying their thickness and density. The thicker and denser the fiber glass batt, the higher the R-value.

 

Johns Manville's higher performance products provide higher R-values through increased density. This allows them to fit within standard wall and cathedral ceiling cavities, while still providing increased resistance to heat transfer. R-15 batts fit within standard 2 x 4-inch walls and R-21 batts are designed to fit within 2 x 6-inch walls. They provide R-values that previously would have required the installation of more expensive foam sheathing.

 

To aid do-it-yourselfers and professional contractors in selecting the correct R-value for their area, building products retailers generally post a chart of recommended R-values for five temperature zones across the United States. The R-values represent the North American Insulation Manufacturers Association's recommendations for optimum thermal performance for average climate zones shown on the map.

 

Vapor barriers, more accurately called vapor retarders, are also crucial in blocking air filtration through walls, ceilings and floors; although its primary purpose is to control moisture. Typically, a family of four produces about ten pounds of water vapor per day.

 

Vapor barriers minimize the amount of interior moisture that passes into the walls and attic. Without effective vapor retarders, mold or mildew can occur and structural components of the building can be damaged. Insulation also can be dampened, temporarily reducing its effectiveness.

 

Vapor retarders are installed on the warm side of walls, ceiling and floors. This means that in ceilings, the vapor retarder faces down, in walls it faces the inside, and in floors over unheated spaces, it faces up. With the exception of reverse-flange insulation, like ComfortTherm's Under Floor, the stapling flanges are on the same side as the vapor retarder. In hot climates, however, where air conditioning is used more than heating, the exterior side of the insulation is often the warm side. In these situations, local construction practices should be followed regarding the use and placement of vapor retarders.

 

ComfortTherm batts carry a Class A fire rating for low flame spread and have been classified FHC 25/50 by Underwriters Laboratories. Avoid stapling into electrical wiring when installing faced batts and rolls.

 

In some construction, separate vapor retarders are used. When required, four-mil or thicker polyethylene sheeting, available in rolls, is rolled out horizontally and stapled to the warm-in-winter side of the framing. The polyethylene should be stapled at the sides and the excess material folded back into the room. If more than one sheet of polyethylene is required, a double fold should be made at the meeting of the two pieces and stapled, or the sheets may be overlapped and taped. If stapled, the pieces should meet only at a stud or a joist. Foil-packed gypsum board also serves as an effective vapor retarder.

 

If uncertain about which vapor retarder to use, contact a local Johns Manville sales representative or building materials retailer to determine the appropriate construction practice and insulation materials for your area.

 

During a time of critical energy supply and constantly rising fuel and energy costs, the benefits of fiber glass insulation and vapor barriers reduces energy consumption in winter and summer by reducing heating and cooling costs.

 

Johns Manville (NYSE: JM) is a leading manufacturer and marketer of premium quality insulation and building products. The 141-year-old Denver-based company had sales of $1.65 billion in 1997. Johns Manville produces and markets insulation products for buildings and equipment; commercial/industrial roofing systems; and engineered products including high-efficiency filtration media, fibers, fabric and nonwoven mats used as reinforcements in building and industrial applications. Johns Manville employs approximately 9,300 people and operates 54 manufacturing facilities in North America, Europe and China. Additional information can be found at www.jm.com

 

For more information on the full line of Johns Manville building insulation products, please contact the Johns Manville Product Information Center, P.O. Box 5108, Denver, CO 80217; phone: 800.654.3103; fax: 303.978.2318.