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All About Insulation

Energy Efficiency, Related Products June 10, 2008 Sonia

Insulation has come a long way from the mud and grass “chinking” and crack fillers of our early ancestors. These days a wide range of insulation products and applications are available to totally envelope and insulate a building. Why insulate? The main reasons are obvious—keep out the cold or the heat, provide energy savings and, of course, lower energy usage and bills. Insulation also provides a more comfortable home because a more constant temperature is maintained. Insulation absorbs sound, reducing the noise from appliances, conversation, radio, television and other audio sources through walls. Insulation can also provide a healthier home as it retards the growth of potentially hazardous mildew and mold in your ceilings and walls caused by trapped moisture. And modern advances in products such as Johns Manville Fiberglass Insulation go one step further, promoting better air quality because the material is Formaldehyde-free.

Heat, a form of energy, always moves from higher to lower temperatures. In the hot summer, heat moves to the cooler indoors. In the cold winter, heat moves to the colder outdoors, transmitted through walls, ceilings and roofs. Insulation creates a thermal barrier that provides resistance to this movement. It’s simple—the more you insulate, the more you save in energy, provide a more comfortable home and add to the life of your house.



Most homes consist of conditioned or heated areas and unheated areas such as a garage, crawlspace and attic. All exterior walls that separate conditioned and unconditioned spaces should be insulated to create a thermal envelope around heated areas and provide a boundary between the heated and unheated spaces. This also includes knee walls that open up into attics or garages. For a total thermal barrier you should also insulate basement floors, walls, slabs, crawlspaces, attics and cathedral ceilings. Interior walls and floors can be insulated for sound control.

Total Insulating System

These days, products are designed for each specific use. For the most energy-efficiency, a combination of products can be used, creating a total insulating system. The Owens Corning Insulation System consists of many products, all working together throughout the building to deliver year-round energy savings and comfort. This includes products for insulating the foundation walls, crawlspace (underfloor), heated crawlspace, under a slab, basement walls, floors, heating and cooling HVAC ducts, exterior walls, interior walls, finished or unfinished attics, and cathedral ceilings. The system reduces heating and cooling costs, reduces air infiltration and controls moisture.

The strategy these days is to create a thermal barrier to totally envelop the house, separating unheated ares from conditioned areas.

Normal, everyday living can put from 5 to 10 pounds of moisture into the home each day. In the winter months this moisture can accumulate and condense on the cold inner sides of exterior surfaces. This can cause paint to blister, form stains on drywall ceilings and walls, even damage the building’s structure. Vapor barriers can help control the amount of moisture passing through insulation and collecting inside exterior walls, ceilings and floors.

The first step is to use Insulated building products in construction.
(Photo courtesy Louisiana-Pacific)

First Things First

The first step in insulation begins with house construction, utilizing insulation-board sheathing where code rules allow and are applicable. For example, TechShield sheathing from Louisiana-Pacific is made of a thin, durable sheet of aluminum overlay laminated to OSB. The overlay serves as a radiant barrier that minimizes heat gain and loss. The TechShield sheathing panels also have channels that allow trapped moisture to escape without affecting radiant-barrier performance.

Vapor barriers are also extremely important, both inside and out. House wraps are the next step in insulation. (Photo courtesy DuPont)

In addition, for new house construction, or when residing, a house-wrap vapor barrier should be used. Dupont Tyvek DrainWrap is an excellent choice, as it offers a unique combination of a weather-resistant barrier with a drainage system. The vertical grooves help drain away water quickly, yet the product has a breathable structure that allows moisture to pass through for quicker drying of walls, thus preventing mildew and mold. All cracks and openings around doors and windows, and where piping or wires enter the house, should be well caulked with DAP SIDE Winder Siding and Window Sealant and/or sealed with foam sealants such as Dow Great Stuff Window and Door Insulation.


All cracks around windows and doors must be properly sealed with caulk or expanding foam. (Photo courtesy Johns Manville)

Insulation is available in a wide range of products, some do-it-yourself, some dealer-installed. All insulation products are based on R-values or thermal resistance. Products with higher R-values provide more insulation. Different portions of the country have different R-value needs. The first step is to determine the recommended R-value by the U.S. Department of Energy for your region. Or, check with your local building supplier as to the R-values needed for your home and area. You can also check out the companies mentioned in this article for specific info on the R-values of their different products.


Fiberglass batt or roll insulation is the most commonly used product. It can be used in both interior and exterior walls, attics and crawlspaces. (Photo courtesy Johns Manville)

The most commonly used do-it-yourself products are the fiberglass batts or rolls. Rolls are long, continuous lengths of insulation rolled up that are measured and cut to fit specific areas. They’re best for insulating long runs in crawl spaces and attics. Batts are pre-cut lengths available for 8- and 9-foot walls. They’re fast and easy to install because they don’t require cutting. In most instances of whole-house insulation, you’ll need some of each.

Do not unroll or remove the insulation from the package until you get into the attic. (Photo courtesy Owens Corning)

Batts or rolls may come unfaced or faced. Some include a vapor barrier on one side and a Kraft paper wrap on the opposite. These are commonly used in crawlspaces. Foil-face or paper-faced batts or rolls have one side covered with those materials and both can be used in walls, attics and sidewalls. Unfaced fiberglass batts do not have a covering and are more economical, but don’t provide moisture control. They are commonly used in unheated attics. 


Install soffit stops to create air flow between the attic and soffits. (Photo courtesy Owens Corning)

Installing batt insulation during new construction is a fairly easy do-it-yourself project. The first step is purchasing the correct insulation. The walls may be framed with 2-by-4 or 2-by-6 studs. Two-by-6 studs allow for more insulation because of their extra depth. Depending on local codes or the desired R-value for the wall, Owens Corning suggests using 5-1/2-inch thick R-21. The choices for 2-by-4 stud walls are R-15 and R-13, both of which are 3-1/2 inches thick. For standard height walls, use pre-cut batts rather than continuous rolls. Each piece of insulation is manufactured to the size of the typical stud framing, which is usually built on 16 or 24 inches on center, and about 92 inches high. These cut-to-size batts make the job go faster and easier.

The insulation should fit snugly against the studs and completely fill the cavity to the top and bottom plates. Cut batt insulation to fit snugly around obstructions, such as electrical boxes, plumbing and plumbing vent lines. When using Kraft-faced batts with flanges, staple the flanges every 8 to 12 inches. The tabs or flanges should be stapled to the inside of the studs, which prevents screw or nail pops in finished drywall. Stapling to the inside of the studs also creates about an inch of dead air space between the paper face of the batt and the wallboard, which helps prevent moisture, mold and mildew from developing on the back of the wall covering. Owens Corning FastBatt insulation does not have stapling flanges.

Stuff unfaced insulation between chimney and wood framing, but not in contact with the flue. (Photo courtesy Owens Corning)

Note: Never leave faced insulation exposed. The facings on Kraft-and-foil insulation will burn and must be installed with substantial contact with an approved ceiling, wall or construction material to help prevent the spread of fire in the wall, ceiling or floor cavities. Unfaced fiberglass is non-combustible.