Building Envelope Components Insulation

Insulation works by slowing down heat as it travels through walls, ceilings, and floors. The amount of insulation you need depends on the building design and location. Many state and local building codes include minimum requirements for insulation. But with the whole-building design approach, you may need or want to exceed them.

When selecting insulation products, several performance characteristics are important:

• Insulation capacity
• Fire resistance
• Moisture control
• Weight
• Convective heat loss
• Settling and loss of insulating capacity

Insulation is rated in terms of its resistance to heat flow, called R-value. The higher the R-value, the greater its thermal resistance. The R-value of thermal insulation depends on the type of material, its thickness, and density.

Once you've determined the R-value needed for each building section you plan to insulate, then you need to consider what type of insulation would be best for each section. Insulation is available in a variety of forms and materials:

•  Rolls and Batts
  Rolls and batts of insulation—or blankets—are flexible products made from mineral fibers, such as fiberglass and rock wool. They are available in widths suited to standard spacings of wall studs and attic or floor joists. Continuous rolls can be hand-cut and trimmed to fit. Insulation is available with or without vapor retarder facings. Insulation batts with a special flame-resistant facing are available in various widths for basement walls where the insulation will be left exposed.
   
•  Foam and Foam Boards
  Foam insulation typically is more expensive than fiber insulation. But it's very effective insulation in buildings with space limitations and where higher R-values are needed. Foam insulation R-values range from R-4 to R-6.5 per inch of thickness (2.54 cm), which is up to 2 times greater than most other insulation materials of the same thickness.

  Foam insulation is often made with one of three materials: molded expanded polystyrene (MEPS insulation), extruded expanded polystyrene (XEPS insulation) or polyurethane, polyisocyanurate insulation, or a related chemical mixture. Some are installed as a liquid insulation while other types come as factory-made panels called rigid foam boards.

  Although batts are typically used between studs or floor joists, rigid foam boards should be considered as an alternate approach. These boards are lightweight, and provide structural support and acoustical insulation. Rigid boards can also be added to basement walls, exposed foundations, cathedral ceilings, exterior walls, and attic access. Such boards may be faced with a reflective foil that reduces heat flow when next to an air space. Check your local fire codes, because often these boards must be covered with a fire barrier, such as gypsum wallboard.

  Liquid foam insulation can be sprayed into building cavities as a liquid or in larger quantities as a pressure-sprayed product (foamed-in-place). It can completely conform to a building cavity, sealing it thoroughly. Therefore, it's good to use in areas where it would be difficult to fit rigid boards. If you spray this insulation into an enclosed space, be careful that you don't use too much, because that could cause other parts of the structure to bend or break.

   

•  Loose Fill
  Loose-fill insulation—usually made of fiberglass, rock wool, or cellulose-comes in shreds, granules, or nodules. These small particles should be blown into spaces using special pneumatic equipment. The blown-in material conforms readily to building cavities and attics. Therefore, loose-fill insulation is well suited for places where it is difficult to install other types of insulation. Additional resistance to air infiltration can be provided if the insulation is sufficiently dense or thick.

  Manufacturers use recycled waste materials in the production of all three primary types of loose-fill insulation. Cellulose loose-fill insulation contains more than 75% recycled materials. Meanwhile, fiberglass insulation manufacturers use increasing amounts of recycled materials in their products, at least 20% to 30% recycled glass content. The production of rock wool uses byproducts that would otherwise be wasted. But loose-fill cellulose insulation require less energy to produce than other forms of insulation.

  The performance of loose-fill insulation is strongly affected by its installation. So be sure to read the labels on the bags, and to pay more attention to the installed R-value than to the installed

   

•  Radiant Barriers
  Radiant barriers—usually fabricated from aluminum foils—can be used to reduce cooling loads. These reflective insulation systems are usually installed directly under the roof rafters to reduce heat gain from the sun. They can also be very effective when used for walls that absorb direct sunlight, especially if an effective roof overhang is not practical (for example walls facing west).

  Radiant barriers are more effective in hot climates than in cool climates. In heating dominated climates, they aren't very economical nor recommended in most cases.

  Unlike other insulation, there currently isn't a standard method for equating how well a radiant barrier works. Many manufacturers use the term "equivalent R-value." This really has no scientific meaning, and it often reflects optimum conditions and not necessarily climate conditions.

  All radiant barriers must have a low emittance (0.1 or less) and high reflectance (0.9 or more). Most of them on the market today have about the same emissivity values. Therefore, you should consider other characteristics (strength, flammability, availability, and cost) before you buy.

   

•  Reflective Insulation
  Reflective insulation systems are fabricated from aluminum foils with a variety of backings such as kraft paper, plastic film, polyethylene bubbles, or cardboard. The resistance to heat flow depends on the heat flow direction, and this type of insulation is most effective in reducing downward heat flow. Reflective systems are typically located between roof rafters, floor joists, or wall studs. If a single reflective surface is used alone and faces an open space, such as an attic, it is called a radiant barrier. Radiant barriers are sometimes used in buildings to reduce summer heat gain and winter heat loss. They are more effective in hot climates than in cool climates. All radiant barriers must have a low emittance (0.1 or less) and high reflectance (0.9 or more).
   
•  Structural Insulated Panels
  Structural insulated panels (SIPs) provide both structure and insulation. They consist of carefully engineered laminate with a foam core 4 to 8 inches thick, with a structural facing on each side. The most common types of facings are drywall and/or structural wood sheathing such as plywood and oriented strand board (OSB).

  R-values for SIPs range from about R-4 to R-6 per inch of thickness, depending on the type of foam core used. Manufacturers construct most SIP foam cores from expanded polystyrene (EPS), also known as beadboard insulation. But some manufacturers choose to use polyurethane and isocyanurate as the insulation material.

  Although SIP insulation cost more than traditional building materials, they require less labor to install. Therefore, the total cost is roughly

  
   

•  Insulating Concrete Forms
  Like Structural Insulation Panels, Insulating Concrete Forms (ICF insulation) serve as both structure and insulation. They are basically forms for poured concrete walls that stay in place as a permanent part of the wall assembly or foundation.

  The forms, made of foam insulation, are either pre-formed interlocking blocks or separate panels connected with plastic ties. The left-in-place forms not only provide a continuous insulation and sound barrier, but also a backing for drywall on the inside, and stucco, lap siding, or brick on the outside.

  Although all ICF insulationare identical in principle, the various brands differ widely in the details of their shapes, cavities, and component parts.

  ICF insulation can cost up to 4% more than standard wood framing. However, houses built with ICF insulation exterior walls require an estimated 44% less energy to heat and 32% less energy to cool than comparable frame houses.