Insulation

The building envelope comprises all heated parts of a building, including the walls, roof, and foundation. By properly insulating your building envelope, you can control the flow of air in and out of the home, which will have a tremendous impact on heat loss, cooling needs, moisture control, and air quality.

Insulation is an important factor in the success of a building envelope, but is not the controlling one. In a building envelope, there are several components that work together, and how they are assembled is the key to lowering energy use and maintaining healthy indoor air quality. The building envelope should be designed to manage the migration of three factors simultaneously—moisture, air, and temperature. Remember to consider the climate and location of the building as it relates to humidity and temperature.

General Implementation

• Install a good drainage plane on the exterior of the home, such as a building paper or house wrap in a lapped or shingle style to provide good drainage. This drainage plane must have an air space provided by furring strips or Home Slicker between it and the siding.
• Use raised heel trusses “energy heels.”
• Consider installing an insulated conditioned crawlspace as one strategy for control of temperature, moisture, and indoor air quality. (Not recommended if moisture is a problem in your area.)
• Use treated wood that does not contain chromium or arsenic.

Air Barriers

Outside walls, foundation and attic openings, openings in exterior walls for doors, windows, pipes, wiring, and cable – ALL openings -- must include a very good air barrier. Neither fiberglass nor cellulose will stop air flow through the wall assembly, so all penetrations in the exterior sheathing—including joints in the sheets of sheathing—must be sealed with caulk or foam prior to installing insulation. An open-cell expanding foam such as IcyneneA renewable-based material made from castor oil used for water blown foam insulation. It is nontoxic, won't lose R-value over time, shrink or sag, provides acoustic insulation, and will stick to many construction materials, allowing less use of petroleum-based products for these purposes. provides the air barrier as well as good thermal resistance. (House wrap is not an air barrier, but a drainage plane).

An air barrier prevents the flow of air through insulation.An air barrier is any material that restricts the flow of air through a construction assembly. In wall assem-blies, the exterior air barrier is typically a combination of sheathing and either building paper, house wrap, or rigid board insulationLightweight thermal insulation, such as polystyrene, manufactured in a rigid or semi-rigid form, for use where structural strength is not an issue. May have a finish side or be used under a finish material..

The interior air barrier is often an interior finish, like gypsum board. A thermal barrier restricts or slows the flow of heat. This is typically accomplished through different insulation materials (e.g., fiberglass, rock wool, cellulose, polystyrene, polyurethane, vermiculite) and applications (battsThe same material as is used in blanket insulation but formed into sheets, often sized to fit easily between studs., blown-in, spray foam, rigid board, and granules).

Installing Insulation

Holes are drilled into the exterior to blow insulation into the walls.Insulation is crucial to controlling home energy use and comfort. But insulation alone won’t do the job – it must be properly installed with an accompanying air barrier (wrap, caulk, foam or other sealant).

To be fully effective, insulation must be aligned with a contiguous air barrier. Insulation works be-cause it incorporates air pockets that resist the flow or slow the conduction of heat. This resistance to heat flow is measured by the R-valueA unit used to measure thermal resistance, derived from the ratio of the temperature difference across an insulator and the heat flux through it; the ability of the structure to hold internal temperature. The larger the number, the more effective the insulation. of the material. However, most insulation (with the excep-tion of spray foam and rigid foam board) does NOT stop air flow. Thus, for most insulation to be effective, a separate air barrier or skin is needed to stop the flow of air. For the air barrier itself to be effective, it must be contiguous and continuous across the entire building envelope, with all holes and cracks fully sealed, and it must be perfectly aligned with the insulation

The following are some guidelines and best practices for insulation implementation:

• Examine insulation materials for their affect on human health and the environment.
• Use total-fill insulation such as blown cellulose, BIBSA patented application process (Blow In Blanket System) that combines loose-fill and mineral wool fiber glass insulation with a fine adhesive mist, then blows it into a home's cavities behind netting., sprayed foamA liquid containing a foaming agent and a polymer is sprayed through a nozzle into wall, ceiling and floor cavities where it expands to fill the space. It does not settle or biodegrade and acts as a wind and air barrier, aiding in the efficiency of the heating and cooling system., or SIP panels that tend to provide better performance. With regard to spray foams, the open-cell foams are highly preferred to closed-cell polyurethane foams. Open-cell foams allow moisture to migrate through the wall as needed, but control air flow completely. The air-sealing step is eliminated.
• Icynene foam lends itself well to being installed along the attic roof line, as opposed to the ceiling. This provides an unvented, semiconditioned attic space, which is excellent for duct workThe structural elements used to deliver and remove air and for HVAC functions within a building. Thermal comfort, energy costs, and air quality can be significantly affected by the planning, methods and materials used for the ductwork system. and me-chanical system performance.
• Utilize continuous insulation on exterior wall.
• Use total fill insulation such as blown cellulose, BIBS, and sprayed foam.
• Use sill sealerA material used to close any gaps between the foundation and the sill plate; some types are foam and rolls of solid fiberglass sized for this purpose. between foundations and sill plate.
• Caulk bottom plate of exterior walls.
• If building a basement, insulate between floor joists with unfaced batts supported by wire or metal rods.
• Fill insulation cavities entirely, leaving no gaps where convection currents can form.
• Install continuous insulation on exterior walls with cathedral ceilings.
• Use treated wood that does not contain chromium or arsenic.
• Seek an independent inspection of insulation.

 
FAST FACT: Instead of continuous framing extending from the garage to conditioned spaces, terminate framing at the boundary wall to the conditioned space so end-blocking can be installed.

Vapor Barrier by Geographic Location

In most cold climates, vapor barriers should be placed on the interior (warm-in winter) side of walls. However the map shows that in some colder climates, the vapor barrier should be omitted, while in hot and humid climates, such as along the Gulf coast and in Florida, the vapor barrier should be placed on the exterior of the wall.

Perm Ratings of Different Materials (Ratings of 1 or less qualifiies as a vapor barrier)Vapor Barrier

• Asphalt-coated paper backing on insulation: 0.40
• Polyethylene plastic (6 mil): 0.06
• Plywood with exterior glue: 0.70
• Plastic-coated insulated foam sheathing: 0.4 to 1.2
• Aluminum foil (.35 mil): 0.05
• Vapor barrier paint or primer: 0.45
• Drywall (unpainted): 50
• Drywall (painted – latex paint): 2-3

Home Energy Audits

A home energy audit is often the first step in making your home more efficient. An audit can help you assess how much energy your home uses and evaluate what measures you can take to improve efficiency. But remember, audits alone don't save energy. You need to implement the recommended improvements. ENERGY STAR provides extensive information about home improvement projects to enhance energy efficiency, lower utility bills, and increase comfort.

You can perform a simple energy audit yourself, or have a professional energy auditor perform a more thorough audit.

Do-It-Yourself Audits

If you have five minutes and your last 12 months of utility bills, use the ENERGY STAR Home Energy Yardstick to compare your home's energy efficiency to similar homes across the country and get recommendations for energy-saving home improvements from ENERGY STAR. You will also need to enter some basic information about your home (such as zip code, age, square footage, and number of occupants). If you don't have your bills, contact your utility for a 12-month summary.

What You Need to Know to Get Started:

Collect this information first, then go to the site and conduct your audit!Get Started with the Home Energy Yardstick

• Your energy use and costs for the last year: You'll need your last 12 months of utility bills OR a 12-month summary statement from your utility company.
• Energy sources for your home: natural gas, electricity, fuel oil, propane and/or kerosene?
• The square footage of your home.

Types of Insulation

LOOSE-FILL CELLULOSE INSULATIONA method of installing loose insulation in wall cavities, using a powerful blower and a fabric containment screen, which is particularly effective for situations with small or unusually shaped areas to insulate. goes into finished walls and is blown into place. When used in walls, it is best when wet because the loose-fill wall insulation could settle. Wet-blown insulation of-fers great insulating qualities and can be trimmed by hand on walls before installing drywall. In attics, be sure to use baffles to keep the material away from soffit vents. Also, do not cover recessed light fix-tures unless the fixtures are certified to accept insulation. Fiberglass, mineral wool (recycled steel slag), and newspaper are all different types of loose-fill cellulose insulation that are treated with boron-based chemicals to make it fire retardant. Cellulose-insulation has R-value of R-3.8 per inch.

BLANKETSA material used for insulation (usually fiberglass) which may be faced or unfaced, comes in rolls, and is flexible so that it can be fit in a wide variety of spaces. There may be a vapor barrier on one side. OR BATTS OF INSULATION are usually fiberglass, mineral wool, or recycled cotton. They can be fitted between studs in unfinished walls or between joists and beams and for all unfinished walls. Fiberglass insulation has R-values R-2.2 to 4.0 per inch.

RIGID BOARD INSULATION includes expanded polystyrene, extruded polystyrene, and polyisocyan-nurate and is useful for sheathing on homes. Polymer insulation has R-values typically R-6.0 to 7.4 per inch. Be sure that the rigid board you choose does not have chlorofluorocarbons (CFCs). Expanded polystyrene usually does not have CFCs. Rigid board may require certified installers, depending upon your local jurisdiction.

Rigid plastic board insulations generally have a higher R- value than batts and therefore require less basement space and a thinner supporting framework. They are also less prone to moisture damage than batts. However, they are more expensive and must have a fire-resistant covering.

Benefits of High Performance Building Insulation

• Natural ventilation can be used for a greater number of hours.
• Smaller HVAC equipment can be purchased.
• Spaces are more comfortable.
• Homes can achieve up to 50 percent less energy for heating and cooling.
• Less emissions of greenhouse gases are produced.
• High-performance insulation lasts longer, is fire-resistant, and reduces maintenance costs
• By not using fiberglass, the health risks associated with inhaling fiberglass.

CASE STUDY: Cobb Housing YouthBuild Reducing Mechanical System Loads by 50 Percent

Cobb Housing YouthBuild found that by properly and completely insulating a home with an open cell expanding foam such as Icynene, a home that would have required a 4-ton cooling system can now perform well with a 2-ton.

A cost-benefit analysis determined that the best insulation for a typical 1500 square foot home in Georgia using cellulose in the walls and an Icynene insulated roofline resulted in savings on a downsized cooling system for Cobb Housing, monthly savings to the homeowner, and reduced health hazards to the youth (fiberglass is very unhealthy to work with).

For a copy of this analysis contact Joseph Martin, Assoc. AIA, LEED AP: josephmartin@bellsouth.net

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