All laboratories performing the thermal tests shall be NANAVLAP- (National Voluntary Laboratory Accreditation Program) approved or otherwise certified as a recognized third party laboratory."⁶

Worker installing exterior batt, formaldehyde-free insulation in wall cavity. Photo couresy of Johns Manville

Polyiso roof insulation is used with a variety of roofing systems, from built-up roofing to ballasted, single-ply membranes. It is a flexible membrane and installers should follow manufacturers' installation guidelines during construction to prevent moisture from the interior from being drawn into the roof system. This insulation is used in both commercial and residential buildings and is a thermal insulation with high fire resistance. Roofing materials are faced with glass fiber facers and walls are faced with either foil or craft paper, and can contain recycled content. In the mid-nineties, companies began investigating the use of soy to make polyisocyanurate, experimenting with making this product more environmentally friendly in addition to its high thermal performance.

Residential Roofs and Formaldehyde-free Fiberglass Insulation
Faced batts and rolls of fiberglass insulation used primarily in residential construction, as well as commercial fiberglass insulation are available with an alternative acrylic binder instead of formaldehyde. Formaldehyde-free fiberglass insulation is recommended in the HOK Guidebook to Sustainable Design.⁷

The EPA reports that "Formaldehyde, a colorless, pungent-smelling gas, can cause watery eyes, burning sensations in the eyes and throat, nausea, and difficulty in breathing in some humans exposed at elevated levels (above 0.1 parts per million). High concentrations may trigger attacks in people with asthma. There is evidence that some people can develop sensitivity to formaldehyde. It has also been shown to cause cancer in animals and may cause cancer in humans. Health effects include eye, nose, and throat irritation; wheezing and coughing; fatigue; skin rash; severe allergic reactions."⁸ Insulation without formaldehyde contributes to the design of good indoor air quality in buildings.

Fiberglass batt insulation can be specified in a variety of R-values from R-11 to R-38. Facing can serve as an integral vapor retarder, reducing the potential for mold and mildew growth.

CONDENSATION

The thermodynamics of heat gain and loss in buildings is complicated. As temperature changes, air can condensate and create moisture in wall cavities or duct systems. In a roof system, the designer should flash all penetrations to waterproof a roofing membrane and provide the proper roof slopes to water drainage systems. In addition, the roof insulation should have a high perm rate to allow air vapor to flow through the product. The California Energy Commission defines Perm Rate as "the amount of water vapor that can move through a material by diffusion. Water vapor moves from high concentrations to lower (wetted areas to dry) because of the diffusion process. A higher perm rate means the material is more €˜breathable,' allowing more water vapor to pass through. Only the movement of water vapor is included in the perm rate, not bulk water."⁹

Condensation occurs when air with a high level of relative humidity meets a cool surface. Mold can grow if moisture is trapped by incorrect applications of insulation materials. Roofing manufacturers can provide the design professional with materials with high perm rates, but the designer must also provide adequate ventilation systems to prevent moisture and mold damage to the building.

Moisture problems can also appear when adding insulation to an existing roof. Lorraine Ross of Intech Consulting explains, "When recovering an existing roof, consider adding roof insulation to bring the roof up to at least the new ASHRAE roof insulation values. Building codes usually contain specific requirements, such as moisture assessment, uplift field testing and other measures to be sure the existing roof is suitable for recover - so be sure to check with the local building department."

Cool Roofs
A cool roof is a roof which reflects the heat gain from the sun's solar energy. The Cool Roof Rating Council defines a cool roof as one that "reflects and emits the sun's heat back to the sky instead of transferring it to the building below. "Coolness" is measured by two properties, solar reflectance (SR) and thermal emittance (EI). Both properties are measured from 0 to 1 and the higher the value, the "cooler" the roof."¹⁰ The thermal benefits of a cool roof can be measured in reductions in air conditioning loads and in the reduction of the "heat island" effect, particularly in urban areas.

The EPA defines albedo or solar reflectance, as a" measure of a material's ability to reflect sunlight (including the visible, infrared, and ultraviolet wavelengths) on a scale of 0 to 1. An albedo value of 0.0 indicates that the surface absorbs all solar radiation, and a 1.0 albedo value represents total reflectivity. EPA ENERGY STATAR specifies an albedo of 0.65 or higher for low-slope roof applications and 0.25 for sloped roofs."¹¹ Roofing materials should be chosen with a high R-Value for good thermal performance as well as a high albedo rating measured as the solar reflectance and infrared emittance to maximize energy savings. The color of a roof is important, but lighter shades may not necessarily have higher SR and EI ratings. Professionals will need to review actual product ratings for solar reflectivity and emittance. Coatings can be applied to roofing materials which will enhance cool roof performance. The DOE provides a cool roof calculator to help evaluate roofing choices.¹² This calculator requires the input of the R-Value, SR, and IE values along with a list of energy costs and equipment efficiencies to calculate annual savings relative to a black roof.

No coatings or additives are added on this clay tile roof which meets CRRC Cool Roof standards. Photo courtesy US Tile Company

One of the oldest building materials on the planet, clay roofs can also have high albedo ratings, as well as moisture protection. Rich Thomas, marketing manager of US Tile Company reports, "When fired at close to 2,000 degrees, clay tile has very low absorption rates so it is extremely durable and moisture resistant, and has natural reflective properties that meet "cool roof" criteria without additional additives or cost."

The weight of a roof can be a concern although not necessarily a factor in thermal or moisture protection. Well constructed garden roofs can provide great thermal and moisture protection benefits, however, they may require additional structural support. Rich Thomas notes that "lightweight clay tile designed for the re-roof market is available. Weighing under the 600 pound per square industry standard for re-roof applications, these products eliminate the need for structural reinforcement."