The physical character of expanded perlite lends itself to a variety of special purposes­ including the use in lightweight formed products. For a detailed explanation of perlite expansion, see the info sheet: “Why Perlite Works” in the Informa­tion library at www.perlite.org

Over half of all the perlite expanded in the United States annually is used to make “formed products:’ These products include ceiling tiles, pipe insulation, roofing board and fire-rated door cores, and are manufactured with a variety of binders.

Perlite formed products are the combination of perlite granules with binders such as fibers, hydraulic cement, plaster, sodium silicate, or even asphalt. These binders give the granules a portable, durable shape suitable for intended use. The use of sodium or potassium silicate binders is discussed below. Other binders are simply blended with the perlite, and water if needed to activate the binder, and then placed in a suitable mold.

Perlite/Silicate Composites

Liquid sodium silicates (water glass) are used as binders in many of the above applications. These sodium silicate binders are solutions of water-soluble glasses manufactured from varied proportions of soda ash and silica, providing a wide range of chemical and physical properties. Sodium silicates are widely used as high-temperature adhesives and binders due to the following properties:

• Low cost
• Inorganic
• Easy to handle
• Rapid controlled set
• High strength
• Insolubility (when cured)
• Chemical stability

Silicate-bonded perlite makes an insulation material that is completely non-flammable, the refractory nature of the bond is a major advantage. Potassium silicate is sometimes preferred for applica­tions where heat insulation and fire resistance are the main objectives. This material has a slightly higher softening point than its sodium counterpart. Sodium silicate is widely used as a binder for molding sand in foundries.

Green building solutions are increasingly called for to balance the world’s need for more human habitation with limited resources. It is said that buildings in the United States use one-third of the total energy consumed, two-thirds of the electricity, one-eighth of the water, as well as impacting the land. Green building initiatives consider a building’s energy use, water use, indoor environmental quality, and the materials used in its construction. In addition, it assesses the effects a building has on its site and uses this information to further sustainable solutions throughout the entire life cycle of a building.

Perlite’s versatility and usefulness have an essential role to play in contributing to different types of green building initiatives. Multiple Attribute ratings programs such as LEED (USGBC) and new building standards such as the National Green Building Standard (IgCC), encourage the use of materials and practices that prioritize more energy-efficient systems and environmentally friendly materials.

Perlite, The Preferred Choice

• 100% natural; produced without harmful chemicals
• Will not off-gas
• Inert and pH balanced
• Will not leach chemicals into the environment
• Is an excellent insulator
• Lightens denser materials like concrete and soil
• Promotes plant growth; reduces irrigation demand
• Can often be locally sourced
• Provides stormwater detention and filtration
• Is durable and has long-lasting benefits

Scoring LEED Points

While the LEED rating system does not promote specific raw or intermediate materials, specifying perlite and products containing perlite gives planners, architects and developers an opportunity to score higher in a variety of ratings categories(summarized in the table above). Total points awarded result in the achievement of one of four graduated levels of certification (Certified, Silver, Gold and Platinum).

Thermal Performance

Perlite is an excellent insulator and is therefore prized for its contribution to Optimized Energy Efficiency and Thermal Comfort. Perlite is applied both as loose fill insulation in cavity walls and below floors, and as an alternative to sand in lightweight insulating concrete roof designs. Further points may be awarded for Low Emitting Materials since perlite is hypo-allergenic and does not o-gas volatile organic compounds.

Water Efficiency

Another area perlite contributes to LEED certification is in Indoor & Outdoor Water Use Reduction. Horticultural perlite can store trace amounts of irrigation or rainwater for later release and uptake by planting and vegetation.

Sustainable Sites

A further area of vital importance involves LEED certification points for Sustainable Sites. Perlite is used to great effect in Rainwater Management as an element in below-grade stormwater filtration solutions, and above-ground in support of landscaping and roof-top vegetation. Gardens and green roofs contribute to Heat Island Reduction, Protect or Restore Habitat for birds and pollinators, and provide people with calming Places of Respite.

Materials and Resources

Finally, Sourcing of Raw Materials and Environmental Product Disclosures are simplified when using perlite. Perlite is often available locally or can be sourced from only a short distance away. Furthermore, perlite is free of contamination from heavy metals and harmful chemicals.