Wednesday, July 6, 2011

Expanded Perlite Insulation - Laying the Foundation for Green Roofs

Chicago City Hall Green RoofImage via WikipediaBy Bernard Novak

The use of green roofs, date back to ancient times. The first recorded reference of a man-made garden on top of a building was during the Mesopotamia period. In France during the 13th century, sod roofs were developed to create a primitive form of thermal insulation for their buildings. Sod roofs are in fact still in use today, being used to create protection against extreme cold in Norway and the United States.

Renowned for their thermal qualities, green roofs are proving popular in high rise buildings throughout the world. Not only do they create an effective thermal insulation, but contribute to creating a recreational area for those in city central areas, improving the skyline for the enjoyment of the multi-story building tenants, these gardens continue to enhance the view in large cities, but they charge high rents.

Nowadays these types of roofs contain only one or two plant species. It is commonly designed for maximum hydrological and thermal insulation. It also provides minimum weight load for the roof, as not to place undue stress on the infrastructure of the building. Tall grasses are often considered to be a fire hazard while succulents are fire resistant.

Almost any plant can be grown in the green roof environment; however, limiting factors include climate, structural design and maintenance budgets. Expanded minerals such as Perlite are widely utilised in the construction of green roofs. This planting medium is distinguished by its mineral content. Expanded perlite is used because it is less dense, absorbs more natural minerals and provides the bases for an ultra-lightweight planting medium. Also used for a similar reason is light weight natural zeolite.

Before the installation of a green roof, a protective layer of light weight, concrete, sheet of rigid insulation, thick plastic sheet or copper foil, in combination with each other or separately, is used for protection of the building structure. It is used for protection against fertilizer and possible root penetration which can surely weaken the installation of a green roof and in some cases, be dangerous. To ensure a water proof system of the green roof, a water proofing layer is also installed.

Green roof designs are becoming increasingly specified in many parts of the world. They do not only provide insulation but also maintain the temperature in accordance to the outer climate. From an environmental point of view it will help reduce pollution related issues.

Perlite, an inert volcanic rock, is the principal material utilised in expanded perlite insulation, expanded by a heating process and often treated with water repellent material. It is renowned for its thermal properties and resistance to fire.

New Zealand Expanded Perlite Insulation is used in lightweight aggregates, and thermal and acoustic insulation.

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