Perlite insulation How to Identify, Use, Purchase Perlite

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Perlite & perlite insulation: this article illustrates and describes perlite materials used for perlite insulation, sound insulation, soil mix, and other applications. Perlite photographs in this article are by the author or were provided courtesy of Redco and their website about perlite insulation.

Description of Non-asbestos perlite materials sometimes mistaken for asbestos in buildings.

This article series assists building buyers, owners or inspectors who need to identify non-asbestos-containing insulation materials as well as asbestos-containing materials (or probable-asbestos) in buildings by simple visual inspection.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Perlite & Perlite

Perlite insulation forms

Perlite, including perlite building Insulation is a non-fibrous non-asbestos-containing material which has an R-value of about 2.7 per inch and would not be expected to contain asbestos.

Perlite is a type of rock (a form of volcanic glass) which is mined, crushed, heated and thus expanded (4 to 20 x original volume) to form an inorganic insulating material.



Building Insulation Images, Properties, Uses

Photographs of Perlite Insulation in Various Uses

Perlite in planting soil mix © Daniel Friedman

Water trapped in the rock causes it to expand. Perlite insulating material is produced in granular forms from coarse to a fine powder which weighs about two pounds per cubic foot. Photo at above left courtesy of Redco .

Perlite is used for the insulation of low-temperature application equipment such as cryogenic (-100 degC or -150 degF) and super-cold storage tanks and test chambers.

Perlite insulation is also used in food processing applications (up to 4 degC or 40 degF - about the minimum food refrigeration temperature).

Our photo ( above left) sows what coarse perlite looks like when added to a planting soil mix.

Perlite under the stereo microscope © Daniel FriedmanExpanded perlite (from our potting soil sample) is easily examined under the stereo microscope (photo at below-left) to show the mechanical properties of the material.

Perlite building insulation is produced in a granular or even a powder form, but by some manufacturers it is formed into an insulating board (by combining perlite with gypsum, for example for use under building roofs).

Perlite insulation materials are resistant to mold, rot, and rodents.

Perlite also resists moisture uptake, making it useful for use in areas exposed to water or dampness such as in floor leveling compounds and under-floor insulation where it may also be used for noise control (as a sound-deadening material, possibly between building floors).

Perlite as an under-floor insulation and as an acoustical insulator is described by the Schundler Company.

Perlite insulation density and weight

Perlite from soil mix, cleaned © Daniel Friedman

Perlite insulating products are produced in a range of densities (weight per cubic foot) from two pounds per cubic foot to fifteen pounds per foot.

Expanded perlite (from our potting soil sample) has been washed in alcohol and photographed again in the stereo microscope (at left).

Perlite has a typical density of 3-4 pounds per cubic foot in building insulation products, and is described by various industry sources as inexpensive and dimensionally stable (doesn't shrink) and non-combustible.

Perlite as a non-fibrous, non-asbestos green building material

Perlite at 600x in alcohol © Daniel Friedman

That perlite is a non-fibrous material is quite apparent in our forensic lab photo at 600x. The sample was prepared in alcohol and washed to remove most potting soil fragments from the source product we used for this examination.

Some writers name perlite insulation products as a "green building material", probably because it is a natural, mined resource (not considering the energy costs of mining and production), and more, because perlite is used as a concrete additive to make insulating and light-weight concrete, or as an insulating material to fill the cores of masonry block constructed walls.

Perlite insulation may also be used to insulate masonry wall cavities (between brick courses in a structural brick wall) or in a building interior to fill the cavity between a masonry exterior wall and the interior finish-wall furring strips and drywall.

More information about perlite insulation is available from Redco II, a perlite insulation manufacturer in North Hollywood, an industry source for this insulating material.

Redco II sells perlite for horticultural purposes (those white particles you see in some brands of potting soil), for industrial and construction applications such as an additive in the formation of concrete, and for general industrial uses including as a filtering medium.

Perlite MSDS, example from Schundler Company [3]

Reader Comment: applications of Perlite

(Mar 19, 2014) Amol Ramning said:

Perlite is applicable in various processes. Starting from LPG, LNG, natural gas tank insulation in factories to Filtration in food and chemical industries. Filler additive material in paints to Horticulture product in Plants and agriculture application and many more.

Construction & Insulation Applications of Perlite

The use of perlite offers many functional and long-term economics advantages to the construction industry. Among the major applications are as a aggregate in lightweight concrete and plasters, as a loose fill insulation product to fill cavities of masonry brick walls, as an ingredient in the manufacture of insulation boards, bricks and tiles.

Thermal Insulation Properties of Perlite

The glassy closed cellular structure gives perlite a very low thermal conductivity, combined with the lightweight and low combustibility making it the ideal material for thermal insulation. Insulation of rooftops with perlite concrete to reduce heat gain into the building is a popular application.

Perlite in Lightweight Floors

The low density of perlite concrete makes it ideal for filling of floors and sunken areas where weight of concrete is to be reduced.

Perlite for Sound Insulation

The large irregular surface area of Perlite Particles make them a useful ingredient in sound absorbing material designed for acoustical treatment to prevent reflection and reverberation of sound from ceiling and upper wall areas. Perlite is also a principle ingredient in acoustical plasters and tiles manufacture.

Perlite for Cryogenic Insulation

Perlite displays a low thermal conductivity through a wide range of temperatures, pressure and densities. This attribute makes it the ideal insulation material for cryogenic products storage even as low as -268 deg.C. Its fine particle size combined with the inert nature and free flowing nature makes filling and removal an easy task.Apart from being used for insulation of big cryogenic tanks, like LNG, Oxygen, Ethylene and Nitrogen.

It is also used to insulate air-separation plants, vacuum and non-vacuum small tanks and small tanks and small cold and hot storage containers like flasks.

Perlite Uses in Horticulture

The capacity of perlite to adsorb water, improve aeration and provide proper drainage makes it an excellent product for horticulture application. Since perlite is inorganic sterile, chemically inert with a neutral pH, the lightweight insulating properties which reduces extremely the soil temperature fluctuations makes perlite use as a unique growing medium and soil conditioner.

Perlite insulation products find wide application in plant propagation, cultivation of crops, domestic gardening, stadium turf lawn conditioning, seed propagation, tissue culture hardening, nurseries, green house growing and landscaping.

Industrial Applications of Perlite & Filtering Aids

Perlite functions as a filter aid to facilitate easy separation of the liquid from the solid particles in industrial filtration by improving flow rate of filtrate and also achieving the required clarity. Perlite does not interfere chemically with the slurry and impart no taste, colour or odour to the filtrate product and this quality has extended its use in the food and beverage industries. Other applications include, pharmaceuticals, chemicals, water, paints and resins, oils, sugar, beer, wine and industrial coatings.

Perlite used in Refractories

Perlite is used as a lightweight, low iron content ingredient in insulating castables used in petrochemical, sponge iron and cement plants.It is also used in refractory bricks that find application of back up insulating layers in boilers, industrial furnaces etc.

Perlite Filters

The fine particle size, high brightness, lightweight, chemically inertness and milding abrasiveness make perlite an excellent filler material.It is used as filler in paints, resins, coatings, synthetic rubber, polishes, cultured marble etc.

Perlite Cleaners

Fine perlite aggregate with a blend of non-ionic surface-active agents can be used as a safe hand and industrial cleanser in work spots like project site where water is scarce. Grease and oils from soiled hands can easily b ....

Perlite Insulation R-Values

Reader Question: relationship between particle size and perlite insulation R-values

(Sept 16, 2014) Jim Tolbert said:
What is the relationship between expanded perlite particle size and R=factor for high temp (chimney) insulation? That is, is coarse, medium, or fine particles have a higher R factor and what particle sizes are in each of the classifications? Many thanx!


Jim here is some research on the effects of particle size on Perlite insulation R-values. It is apparent that smaller particles are likely to yield higher R-values. But you'll want to be careful to consider more than just particle size. The amount of moisture in perlite can have a significant effect on its insulating and heat retaining properties.


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