The Schundler Company
10 Central Street
Nahant, MA 01908



Perlite loose fill insulation is an inert volcanic glass expanded by a special heat process. The resultant lightweight product is a white granular material, which handles and pours easily. It provides a quick, inexpensive and permanent method for efficiently insulating masonry walls. Depending on design conditions, reductions in heat transmission of 50 percent or more may be obtained when perlite loose fill is used in the hollow cores of concrete block or cavity type masonry walls.

Basic Product Properties: Thermal Insulation--Perlite contains countless tiny air cells that account for its excellent thermal insulation and lightweight. Thermal conductivity factors at the recommended density range of 2-11 pcf (32-176 kg/m3) are normally 0.27 k to 0.42 k.

The efficiency and economy of perlite loose fill insulation has been proven many years in the insulation of storage tanks for liquid gases, such as oxygen, liquid natural gas and nitrogen at temperatures as low as -400o degrees F (-240 degreeso C).

Calculated Transmittance Values Are Not the Answer-- Concrete masonry walls with different types of core insulation are frequently compared by the relative ranking of published calculated U and R values. However, extensive Guarded Hot Box tests 1 of full scale wall systems at Dynatherm Engineering2 have determined that thermal performance of insulated masonry walIs is not solely proportional to thermal transmittance of the insulation but also depends on block geometry, concrete thermal conductivity and the degree to which the insulation fills the core spaces.

High heating and cooling costs and the need for energy conservation have resulted in heightened awareness of the thermal performance of building envelopes. Contributing to the overall energy efficiency of the building envelope is the thermal performance of exterior walls. Selection of an optimal wall system is based on thermal performance as well as construction costs, structural requirements and aesthetic


The case for selecting insulation based on actual full scale wall measurements vs. calculated values is clearly indicated in the perlite and EPS insert testing to date. Although calculated R-values for EPS inserts appear more favorable, full scale laboratory wall testing reveals that perlite masonry loose-fill insulation is actually 22% more effective3 than EPS inserts.

A key to perlite’s outstanding performance is the fact all block cores, voids, and mortar areas are completely filled with free flowing perlite. With perlite, convective loops within the block are filled, thus eliminating convective heat flow (chimney effect) and subsequent heat losses.

But perlite offers more. Perlite is non-combustible with fusion point of approximately 2300°F (1260°C) and improves the fire rating of an 8 inch (20 cm) concrete block from 2 to 4 hours---a 100% improvement.


Wall tests conducted conclude that perlite is 12% more effective3 than EPS beads. Perlite’s superiority is related to its free-flowing characteristics. EPS beads are extremely light in weight making installation difficult. Further more, they suffer "static cling" and tend to adhere to the walls of cores upon installation, As a result, voids can exist in masonry walls insulated with EPS beads. It is these unfilled voids that are largely responsible for the poorer performance of masonry walls insulated with EPS beads.

Perlite loose-fill masonry insulation assures a completely filled wall with no unfilled areas to drain away expensive heat. In addition, perlite has been fully tested and meets fire safety, thermal peformance, and quality assurance standards of federal and state agencies as well as international and local building code organizations.


Tests peformed by Dynatherm Engineering reveal that perlite is 6% more eflective as a core fill insulation than vermiculite. Although the physical characteristics of the two materials are similar, the closed cell structure and lower thermal conductivity of perlite account for perlite’s superiority.

Heat loss through the walls of a masonry building can be huge over the life of a building. The amount of heat saved by using perlite can very well more than offset the cost of the insulation.

(1)ASTM C236, Standard Test Method for Steady State Thermal Peformance of Building Assemblies by Means of a Guarded Hot Box.
(2)Dynatherm Engineering, Lino Lakes, Minnesota.
(3)Thermal effectiveness is based on a comparison of total R-values corrected to ASHRAE winter design with 15 mph wind outside, stilI air inside and 8 inch (20 cm), 103 lb/ft3 (1653 kg/m3) two-core bIocks. The percent improvement will be greater if lighter weight (lower k value) blocks are used and less if higher weight (higher k value) blocks are used.
(4)Construction Technology Laboratories, Skokie, illinois.

PERLITE IS THE SUPERIOR INSULATION--Dynatherm Engineering’s testing has shown conclusively that perlite masonry loose-fill insulation is the superior concrete block insulation when compared to expanded polystyrene (EPS) inserts, expanded polystyrene (EPS) beads, and vermiculite.

EFFECT OF DIMENSIONAL VARIATIONS-- Variations found in block dimensions and the effect of these variations lend further validity to the selection of masonry insulating material on the basis of actual tests of wall systems rather than on the use of published or calculated values based on nominal concrete block. In an analysis conducted by the Construction Technology Laboratories4 , variations in block dimensions can cause thermal transmittance to vary from 19% to as much as 36% depending on face shell and web thickness. Accordingly, calculated and published values do not take these dimensional differences into account while tested wall systems do consider all variables.

FREE-FLOWING PERLITE ASSURES SUPERIOR PERFORMANCE-- A key to perlite loose-fill insulation's excellent performance in masonry wall systems is its free flowing characteristic. In a masonry wall system, granules of perlite seek out and completely fill the smalllest crevices, voids, and mortar areas without bridging. This flowability of perlite loose-fill insulation assures a completely and efficiently insulated masonry wall and avoids the "chimney effect" or "static cling" effect characteristic of EPS products. Perlite’s flowability also allows the masonry contractor to install several courses of block prior to the installation of insulation into core and ear holes.

Published and calculated thermal transmittance values do not consider the physical properties of insulation with regard to flowability, settling and the amount of the core that is actually filled.

Flowability of perlite combined with non-settling properties assures permanent thermal performance for the life of the structure.

PERLITE IS MORE THAN JUST A BETTER INSULATION-- In addition to its excellent thermal performance, perlite insulation offers a number of additional advantages to architects, engineers, contractors and building owners.

  • EASY INSTALLATION-- Perlile loose-fill insulation is easy to install and requires no special training or equipment. In addition, it may be installed at any reasonable wall height as construction progresses.

  • PRICE COMPETITIVE-- Perlite loose-fill insulation is cost-competitive with other masonry block insulations. When you consider that perlite insulation will reduce heat loss through masonry walls by more than 50%, it may be the best investment you’ve ever made!

  • 100% IMPROVEMENT IN FIRE RATING-- Independent studies show that the fire rating of concrete block is improved from 2 hours to 4 hours when the cores are filled with perlite loose-fill insulation.

WHAT IS PERLITE LOOSE-FILL INSULATION?-- Perlite loose-fill insulation is an inert volcanic glass expanded by heating to 1600 F (850 C). The resulting granular product is lightweight with countless tiny, sealed air cells which account for its excellent thermal performance. The characteristics of perlite loose-fill insulation provide many additional benefits including:

  • Perlite loose-fill insulation is free flowing and will uniformly and completely fill all cores and voids in masonry wall units.
  • Perlite loose-fill insulation is inorganic and is rot, vermin and termite resistant.
  • Perlite loose-fill insulation is non-combustible with a fusion point of approximately 2300 F (1260 C), while EPS products are combustible.
  • Perlite loose-fill insulation improves the fire-rating of an 8 inch concrete block from 2 hours to 4 hours --- a 100% improvement!
  • Perlite loose-fill insulation is non-sealing and supports its own weight in masonry wall cavities and masonry block cores.
  • Perlite loose-fill insulation may be easily installed without special training or equipment.
  • Thermal performance tests using ASTM C-236 Guarded Hot Box Method have shown conclusively that perlite masonry loose fill insulation is the superior concrete block insulation when compared to expanded polystyrene (EPS) inserts, expanded polystyrene (EPS) beads, and vermiculite.

  • Other test conducted by independent laboratories also confirm the superior qualities of perlite loose fill insulation:

Applicable Standards, Specifications, and References:

  • ASTM Specification C549 for Perlite Loose Fill Insulation
  • ASTM Specification C520 Density of Granular Loose Fill Insulation
  • ASTM Specification C236 Test Method for Steady-State Thermal
  • Performance of Building Assemblies by Means of a Guarded Hot Box
  • ASTM Specification E84 Test for Surface Burning Characteristics of Building Materials
  • FHA Use of Materials Bulletin UM-37
  • GSA Commercial Item Description A-A-903 Insulation, Thermal(Expanded Perlite)
  • Brick Institute of America Technical Notes No 21A
  • Federal Specification HH-I-515D

For more information, please call or contact:

The Schundler Company

10 Central Street
Nahant, MA 01908
732-287-2244 or

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