Masonry Magazine February 1966 Page. 17
Perlite Insulation in Masonry Walls
A severe water permeability test was conducted at the Structural Clay Products Research Foundation according to procedures developed by the National Bureau of Standards. A brick and tile cavity wall with a 2½ in. cavity filled with silicone treated perlite loose fill insulation was purposely made to leak at the rate of 3.93 quarts per hour. For six consecutive days this wall was subjected to an equivalent rainfall of 5½ inches per hour accompanied by a 50 mph wind.
Although 136 gallons of water entered the cavity during this 144-hour test, no water permeated across the space through the silicone treated perlite. When the perlite was removed from the wall it was dry to the touch and had a moisture content of only 2.14 percent by weight. This was the lowest moisture content of any of the three cavity wall insulating materials tested by the Foundation. The comparative results are reported in SCPI's "Technical Notes No. 21."
At the request of Perlite Institute, Johns-Manville Research and Engineering Center performed tests to determine the ability of silicone-treated perlite to maintain its water repellency. After 75 soaking and drying cycles over a four month period, it was concluded silicone treated perlite will maintain its water repellency indefinitely.
These two tests also prove the perlite fill can support its own weight without settling. There was no evidence of consolidation or slump of the perlite.
In terms of improved human comfort, savings in mechanical equipment and heating and cooling costs, perlite increases the insulating value of most masonry walls by more than 50 percent. Tests prove its maximum thermal conductivity, k-factor, is 0.38, and these data are included in the 1965 Guide and Data Book of the American Society of Heating. Refrigerating and Air Conditioning Engineers.
Silicone treated perlite meets all the criteria for cavity wall insulation as adopted by Structural Clay Products Institute. It is inorganic, non-combustible and rot proof. It resists termites and vermin.
Installation is easy and economical. Perlite insulation is usually installed by the masonry contractor as he builds the wall. It can be poured directly into the cores of concrete block or masonry cavity walls at any convenient level. Wall sections under windows are filled before sills are placed. Rodding or tamping is not needed, and it flows readily around conduit, electric boxes and wall ties.
Perlite Institute sponsored tests at The Pennsylvania State University which proved that a vapor barrier can be omitted from masonry cavity walls insulated with silicone treated perlite if interior relative humidity conditions do not exceed 50 percent. These conditions would normally apply to most buildings and geographic areas in the United States.
Water-repellent silicone treated perlite is available nationally and in Canada through member companies of Perlite Institute. It is packaged in 4 cubic foot bags weighing about 30 pounds. One bag of silicone treated perlite will insulate sixteen 8-in. concrete blocks or 20 sq. ft. of wall area with a 2½ in. cavity. When a "Certificate of Conformance" is included in project specifications, the manufacturer is required to certify his product conforms to specifications adopted by Perlite Institute.
View of perlite mill at No Agua, New Mexico. Building contains system of conveyors and elevators which automatically move the perlite ore through all stages of crushing, milling, drying and screening. (Photo courtesy of Johns-Manville Perlite Corporation.)
Insulating the cores of a block wall with silicone treated perilte. MASONRY. February, 1966
Blending and loading plant at the Antonito, Colorade, railhead 24 miles north of the mill. Perlite are is blended to specifications and loaded into railroad cars for shipment. (Photo courtesy of Johns-Manville Perlite Corporation.)
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