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History of Insulation with Masonry HIGHER ENERGY COSTS AND CODES DEMAND GREATER EFFICIENCY There is a story of a young architect today analyzing a building constructed in the 1950s with solid masonry walls and single paned glass used on the exterior of the structure. That young architect referred to the building as an "old, masonry, energy inefficient building." In the present context of the 21st century, it is not energy efficient using today's standards. But, when it was built, as with most other buildings at that time, very little insulation was used because energy was a cheap commodity and architects and owners did not require use of insulation in their building envelopes. Insulation and other techniques for energy conservation are coming to the fore today. Therefore, masonry buildings and other building types have been upgraded with different types of insulation strategies. The use (in the 1950s and 1960s) of zonolite, vermiculite and perlite was used initially in the cores of concrete masonry units and wall cavity's to increase the masonry's marginal thermal performance. This satisfied the increased energy demands. In the earlier part of the 20th century, some insulation materials utilized on the inside of ice houses built in Chicago were horse hair and cork.
CAVITY WALL HISTORY: 200 YEARS
Cavity walls are not new, they have been observed in ancient Greek and Roman structures. At the Greco-Roman town of Pergamum, on the hills overlooking the Turkish town of Bergama, a stone wall of cavity type construction still exists. Sometime in the early part of the 19th century, the cavity wall was rediscovered by the British. Plans dating as early as 1805 suggest a type of cavity wall construction. It featured two leaves (wythes) of brick, bonded by brick headers, spanning across a 6" cavity. An early British publication (dated 1821) suggests the use of cavity walls as a means of protection against moisture penetration. The use of metal ties was introduced in Southern England sometime after 1850 . These original ties were made of wrought iron. Cavity walls were first built in the United States late in the 19th century. Figure 1 illustrates an alternate type of cavity wall system originally featured in an 1899 text book assembled for people engaged in the engineering professions and construction trades. However, it was not until 1937 that this type of construction gained official acceptance by any building or construction agency in the United States. Since then, interest in and use of cavity walls in this country has rapidly increased. This has resulted in extensive testing to determine cavity wall properties and performance.
The early use of cavity walls in this country was limited primarily to exterior load -bearing walls in low rise construction. In the 1940s, designers began to recognize the advantages of cavity walls in high-rise buildings. Today, masonry cavity walls are the preferred wall system and are used extensively throughout the United States in all types of buildings. The primary reasons for their popularity are: superior resistance to rain penetration, excellent thermal properties, excellent resistance to sound transmission and high resistance to fire. At the first North American Masonry Conference (1978), at the University of Colorado Boulder, masonry design professionals and research professors gathered from around the world for paper presentations and discussion. Water penetration and solid masonry walls were being discussed along with the now more accepted insulated cavity wall currently being designed and constructed in America. Timber West, an elder scholar from England, who had an Albert Einstein white head of hair and a white handle bar mustache, addressed the crowd. He cleared his throat and said, "When are you bloody Colonialists going to learn that if you want to build brick masonry walls that won't leak, you have to build a cavity wall. We (British) have been doing it for the last 200 years" He silenced the audience.
MODERN ERA OF INSULATED MASONRY WALLS The insulation used in masonry buildings changed drastically in the mid 70s due to the Arab oil embargo. Long lines of cars waiting to get gas along with increased energy demands promulgated new energy codes Ð this phenomenon changed the design world. Requirements for minimum R-values for various types of construction came into being. Masonry, concrete and precast industries were given credit for their mass in tempering the exterior temperature fluctuation. To meet these needs, a variety of insulations were used.
DESIGN CHALLENGES The need for higher R-valued walls presented a design problem for architects. Traditionally architects designed buildings for commercial, industrial and residential applications. The most economical wall system in the past was solid masonry walls composed of three wythes (or layers) of brick and/or one wythe of brick tied into an 8" concrete masonry back up. The only place you could put rigid insulation in solid walls was on the inside of the building. This gave rise to the use of cavity walls composed of an exterior 4" brick wythe of masonry, a cavity consisting of an air space and closed cell rigid insulation and an interior wythe of the 8" concrete masonry. (Figure 2) The history of cavity walls goes back many hundreds of years, but the greatest impetus for its use is for a more rain resistant type of wall system compared to solid masonry. In addition, it was more energy efficient as a corollary. Below are various wall cross sections and the R-value of the total wall system including the insulation selected. It is hoped this is of assistance to you in designing energy efficient walls in the future.
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