Masonry Magazine June 1978 Page. 20
Wythe
Because of the complete separation of the exterior brick wythe from the rest of the wall and the lack of restraint, the exterior brick wythe will undergo its maximum of expansion and contraction due to thermal changes. Therefore, the number of expansion joints required will be a maximum, and special care must be exercised in both design and detailing, see Technical Notes 18A Series.
Sound Transmission
The benefits of cavity walls in reducing sound transmission as listed in Technical Notes 21 Revised are not affected by the addition of an insulating material into the cavity.
Fire Resistance
The fire resistance rating of a cavity wall will remain unchanged with the addition of an insulating material into the cavity. Although some insulation materials must be considered combustible, the insulation is sandwiched between two layers of masonry and will not be directly exposed to continuous fire sources.
SUMMARY
This Technical Notes is the second in a series directed to brick masonry cavity walls. It is concerned primarily with insulated cavity walls, including the selection of insulation materials, the installation of these materials, and the overall advantages of using insulated cavity walls. Other Technical Notes in this series discuss cavity walls in general, their detailing, and construction.
The information and suggestions contained in this Technical Notes are based on the available data and the experience of the Institute's technical staff for a period of over 40 years. In any case, this information should be recognized as recommendations and suggestions for the consideration of the designers, specifiers, and owners of buildings when anticipating the use of the types of products discussed here. The final decision to use or not to use these types of products in brick masonry cavity walls is not within the purview of the BIA and must rest with the project designer and owner.
REFERENCES
1. Monk, C. B., "Thermal Performance of Masonry Walls," Modern Masonry, Building Research Institute, National Academy of Sciences, National Research Council, Washington, D.C., Publication 466, 1956.
2. Insulated Masonry Cavity Walls, Building Research Institute, National Academy of Sciences, National Research Council, Washington, D.C., Publication 793, 1960.
3. Technical Notes 4 Series, "Heat Transmission Coefficients of Brick Masonry Walls," "Heat Gain," and "M Factor," Brick Institute of America. Aug/Sept 1974, Apr/May 1974, and Mar/Apr 1977.
4. Technical Notes 7C, "Moisture Control in Brick and Tile Walls-Condensation," Brick Institute of America, February 1965.
5. Technical Notes 7D, "Moisture Control in Brick and Tile Walls Condensation Analysis," Brick Institute of America, June 1968.
6. Technical Notes 18A, "Differential Movement-Expansion Joints-Part II," Brick Institute of America, May 1963.
7. "Urea-Formaldehyde Based Foam Insulations: An Assessment of Their Properties and Performance," NBS Technical Note 946, U.S. Department of Commerce, July 1977.
8. Griffin, Jr., C. W., Manual of Built-up Roof Systems, AIA, McGraw-Hill, 1970.