Masonry Magazine January 1981 Page.21
Thermal Storage Components
Thermal storage components may be direct gain floors and walls or direct gain floors and vented or unvented thermal storage walls.
Construction
Solid brick masonry used as a thermal storage medium, as in all brick masonry construction, requires that all head, bed and collar joints be solidly filled with mortar. Solid brick are units which are cored less than 25 percent of the gross cross-sectional area parallel to the bedding plane. In typical running bond or stack bond construction, the brick should be shoved into full bed joints. This results in sufficiently filled cores so that there is little or no effect on the overall thermal performance of the wall. When soldier courses or projected headers are being considered, uncored units may be preferred.
Hollow brick are brick units in which the coring is less than 40 percent and greater than 25 percent of the gross cross-sectional area in the bedding plane. Hollow brick masonry used for thermal storage requires all head and collar joints and bedding surfaces to be solidly filled with mortar and all cores fully grouted. Projected headers and corbels may best be achieved by combining solid brick masonry with hollow brick masonry construction.
Grouted hollow walls are discussed in Technical Notes 17, 17C and 17D. When considering the use of grouted hollow walls, constructed of two wythes of brick separated by a fully grouted space, the only control over thickness will be requirements for adequate thermal storage. Thus, grouted hollow brick masonry walls may be advantageous when the thickness desired is not easily achieved by using modular sizes of brick. As in all brick masonry construction, the brick wythes should have all head and bed joints solidly filled with mortar.
Miscellaneous Considerations
# Thermal Expansion
For most applications of brick masonry as interior direct gain thermal storage, the temperatures within the brick masonry will probably range from 72 to 96°F. Thus, thermal expansion will not normally be a problem except where long interior walls or floors are used. Interior brick masonry used for direct gain thermal storage occurring in lengths longer than 100 ft or exposed to a higher maximum temperature should be analyzed for thermal expansion. The thermal expansion of brick masonry is discussed in Technical Notes 18A.
Thermal storage walls may be subjected to larger temperature fluctuations than direct gain thermal storage components. Usually, the difference between the maximum temperature and minimum temperature at the center of the thermal storage wall is small and no provision for thermal expansion is necessary. Generally, thermal expansion need only be considered for long or high thermal storage walls or for walls exposed to extreme temperature fluctuations.
The maximum mean temperature of brick thermal storage walls may be determined by using the temperature fluctuation equation in Technical Notes 43E. The minimum mean temperature may be determined by using the steady-state temperature gradient through the wall as discussed in Technical Notes 7C.
Flashing
Flashing brick masonry thermal storage components is usually not required because the brick masonry is on the interior of the building. Cavity walls will require flashing as discussed and shown in Technical Notes 21B. Flashing may be required for thermal storage wall systems, depending on the type of glazing assembly and how it is mounted in front of the thermal storage wall.
Reinforced Brick Masonry
Reinforced brick masonry, as discussed in Technical Notes 17 Series, may be required depending on the structural design loads. For thermal storage walls, this is easily accomplished by using reinforced grouted hollow brick or reinforced hollow wall construction. Reinforced brick masonry may be designed so that the wall will be able to sustain lateral thrust.
Typically in reinforced brick masonry construction, the reinforcement is both horizontal and vertical, placed as near to the center of the wall as practical. This, in combination with the minimum required spacing to sufficiently reinforce a brick masonry wall does not result in any significant decrease in the wall's thermal performance due to thermal bridges.
Lintels and Sills
The thermal storage wall details provide several options for constructing lintels and sills. Additional information on lintels is provided in Technical Notes 17H and 31B. Information regarding the construction of brick masonry arches is provided in Technical Notes 31 Series. Brick masonry sill details are provided in Technical Notes 36 Series, however, most sills for thermal storage walls do not require a sloped top surface or a drip since they are not exposed to exterior weather.
Fireplaces
Interior fireplaces may be used to obtain additional mass to decrease the interior temperature fluctuations. Brick masonry fireplaces may be incorporated in the thermal storage component in any of these passive solar heating systems. A fireplace may be used for direct gain storage or may be constructed in a thermal storage wall. The design and construction of fireplaces is discussed in Technical Notes 19 Series.