Three millennia ago Ancestral Pueblo Indians of the North American southwest utilized thermal mass for warmth in the winter. In the winter, the thermal mass of the stone and clay is bathed by the low angle sun absorbing the heat and re-radiating it at night to the interior helping warm the inhabitants.  The cliffs shaded the adobe dwellings from the high summer sun enabling the thermal mass of the stone and clay to stay cool and comfortable. The Thermal Wall Technology utilizes three millennia of building technology to achieve superior energy efficiencies. 

Pueblo Indian's Adobe Cliff Dwellings

Thermal mass in construction for the most part was abandoned in modern times and replaced with light-weight frame structures when fossil fuel heat sources were moved to the interior of the homes (either directly or indirectly) and the heat losses retarded utilizing thermal insulation and glass windows. The TWT combines both the ancient technology of thermal mass and modern technology of glass and thermal insulation. Unlike the thermal mass utilized by Native Americans the TWT thermal mass can be thermally insulated to store heat, be regulated to the appropriate temperature, accept heat from external sources (e.g., solar collectors, heat pumps, wood stoves) and transfer the stored heat in the thermal mass throughout the structure.

The idea for the Thermal Wall Technology was first identified while constructing an addition for a quadriplegic family member. Being in a tornado prone area and since she could not easily exit to safety it was decided to construct a substantial building which under most circumstances would provide in-situ safety. The addition was constructed utilizing insulated concrete forms (ICFs) which consist of two reinforced expanded polystyrene panels, separated by polymer or metal webbing, which enables concrete to be poured in the center cavity. The ICFs provided both the insulation and structural support for the construction.

BuildBlock ICFs Utilized in Construction

To take advantage of solar energy tax incentives in Indiana for structures which incorporated either solar collection, storage or distribution; hydronic tubes were incorporated in the ICF concrete walls establishing the walls as a solar storage and delivery system. Traditional ICFs have insulation on both the interior and exterior of the structure. At that time Mike Sandefur, the innovator, mentally reflected on how the thermal mass of the wall could communicate to the interior if the interior insulation was removed. A few years later in planning a retirement home Mike conducted heat loss calculations on traditional ICFs and a new innovative single-sided ICF (SSIFC) such as BuildBlock Building Systems HardWall product which uses a removable structural plywood on one side. The calculations on the amount of heat energy, the temperature of the walls and floors and how the exposed walls communicated (transferring heat back and forth) to the interior were very favorable. Research is also underway to determine the feasibility of TWT construction utilizing a concrete masonry unit (CMU) (concrete blocks) and Architectural CMU. Initial indicators suggest CMUs could be utilized in many TWT applications. 

Mike’s calculations and modeling revealed the large surface area resulted in a drastic reduction of the heating system's operating temperature. From there Mike conducted additional models on the various TWT efficiencies created by the use of a solar thermal hydronic system, passive solar and traditional heating and cooling systems. The numbers continued to be exceptionally favorable; at which time Mike contracted the University of Southern Indiana (USI) and worked with Dr. Brandon Field, Associate Professor of Engineering, to provide an independent third party verification on the mathematical calculations of the Thermal Wall Technology. Dr. Brandon Field, utilizing a robust computer model, performed an analysis of the thermal wall technology and confirmed the equations were correct and appropriate. Dr. Field conducted additional modeling related to heat pump efficiencies related to the lower operating temperatures.  Subsequently, Mike and USI collaborated to seek a National Science Foundation grant to further the research and develop the technology.  To date 19 specific energy, health/safety and comfort benefits related to the Thermal Wall Technology have been identified.

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