Thermal Efficiency of CarbonCast®
The U.S. Department of Energy estimates that 42 percent of energy consumed in a building is ultimately lost through the building envelope, or the barrier between the building interior and outdoor environment. A significant portion of any commercial envelope is the exterior wall.
The building envelope is critical in regulating internal building temperatures and determining how much energy is required to heat or cool a structure for occupant comfort. Heat transfer through envelope components such as walls wastes energy. Thermally efficient exterior wall systems aim to mitigate heat transfer and energy loss. They are engineered to minimize the opportunities for heat to flow from the interior surface through the wall to the building’s exterior.
The role of wythe connectors
In insulated precast concrete wall panels, wythe connectors act as a mechanical connection between the inner and outer layers of concrete. Because they form a connection through the insulation, there is an opportunity for thermal bridging to occur as well. Traditional wythe connection options such as solid zones of concrete or metal connectors – while providing a reliable mechanical connection – permit heat transfer between the wall because of the materials inherent conductivity.
What is important is designing a performance specification on the overall wall system rather than just the connector alone. A specification based on the overall wall system is on of the best ways of ensuring that the enclosure will meet the owner’s standards.
The role of insulation
Insulation helps to prevent the flow of heat across the exterior envelope. The use of continuous insulation further stems the flow by eliminating the presence of building materials that could facilitate thermal transfer.
Continuous insulation is defined in ASHRAE 90.1 as “insulation that is continuous across all structural members without thermal bridges other than fasteners and service openings. It is installed on the interior or exterior or is integral to any opaque surface of the building envelope.”
The thermal performance of edge-to-edge insulated precast sandwich wall panels with no or minimal thermal bridges and no solid zones maintains the R-values for continuous insulation as defined in ASHRAE 90.1, thereby lowering energy costs for the owner and occupant.
~ Courtesy of AltusGroup