Whether used as a structural, architectural or both (ArchiStructural) building component, precast concrete wall systems can also serve as thermal and moisture protection, making precast concrete a natural choice for increasing the energy efficiencies of any building. One major factor contributing to the energy efficiency of a building is dependent upon how well the exterior wall system performs. While the inherent characteristics of concrete are naturally energy efficient; how well buildings perform depends on how well, and in what manner, their exterior wall systems perform.
Two of the most important factors in a thermally efficient exterior wall system involve thermal performance and moisture management. With heating and cooling costs accounting for the majority of energy being generated by buildings, thermal efficiency and moisture control have become areas of concern for building owners, who want energy efficient buildings that limit heating, venting and air condition costs while contributing to a sustainable environment.
An easy way to understand precast concrete’s contribution towards energy efficient buildings can be explained through the concept known as “WAVE” or Water, Air, Vapor, and Energy. High performance Precast concrete addresses all of these topics in order to provide a properly designed building envelope, and a resulting energy efficient building.
Two systems currently exist to control water entry within the building envelop. A Cavity System consists of two wall components separated by a hollow space or cavity. Oftentimes connections and components are also hidden inside the cavity, where issues may go undetected for years. An alternative system is a Barrier System, which relies on the integrity of the outermost wall to resist the bulk of the water attempting to penetrate the wall system. While precast concrete can satisfy both water ingress systems, a precast concrete barrier system provides a high integrity outermost wall system. This is typically more cost-effective, and any problems that may occur are easier to detect. A successful barrier system is also dependent upon detailing. Working with a Clark Pacific representative early on in the design process will ensure a successful barrier system.
The physical movement of air through the building envelope can include substantial amounts of moisture, which can affect the overall performance of a building. Building envelopes constructed with different building materials oftentimes allow a certain amount of air to pass through them, including unsealed joints, window openings, flashings and other thermal bridges. Studies have shown that 5% to 20% of air leakage in buildings occurs at doors and windows, while 20% to 50% occurs at the walls. While various cladding systems and insulation products leak some amounts of air through a building, tests performed on solid precast concrete walls showed no measurable leakage of air. Despite air leakage having a negligible impact on concrete, a panel’s connectivity, joint treatment and continuous insulation is critical to all aspects of the WAVE concept.
Vapor inherently tries to equalize pressure between areas of a building with varying vapor pressure. This means that the moisture of a wet, exterior face of a wall assembly will attempt to spread in the dryer, interior side of the wall system in an attempt to equalize pressure. This process of vapor pressure looking to equalize by moving from cooler air to drier spaces within a wall system is called vapor diffusion. Prevention of vapor diffusion relies on the materials that comprise a particular wall system. Concrete’s Perm rating qualifies as a vapor barrier, and at 3 inches thick, precast concrete qualifies as a vapor retarder. Insulated wall systems such as Clark Composite Architectural Precast Panels (C-CAPP) and Thermomass Insulated Precast Concrete Systems by Clark Pacific create a unified architectural system that enhances the thermal mass effect while providing an integral air and vapor barrier with continuous insulation.
There are several variables that affect thermal performance and energy efficiency of building envelope systems. One major influencer is insulation. The measurement of the insulating power of a building material is typically referred to as an R-Value. An R-Value means more resistance to heat flow and a better insulating performance for whatever material is being measured. Concrete possesses the ability to store heat above and beyond other building materials. The natural density of precast concrete to absorb and release heat slowly is known as Thermal Mass. The thermal mass effect of concrete reduces demand for air conditioning and heating, resulting in a more moderate room temperature with efficient heating, ventilating, and air conditioning (HVAC) systems.
Given how crucial the design of the exterior wall system is to a structure’s performance and longevity, and the inherent abilities of concrete to address issues effecting performance of the building envelope, concrete is the natural choice for increasing the energy efficiencies of any building
Contact Clark Pacific about using precast concrete wall systems on your next project, providing building owners and tenants alike the benefits of an energy efficient building.