Americans spend almost 90% of their time inside buildings. According to the U.S. Energy Information Administration, more than 2⁄3 of the electricity generated and more than 1⁄3 of the total energy (including fossil fuels and electricity) in the U.S. are used to heat, cool, and operate buildings. Significant energy could be saved if all buildings, including current building stock, were built to or exceeded minimum national energy code standards. Saving energy will result in fewer power plants and natural resources being used to provide electricity and natural gas. It also means fewer emissions to the atmosphere. Emissions have been attributed to smog, acid rain, and global climate change.
Energy codes provide minimum building requirements that are intended to reduce energy consumption. The U.S. Energy Conservation and Production Act (ECPA) requires that each state certify that it has a commercial building code that meets or exceeds ANSI/ASHRAE/IES Standard 90.1.1 When subsequent versions of 90.1 are published, the Department of Energy determines whether these more-recent versions meet the requirements of ECPA. The most-recent version of the standard was published in 2013 and has been determined to meet the provisions of ECPA. The International Energy Conservation Code (IECC) allows Standard 90.1 as a compliance path and also generally complies with ECPA. The most recent version of the IECC is 2015. In this sense, “commercial” means all buildings that are not low-rise residential (three stories or less above grade). This includes office, industrial, warehouse, school, religious, dormitories, and high-rise residential buildings. Some states implement codes similar to ASHRAE Standard 90.1 and some have other codes or no codes. The status of energy codes by states is available from the Building Codes Assistance Project (BCAP). Building to minimum energy codes is a cost-effective method of saving energy. The designer is not constrained in aesthetic expression in applying the range of available high-performance building systems to meet the performance criteria of ASHRAE 90.1 or the IECC.
Sustainability or green building programs such as LEED™, 4 Green Globes, or EnergyStar encourage energy savings beyond minimum code requirements. The energy saved is a cost savings to the building owner through lower monthly utility bills and smaller, and thus less expensive, heating, ventilating, and air-conditioning (HVAC) equipment. Less energy use also means fewer emissions to the atmosphere from fossil fuel power plants. Some government programs offer tax incentives for energy-saving features. Other programs offer reduced mortgage rates. The EnergyStar program offers simple computer programs to determine the utility savings and lease upgrades associated with energy saving upgrades. Sustainable buildings often have features that have been shown to increase worker productivity, decrease absenteeism, and increase student test scores in schools.
The planned design of an energy-conserving or sustainable building requires the architect’s understanding of the effects of design decisions on energy performance. More than half of the true total costs incurred during the economic life of a building may be attributable to operating and energy costs. An integrated design approach considers how the walls interact with the building and its HVAC system. Using this approach early in the design phase helps optimize initial building costs and reduce long-term heating and cooling energy costs. This integrated design approach is recommended for cost-effective, energy efficient, sustainable buildings.
Precast concrete wall panels have many built-in advantages when it comes to saving energy and protecting the building from the environment. Their versatility leads to unique solutions for many energy conservation problems. The relative importance of particular design strategies for any given building depends to a large extent on its location and climate. For instance, buildings in northern, heating-season-dominated climates are designed differently than those in southern, cooling-season-dominated climates.
Several factors influence the actual energy performance of the building envelope. Some of these are recognized in energy codes and sustainability programs because they are relatively easy to quantify. Others are more complex and are left to the discretion of the designer.
Much of the information and design criteria that follow are taken from or derived from the ASHRAE Handbook: Fundamentals and the ANSI/ASHRAE/IES Standard 90.1. It is important to note that all design criteria are not given and the criteria used may change from time to time as the ASHRAE Handbook and Standard are revised. It is therefore essential to consult the applicable codes and revised references for the specific values and procedures that govern in a particular area when designing the energy conservation systems of a particular structure.
~Information courtesy of PCI.