Copyright Goodheart-Willcox Co., Inc. Unit 7 Construction Materials—Types and Uses 129 emit volatile organic compounds (VOCs) when applied. Water-based products may be available and may offer a safer alternative. Thermal efficiency is another important consid- eration in material selection. Products with good insulating characteristics help conserve energy. Well- sealed windows with low thermal transmission, such as low-e and argon-filled units, have high R-values and are highly efficient. These types of windows are designed to reduce heat loss or gain but permit light gain. Water Efficiency A clean and plentiful water supply is a valuable resource. In green building projects, water conservation is an important priority. There are many ways water can be used more efficiently. Roof runoff water (recycled water) can be used for toilet flushing, garden irrigation, and other purposes. Many products used in plumbing work are designed for water efficiency, including low- volume fixtures, faucets, and shower heads. Energy- efficient appliances, such as point-of-use water heaters, help conserve water and provide other advantages, such as reduced heat loss. In three-dimensional (3D) design and modeling, simulation and analysis software is commonly used to test energy-efficient structures that utilize green building principles. When used with a 3D building model in building information modeling (BIM), simulation and analysis programs can be used to optimize electrical and mechanical systems. The software evaluates the design data of the building and generates information related to energy performance, including estimated usage and costs. Material Selection Material selection plays a significant role in green building construction. The use of recycled and renewable (recyclable) materials helps conserve resources and directly impacts the sustainability of the structure. Sustainable materials such as steel and engineered lumber are used in framing to maintain long-term building performance. When selecting materials, the entire life cycle of the structure is considered. For example, products such as steel, aluminum, and plastic are recyclable and can be reclaimed when a building is demolished. Cost is another factor in material selection. Using sustainable building products may come at greater expense, but it may prove more economical. A sustainable building product may cost more than a less efficient product, but it may last twice as long. Costs associated with transporting materials and building products to the site are also important consid- erations. When possible, local or regional resources and materials are used to save fuel and other transportation costs. Environmental concerns are also weighed when selecting materials. Certain materials and construction processes release toxins and may be harmful to the environment. For example, some adhesives and finishes LiveRooff® f Hybrid Green Roof System courtesy of LiveRoof, LLC Figure 7-28. The green roof system installed on this commercial building uses 1′ × 2′ modules with mature plants. Green roofs have both environmental and economic benefits, including reduction of roof temperature, capture and absorption of storm water, and runoff reduction. Goodheart-Willcox Publisher Figure 7-29. The lighting system in this warehouse utilizes motion-activated lights to reduce energy use.