Glossary of building science terms used in Homes Across America

Advanced Framing - Refers to framing techniques that reduce the amount of lumber used to build a home while maintaining the structural integrity of the building. Using these techniques results in lower material and labor costs and improved energy performance for the building. Because these techniques are not universally known by builders, more planning and training may be needed when using them. Advanced sealing – In addition to basic sealing, advanced sealing adds protection to top and bottom plates of walls, at corners, in attics, and between cavities at penetrations for plumbing, electrical, and ventilation. Air Barrier - A system of materials that enclose a volume of air with minimal air leakage between the enclosed air and the exterior. The effectiveness or adequacy of the air barrier can be measured by the volume of air (in cubic feet per minute) that must be added or removed from the enclosure to maintain a certain pressure difference across the pressure boundary. Autoclaved Aerated Concrete (AAC) - A precast, manufactured building stone made of allnatural raw materials. It is an economical, environmentally friendly, cellular, lightweight but structurally sound material that features thermal and acoustic insulation, as well as fire and termite resistance. AAC is available in a variety of forms, ranging from wall and roof panels to blocks and lintels. Blower Door Test - Blower doors are designed to measure how airtight (or leaky) a home is, normally using the parameter of air changes per hour (ach). These tests can be used to determine construction quality and compliance with design or program standards (such as utility home efficiency programs) and to diagnose comfort, indoor air quality, and durability problems. Building envelope - The building envelope includes everything that separates the interior of a building from the outdoor environment, including the windows, walls, foundation, basement slab, ceiling, roof, and insulation. It controls the transfer of energy (heat) between the inside and the outside. Conditioned Space - The interior area supplied with conditioned air from HVAC system. Daylighting - The efficient use of natural light in ways that minimize the need for artificial light in buildings. It is achieved by control strategies and adapted components which fall mainly into three categories:

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conduction components - spaces used to guide or distribute light towards the interior of a building

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pass-through components (e.g. windows, solar tubes) - these allow light to pass from one room or section of a building to another

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control elements - specially designed to control the way in which light enters through a pass-through component.

Embodied Energy - All of the energy invested in bringing a material to its final product, including transportation. Engineered Lumber - Recycled or reconstituted wood materials, which employ laminated wood chips or strands and finger-jointing (gluing large pieces together). Energy Star – A government-backed program helping businesses and individuals protect the environment through superior energy efficiency. Go to http://www.energystar.gov for more information. Frost Protected Shallow Foundations (FPSF) protect foundations against frost damage without the need for excavating below the frost line. A FSPF has insulation placed strategically around the outside of a foundation to direct heat loss from the building toward the foundation, and also to use the earth’s natural geothermal energy. French Drain - The basic french drain is a drainage system that consists of a trench dug into the ground through and out of an area with poor drainage. The trench is filled with a porous material, usually gravel, crushed stone or slag, along with a perforated pvc plastic pipe to collect and channel unwanted ground water. It is better to install the drain during construction, rather than later, to avoid problems digging around utilities, porches, and other obstacles. French drains will clog over time, so they need to be cleaned periodically. Fly ash - A by-product of coal burning, fly ash is a fine, glass-like powder recovered from gases created by coal-fired electric power generation. Fly ash is an inexpensive replacement for Portland cement used in concrete, while it actually improves strength, segregation, and ease of pumping of the concrete. Fly ash is also used as an ingredient in brick, block, paving, and structural fills. Using coal fly ash conserves energy by reducing the demand for typical pavement materials such as lime, cement and crushed stone, which take energy to produce. Coal fly ash can also replace clay, sand, limestone and gravel, and save the energy costs of mining such materials. Each ton of fly ash used to replace a ton of cement, for example, saves the equivalent of nearly one barrel of oil. Forest Stewardship Council Certified Wood Products - The Forest Stewardship Council (FSC) has developed an internationally recognized third party certification system for harvesting wood from sustainable sources. Such products are becoming more available from building suppliers. Fiber-cement Siding – Siding composed of cement, sand, and cellulose fiber that has been autoclaved (cured with pressurized steam) to increase its strength and dimensional stability. The fiber is added to reinforce the concrete and to prevent its cracking. Planks come in 5¼” to 12"

widths and are about 5/16 inches thick. Fiber-cement siding is termite-resistant, non-combustible, and may be warranted for up to 50 years. Geothermal Heat Pumps - These ground-source heat pumps use the natural heat storage capacity of the earth or ground water to provide energy efficient heating and cooling. GHPs should not be confused with air-source heat pumps that rely on heated air. They use the relatively constant temperature of the ground or water several feet below the earth’s surface as source of heating and cooling. GHPs can also provide domestic hot water. They can be used for virtually any size home or lot in any region of the U.S. Housewrap - Any of several spun-fiber polyolefin rolled sheet goods for wrapping the exterior of the building envelope. Marketed as an air barrier that can “breathe” with respect to water in the vapor phase but repel liquid water, its properties do not include uni-directional vapor permeability. Builders should understand their region before determining how to use housewrap and other barriers, if any, before building. Hydronic heating – In-floor hot water heating system where hot water is pumped through a thermal mass floor which absorbs the heat and evenly radiates it over an extended period of time. Insulating Sheathing – These are non-structural insulating board products that are most often cited for their varying R-values. Also important to know are their other properties important to how well a house performs: vapor permeability, bonding qualities of surfaces to various other construction materials, and how well they act as a drainage plane. Infill - The use of vacant land and property within a built-up area for further construction or development, especially as part of a neighborhood preservation or limited growth program. Low-E - Most often used in reference to a coating for high-performance windows, the “e” stands for emissivity or re-radiated heat flow. The thin metallic oxide coating increases the U-value of the window by reducing heat flow from a warm(er) air space to a cold(er) glazing surface. The best location for the coating is based on whether the primary heat flow you want to control is from the inside out (heating climates) or the outside in (cooling climates). Low Volatile Organic Compounds (VOC) Paints and stains - Many low-VOC versions of products reduce risks to human health and the environment, and are the preferred alternative to people concerned with indoor air quality. Harmful VOCs evaporate (volatilize) easily at room temperature and often have a sharp smell. They are contained in many products, such as office equipment, adhesives, carpeting, upholstery, manufactured wood products, paints, solvents, pesticides, and cleaning products. National Association of Home Builders (NAHB) Research Center - The NAHB Research Center is a wholly-owned subsidiary of the National Association of Home Builders. It is a “green building” pioneer, researching many new resource-efficient techniques and technologies, and promoting results to green builders throughout the country. Net Metering - Net-metering is a simplified method of metering the energy consumed and produced at a home or business that has its own renewable energy generator, such as a wind turbine. Under net metering, excess electricity produced by the wind turbine will spin the existing

home or business electricity meter backwards, effectively banking the electricity until it is needed by the customer. This provides the customer with full retail value for all the electricity produced. Oriented Strand Board (OSB) - OSB is manufactured from waterproof heat-cured adhesives and rectangularly shaped wood strands that are arranged in cross-oriented layers, similar to plywood. This results in a structural engineered wood panel that shares many of the strength and performance characteristics of plywood. Optimum Value Engineering – See Advanced Framing PATH - The Partnership for Advancing Technology in Housing (PATH) is a government/industry initiative that seeks to accelerate the development and widespread use of advanced technologies to radically improve the affordability, quality, durability, environmental performance, and energy efficiency of our nation’s housing. Click here to learn more about PATH. Pressure-treated lumber - The EPA no longer allows Chromated Copper Arsenate (CCA) treated wood to be used in homes. A list of alternatives and suggested uses is available from this fact sheet by the Consumer Product Safety Commission. R-Value – The R-value depicts the resistance a material has to heat transfer. (See U-Value for more information) Radon - Radon is a cancer-causing, radioactive gas. Radon comes from the natural (radioactive) breakdown of uranium in soil, rock and water and gets into the air we breathe. Radon can be found all over the U.S. It can reach toxic levels in any type of building that does not have adequate ventilation. The Surgeon General says radon is the second leading cause of lung cancer in the United States. Radon Mitigation - Radon-resistant construction techniques can be effective in preventing radon entry. When installed properly and completely, these simple and inexpensive techniques can help reduce indoor radon levels in homes. In addition, installing them at the time of construction makes it easier and less expensive to reduce radon levels further if these passive techniques don’t reduce radon levels to below 4 picoCurie per liter (pCi/L), the level considered safe. Every new home should be tested after occupancy, even if it was built radon-resistant. Sealed-combustion appliances - Appliances with the ignition heating element sealed and vented to prevent gases from mixing with and polluting indoor air. Slab-on-grade foundation - These floors are often the least expensive foundation system and can expedite the construction process. The foundation consists of a concrete slab poured over at least 4 inches of gravel and a layer of 10-mil polyethylene. Virtually any floor covering works well with a slab, although wood flooring systems may require installation of wooden furring strips prior to attaching the wood flooring material. There are benefits and liabilities to a slab on grade foundation the homeowner is encouraged to understand before using this technique. Solar Tube - A solar tube is a skylight on top with a silverized tube that usually goes through the attic. It ends in a skylight in the ceiling of a room that does not have direct sunlight, such as a north facing room, or where putting in a window would be impractical, such as a bathroom.

Transom windows - A window that fits over the top of a door or the upper part of an interior wall, primarily for additional light and aesthetic value. U-value - The measurement of heat transfer through a given building material, such as glass, wood, or insulation, whereas the R-value depicts the resistance a material has to heat transfer. These terms refer to conductive heat transfer. In number values, R-value is the direct inverse of Uvalue (R-value=1/U-value). If a material has a U-value of .5, it has an R-value of 2. If it has a Uvalue of .25, it has an R-value of 4. VOC: Volatile organic compound - Highly evaporative, carbon-based chemical substances that produce noxious, often toxic, fumes. They are found in many paints, caulks, stains, adhesives, carpet, and manufactured products used in cabinets and furniture. Vapor Barrier - A material that severely restricts the movement of water vapor from one side of the material to the other. Properly choosing where and how to use vapor and air barriers is complicated, and based on the interaction of climate factors. Xeriscaping - Climate-tuned landscaping that minimizes outdoor water use while maintaining soil integrity and building aesthetics. Typically includes emphasis on native plantings, mulching, and no irrigation or limited drip/subsurface irrigation. Zero Energy House – This is any house that averages out to net zero energy consumption. A zero energy home can supply more than its needs during peak demand, typically using one or more solar energy strategies, energy storage and/or net metering. In a zero energy home, a tight building envelope and efficient HVAC systems, appliances and lighting all significantly contribute to less demand for energy.