Glossary
Air Changes Per Hour (ACPH, ACH): The number of times in one hour the entire volume of indoor air in a house or room is replaced with outdoor air through ventilation and infiltration, usually measured in cubic feet per hour. Your house should have minimum whole house ventilation equal to 0.35 air changes per hour.
Advanced Framing Techniques (AFT): AFT results in lower material and labor costs and improved energy performance for the building, while reducing the amount of lumber used in construction.
Air Infiltration: The amount of air leaking into the home through the walls, floor and ceiling via attic hatches, chimneys, and electrical penetrations. Excessive amounts of air infiltration cause uncomfortable, drafty rooms and high energy bills.
Air Sealing: The practice of sealing penetrations in the walls, floor, and ceiling where outside air enters the home in order to improve energy efficiency. This is the most cost effective way to increase efficiency.
Annual Fuel Utilization Efficiency (AFUE): A widely used measure of a furnace's heating efficiency. The higher the AFUE, the more efficient the equipment.
Backdrafting: The flow of air into a house caused by low indoor air pressure. This occurs via a flue or chimney when several fans or fireplaces are in use or if the house is very tight.
Baseload: Baseload energy usage is more or less constant each month, year round. It includes energy used for water heating, refrigeration, clothes dryer, lighting, electronics and more. Seasonal items (cooling and heating) are subtracted from the total.
Batt Insulation: Insulation used in walls and ceiling cavities made of glass or mineral wool, which may be faced with paper, aluminum, or other vapor retarder.
Blown-in Batt: Loose insulation that is installed in wall cavities using a powerful blower and a fabric containment screen.
Blower door: A variable speed fan used to measure air leakage and energy loss. It is mounted in an adjustable frame that fits snugly in the doorway and is used to pressurize and depressurize a building.
British Thermal Unit (BTU): The amount of heat required to raise the temperature of one pound of water one degree Fahrenheit; equal to 252 calories.
Building Envelope: The building shell; consists of structural elements (walls, roof, floor, foundation) of a building that enclose conditioned space.
Carbon Monoxide: Poisonous combustible gas. Carbon monoxide is produced in the incomplete combustion of carbon and carbon compounds such as fossil fuels (i.e. coal, petroleum), their products (e.g. liquefied petroleum gas, gasoline) and biomass. It is colorless and odorless.
Cellulose Insulation: Thermal insulation manufactured from recycled newspaper. It is generally treated with natural borates to provide vermin and fire protection, although recently, fungicides and chemical fire retardants have been used and may prove problematic for sensitive individuals.
Compact Fluorescent Lights (CFLs): A smaller version of fluorescent lamps that reduce energy usage by 75% and last 6-10 years. These lights consist of a gas-filled tube and a magnetic or electronic ballast. They fit in most light fixtures and have warmer color tones and longer life. They reduce energy use by 75% over an incandescent bulb and last 6-10 years.
CFM50: The measurement of amount of cubic feet per minute (CFM) of air moving through a structure and measured at 50pascal pressure
CFMnatural: The measurement of cubic feet of air flowing through a house from indoors to outdoors during typical, natural conditions. This figure can be roughly estimated using a blower door.
Chimney Effect: The tendency of heated air or gas to rise in a duct or other vertical passage, such as in a chimney, small enclosure or building, due to its lower density compared to the surrounding air or gas.
Convective Air Flow: Air movement where less dense (warmer) air is displaced by more dense (cooler) air; often expressed by the phrase "hot air rises." Convective air flow can be useful if controlled, as in gravity hot air heating systems, but is more often a contributor to heat loss.
Daylighting: The use of natural light to minimize the need for artificial lighting during the day. Common daylighting strategies include the proper orientation and placement of windows, use of light wells, skylights, windows, light shafts or tubes, light shelves, reflective surfaces and shading, to allow light into adjacent spaces.
Degree Day: A unit for measuring the extent that the outdoor daily average temperature (the mean of the maximum and minimum daily dry-bulb temperatures) falls below or above an assumed base temperature, normally taken as 65 degrees Fahrenheit, unless otherwise stated. One degree day is counted for each degree below (for heating) or above (in the case of cooling) the base, for each calendar day on which the temperature goes below or above the base.
Dense-pack Insulation: Loose-fill insulation (like cellulose) that is blown into enclosed building cavities at a relatively high density so that it will stop air movement and insulate the cavity.
Dual Flush Toilet: A high-efficiency toilet designed to reduce water use. These are often equipped with two buttons or a specialized lever that allows the user to select a short or long flush.
Ducts: Round or rectangular tubes, generally constructed of sheet metal, fiberglass board, or a flexible plastic-and-wire composite, located within a wall, floor, or ceiling that distribute heated or cooled air in buildings. It is important that ducts be insulated and sealed properly when in unconditioned space to avoid unnecessarily high utility bills. The best practice would be to not put ducts in unconditioned space.
Duct Blower: A fan that tests how leaky the duct system is and determines where the holes are. Duct leakage should be below 5%. Most new homes have 10%-20% leakage, while old homes can have up to 50% duct leakage.
Embodied Energy: Consists of the energy required to grow, harvest, extract, manufacture, refine, process, package, transport, install, and dispose of a particular product or building material. This is a useful measure of ecological cost.
Energy Efficiency: Using less electricity or fuel than a conventional technology to perform the same task.
Energy Efficiency Ratio (EER): The measure of the instantaneous energy efficiency of room air conditioners; the cooling capacity in Btu / hr divided by the watts of power consumed at a specific outdoor temperature (usually 95 degrees Fahrenheit). EER is a measure of the maximum use at a given time (kW), while SEER considers yearlong efficiency (kWh).
Energy Star: A program sponsored jointly by the U.S. Environmental Protection Agency and the U.S. Department of Energy that promotes energy-efficient products, homes, and technologies for consumers and businesses. Energy Star qualified appliances and products are often 10-50% more efficient than their conventional counterparts.
Engineered Wood: Building products, including beams, framing lumber, floor, and roof joists made from wood fibers bound with adhesives. Engineered products use less wood or wood from smaller trees and are generally stronger, straighter, and of more consistent quality than dimensional lumber.
Fiber-Cement Siding: An exterior siding made from a blend of cement, sand, cellulose fiber and additives. It is typically sold as panels or planks, with a smooth or textured finish.
Fly Ash: Fine, non-combustible particulate found suspended in flue gases during coal combustion. This byproduct is most commonly used to replace a portion of Portland cement in concrete. Fly ash is also used for soil stabilization, fill material, and waste remediation.
Forest Stewardship Council (FSC): An independent, non-profit organization that promotes responsible forest management by evaluating and accrediting certifiers. The FSC encourages the development of national and regional forest management standards and provides public education about independent, third-party certification.
Formaldehyde: Poisonous, reactive, flammable gas with pungent suffocating odor. May cause irritation of the eyes, nose, throat and respiratory system. Contact may result in sensitization. Carcinogen. Commonly used in wood products, plastics, fertilizer, and foam insulation. Incorporated in synthetic resins by reaction with urea, phenols, and melamine. Urea-formaldehyde (UF) resin is used in particleboard, hardwood plywood paneling, and medium-density fiberboard (MDF). MDF is generally the highest formaldehyde-emitting pressed wood product. Softwood plywood and oriented strand board (OSB) produced for exterior applications contain phenol-formaldehyde (PF) resin. Pressed wood products containing PF resin generally emit less formaldehyde than those containing UF resin.
Green Building: The practice of increasing the efficiency with which buildings use resources - energy, water, and materials - while reducing building impacts on human health and the environment during the building's lifecycle through better siting, design, construction, operation, maintenance and removal. Green buildings are designed to reduce the overall impact of the built environment on human health and the natural environment by: efficiently using energy, water, and other resources; protecting occupant health and improving employee productivity; reducing waste, pollution, and environmental degradation. Practitioners of green building often seek to achieve not only ecological but aesthetic harmony between a structure and its surrounding natural and built environment, although the appearance and style of sustainable buildings is not necessarily distinguishable from their conventional counterparts.
Green Roof: A roof with a layer of soil or other growing medium on top of a waterproofing membrane. The soil and vegetation slow storm water runoff, reduce the heat island effect, provide habitat, and insulate the building.
Grey Water: Wastewater that does not contain sewage and can be reused for irrigaton. Grey water typically comes from sinks, showers, and washing machines.
Harvested Rainwater: Rain collected from a roof or yard and channeled to a storage tank, also known as a cistern.
Heat Gain: The amount of heat introduced to a space from all heat-producing sources, including building occupants, lights, appliances, as well as environmental sources like solar energy.
Heat Island Effect: The rise in ambient temperature that occurs over large paved areas. Strategic placement of trees can reduce this effect and reduce energy consumption for cooling by 15-30%.
Heat Loss: Heat that escapes through leaks in the building envelope and to the outdoor environment.
Home Heating Index: The number of BTUs of energy used by a home divided by its area in square feet, then divided by the number of heating degree days during the time period.
Home Performance with ENERGY STAR: A national program from the EPA and DOE that offers a comprehensive, whole-house approach to improving energy efficiency and comfort at home, while also helping to protect the environment. Specially trained contractors who participate in the program can evaluate your home using state-of-the-art equipment and will recommend comprehensive improvements that will yield the best results. They can also help you take advantage of federal tax credits for energy efficiency improvements.
House as a System (Whole House System): The approach to home design, building, remodeling and weatherization that recognizes how all the features in a home are connected -- and that changing one component can greatly affect another part of the house. This approach is based on the principles of building science and relies on diagnostics to verify results. Using this approach will improve the overall energy efficiency of the home, as well as its comfort, indoor air quality, safety, durability and affordability.
House wrap: Material, such as Tyvek or Typar, which acts as a barrier to protect the building interior from the outdoor environment. House wrap has some air sealing qualities.
HVAC Heating, Ventilation, and Air-Conditioning System: All the components of the appliance used to condition the interior air of a building.
I-joist: A manufactured wood product so named because in cross-section it looks like an upper case letter "I." The top and bottom chord are lumber or laminated wood and the vertical web is plywood or oriented strand board.
Indoor Air Quality (IAQ): The quality of indoor air relative to its acceptability for healthful human habitation. Assessing and improving, when necessary, the quality of indoor air is a major concern of home performance and weatherization. In particular, all by-products created by major combustion appliances must be directly evacuated to the outdoors under all operating conditions. IAQ is heavily influenced by choice of building materials (and cleaning procedures) and ventilation rates. See Formaldehyde and VOC's.
Infiltration: The movement of air into a building through leaks and penetrations in the building envelope. Cold air often enters the structure due to exfiltration, depressurization, wind, stack effect, and/or convective airflow.
Infrared Thermography: The practice of using infrared imaging to detect radiant energy or heat loss in a building. The infrared camera or scanner electronically senses heat radiated by objects and converts that thermal energy into images visible to the human eye. Some scanners can automatically record these images on video. When used in conjunction with a blower door, the scanner can provide valuable data about air leakage sites and thermal bypasses.
Insulation: Material that has a resistance to heat flow.
Kilowatt-hour (kWh): A measure of energy usage equal to the amount of power used multiplied by the amount of time the power is used. A 100-watt light bulb burning for ten hours uses one kilowatt-hour of power.
Leadership in Energy and Environmental Design (LEED): A building rating and certification program created and operated by the U.S. Green Building Council (USGBC).
Light Shelf: Horizontal projections at the building interior that work to reflect direct sun rays onto the ceiling deep into a space and at the same time shield direct sunlight from the area immediately adjacent to the window. The upper surface of the shelf may be specular or nonspecular but should be highly reflective (that is, having 80% or greater reflectance). Light shelves generally work best on facades that are south facing.
Linoleum: Natural linoleum is made from natural, minimally processed ingredients, including linseed oil, cork dust, pine rosin, wood flour, limestone, mineral pigments, and jute backing. Offgassing depends primarily on the adhesive used for installation. Some long-term offgassing will occur with the linoleum due to oxidation of the linseed oil, resulting in the emission of a mixture of aldehydes and carboxylic acids which are not considered hazardous, but may affect sensitive individuals. Do not confuse natural linoleum with Vinyl.
Loose-fill Insulation: Loosely packed insulation made from vermiculite, perlite, glass, mineral or shredded wood or shredded paper. For use in wall and ceiling cavities to allow pockets of dead air space.
Low-Emissivity Window (Low-E): Windows that have special coatings to permit most of the sun's light radiation to enter the building, but prevents heat radiation from passing through.
Manual J: The standard method for calculating residential cooling loads. Developed by the Air-Conditioning and Refrigeration Institute (ARI) and the Air Conditioning Contractors of America (ACCA), and based largely on the American Society of Heating, Refrigeration, and Air-Conditioning Engineer's (ASHRAE) "Handbook of Fundamentals."
Mechanical System: The system and equipment used to provide heating, ventilation, and air conditioning functions. Additional functions not related to space conditioning include, but are not limited to, freeze protection in fire protection systems and water heating.
Medium Density Fiberboard (MDF): Composite panel product made from wood fibers combined with a synthetic resin or other bonding system, and joined together under heat and pressure. Commonly used in kitchen cabinets, paneling, doors, laminate flooring, jambs, and millwork.
MERV (Minimum Efficiency Reporting Value): Measures the efficiency of air filters. The higher the MERV number, the better an air filter works in capturing airborne contaminants.
Moisture Barrier: A material, membrane or coating used on the inside of the foundation, below grade, or in a crawl space to keep moisture from penetrating the building envelope.
Natural Cooling: Cooling a building through passive means rather than mechanical systems such as air conditioning. Natural cooling strategies include shading, cross ventilation, and the use of thermal mass to moderate temperatures inside a space.
Negative Indoor Pressure: When air is exhausted from a building faster than it is replaced.
Net Metering: Net metering allows for the flow of electricity both to and from customers who have their own electricity generating units. With net metering, during times when the customer's generation exceeds his or her use, electricity flow from the customer to the utility offsets electricity consumed at another time.
Occupancy Sensor: A device that detects the presence or absence of people within a space and causes any lighting, equipment, or appliances to operate.
Offgassing: The release of gases or vapors into the air through the process of evaporation or chemical decomposition.
Organic Compound: Chemical compound based on carbon chains or rings and containing hydrogen with or without oxygen, nitrogen, or other elements. Organic compounds are the basis of all living things; they are also the foundation of modern polymer chemistry.
Orientation: The relation of a building and its associated fenestration and interior surfaces to compass direction and, therefore, to the location of the sun. It is usually given in terms of angular degrees away from south.
Oriented Strand Board (OSB): A manufactured wood sheet product made from large flakes of wood pressed together with glue, typically a dry phenolic type. OSB can be used for structural sheathing, subfloors, and in place of plywood.
Passive Cooling: Occurs when the building's structure or elements of it are designed to permit increased ventilation and retention of coolness within the building components. The intention is to minimize or eliminate the need for mechanical means of cooling.
Passive Solar: A building specifically designed to collect the sun's radiant heat and release that heat into the building's interior spaces to help warm the rooms naturally. Depending on the building design and climate, passive solar heating can be the sole source of heat or can be supplemented with a heating system. Thermal mass and proper shading play a key part in passive solar design.
Phantom Load: Phantom loads, also known as energy vampires, power supplies, and wall warts, can be a significant part of a household's electric use and are comprised of the power used by any appliance that consumes power even when it is turned off. Examples of phantom loads include equipment chargers, appliances with electronic clocks or timers, appliances with remote controls.
Photovoltaic (PV) Cells: Thin silicone wafers that convert any light, not only sunlight, directly into electricity.
Polyvinyl Chloride (PVC): Thermoplastic polymer of vinyl chloride. Rigid material with good electrical properties and flame and chemical resistance. PVC is a known human carcinogen. Due to environmental releases during the manufacturing process, it is banned in many parts of Europe. Greenpeace has developed an online resource to PVC alternatives. Used in soft flexible films, including flooring, and in molded rigid products like pipes, fibers, upholstery, and siding. Identified by a "3" inside a recycling triangle found on packaging. Dioxin is a harmful byproduct of PVC manufacturing and when PVC is burned.
Positive Indoor Pressure: When air is delivered into a space faster than it is exhausted.
Pressurization (Blower Door) Testing: A diagnostic technique that uses a blower door to locate areas of air infiltration by exaggerating the defects in the building shell. This test only measures air infiltration at the time of the test. It does not take into account changes in atmospheric pressure, weather, wind velocity, or any of the occupants' activities that may affect air infiltration rates over a period of time.
R-value: R-values are used to rate insulation and measure the insulation's resistance to heat flow. The higher the R-value, the better the insulation. R-value is the reciprocal of U-factor.
Radiant Barrier: A material that is good at blocking the transfer of radiant heat across a space. In a hot climate it is often installed in attics under the roof decking to keep the attic cooler.
Radon Gas: A radioactive, colorless, and odorless gas that occurs naturally in the soil in many ways. When trapped in buildings, radon concentrations build up and can cause health hazards.
Rain Screen Wall System: Exterior walls built with an air space between the siding and sheathing so that water will drain away, reducing the likelihood that moisture will enter the building.
Rapidly Renewable Wood: Fast growing trees that offer the general benefits of trees (helping replenish oxygen in the air and removing harmful CO2), and a more sustainable supply of wood for construction. Aspen tress and OSB are two good examples.
Recirculating Water System: A distribution system that keeps hot water circulating in the pipes to provide immediate hot water at points of use. An on-demand recirculating water system is the more efficient than a system used on a timer.
Relative Humidity: A measure of the percent of moisture actually in the air compared with what it would be if it were fully saturated at that temperature. When the air is fully saturated, its relative humidity is 100 percent.
Return Air: Air that has circulated through a building as supply air and has been returned to the HVAC system for additional conditioning or for release from the building.
Return Ducts: Ducts in a forced-air heating or cooling system that bring house air to the furnace or air conditioner to be heated or cooled.
Ridge Vent: A vent installed continuously along the ridge of the attic peak to allow ventilation air from the soffit vents to flow out of the attic.
Rigid Insulation: Insulation, such as foamed plastic, wood, cork, glass or mineral fibers, pressed into standard-sized boards for easy handling. Used as a surface insulation.
Seasonal Energy Efficiency Ratio (SEER): The total cooling output of an air conditioner during its normal annual usage period for cooling, in Btu/h (W), divided by the total electric energy input during the same period, in watt-hours. Higher SEER ratings indicate more efficient equipment and a lower cost to operate the equipment. New equipment ranges from about 10 to 16 SEER.
Solar Heat Gain Coefficient (SHGC): Glazing's effectiveness in rejecting solar heat gain. SHGS is part of a system for rating window performance used by the National Fenestration Rating Council (NFRC). SHGC is gradually replacing the older index, shading coefficent (SC), in product literature and design standards. If you are using glass whose performance is listed in terms of SC, you may convert to SHGC by multiplying the SC value by 0.87.
Solar Water Heater: A water heating system in which heat from the sun is absorbed by collectors and transferred by pumps to a storage unit. The heated fluid in the storage unit conveys its heat to the domestic hot water of the building through a heat exchanger.
Structural Insulated Panels (SIPs): A type of building system combining exterior sheathing, structural support, insulation, and interior sheathing into a modular factory-assembled unit, thus reducing the number of vertical joints, interior voids, and assembly time.
Superwindows: Double- or triple-glazed window sandwiches that contain a center sheet of coated mylar "low-emissivity" film and are filled with argon or krypton gas. This construction and the coating on the film allow short-wave radiation (visible light) to pass through, but reflects long-wavelength radiation (infrared or heat) so heat cannot pass through. R-values of 4.5 or more are achieved.
Supply Air: Supply air consists of a mixture of return air and outdoor air that is appropriately filtered and conditioned.
Supply Ducts: The ducts in a forced-air heating or cooling system that supply heated or cooled air from the furnace or air conditioner to the house.
Tankless Water Heater: A water heater that heats water as needed without the need for a storage tank using large electric elements or gas burners.
Therm: A unit of heat containing 100,000 British thermal units (BTU).
Thermal Boundary: The border between conditioned and unconditioned space where insulation is placed. The thermal boundary should be lined up with the air barrier.
Thermal Break: A material of low heat conductance used to reduce the flow of heat. For example, the vinyl separating the interior and exterior frames in some metal windows.
Thermal Bridge: A component, or an assembly of components, in a building envelope through which heat is transferred at a substantially higher rate than through the surrounding envelope area.
Thermal Mass: Materials that have a high capacity for absorbing heat and which generally change temperature slowly. These materials are used to absorb and retain solar energy during the daytime for release at night or during cloudy periods. They include water, rocks, masonry, tile, and earth.
Tight Buildings: Buildings that are designed to let in minimal infiltration air in order to reduce heating and cooling energy costs. In actuality, buildings typically exhibit leakage that is on the same order as required ventilation; however, this leakage is not well distributed and cannot serve as a substitute for proper ventilation.
Title 24: The State of California building code, which includes regulations for building energy efficient practices.
U-factor: A measure of how well a material or series of materials conducts heat. U-factors for window and door assemblies are the reciprocal of the assembly R-value. The smaller the number, the less the heat flow.
Unconditioned Space: An enclosed space within a building that is not insulated and/or heated.
Vapor Barrier: A material that prevents or drastically reduces the passage of water in vapor form. In cold climates, vapor barriers are typically installed on the inside of the wall frame. In hot humid climates, they are installed on the outside or preferably omitted entirely. In hot dry climates they are not needed.
Volatile Organic Compound (VOC): A class of chemical compounds that can cause nausea, tremors, headaches, and, some doctors believe longer-lasting harm. VOCs can be emitted by oil-based paints, solvent-base finishes, and other products in construction materials.
Weatherization: Modifying a home or building to increase energy efficiency. Methods include: sealing windows and doorframes with caulking or gaskets, installing storm doors and windows, adding or increasing the insulation value, and upgrading appliances and equipment.
Weatherstripping: Thin strips of metal, rubber, vinyl, or foam around doors and windows that prevent infiltration of air or moisture.
Xeriscaping (Zero-Scaping): Landscaping design for conserving water that uses drought-resistant or drought-tolerant plants.
