Title: Unit 8 Glossary
Course: HAC 140 Weatherization > Section: HAC 140 Weatherization

Unit 8 Glossary

Terms

Term | Definitions
Absolute humidity | Air moisture content expressed in grains (or pounds) of water vapor per pound of dry air.
Air barrier (air boundary) | Any part of the building shell that offers resistance to air leakage. The air barrier is effective if it stops most air leakage. The primary air barrier is the most effective of a series of air ba ...
Backdrafting | Continuous spillage of combustion gases from a combustion appliance.
Carbon monoxide (CO) | Carbon monoxide is a tasteless, odorless, colorless, and poisonous gas that is a by-product of incomplete combustion of fossil fuels. It is usually caused by a lack of air to support combustion or ...
Combustion air | Air that chemically combines with a fuel during the combustion process to produce heat and flue gases, mainly carbon dioxide and water vapor.
Combustion efficiency | Percentage of fuel burned during combustion, also referred to as steady state efficiency.
Combustion gases | Combustion byproducts.
Condensation | The conversion of a gas to a liquid. Typically used here in relation to water when discussing moisture dynamics in the home.
Crawl space | The low space beneath the ground floor of a building that gives workers access to wiring and plumbing.
Dehumidification | The removal of water from the air. Excess humidity can cause mold.
Dew point | The warmest temperature of an object in an environment where water condensation from the surrounding air would form on that object.
Direct-vented appliance | Appliances that draw combustion air directly from the outdoors, e.g., most 90+ condensing furnaces.
Evaporation | The change that occurs when a liquid becomes a gas. Evaporation is the key process in the operation of air conditioners and evaporative coolers.
Grade | The pitch of a slope such as a roof or a hill.
Heat exchanger | Furnace component that transfers the heat from the combustion gases to the surrounding air. Combustion gases travel from the burner through the heat exchanger and then out the flue in properly fun ...
Hygrometer | A tool for measuring relative humidity. A psychrometer, which uses two thermometers, one with a dry bulb and one with a wet bulb, is a simple hygrometer.
Indoor air quality (IAQ) | The quality of indoor air relative to its acceptability for healthful human habitation. Assessing and ameliorating, when necessary, the quality of indoor air is a major concern of the weatherizati ...
Material Safety Data Sheets (MSDS) | Designed to provide both workers and emergency personnel with the proper procedures for handling or working with a particular substance. An MSDS includes information such as toxicity, health effec ...
Moisture meter | An instrument for measuring the percentage of water in a substance.
Mud sill | A wood component attached to the foundation of a building that creates a means of attaching various components of the framing to the foundation.
National Institute for Occupational Safety and Health (NIOSH) | NIOSH is the Federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH issues recommendations for respirator use.
Natural draft | Used in reference to combustion appliances. Natural draft appliances draw combustion air from the room where they are located. Although the term "atmospheric" is often used to describe these appli ...
Parts per million (ppm) | Unit for quantifying very dilute concentrations of substances.
Relative humidity (RH) | The amount of water vapor in the air, expressed as a percentage of the maximum amount that the air could hold at a given temperature.
Saturation | The condition in which the air cannot hold any more moisture, as a function of temperature and vapor pressure.
Thermal boundary/thermal barrier | The continuous layer of building components, such as insulation, that retard conductive heat flow. See also thermal envelope.
Vapor pressure | The ratio of water vapor to a given volume of air (also known as absolute humidity).
Vapor retarder | A material that impedes the passage of water vapor.
Vent pipe | The pipe carrying combustion gases from the appliance to the chimney.
Vented crawl space | Crawlspace with grilles or vents installed to allow for passive ventilation beneath the home.
Worst case CAZ testing | A safety test, performed by specific procedures, designed to assess the probability of backdrafting in the home.