Title: Unit 2 Glossary
Course: HAC 140 Weatherization > Section: HAC 140 Weatherization

Unit 2 Glossary

Terms

Term | Definitions
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.
British thermal unit (BTU) | The quantity of heat required to raise the temperature of one pound of water one degree Fahrenheit.
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.
Conduction | The transfer of energy through matter from particle to particle. When a teaspoon handle becomes hot while stirring hot tea, that is an example of heat transfer through conduction.
Convection | The transfer of heat caused by the movement of a fluid like water or air. When a fluid becomes warmer, it becomes lighter and rises. The stack effect is an example of convective currents at work.
Cubic feet per minute (CFM) | A measurement of air movement past a certain point or through a certain structure. Used in pressure diagnostics to quantify air leakage.
Delta T | Temperature difference.
Direct leakage | Air enters and exits at same location; occurs at direct openings to outdoors.
Direct-vented appliance | Appliances that draw combustion air directly from the outdoors, e.g., most 90+ condensing furnaces.
Exfiltration | This term describes the movement of air out of a building. Often refers to warm air leaving a building due to pressurization, infiltration, wind, stack effect, and/or convective flow.
Heat | Molecular movement.
Heat recovery ventilation (HRV) | Most common in cold climates, these are typically whole-house systems that reclaim some of the heat from exhaust air and pass that heat on to the intake air so less energy is needed to heat the ho ...
Indirect leakage | When air leaks into the home at one point, and out at a different opening. Indirect leakage is more difficult to find, and is associated with interior bypasses or chaseways of a home's interstitia ...
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 ...
Infiltration | The movement of air into a building through cracks and penetrations in the building envelope. Cold air often enters the structure due to depressurization, exfiltration, wind, stack effect, and/or ...
Kinetic energy | Moving or transitional energy.
Latent heat | The amount of heat absorbed or released in a phase change.
Laws of thermodynamics | Statements of basic thermodynamic relationships in a system. The first law states that energy is neither created nor destroyed. The second law states that energy always goes from high to low (abse ...
Manual J | Load calculation that allows the user to properly size HVAC systems for single-family-detached homes, small multi-unit structures, condominiums, town houses, and manufactured homes.
Phase change | The act of changing from one state of matter to another, e.g., solid to liquid or liquid to gas.
Potential energy | Stored energy.
R-value | A measurement of thermal resistance for materials and related surfaces.
Radiation | Used in reference to heat transfer, independent of any medium.
Sensible heat | The heat absorbed or evolved by a substance during a change of temperature that is not accompanied by a change of state.
Stack effect | The term describes the effect of higher pressure at the top of a structure, lower pressure at the bottom of a structure, and neutral pressure somewhere in between, relative to the ambient (surroun ...
Temperature | A measure of the heat present.
Thermal boundary/thermal barrier | The continuous layer of building components, such as insulation, that retard conductive heat flow. See also thermal envelope.
Thermal envelope | The continuous layer of building components, such as insulation, that retard conductive heat flow. See also thermal boundary.
Ventilation | Controlled air leakage usually created with mechanical exhausting devices such as fans and dryers.
Vermiculite | A heat-expanded mineral once commonly used for insulation.