EFS Chapter 6 Energy Efficiency for Buildings

Energy for buildings

The energy needed to provide heating, cooling, lighting, water heating, and other energy demands for building operations.

U.S

The total energy demand in the United States, with buildings accounting for 40% of it.

Embodied energy

The energy needed to manufacture building materials, transport them to construction sites, and repair and remodel buildings over time.

Building sector

The sector that includes residential and commercial buildings, responsible for almost half of all U.S. primary energy demand and 40% of carbon emissions.

Space heating and cooling

The largest energy demand in buildings, including residential and commercial spaces.

Lighting

The second most important energy demand in commercial buildings, with potential for reduction through natural daylighting.

Site energy

The energy demand of a building that includes all energy inputs, including losses in power generation and transmission.

Primary energy

The energy demand of a building that excludes losses in power generation and transmission.

Subscript "e"

It indicates that the term is referring to electricity.

Subscript "t"

It reminds us that the term is referring to a fuel that will be burned on-site to heat the building.

Site energy

The energy consumed at the site or building.

Primary energy

The total energy consumed, taking into account the more versatile value of electricity.

Normalized efficiency ratings

Efficiency ratings that consider a mix of different energy sources and demands, allowing for comparisons between individual buildings.

Passive House Institute

An organization that uses an overall efficiency measure of 120 kWh/m2 of primary energy per year for household space heating, water heating, and domestic electricity as the basis for its certification program.

Heat loss calculations

Calculations that determine the rate of heat loss through different components of the building envelope.

Infiltration

The heat load associated with warm room air leaking out of the building, which is replaced by colder outside air coming in.

Ventilation

The intentional bringing in of fresh air into the building.

Heat loss rate

The rate at which heat is lost through each component of the building envelope.

Thermal conductance

The proportionality constant that relates the heat loss rate to the area and temperature difference.

U-value

The thermal conductance measured in Btu/hr of loss per square foot of area, per °F of temperature difference between the inside and outside air.

Site energy vs

The difference between characterizing building energy demand using site energy or primary energy.

Gas-fired space heater

A space heater that uses gas as fuel for heating.

Electric resistance heating

A heating system that converts electricity to heat with 100% efficiency.

Power plant and grid losses

The energy losses that occur during the generation and transmission of electricity.

Efficiency

The measure of how effectively energy is used or converted into useful work.

R-value

The inverse of the U-value, used to describe the thermal resistance of a building component.

U-value

The inverse of the R-value, used to describe the rate of heat transfer through a building component.

Thermal resistance

The measure of a material's ability to resist heat flow, represented by the R-value.

Heat transfer mechanisms

The processes of radiation, convection, and conduction that contribute to heat transfer.

Conduction

The mode of heat transfer where heat flows through a material due to temperature differences.

Thermal conductivity

The proportionality constant that determines the rate of heat flow through a material.

R-value per inch

The measure of thermal resistance per inch thickness of a material.

Insulator

A material with a high R-value, which resists the flow of heat.

Convection

The mode of heat transfer where heat is transferred through a fluid (liquid or gas) by the movement of molecules.

Thermal mass

The ability of a material to absorb and store heat energy.

Heat flow

The transfer of thermal energy from a warmer object to a cooler object.

Surface temperature

The temperature of the surface of a material or object.

Thermal conductivity

The measure of a material's ability to conduct heat.

Homogeneous material

A material that has the same properties throughout its structure.

Thermal resistance

The measure of a material's ability to resist heat flow, represented by the R-value.

Convective heat transfer

The transfer of heat through the movement of air or fluid.

Conduction

The transfer of heat through direct contact between objects or substances.

Convection

The transfer of heat through the movement of air or fluid.

Radiation

The transfer of heat through electromagnetic waves, even in a vacuum.

Emissivity

The ability of a surface to emit thermal radiation.

Absorptivity

The ability of a surface to absorb thermal radiation.

Reflectance

The ability of a surface to reflect thermal radiation.

R-value

A measure of the resistance of a material to heat flow.

Rcvi

The combined convective-radiative R-value for indoor surfaces.

Rcvo

The combined convective-radiative R-value for outdoor surfaces.

Energy Efficiency

The practice of using less energy to achieve the same level of performance or output.

Heat Loss

The transfer of heat energy from a warmer object or space to a cooler object or space.

Windows

Openings in a building's walls that allow light and air to enter, and provide views to the outside.

Single-Pane Window

A window with only one sheet of glass, which is less energy efficient and loses more heat compared to double-pane windows.

Double-Glazing

Windows with two sheets of glass separated by an air or gas-filled gap, providing better insulation and reducing heat loss.

R-Value

A measure of the resistance of a material or assembly to heat flow, indicating its insulation effectiveness. Higher R-values indicate better insulation.

Low-E Coatings

Thin, transparent coatings applied to the glass surface of windows to reduce heat transfer and improve energy efficiency.

Argon and Krypton Gas Fillings

Filling the air gap between double-pane windows with low-conductivity gases like argon or krypton to further enhance insulation and improve the R-value.

Edge Effects

The cooling effect near the window frame that can reduce the overall insulation performance of windows.

Dew Point

The temperature at which air becomes saturated with moisture and condensation occurs.

Condensation

The process of water vapor turning into liquid when it comes into contact with a cold surface, such as a window, due to temperature differences.

Occupant Comfort

The level of satisfaction and well-being experienced by individuals in a building environment, influenced by factors such as temperature, humidity, and lighting.

R-value

A measure of the resistance of a material or assembly to heat flow, indicating its insulating effectiveness.

Window frame

The structural framework that holds the glass panes of a window in place.

Fiberglass frame

A window frame made of fiberglass material, which provides better insulation and increases the overall R-value of the window.

Aluminum frame

A window frame made of aluminum material, which has a lower R-value compared to fiberglass frames.

Cross-sections

Diagrams or illustrations showing a cutaway view of an object or structure.

High-performance windows

Windows designed to have superior energy efficiency, often featuring low-e coatings and krypton gas fillings.

Low-e coatings

Thin, transparent layers applied to window glass to reduce heat transfer and improve energy efficiency.

Krypton gas fillings

Filling the space between window panes with krypton gas, which has lower thermal conductivity than air, to enhance insulation.

Heat transfer pathways

The routes through which heat is transferred, such as through the window frame, the glass area near the frame, and the center-of-glass area.

Center-of-glass (COG) area

The central area of a window pane, typically used to measure the R-value.

Heat loss

The amount of heat that escapes from a building or structure.

Walls

Vertical structures that enclose and separate spaces within a building.

Ceilings

The upper interior surface of a room, often referred to as the "roof" of a room.

Floors

The lower surface of a room on which people walk.

Conduction paths

The pathways through which heat is conducted, such as through framing members and wall cavities.

Insulation

Material used to reduce heat transfer and improve energy efficiency by providing resistance to heat flow.

U-values

A measure of the rate of heat transfer through a material or assembly, indicating its thermal conductance.

Framing members

Structural components, usually made of wood, that form the framework of a wall.

Cavity area

The space between framing members in a wall, which can be filled with insulation.

Sheathing

Protective covering or layer applied to the inside and outside surfaces of a wall.

Framing factor

A factor that represents the proportion of framing area to the total wall area.

RAVG

Average R-value of a wall, calculated based on the U-values of framing and cavity areas.

Studs

Vertical framing members in a wall, typically made of wood or metal.

Rigid isocyanurate sheathing

A type of insulation board made from isocyanurate foam, used to provide additional insulation to the exterior side of a wall.

Solution Box

A section in the text that provides an example or solution to a problem discussed in the main content.

Ceilings and Roofs

The uppermost part of a building that protects the interior from heat loss and weather elements.

R-value

A measure of the thermal resistance of a material, indicating how well it insulates against heat transfer.

Heat loss rate

The amount of heat that escapes from a space over a given period of time.

Ventilated attic spaces

Attic spaces that have air circulation to prevent moisture buildup and improve energy efficiency.

Floors

The lower surface of a room that separates it from the ground or other levels of a building.

Crawl spaces

Enclosed areas beneath a building that provide access to utilities and allow for ventilation.

Basements

The lowest habitable level of a building, partially or entirely below ground level.

Slab-on-grade floors

Floors that are directly in contact with the ground, without a basement or crawl space.

Heat transfer

The movement of heat from one object or space to another.

Perimeter

The boundary or outer edge of a space or object.

Infiltration

The unintentional entry of outside air into a building through cracks, gaps, or openings.

Stack-driven infiltration

Infiltration caused by the difference in indoor and outdoor temperatures, resulting in air movement due to buoyancy.

Wind-driven infiltration

Infiltration caused by pressure differences created by wind blowing against the walls of a building.