Thermal

Question 1

Balance point

Answer 1

The temperature at which a building needs inside cooling above, or inside heating below.

Question 2

Skin-loaded buildings

Answer 2

Buildings that lose and gain heat more readily through their exterior skin, resulting in a higher balance point.

Question 3

Internally-loaded buildings

Answer 3

Buildings that generate a significant amount of heat inside from people, lights, and equipment, resulting in a lower balance point.

Question 4

Heating Degree Days

Answer 4

Sum of the absolute difference between the average daily temperature and a base temperature over time to estimate heating energy.

Question 5

Cooling Degree Days

Answer 5

Sum of the absolute difference between the average daily temperature and a base temperature over time to estimate cooling energy.

Question 6

Psychrometry

Answer 6

The study of the thermodynamic properties of moist air.

Question 7

Psychrometric chart

Answer 7

A graphical representation of the physical properties of moist air at a constant pressure used in HVAC design.

Question 8

Sensible heat

Answer 8

Heat that changes the temperature of a substance without a phase change

Question 9

Latent heat

Answer 9

Hidden heat that is released or absorbed during a state change

Question 10

Relative humidity

Answer 10

The amount of water vapor actually in the air divided by the maximum amount of water vapor the air can hold at that specific temperature.

Question 11

Dew point / saturation point

Answer 11

The point at which there is 100% relative humidity.

Question 12

Enthalpy / Total heat

Answer 12

The total heat content of an air-water vapor mixture.

Question 13

Enthalpy line

Answer 13

A line on a psychrometric chart showing processes where the total heat content remains constant.

Question 14

Wet Bulb Temperature

Answer 14

Accounts for latent heat and is measured by a thermometer with a bulb covered in a water-soaked wick.

Question 15

Dry Bulb Temperature

Answer 15

Does not account for moisture in the air (latent heat).

Question 16

BTU (British Thermal Units)

Answer 16

Heat required to move 1 LB of water by 1 degree Fahrenheit.

Question 17

Absolute Humidity

Answer 17

The mass of water vapor present in a unit volume of air.

Question 18

Condensation

Answer 18

When warm, humid air cools and loses moisture to surfaces. Condensation releases heat.

Question 19

Adiabatic shift

Answer 19

Temperature change in a gas due to expansion or compression without heat exchange.

Question 20

Phase Change

Answer 20

Transitioning between states, which takes a ton of energy (latent heat).

Question 21

Solar Heat Gain Coefficient (SHGC)

Answer 21

Fraction of solar radiation that goes through a window (between 0 and 1).

Question 22

Solar Insolation

Answer 22

Radiant energy per square foot of the sun.

Question 23

Emissivity

Answer 23

How much energy is transferred through glass, or the property of a material to emit energy as radiation.

Question 24

Conductivity

Answer 24

k value. How quickly energy moves through a 1” thick, 1 ft x 1 ft homogenous material.

Question 25

Conductance

Answer 25

C value: k-value divided by thickness.

Question 26

Resistivity

Answer 26

r value: The inverse of conductivity per inch (1/k).

Question 27

Thermal Resistance

Answer 27

R-value: r multiplied by thickness. Inverse of Conductance.

Question 28

Overall Heat Transfer Coefficient

Answer 28

U value: Reciprocal of the total R of the assembly.

Question 29

Outdoor design temp

Answer 29

The temperature you design the building for.

Question 30

Air gap

Answer 30

An airspace that adds an R value of about 1 to an assembly. An air gap of at least 0.5” and less than 4” inches adds an R value of about 1 to an assembly (larger gaps allow a convective loop and aren’t helpful).

Question 31

Air film

Answer 31

Air that catches on a surface that’s not smooth on a molecular level. Air film on the interior surface of smooth gyp may be about 0.7. On exterior, it’s about 0.2

Question 32

ACH (Air Changes Per Hour)

Answer 32

A measure of the air volume exchanged in a space per hour.

Question 33

Solar radiation

Answer 33

Heating through electromagnetic waves from the sun. (Instant, while insolation is cumulative over a period)

Question 34

Humidity

Answer 34

Moisture content in the air.

Question 35

Thermal bridge

Answer 35

When structure crosses the insulation, making the insulation non-continuous.

Question 36

Thermal break

Answer 36

Low-conductive material (like insulation) inserted between conductive building components to interrupt thermal energy flow (resolving or mitigating a thermal bridge)

Question 37

Convection

Answer 37

Heating gas (including air) through the movement of fluid/air currents.

Question 38

Conduction

Answer 38

Heating through solids by direct molecular contact.

Question 39

Radiation

Answer 39

Heating through electromagnetic waves.

Question 40

Absorptivity

Answer 40

The property where dark and matte materials absorb more radiation.

Question 41

Delete

Answer 41

How readily energy exchanges between materials.

Question 42

Thermal mass

Answer 42

Higher mass means more energy can be stored to temper temperature swings.

Question 43

Mean Radiant Temperature (MRT)

Answer 43

The weighted average temperature of all surrounding surfaces (walls, ceiling, floor, windows) in an environment, representing the total radiative heat exchange between an occupant and their surroundings

Question 44

Vapor Barrier (Vapor Retarder)

Answer 44

A material or system used to slow or prevent the diffusion of water vapor.

Question 45

Vapor Permeance

Answer 45

The property of a material to allow water vapor to pass through it, measured in perms.

Question 46

Weather Barrier (WRB)

Answer 46

A material or system applied to prevent liquid water from penetrating the wall assembly.

Question 47

Thermal Lag

Answer 47

The time delay between when heat energy enters a material and when it is released. Greater lag is one of the benefits of greater thermal mass.

Question 48

Infiltration

Answer 48

Uncontrolled air leakage into or out of a building.

Question 49

Ventilation

Answer 49

Intentional introduction of outside air into a building.

Question 50

Comfort Zone

Answer 50

The area on the psychrometric chart representing temperatures and humidity levels where most people feel comfortable.