Final CME 305

Definitions for CME 305 Final Exam Topics

1. Heat Loss Due to Transmission

Heat loss due to transmission refers to the transfer of heat through building envelopes, such as walls, roofs, and floors. This loss can occur due to differences in temperature between the inside and outside environments.

2. Heat Transfer by Convection, Conduction, and Radiation

  • Convection: Transfer of heat through the movement of fluids (liquids or gases). Example: Warm air rising and cool air descending.

  • Conduction: Direct transfer of heat through a material due to temperature difference. Example: Heat moving through a metal rod.

  • Radiation: Transfer of heat through electromagnetic waves. Example: Heat from the sun warming your skin.

3. Calculating Energy and Power for Heat Loss (q and Q)

  • q (heat transfer rate): Amount of heat transferred per unit time (W or Btu/hr).

  • Q (energy): Total amount of heat transferred over time (J or kWh).

4. Insulation

  • Cavity vs. Assembly Values:

    • Cavity Value: R-value of insulation within the cavity of a building component, like a wall.

    • Assembly Value: Overall R-value of the entire building assembly, including insulation, framing, and other components.

  • Proper Installation: Ensuring that insulation is installed without gaps, voids, or compression to maximize its effectiveness.

  • Types – Advantages and Disadvantages:

    • Fiberglass: Inexpensive, easy to install, but can irritate skin and lungs.

    • Spray Foam: High R-value, air barrier, but more expensive and requires professional installation.

    • Cellulose: Made from recycled materials, good air sealing, but can settle over time.

  • Types – Cost Differentials: Different insulation types vary in cost, with spray foam generally being more expensive than fiberglass or cellulose.

  • Types – Embodied Carbon Differences: Refers to the total carbon emissions associated with the production, transportation, and installation of the insulation materials.

5. Windows and Doors (Fenestration)

  • Ratings (U-value): Measure of heat transfer through windows and doors. Lower U-value indicates better insulating properties.

  • Technologies: Various technologies like double/triple glazing, low-emissivity (Low-E) coatings, and gas fills between panes.

  • Relative Performance Compared to Opaque Walls: Windows and doors generally have higher U-values (poorer insulating properties) compared to insulated walls.

6. Lighting, Appliances, and DHW

  • Lighting Technologies: Different types such as incandescent, fluorescent, LED, and their qualities like color temperature and efficacy (lumens per watt).

  • Energy Star: A government-backed symbol for energy efficiency, providing simple, credible, and unbiased information that consumers and businesses rely on to make well-informed decisions.

  • Types of DHW Losses:

    • Standby Losses: Heat lost from the water heater tank to the surrounding environment.

    • Distribution Losses: Heat lost as hot water travels through pipes.

    • Demand Losses: Heat lost while waiting for hot water to reach the tap.

Equations:



q =U x A x ΔT 


Q = U x A x HDD x 24