BIM Energy Design Glossary
Building Physics
Illuminance Simulations
Illuminance Analysis
Beer-Lambert Law of Transmission
Fresnel Equation for reflection and refraction of light at a uniform plane interface
Fresnel Equations
Also known as Beer’s Law, Lambert-Beer Law, or Bouguer-Lambert-Beer Law, this fundamental principle describes how light is absorbed as it passes through a medium.
Reflectivity
Reflection Coefficient
Specular Reflectivity
Specular Reflection Coefficient
Diffuse Reflectivity
Diffuse Reflectance Coefficient
Luminous Flux
Luminous flux represents the power of light perceived by the human eye.
Daylight Factor
Daylighting Coefficient
Equinox
The Equinox marks the time of equal day and night, occurring in spring (Spring Equinox) or autumn (Autumn Equinox).
Irradiance
Irradiance
DNI (Direct Normal Irradiance)
Direct solar radiation received per unit area.
DHI (Diffuse Horizontal Irradiance)
Diffuse solar radiation on a horizontal surface.
Energy Saving Calculations
1 kWh = 3.6 MJ
1 KBTU/SQFT-YR = 3.152480 kWh/m²
Lettable Floor Area (Rental Area)
DHW: Domestic Hot Water for household use.
COP (Coefficient of Performance): The refrigeration coefficient indicating the cooling output per unit of power consumed.
EER (Energy Efficiency Ratio): This ratio measures an air conditioner’s cooling efficiency, representing the cooling capacity per unit of power consumption. A higher EER means more heat is removed using less electricity, leading to lower operational costs.
The formula for EER is: EER = cooling capacity / cooling power consumption.
CIBSE — Chartered Institution of Building Services Engineers
CEI (Climate Energy Index) (per m³/hr)
HDD (Heating Degree Days): This index measures the degree of coldness by comparing the daily average temperature with 65°F, indicating the heating demand. It is calculated as: HDD = max(0, 65°F – daily average temperature). For example, if the daily average temperature is 40°F, HDD is 25; if it is 67°F, HDD is 0.
The CME HDD index accumulates daily HDD over a month, with each point valued at $100 at settlement. For example, if the daily average HDD in November is 25, over 30 days this totals 750 HDD points, representing a futures contract nominal value of $75,000 (750 × $100).
CDD (Cooling Degree Days): This index measures the degree of warmth by comparing the daily average temperature with 65°F, indicating cooling demand. It is calculated as: CDD = max(0, daily average temperature – 65°F). For instance, if the daily average temperature is 75°F, CDD is 10; if it is 58°F, CDD is 0.
Notes for Building a Basement in IESVE:
- Define the average soil temperature around the basement; do not use outside air temperature.
- Add a thicker soil layer to the outermost layer of the basement enclosure to accurately simulate heat transfer between soil and basement.
Distinguishing Between Finite Difference Method, Finite Volume Method, and Finite Element Method:
Finite Difference Method (FDM): This method is intuitive and theoretically well-established, offering adjustable accuracy. Handling irregular domains is challenging, and although grid generation can extend FDM to irregular areas, it requires strict continuity conditions. The main advantages are ease of programming and parallelization.
Finite Element Method (FEM): Well-suited for complex geometries with adjustable accuracy. Its drawbacks include high memory and computational demands. Parallelization is less straightforward compared to FDM and FVM, but ongoing developments make FEM parallelism a promising direction.
Finite Volume Method (FVM): Ideal for fluid dynamics, applicable to irregular grids, and supports parallel computation. Its accuracy is generally limited to second order. However, FVM’s strengths are increasingly recognized, especially in stress-strain analyses and high-frequency electromagnetic field simulations.
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