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BEM class 3 Climate & Human Comfort

BEM class 3 Climate & Human Comfort. Class (lecture) objectives. Appreciation of the indoor and outdoor environments and how they relate to our energy models Understand design decisions in selecting conditions

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BEM class 3 Climate & Human Comfort

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  1. BEM class 3Climate & Human Comfort

  2. Class (lecture) objectives • Appreciation of the indoor and outdoor environments and how they relate to our energy models • Understand design decisions in selecting conditions • Know key terminology and manual methods for annual weather normalization and energy use

  3. Human Comfort in the Indoor Environment • ASHRAE Std. 55 (-2013) “Thermal Environmental Conditions for Human Occupancy” • Heat Exchange at the Human Body boundary • Sensitivity to air temperature, surface (radiant) temperatures, humidity, air movement • Dependence on clothing, activity. Role of culture and expectations.

  4. Comfort Conditions • Temperature range • 70 – 78 dF • Humidity control – Psychrometrics • Zoning for gain, loss and use factors The Psychrometric Chart

  5. Comfort Conditions – Psychrometric Chart • Dry bulb (db) temperature • Absolute humidity • Dew point • Wet bulb (wb) temperature • Relative humidity From Tao & Janis Mechanical and Electrical Systems in Buildings

  6. Interior Air Movement • Evaporative effects of air movement • HVAC System Effectiveness • ASHRAE 62 (2013) Ventilation for Acceptable Indoor Air Quality • Different types of air distribution systems • Air distribution under varying conditions • Short-circuits. Stratification. • "droop" at low flows in variable volume systems. • Use of CFD.

  7. Radiant Heat Effects • Comfort / Discomfort from building surfaces • Especially important in all-glass buildings. Why? • Function of distance and angle from warm or cold surface Calculating MRT (Mean Radiant Temperature)

  8. Thermal Lags Low- and High-Mass Constructions • Building dynamics, non-steady-state effects of “thermal mass” • Most important as weather conditions swing daily

  9. Outdoor Conditions & Thermal Loads • Thermal loads driven most significantly by outside TEMPERATURE • 2 aspects: • (1) Design - selection of mechanical equipment • (2) Annual Energy Use

  10. Outdoor Design Conditions for Heating & CoolingASHRAE Handbook - Fundamentals (2013) So now, for NYC you have heating design delta-T of 74 – 17 = 57 dF. AC SIZING ALSO REQUIRES CONSIDERATION OF HUMIDITY, SOLAR GAIN AND INTERNAL GAINS

  11. From Peak (design) to Annual – how hot/cold over time? • Hourly outdoor temperatures – recorded by US Weather Service • Manual Methods • Bin data – hourly occurrences in 5-degree “bins” (see next slide) • Degree-days – reported in newspapers on running daily basis • Weather “Tapes” for use in models • Typical Meteorological Year (TMY) (see Hensench 3) HDD: 65 – daily avg temp eg – high 25 low 15 avg 20 HDD= 45 CDD: daily avg temp – 65 eg – high 90 low 70 avg 80 CDD = 15

  12. Sample Bin Data

  13. Weather & Climate • Not the same - • Weather is highly variable. Climate shows patterns over time. • What does climatic variation say to us about our design-conditions? • Climate “regions” or “zones” • Comparison issues. Normalize by DD? • “Design-for-climate” approaches. • Resilience and climate adaptation.

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