Presentation on theme: "BEM class 3 Climate & Human Comfort. Class (lecture) objectives Appreciation of the indoor and outdoor environments and how they relate to our energy."— Presentation transcript:
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
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.
Comfort Conditions Temperature range 70 – 78 dF Humidity control – Psychrometrics Zoning for gain, loss and use factors The Psychrometric Chart
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
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.
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)
Thermal Lags Building dynamics, non-steady-state effects of “thermal mass” Most important as weather conditions swing daily Low- and High-Mass Constructions
Outdoor Conditions & Thermal Loads Thermal loads driven most significantly by outside TEMPERATURE 2 aspects: (1) Design - selection of mechanical equipment (2) Annual Energy Use
Outdoor Design Conditions for Heating & Cooling ASHRAE Handbook - Fundamentals (2013) AC SIZING ALSO REQUIRES CONSIDERATION OF HUMIDITY, SOLAR GAIN AND INTERNAL GAINS So now, for NYC you have heating design delta-T of 74 – 17 = 57 dF.
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 Hensen ch 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
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.