Course Description

Thermal comfort is not simply "the air temperature is 22 degrees." ASHRAE Standard 55 defines it as "that condition of mind which expresses satisfaction with the thermal environment." Notice the phrasing: condition of mind. This is deliberately psychological. Two people can sit in the same room at the same measured temperature, and one will be comfortable while the other is miserable. That is not a malfunction of the HVAC system; it is a demonstration that comfort is subjective. However, as engineers, we cannot design for every individual. So we design for the average occupant, using statistical models that predict satisfaction for 80 percent of people in a given space. Thermal dissatisfaction can come from whole-body sensations - feeling generally too hot or too cold - or from local discomfort: a draft on the neck, cold feet, a warm head, or one side of the body being warmer than the other. A critically important insight is that a building can meet every temperature setpoint on the thermostat and still feel uncomfortable. I have personally commissioned buildings where the temperature log was perfect, but occupants were furious. The problem was radiant asymmetry from uninsulated windows, or high humidity that made the air feel heavy, or air movement that was too low to provide any cooling effect. That is why we must use objective metrics like PMV, not just thermostat readings. Engineers who ignore the six factors and focus only on dry-bulb temperature are building complaints into their designs from day one.

What you'll learn in this course?

• Define thermal comfort and list the six primary factors that influence human comfort in indoor environments according to ASHRAE Standard 55.

• Interpret a standard psychrometric chart and correctly identify dry-bulb temperature, wet-bulb temperature, dew point, relative humidity, humidity ratio, and specific enthalpy.

• Apply at least 10 essential thumb rules for comfort HVAC design, including recommended temperature ranges, humidity limits, air movement criteria, and supply air conditions.

• Analyze common thermal comfort complaints (too cold, too hot, drafty, sticky, dry) and map each one to a specific psychrometric correction strategy.

• Solve practical HVAC problems using psychrometric processes including sensible cooling, sensible heating, humidification, dehumidification, and adiabatic mixing.

• Complete a 20-question multiple-choice assessment with 80% accuracy to verify CPD learning outcomes.

Prerequisites

• Basic knowledge of HVAC systems, temperature, humidity, and engineering units

• Familiarity with building comfort and air-conditioning terminology is helpful