Building Technology 2: Thermal Comfort Week 6

Building Technology 2: Mechanical & Safety Systems - Week 6

• Course: INTD 3007
• Instructor: Claudina Sula
• Week: 6
• Topic: Thermal Comfort & Air Quality

Thermal Comfort & Air Quality

• The topic is about creating comfortable interior spaces using HVAC systems
• Heating is governed by OBC (Office Building Code)
• Key reading material: Binggeli, chapters 12-14
• Includes principles of:
  • Thermal comfort
  • Heat transfer in buildings
  • Humidity
  • Indoor air quality

What is Thermal Comfort?

• Thermal comfort involves providing and achieving satisfaction with save and comfortable interior environments for human beings.
• It is about the provision of a stable, normal body temperature that results in satisfying the environment.
• This is subjective and assessed through evaluation (ANSI/ASHRAE Standard 55).

Thermal Comfort Factors - Personal Factors

• Occupants need to be considered for proper thermal comfort
• These factors include:
  • Metabolic rate
  • Clothing levels
  • Activity levels
  • Age
  • Gender
  • Adaptation
  • Circadian rhythms
  • Cultural influences
  • Stress level

Thermal Comfort Factors - Environmental Factors

• Factors relating to the thermal environment include:
  • Air temperature
  • Temperature of surrounding surfaces (mean radiant temperature)
  • Humidity levels
  • Air movement (natural ventilation)
  • Non-uniformity of environment
• Standards usually refer to a steady state to study thermal comfort, and accommodate limited temperature variations.

Thermal Comfort Standards

• CBE Thermal Comfort Tool: can be used to calculate comfort according to standards such as ANSI/ASHRAE Standard 55, EN 15251, and ISO 7730.

Thermal Comfort Conditions

• There is a range of variability in thermal comfort based on physiological and psychological factors.
• Lab and field data are used to define optimal conditions for a specified percentage of occupants.

Bioclimatic Design

• An integrated approach to architectural regionalism.
• Integrates design and performance architecture.
• Employs natural energies to harmonize buildings with their local conditions, including solar radiation and wind convection.
• Revolves around four interconnecting circles: Biology, Climatology, Technology, and Architecture

Thermal Comfort - Bioclimatic Index

• Bioclimatic diagram: based on maximum and minimum average registers, minimum and maximum average of dry bulb temperature and relative humidity.
• Important to consider the 'comfort zone' versus 'comfort point' to create a space conducive for thermal satisfaction for many people.

Thermal Comfort Values

• The suitable temperature range for human occupancy is 15 °C (59 °F) to 25 °C (77 °F).
• Factors such as humidity, air circulation, can influence and extend this range.
• Winter comfort temperature: 20-24 °C (68-75.2 °F)
• Summer comfort temperature: 23-26 °C (73.4-78.8 °F)

How to convert Celsius to Fahrenheit

• °C to °F Conversion: T(°F) = T(°C) × 1.8 + 32

Human Comfort: Natural vs Mechanical

• Proper thermal comfort is supported by proper HVAC systems (Heating, Ventilation, and Air Conditioning) in interior spaces and protects structures and contents.
• HVAC system design is not enough for comfort, and material selection & space planning are also key to comfort.

Principles of Heat Transfer

• Heat always moves from warmer to cooler spaces or surfaces.
• Thermal equilibrium occurs when there is no temperature difference between adjacent spaces or surfaces.
• The greater the temperature difference, the faster heat moves.

Heat Transfer Methods

• Heat transfer occurs in various ways including conduction, convection, and radiation.

Heat Transfer Methods - Conduction

• Heat transfer through physical contact between molecules, surfaces.

Heat Transfer Methods - Radiation

• Heat transfer without direct contact through electromagnetic waves.
• Example of the heat reaching Earth from the Sun.

Heat Transfer Methods - Convection

• Heat transfer through the movement of fluids (air).

Heat Transfer - Terminologies

• Thermal capacity: ability of a material to store heat, proportional to mass.
• Thermal resistance: opposite concept to thermal capacity, materials with higher thermal resistance result in slower heat loss.
• R-value: a measure of thermal resistance, higher value means greater heat resistance of that material.

Thermal Comfort - Humidity

• High humidity can cause issues in the interior environment, including mold growth and warping of materials, and irritation to occupants.
• Low humidity can cause dry skin, nose, and throat irritation, and discomfort for occupants.

Indoor Air - Introduction

• Most of human time is spent indoors.
• Indoor Environments are susceptible to a wide array of air pollutants typically emitted from building products, equipment and cleaning products.
• Limiting sources, moisture control, and proper ventilation are important for healthy indoor environments.

Indoor Air Quality

• Consideration of indoor air quality is increasing due to tightly controlled building environments.
• Presence of indoor air pollution sources, poorly designed ventilation, and unanticipated uses of buildings contribute to poor IAQ.
• Designing for good IAQ involves selecting materials and equipment that limit pollution, isolating unavoidable sources, and using effective ventilation/filtration/cleaning systems of the built environment.

Indoor Air Quality - Illnesses

• Poor IAQ can lead to illnesses.
• Building codes are balancing energy efficiency needs with good IAQ.

Indoor Air Quality - Sources of Pollution

• Key indoor pollutants include carbon dioxide, carbon monoxide, ozone, VOC's, some bacteria and fungi, including radon.
• Control strategies for each type of indoor air pollution are recommended.

Indoor Air Quality - Volatile Organic Compounds (VOCs)

• VOCs are chemical compounds that evaporate from surfaces at room temperature.
• They are off-gassed by various materials.
• VOC levels can increase in places where new furnishings, materials, etc., have been installed.

Indoor Air Quality - Equipment

• HVAC systems are crucial in managing indoor air quality.
• Air cleaning equipment, such as filters, cleans and efficiently circulates air.
• Appropriate equipment size matches the size of the building/space.

Relevant Resources

• Relevant external website resources for further research.