Thermal Comfort and Cooling System Design: Bridging Theory and Application

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Thermal comfort is a fundamental consideration in building design that directly influences occupant well-being, productivity, and overall satisfaction with indoor environments. Achieving optimal thermal comfort requires a sophisticated understanding of human physiology, environmental parameters, and the cooling systems designed to maintain ideal conditions. This comprehensive guide explores the intricate relationship between thermal comfort principles and cooling system design, providing insights into how theory translates into practical application for creating healthier, more efficient built environments.

Understanding Thermal Comfort: The Foundation of Indoor Environmental Quality

Thermal comfort is defined as “that condition of mind that expresses satisfaction with the thermal environment” in the globally recognized ASHRAE 55 and ISO 7730 standards for evaluating indoor environments. This definition acknowledges that thermal comfort is inherently subjective, representing a psychological state influenced by multiple physiological and environmental factors. Understanding these factors is essential for designing cooling systems that effectively serve building occupants.

The Six Primary Factors Affecting Thermal Comfort

Thermal comfort depends on a complex interplay of six key variables, which can be categorized into environmental and personal factors. The calculation involves four environmental factors (air temperature, mean radiant temperature, air velocity and relative humidity) and two personal factors (clothing insulation and metabolic rate).

Environmental Factors:

  • Air Temperature: The dry-bulb temperature of the surrounding air, which represents the most commonly measured thermal parameter in buildings.
  • Mean Radiant Temperature (MRT): The weighted average temperature of all surrounding surfaces, accounting for radiant heat exchange between the occupant and their environment.
  • Air Velocity: The speed of air movement, which affects convective heat loss from the body and can significantly influence thermal sensation.
  • Relative Humidity: The moisture content of air, which impacts the body’s ability to cool itself through evaporative processes.

Personal Factors:

  • Clothing Insulation: Measured in “clo” units, this factor accounts for the thermal resistance provided by garments worn by occupants.
  • Metabolic Rate: Measured in “met” units, this represents the heat generated by the human body during various activities, from sedentary work to vigorous exercise.

The air temperature and mean radiant temperature are often combined to determine the operative temperature, which better represents what humans actually feel. Air velocity affects heat loss through convection, while relative humidity impacts evaporative cooling from the skin.

The Science of Heat Balance and Thermal Equilibrium

Thermal equilibrium is obtained when an occupant’s internal heat production is the same as its heat loss. The human body continuously generates heat through metabolic processes and must dissipate this heat to maintain a stable core temperature. When the environment prevents adequate heat dissipation, occupants feel too warm; conversely, when heat loss exceeds production, they feel too cold.

The human body can be viewed as a heat engine where food is the input energy. The human body will release excess heat into the environment, so the body can continue to operate. The heat transfer is proportional to temperature difference. This fundamental principle underlies all thermal comfort calculations and cooling system design strategies.

Thermal Comfort Indices: PMV and PPD Models

To quantify thermal comfort and guide HVAC design decisions, engineers rely on standardized indices that predict occupant satisfaction under various conditions. The most widely used models are the Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD) indices.

Predicted Mean Vote (PMV)

PMV predicts the average thermal sensation of a large group of people on a seven-point scale from −3 (very cold) to +3 (very hot), with 0 representing thermal neutrality. The Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD) are the standard indices for evaluating thermal comfort in indoor environments. Developed by P.O. Fanger and codified in ISO 7730 and ASHRAE Standard 55, they allow HVAC engineers to quantify how a given combination of environmental conditions and occupant characteristics translates into thermal sensation.

In order to comply with ASHRAE 55, the recommended thermal limit on the 7-point scale of PMV is between -0.5 and 0.5. This range represents conditions where the majority of occupants will find the environment thermally acceptable, though it’s important to recognize that individual variations mean universal satisfaction is impossible to achieve.

Predicted Percentage of Dissatisfied (PPD)

PPD estimates the fraction of occupants who would find the thermal environment unacceptable. Even under ideal conditions (PMV = 0) approximately 5 % of people will still feel too warm or too cold — individual variation makes it impossible to satisfy everyone. This inherent limitation reflects the diversity of human thermal perception and physiological responses.

As PMV deviates from zero in either direction, PPD rises steeply: at PMV = ±1.0 about 25 % are dissatisfied, and at PMV = ±2.0 the figure reaches approximately 75 %. In order for comfort ranges to comply with standards, no occupied point in space should be above 20% PPD. All occupied areas in a space should be kept below 20% PPD in order to ensure thermal comfort according to the known standards (ASHRAE 55 and ISO 7730).

Practical Application and Limitations of PMV-PPD Models

In practice, achieving a PMV between −0.5 and +0.5 (PPD < 10 %) not only improves occupant satisfaction but also enhances productivity, reduces absenteeism and helps avoid energy waste from over-conditioning the space. These criteria are embedded in international standards including ISO 7730 and ASHRAE 55, making them essential tools for architects, HVAC engineers and facility managers.

However, it’s important to acknowledge the limitations of these models. The PMV/PPD model has a low prediction accuracy. Using the world largest thermal comfort field survey database, the accuracy of PMV in predicting occupant’s thermal sensation was only 34%, meaning that the thermal sensation is correctly predicted one out of three times. The PMV/PPD accuracy varies strongly between ventilation strategies, building types and climates.

The Adaptive Comfort Model

The adaptive model, on the other hand, was developed based on hundreds of field studies with the idea that occupants dynamically interact with their environment. Occupants control their thermal environment by means of clothing, operable windows, fans, personal heaters, and sun shades. This model recognizes that people in naturally ventilated buildings often accept and adapt to a wider range of temperatures than the PMV model would predict.

The PMV model can be applied to air-conditioned buildings, while the adaptive model can be applied only to buildings where no mechanical systems have been installed. There is no consensus about which comfort model should be applied for buildings that are partially air-conditioned spatially or temporally. This distinction is crucial for designers selecting appropriate comfort criteria for different building types.

Principles of Effective Cooling System Design

Designing cooling systems that achieve thermal comfort while optimizing energy efficiency requires a systematic approach grounded in engineering fundamentals and industry best practices. The design process encompasses multiple stages, from initial load calculations to equipment selection and system configuration.

Load Calculation: The Foundation of System Sizing

The first step in designing an HVAC system is determining the heating and cooling load required to maintain a comfortable interior environment. A load calculation considers several factors, including the size and orientation of the building, the number of occupants, the amount of insulation, and the type of windows and doors. This information determines the heating or cooling required to maintain a comfortable indoor temperature.

Completing an accurate load calculation to right-size equipment is critical. Too often designers are tempted to add multiple safety factors, causing the equipment to be oversized and operate poorly. Oversized systems cycle on and off frequently, reducing efficiency, increasing wear on components, and failing to adequately control humidity levels.

Design cooling load takes into account all the loads experienced by a building under a specific set of assumed conditions. These assumptions include weather conditions selected from statistical databases, full design occupancy, maximum ventilation rates, and typical operation of lights and appliances. Both sensible and latent loads must be considered to ensure proper temperature and humidity control.

Equipment Selection and Sizing

Once the load calculation is complete, selecting the appropriate heating and cooling equipment is next. The equipment must be properly sized to ensure optimal performance and energy efficiency. The selection process involves considering several factors, including the system’s SEER (seasonal energy efficiency ratio) rating, the type of fuel used (e.g., electricity, natural gas, or propane), and the system’s airflow requirements.

According to the National Institute of Building Sciences, the use of high-performance HVAC equipment can reduce energy, emissions, and costs anywhere from 10 to 40 percent. This significant potential for savings underscores the importance of selecting efficient equipment that matches the building’s actual needs.

Distribution System Design

The final step in the design process is to design the ductwork that will distribute heated or cooled air throughout the building. The ductwork must be properly sized and designed to ensure air flows smoothly and efficiently. Ductwork design considers several factors, including the size and layout of the building, the type of heating and cooling equipment, and the required airflow rate.

Every additional bend and turn in ductwork and piping requires more energy from the pump or fan. This is especially true immediately downstream of any fan or pump, where the effect of a turn can result in 10 times or greater drop in pressure. Minimizing pressure drops through careful layout planning is essential for energy-efficient operation.

Thermal Zoning Strategies

Thermal zoning is a method of designing and controlling the HVAC system so that occupied areas can be maintained at a different temperature than unoccupied areas using independent setback thermostats. A zone is defined as a space or group of spaces in a building having similar heating and cooling requirements throughout its occupied area so that comfort conditions may be controlled by a single thermostat.

Proper zoning allows different areas of a building to be conditioned according to their specific needs, accounting for variations in solar exposure, occupancy patterns, internal heat gains, and usage schedules. This targeted approach improves both comfort and energy efficiency compared to treating an entire building as a single zone.

Types of Cooling Systems: Technologies and Applications

Modern buildings employ a diverse array of cooling technologies, each with distinct characteristics, advantages, and ideal applications. Understanding these options enables designers to select the most appropriate system for specific building types, climates, and performance requirements.

Central Air Conditioning Systems

Central air conditioning systems are among the most common cooling solutions for large buildings and homes. These systems use a network of ducts to distribute cooled air throughout a building. A central unit, typically located outside, houses the compressor, condenser, and evaporator. The system circulates refrigerant to absorb heat from indoor air, which is then expelled outdoors.

Central systems are highly effective for cooling multiple rooms or large spaces and offer precise temperature control. However, they require significant installation and maintenance efforts due to their ductwork and complex components. Central systems are particularly well-suited for new construction where ductwork can be integrated into the building design from the outset.

Split Systems and Ductless Mini-Splits

Split air conditioning systems divide the cooling equipment into indoor and outdoor components connected by refrigerant lines. The outdoor unit contains the compressor and condenser, while the indoor unit houses the evaporator and air handler. This configuration offers flexibility in placement and can serve single rooms or multiple zones.

Ductless mini-split systems are an alternative to central air conditioning, ideal for homes or buildings without ductwork. These systems provide individual zone control, allowing different areas to be maintained at different temperatures according to occupant preferences and usage patterns. They’re particularly valuable for retrofitting older buildings or adding cooling to specific areas without extensive ductwork installation.

Evaporative Cooling Systems

Evaporative coolers, also known as swamp coolers, use the principle of water evaporation to cool air. These systems draw warm air through water-saturated pads, where the air is cooled by evaporation before being circulated into the space.

Evaporative coolers are energy-efficient and environmentally friendly, as they use minimal electricity and no refrigerants. However, they are most effective in dry climates and may increase indoor humidity, making them unsuitable for humid regions. In appropriate climates, evaporative cooling can provide substantial energy savings compared to conventional refrigeration-based systems, sometimes reducing cooling energy consumption by 75% or more.

Chilled Water Systems

Chilled water systems are commonly used in large commercial or industrial buildings. These systems use a chiller to cool water, which is then circulated through coils in air-handling units or fan-coil units to absorb heat from indoor air. Chilled water systems are highly efficient for large-scale cooling and can be integrated with other HVAC components for comprehensive climate control.

These systems offer several advantages for large buildings, including centralized equipment that simplifies maintenance, the ability to serve multiple buildings from a central plant, and excellent load-matching capabilities through variable-speed pumping and staging of multiple chillers. The water distribution system also requires less space than equivalent ductwork for air distribution.

Radiant Cooling Systems

Radiant cooling systems represent an innovative approach that conditions spaces primarily through radiant heat exchange rather than air movement. These systems typically circulate chilled water through panels installed in ceilings, floors, or walls. The cool surfaces absorb radiant heat from occupants and other heat sources, creating a comfortable environment with minimal air movement.

Radiant cooling offers several benefits including silent operation, no drafts, reduced air distribution requirements, and the potential for high energy efficiency when combined with appropriate control strategies. However, these systems require careful design to prevent condensation on cool surfaces and work best when paired with a separate ventilation system to manage humidity and provide fresh air.

Passive Cooling Techniques

Passive cooling strategies leverage natural phenomena and building design features to reduce or eliminate the need for mechanical cooling. These techniques include:

  • Natural Ventilation: Using operable windows, vents, and building orientation to promote air movement and heat removal through stack effect and cross-ventilation.
  • Thermal Mass: Incorporating materials with high heat capacity that absorb heat during the day and release it at night when temperatures drop.
  • Solar Shading: Employing overhangs, louvers, vegetation, and other shading devices to prevent solar heat gain through windows and building surfaces.
  • Cool Roofs: Using reflective roofing materials to minimize solar heat absorption and reduce cooling loads.
  • Night Cooling: Ventilating buildings with cool outdoor air during nighttime hours to purge accumulated heat.

While passive cooling alone may not provide complete thermal comfort in all climates and building types, integrating passive strategies with mechanical systems can significantly reduce energy consumption and peak cooling loads.

Design Conditions and Climate Considerations

The desirable ranges of temperatures, humidities, and ventilation rates (the thermal comfort zone) discussed earlier constitute the typical indoor design conditions, and they remain fairly constant. For example, the recommended indoor temperature for general comfort heating is 22ºC (or 72ºF).

The outdoor conditions at a location, on the other hand, vary greatly from year to year, month to month, and even hour to hour. The set of extreme outdoor conditions under which a heating or cooling system must be able to maintain a building at the indoor design conditions is called the outdoor design conditions.

Balancing Economics and Comfort

Sizing an HVAC system on the basis of the most extreme weather on record is not practical since such an oversized system will have a higher initial cost, will occupy more space, and will probably have a higher operating cost because the equipment in this case will run at partial load most of time and thus at a lower efficiency. Most people would not mind experiencing an occasional slight discomfort under extreme weather conditions if it means a significant reduction in the initial and operating costs of the heating or cooling system.

Industry standards typically recommend designing cooling systems based on conditions that will be exceeded a certain percentage of the time rather than absolute extremes. For example, using the 1% or 2.5% design conditions means the system is sized for temperatures that are exceeded only 1% or 2.5% of the hours during the cooling season. This approach balances initial cost, operating efficiency, and occupant comfort.

Energy Efficiency and Sustainability in Cooling Design

As energy costs rise and environmental concerns intensify, designing cooling systems for maximum efficiency has become a critical priority. Modern cooling system design must balance thermal comfort with energy conservation and environmental responsibility.

High-Efficiency Equipment Selection

Selecting equipment with high efficiency ratings is fundamental to reducing energy consumption. For air conditioning systems, the Seasonal Energy Efficiency Ratio (SEER) indicates cooling efficiency over an entire season. Higher SEER ratings indicate better efficiency, with modern high-efficiency units achieving SEER ratings of 20 or higher compared to minimum standards of 13-14 SEER.

For chilled water systems, chiller efficiency is measured by kilowatts per ton (kW/ton) or Coefficient of Performance (COP). Variable-speed compressors, advanced refrigerants, and optimized heat exchangers contribute to improved chiller performance, particularly at part-load conditions where systems operate most of the time.

Variable Flow and Capacity Modulation

Traditional cooling systems operate at fixed capacity, cycling on and off to match varying loads. This approach wastes energy and provides poor humidity control. Modern systems employ variable-speed drives on compressors, fans, and pumps to modulate capacity continuously, matching output to actual demand.

Variable air volume (VAV) systems adjust airflow to different zones based on actual cooling needs, reducing fan energy and improving comfort. Variable refrigerant flow (VRF) systems provide similar benefits for refrigerant-based systems, allowing simultaneous heating and cooling in different zones while recovering heat from areas being cooled to warm other areas.

Heat Recovery and Free Cooling

Many cooling applications generate waste heat that can be recovered and used productively. Heat recovery chillers can simultaneously provide cooling and heating, using rejected heat from the cooling process to generate hot water for domestic use or space heating. This approach significantly improves overall system efficiency.

Economizer systems take advantage of cool outdoor air to provide “free cooling” when outdoor conditions permit. Air-side economizers bring in outdoor air directly when it’s cooler than return air, while water-side economizers use cooling towers or other heat rejection equipment to cool chilled water without operating chillers.

Advanced Control Strategies

Sophisticated control systems optimize cooling system performance by continuously adjusting operation based on actual conditions and occupancy. Key strategies include:

  • Demand-Based Ventilation: Adjusting outdoor air intake based on actual occupancy using CO2 sensors rather than assuming maximum occupancy at all times.
  • Optimal Start/Stop: Learning building thermal characteristics to start systems at the latest possible time while still achieving comfort when occupants arrive.
  • Reset Strategies: Adjusting supply air temperatures, chilled water temperatures, and other setpoints based on actual loads to minimize energy consumption.
  • Predictive Control: Using weather forecasts and building models to anticipate loads and optimize system operation proactively.

Occupant Control and Satisfaction

Occupants who are able to modify their thermal environment through thermal controls will perceive more comfort regardless of conditioning strategy, and they may exhibit additional satisfaction and productivity. Providing occupants with some degree of control over their thermal environment can significantly improve satisfaction even when actual conditions remain within the same range.

For example, a flexible dress code that permits seasonally appropriate clothing can allow design air temperatures to be adjusted upward during the cooling season and downward during the heating season without affecting occupants’ perception of comfort. This simple administrative measure can yield substantial energy savings while maintaining or even improving occupant satisfaction.

Individual control options include operable windows in naturally ventilated buildings, personal fans, local thermostats for individual zones, and radiant heating/cooling panels that allow occupants to adjust their immediate environment. Even perceived control—such as a thermostat that provides feedback but limited actual adjustment range—can improve satisfaction.

Local Thermal Discomfort Factors

Beyond overall thermal comfort, designers must address local discomfort factors that can cause dissatisfaction even when general conditions meet comfort criteria. These factors include:

Draft and Air Movement

While air movement can be pleasant and provide comfort in some circumstances, it is sometimes unwanted and causes discomfort. This unwanted air movement is called “draft” and is most prevalent when the thermal sensation of the whole body is cool. People are most likely to feel a draft on uncovered body parts such as their head, neck, shoulders, ankles, feet, and legs, but the sensation also depends on the air speed, air temperature, activity, and clothing.

Cooling system design should minimize drafts in occupied zones by properly locating supply diffusers, selecting appropriate diffuser types, and controlling supply air velocities and temperatures. In warm conditions, increased air movement can enhance comfort through elevated convective and evaporative cooling.

Floor Temperature

Floors that are too warm or too cool may cause discomfort, depending on footwear. ASHRAE 55 recommends that floor temperatures stay in the range of 19–29 °C (66–84 °F) in spaces where occupants will be wearing lightweight shoes. This consideration is particularly important for radiant cooling systems and spaces with significant floor-to-ceiling temperature stratification.

Vertical Temperature Differences and Radiant Asymmetry

Excessive temperature differences between head and ankle level can cause discomfort, as can radiant temperature asymmetry from warm or cool surfaces. Cooling systems should be designed to minimize vertical stratification through proper air distribution, and radiant cooling panels should be configured to avoid excessive asymmetry.

Integration of Thermal Comfort Principles in Design Process

Successfully bridging thermal comfort theory and cooling system application requires integrating comfort considerations throughout the design process, from initial concept through commissioning and operation.

Early Design Phase

During early design, establish thermal comfort goals based on building type, occupancy, and climate. Select appropriate comfort models (PMV/PPD for mechanically conditioned spaces, adaptive model for naturally ventilated buildings) and determine target comfort ranges. Consider passive design strategies that can reduce cooling loads and expand the range of conditions achievable through natural means.

Detailed Design Phase

Perform detailed load calculations accounting for all heat gains and losses. Size equipment to match actual loads without excessive safety factors. Design distribution systems to deliver conditioned air or water efficiently to all zones. Model system performance under various operating conditions to verify that comfort criteria will be met throughout the occupied space and across the range of expected conditions.

Model energy use throughout the year. Calculating the load is important but understanding equipment efficiencies over the entire load profile may lend more insight into an efficient design. Annual energy modeling helps identify opportunities for efficiency improvements and validates that the system will perform well under actual operating conditions, not just peak design conditions.

Commissioning and Verification

Commission cooling systems thoroughly to ensure they operate as designed. Verify that temperature, humidity, and air velocity in occupied spaces meet design criteria. Test control sequences to confirm they respond appropriately to varying loads and conditions. Provide training to building operators on proper system operation and maintenance.

Post-Occupancy Evaluation

After occupancy, evaluate actual thermal comfort through surveys and measurements. Compare actual conditions to design predictions and adjust systems as needed to address any deficiencies. Use feedback from occupants to refine control strategies and identify opportunities for improvement.

The field of thermal comfort and cooling system design continues to evolve, driven by technological advances, changing climate conditions, and growing emphasis on sustainability and occupant well-being.

Personalized Comfort Systems

Rather than attempting to satisfy all occupants with a single set of conditions, personalized comfort systems provide individual control over local conditions. These include desk-mounted fans, radiant panels, and personal ventilation systems that deliver conditioned air directly to individual workstations. This approach acknowledges individual differences in thermal preference while potentially reducing overall energy consumption by allowing more moderate ambient conditions.

Smart Buildings and IoT Integration

Internet of Things (IoT) sensors and smart building platforms enable unprecedented monitoring and control of thermal conditions. Wireless sensors throughout buildings provide real-time data on temperature, humidity, occupancy, and other parameters. Machine learning algorithms analyze this data to optimize system operation, predict maintenance needs, and continuously improve comfort while minimizing energy use.

Climate-Responsive Design

As climate change alters temperature patterns and increases the frequency of extreme weather events, cooling system design must adapt. This includes designing for higher peak temperatures, longer cooling seasons, and greater temperature variability. Resilient design approaches ensure buildings can maintain acceptable conditions even during grid outages or equipment failures.

Low-Carbon Cooling Technologies

Reducing the carbon footprint of cooling systems is increasingly critical. This drives adoption of natural refrigerants with low global warming potential, solar-powered cooling systems, and thermal energy storage that shifts cooling loads to times when renewable energy is abundant. District cooling systems that serve multiple buildings from central plants can achieve higher efficiencies and facilitate integration of renewable energy and waste heat sources.

Best Practices for Bridging Theory and Application

Successfully translating thermal comfort principles into effective cooling system design requires attention to several key best practices:

  • Understand Occupant Needs: Different building types and occupancies have different comfort requirements. Office workers have different needs than hospital patients or manufacturing workers. Design systems appropriate to actual use patterns.
  • Use Appropriate Standards: Select comfort standards and criteria suitable for the building type, climate, and conditioning strategy. Don’t apply standards developed for mechanically conditioned buildings to naturally ventilated spaces or vice versa.
  • Perform Accurate Calculations: Invest time in detailed, accurate load calculations and system modeling. Shortcuts in analysis often lead to poorly performing systems that waste energy and fail to provide comfort.
  • Design for Part-Load Performance: Systems operate at peak load only a small fraction of the time. Ensure good performance across the full range of operating conditions through proper equipment selection and control strategies.
  • Consider the Whole Building: Cooling systems don’t operate in isolation. Coordinate with architectural design, lighting systems, plug loads, and other building systems to optimize overall performance.
  • Plan for Flexibility: Building uses and occupancy patterns change over time. Design systems with flexibility to adapt to changing needs without major reconstruction.
  • Prioritize Maintenance: Even the best-designed system will fail to perform if poorly maintained. Design for easy access to equipment, provide clear documentation, and establish maintenance programs to ensure long-term performance.

Conclusion: Creating Comfortable, Efficient Indoor Environments

Thermal comfort and cooling system design represent a sophisticated intersection of human physiology, physics, engineering, and architecture. Maintaining this standard of thermal comfort for occupants of buildings or other enclosures is one of the important goals of HVAC (heating, ventilation, and air conditioning) design engineers. Successfully achieving this goal requires understanding the complex factors that influence thermal comfort, selecting appropriate technologies and design strategies, and carefully integrating all elements into cohesive, well-performing systems.

The principles outlined in this article—from the six factors affecting thermal comfort to PMV/PPD indices, from load calculation fundamentals to advanced control strategies—provide a framework for creating indoor environments that support occupant health, productivity, and satisfaction while minimizing energy consumption and environmental impact. As technologies evolve and our understanding of thermal comfort deepens, the opportunities to create better buildings continue to expand.

For building designers, engineers, and facility managers, the challenge is to bridge the gap between theoretical understanding and practical application. This requires not only technical knowledge but also careful attention to the specific needs of each project, collaboration across disciplines, and commitment to continuous improvement through monitoring, evaluation, and refinement of systems after occupancy.

By grounding design decisions in sound thermal comfort principles, leveraging appropriate technologies, and maintaining focus on both occupant needs and energy efficiency, we can create built environments that truly serve their occupants while contributing to broader sustainability goals. The future of cooling system design lies in this holistic approach that recognizes thermal comfort not as a simple temperature setpoint but as a complex, multifaceted aspect of indoor environmental quality that deserves careful consideration and sophisticated solutions.

For more information on HVAC design standards and thermal comfort, visit the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) website. Additional resources on sustainable building design can be found at the U.S. Green Building Council. For tools to calculate thermal comfort parameters, the CBE Thermal Comfort Tool provides free access to ASHRAE 55 compliance calculations.