Objective definition of comfort ISO 7730 EN 15251

Advantages

• Objective, engineered, concrete definition of quality and thermal comfort
• Protection for the specifier
• Recognises impossible to satisfy everyone due to individual differences
• Greater comfort achievable with greater investment

Can we define quality objectively?

• ISO 7730
• What is Thermal Comfort?
• 6 Factors affecting Thermal Comfort
• Objective Measurements of Comfort – PMV and PPD
• EN 15251
• Designing for Thermal Comfort – simulation software
• Products
• Post-occupancy evaluation

ISO 7730

• Defines thermal comfort
• Describes 6 factors that control it
• Provides standard models to quantify it

EN 15251

• Design and sizing of ventilation system and other building systems
• Comfort and energy efficiency

Contents

• Can we define quality objectively?
• ISO 7730
• What is Thermal Comfort?
• 6 Factors affecting Thermal Comfort
• Objective Measurements of Comfort – PMV and PPD
• EN 15251
• Designing for Thermal Comfort – simulation software
• Products
• Post-occupancy evaluation

What is Thermal Comfort?

‘that condition of mind which expresses satisfaction with the thermal environment’  ISO 7730

6 Factors affecting Thermal Comfort

Environmental Factors

1.Air temperature (K)

2.Radiant temperature (K)

3.Air velocity (m/s)

4.Humidity (%)

Personal Factors:

5.Clothing insulation   (clo or K.m2/W)

6.Metabolic heat  (Met or W/m2)

6 Factors affecting Thermal Comfort

1. Air temperature

• Temperature of air around human body
• Dry bulb temperature
• Measured using standard thermometer or temperature probe
• 22°C – 26°C optimum
• Motivation and performance significantly affected

2. Radiant temperature

• Measured with black globe thermometer
• Greater influence than Tair
• Skin ~ black object
• Sources: the sun, fires, hot surfaces, ovens, radiant panels

3. Air velocity

• Varies over time
• Human sensitivity
• Too low -> stagnant air with odour
• Too high -> draught

4. Humidity

• Relative Humidity (RH): 40-70% – no major impact on thermal comfort
• High humidity prevents cooling through perspiration

2 Personal Factors:

• Clothing insulation and metabolic heat
• Variable
• Sample values in ISO 7730

PMV

• Equations developed based on surveys of occupants in tightly controlled environment
• Enter room characteristics related to 6 factors
• Predicts mean occupant rating of room
• Zero = Thermal neutrality (ideal)
• Decreasing quality at extremes
• First objective means to define quality

Calculate PMV

PPD

• Percentage people dissatisfied
• Equation to relate PMV to PPD
• Second objective means to define quality
• ASHRAE 55 requires at least 80% of occupants to be satisfied

Calculate PPD

ISO 7730 – Draught Rating

ISO 7730 – Vertical air

temperature difference

Acceptable thermal environments for comfort:

• 3 categories of environment defined

Specifying using EN 7730

1.Value of PMV or

2.PPD or

3.Category (A/B/C)

Specifying using EN 7730

Advantages

• Objective, engineered, concrete definition of quality and thermal comfort
• Protection for the specifier
• Recognises impossible to satisfy everyone due to individual differences
• Greater comfort achievable with greater investment

Contents

• Can we define quality objectively?
• ISO 7730
• What is Thermal Comfort?
• 6 Factors affecting Thermal Comfort
• Objective Measurements of Comfort – PMV and PPD
• EN 15251
• Designing for Thermal Comfort – simulation software
• Products
• Post-occupancy evaluation

EN 15251

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Design Input Criteria for HVAC System Dimensioning

Demand-controlled Ventilation (VAV)

Reduce Fan Energy Use

Meeting Rooms/Conference Rooms/Lecture Theatres

PIR/CO2 Sensors

Design Input Criteria for HVAC System Dimensioning

Humidity

• Small effect on thermal sensation and perceived air quality
• High = microbial growth
• Low = dryness and irritation
• Requirements influence dehumidifying (cooling) load
• Special requirements for buildings such as museums, historical buildings, etc