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Thermal Comfort

MES Seminar

Paul Shipley

on 11 May 2018

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Transcript of Thermal Comfort

Those involved in the design, specification and delivery of buildings need a good appreciation of comfort requirements.

Building owners and users should to be able to explain their comfort requirements and to be aware of the constraints.
Thermal Comfort in the Working Environment
This seminar looks at the factors influencing occupants’
thermal comfort and explores how we can build and
control commercial buildings to better achieve
satisfactory thermal comfort as well as providing
guidance on how to manage overheating in existing
What is Thermal Comfort?...
Key environmental factors
Key Factors:

Air Temperature


Air Movement

Air Quality
Comfort has been defined as:
‘that condition of mind that expresses satisfaction with the ... environment’
When services go bad...
Conventional Heating
Mechanical Cooling
Passive Cooling
Thermal Mass
Earth Tubes
Natural Ventilation
Existing Buildings Tackling overheating
Thermal Comfort
Thermal Discomfort
Thermal Stress
Broad satisfaction with the thermal environment
People start to feel uncomfortable
Potentially harmful medical conditions, such as dehydration or heat exhaustion, hypothermia or frost bite
The Workplace (Health, Safety and Welfare) Regulations 1992 state that
‘During working hours, the temperature in all workplaces inside buildings shall be reasonable’.

The Approved Code of Practice (ACOP) to these regulations defines a ‘reasonable temperature’ as that which secures the thermal comfort of people at work, without the need for special clothing. This is further defined as being met by ‘maintaining a ‘reasonable’ temperature of at least 16 °C (or at least 13 °C if the work involves physical effort)’.

At present, there is no upper limit in the Regulation or the ACOP. In practice, the CIBSE guidelines on comfort, given in CIBSE Guide A(1), are often taken as a good practice indication of thermal comfort and are used for design purposes.
UK Legislation
Buildings are designed to meet our basic need for:
— shelter
— security
— comfort
Nowadays, although we might expect more sophistication in delivery and more facilities,
the fundamental needs remain the same.
Internal Environment - Simple?
Comfortable: at ease; free from want,
trouble, hardship or pain; quietly happy.
Cassel Concise English Dictionary
Achieving the ‘right’ environment is the main goal of good building services design

People - Work or Leisure

Equipment - Operating conditions
The main factors that influence comfort for people relate broadly to our senses.
Good building services must provide:
a good thermal,
aural and
visual environment
"Keep most of the people happy most of the time"
Many Factors...
Hot ?
What determines
thermal comfort?
Draughty ?
Stuffy ?
People are really responding to the transfer of heat from their body and to the quality of the air


Cool Evening
Sunny Day
Air Temperature
Relative Humidity
Mean Radiant Temperature
Air Velocity
Can't measured directly
Determined from radiant energy,
air temperature and velocity
Operative temperature is common in design which uses
radiant and air temp plus air velocity to some extent.
See CIBSE guide A.
Other factors
Room Air Diffusion (RAD)
Temperature variations in the space

Air and radiant temperature differences

Localised radiation

Warm or cold floors



Ventilation and air quality
to irritants
Fresh air is required for:
Dilute carbon dioxide
Dilute contaminants
Feeling of "freshness"
There is no generally accepted measurement criteria for IAQ. For contaminants in the workplace-
Control of Substances Hazardous to Health Regs. 1994
The adaptive approach...
Laboratory based studies
PO Fanger
PMV (predicted mean vote)
PPD (predicted % dissatisfied)
Field studies
leading to the adaptive approach -
% of people happy / dissatisfied
The adaptive approach to comfort
People naturally
How hot is too hot?
Warm Summer Weather
Indoor Operative Temp
Design Summer Overheating Criteria
Briefing Stage:
Key comfort criteria
21 deg. C
50% RH
10 lts/s per person
+/- 1 deg C
+/- 10% RH
Also consider:
Summer / Winter temps
Relaxation for non-A/C
Wider RH 40 - 70 %
Air Velocities 0.1 to 0.3 m/s
Variance within spaces
From CIBSE Guide A
From CIBSE Guide A
Practical Issues
Understanding what is required
21 deg C +/- 1? +/-2 ?
Conditions will fluctuate
Temperature variations in the space

Radiant temperature differences



System inertia

Equipment Limitations

Thermal Response

System Type
Danger! Lack of Knowledge
9 Recorded fatalities in Europe ~ wood pellet stores
Wet pellets self-heat 105 deg C, combustion
Cross bonding and earthing
Rain / Condensation - mould / spores - Farmers Lung
Sizing Chimneys - retired skill base
Power interruption - flue / pumps - UPS
Complex controls - 30mins to 2hrs min. operation.
' at the end of 2012, there may be less than 12
people in the UK with adequate knowledge
(of procuring biomass boiler systems)'
CIBSE Journal Dec. 2012
Gas & Oil Fired
Night Cooling
Reduce internal gains
Windows, blinds & ventilation
Efficient air conditioning
Staff comfort
Amount Fresh air required for each
ASHRAE Standard 55-04
Discomfort will occur where temperatures:
- change too fast
- outside normal limits
- are unexpected
- are outside individual control
Quote: James Bruce -
Travels to Discover the Sources of the Nile.
(London 1804)
Q & A
Our Services - don't gamble with building compliance
It has never been more important to ensure you have robust, professional advice on how to get your development to comply with regulations. Our services include the following:
Residential & commercial air leakage testing
Code for Sustainable Homes, Eco Homes & BREEAM
Renewable energy evaluations
Sustainability statements
Daylighting & Right of Light services
Ventilation and Overheating issues
Water efficiency
Thermal bridging
Dynamic simulation modelling (DSM)
Building Pathology
Building Services Commissioning

1. Exceedance
2. Severity
3. Threshold
TM52 Computer Thermal Modelling
T max = 0.33 x T rm + 21.8
ΔT = T op - T max
ΔT should not > 1deg. for more than 3% of total occupied hours
Trend or running mean outdoor temperature (Exponentially weighted)
Weighted exceedence shall be less than or equal to 6.
Maximum ΔT shall not exceed 4 deg.
Full transcript