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Transcript of Thermal Comfort
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
Comfort has been defined as:
‘that condition of mind that expresses satisfaction with the ... environment’
When services go bad...
Existing Buildings Tackling overheating
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.
Buildings are designed to meet our basic need for:
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,
"Keep most of the people happy most of the time"
People are really responding to the transfer of heat from their body and to the quality of the air
Mean Radiant Temperature
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.
Room Air Diffusion (RAD)
Temperature variations in the space
Air and radiant temperature differences
Warm or cold floors
Ventilation and air quality
Fresh air is required for:
Dilute carbon dioxide
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
PMV (predicted mean vote)
PPD (predicted % dissatisfied)
leading to the adaptive approach -
% of people happy / dissatisfied
The adaptive approach to comfort
How hot is too hot?
Warm Summer Weather
Indoor Operative Temp
Design Summer Overheating Criteria
Key comfort criteria
21 deg. C
10 lts/s per person
+/- 1 deg C
+/- 10% RH
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
Understanding what is required
21 deg C +/- 1? +/-2 ?
Conditions will fluctuate
Temperature variations in the space
Radiant temperature differences
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
Reduce internal gains
Windows, blinds & ventilation
Efficient air conditioning
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.
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
Daylighting & Right of Light services
Ventilation and Overheating issues
Dynamic simulation modelling (DSM)
Building Services Commissioning
SAP & SBEM
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.