Idea Transcript
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2 th Module Manuela Almeida | Luis Bragança Sandra Silva | Ricardo Mateus | Ricardo Barbosa University of Minho Portugal
1. Thermal Comfort Fundamentals 2. Measurements and Models
3. Building regulations 4. Impact of renovation solutions
Introduction No matter how long ago, no matter how long after now, no matter where, people create shelters so as to: 1. be protected by natural phenomena and
2. feel good = feel comfortable Caves*
Means may change, efficiency too, but end always remains the same.
Prehistoric pile house**
Source: *Wikipedia, **UNESCO, ***Wikipedia, ****Wikipedia Modern house***
The international modular space station****
Introduction And feeling good includes: • Not too hot
• Not too cold • Not too dry
• Not too humid Or as per EN ISO 7730:2005/par. 7 definition on thermal comfort: Thermal comfort is that condition of mind which expresses satisfaction with the thermal environment
A subjective parameter.
An objective parameter (thermodynamics)
Introduction
Applicable to shelters
Thermal Comfort
Subjective parameters
Stable over timeline
Objective parameters
Change over timeline
Today: 1. More people use shelters around the world 2. More architects and engineers familiarize with thermal comfort context. 3. Scale economies gradually makes technology available to greater population proportion. More and more people live in a thermally comfortable environment
Technical Means
Technical Means
Knowledge
Introduction • And as per EN ISO 7730:2005/par. 7: Due to individual differences, it is impossible to specify a thermal environment that satisfy everybody. There will always be a percentage dissatisfied occupants. But it is possible to specify environments predicted to be acceptable by a certain percentage of the occupants.
Thus, thermal comfort context is about more
i.e. making more people feel thermally comfortable
Introduction
•
Is it about thermodynamics?
•
How thermal comfort correlates to human activity?
Comfort
•
How our body respond?
•
What are the very factors affecting thermal comfort?
Thermodynamics • Thermodynamics is a branch of physics concerned with heat and temperature and their relation to energy and work. • It defines macroscopic variables, such as internal energy, entropy, and pressure, that partly describe a body of
matter or radiation. • It states that the behavior of those variables is subject to general constraints, that are common to all
materials, not the peculiar properties of particular materials. • These general constraints are expressed in the four laws of thermodynamics.
Source: Wikipedia
Thermal balance Thermodynamic laws apply: Food energy = Heat + Work + Energy stored (fat)
Environment Radiation
Convection
Conduction
What is heat? • Heat is energy in transfer other than as work or by transfer of matter.
• When there is a suitable physical pathway, heat flows from a hotter body to a colder one. • Heat refers to a process of transfer, not to a property of a system.
Source: Wikipedia
How is heat transferred?
Source: Wikimedia, By Kmecfiunit (Own work)
Sensible Heat Loss
Environment Radiation Convection
Conduction
Evaporative heat loss
Environment
Convection
• M = W+(R+C+K)+E+S • M = metabolic rate • W = external work
• R = radiant heat exchange • C = convective heat exchange • K = conductive heat exchange • E = evaporative heat transfer • S = Energy storage
What is temperature? • Temperature is a comparative objective measure of hot and cold.
• Thus, temperature scales is a comparative measurement from a conventional defined point.
Celsius scale: Measure of comparison = Ice formation conventionally set at 0 ºC Kelvin scale: Measure of comparison = Absolute zero, i.e. molecules not moving Absolute zero = 0 ºK = -273,15 ºC
So… • Thermal comfort is about applying thermodynamics to the medium that surrounds humans, i.e. air.
• But what is air just a gas?
Source: Wikipedia, "Antarctic Air Visits Paranal" by ESO/G. Brammer Acknowledgement: F. Kerber (ESO) Source: Wikipedia, "Cloud forest mount kinabalu"
Air composition
+
Source: Wikipedia, "Atmosphere gas proportions" by Mysid
Water vapour
Psychrometrics Psychrometrics or psychrometry or hygrometry are terms used to describe the field of engineering concerned with the determination of physical and thermodynamic properties of gas-vapor mixtures. The term derives from the Greek psychron (ψυχρόν) meaning "cold“ and metron (μέτρον) meaning "means of measurement"
Source: Wikipedia
Basic terms of psychrometry • Humidity is the amount of water vapor in the air. • Relative humidity or RH (φ) is the ratio of the partial pressure of water vapor to the equilibrium vapor pressure of water at the same temperature.
• Absolute humidity is the mass of water vapor per unit volume of air containing the water vapor. • Dry-bulb temperature (DBT) is the temperature of air measured by a thermometer freely exposed to the air but
shielded from radiation and moisture. • Wet-bulb temperature is the temperature a parcel of air would have if it were cooled to saturation (100% relative humidity) by the evaporation of water into it. • Dew point or saturation temperature is the temperature at which the water vapor in a sample of air at constant barometric pressure condenses into liquid water at the same rate at which it evaporates.
Basic terms of psychrometry • Sensible heat is the heat that changes the temperature of a substance when added to or abstracted from it.
• Latent heat is the heat that does not affect the temperature but changes the state of substance when added to or abstracted from it.
• Enthalpy (h) is the combination energy which represents the sum of internal and flow energy in a steady flow process. It is determined from an arbitrary datum point for the air mixture and is expressed as kJ per kg of dry
air.
Psychrometric chart
Specific humidity
Relative humidity lines
Dry Bulb Temperature
Psychrometric chart
Flip
Psychometric chart
Heating
Cooling
Dehumidification Dry Bulb Temperature
Specific humidity
Humidification
Mixing
𝑚1 𝑊3 − 𝑊2 ℎ3 − ℎ2 = = 𝑚2 𝑊1 − 𝑊3 ℎ1 − ℎ3 h1 𝑚3, 𝑊3 , ℎ3
h3 h2 1
W1
3 W3
2
W2
t2
t3
t1
Sensible heating Power needed 𝑄ሶ = 𝑚ሶ ∗ Δh
Specific humidity
Specific humidity stays put, but relative humidity changes
Air becomes warmer. Dry Bulb Temperature
Sensible cooling
t>dp
Power needed 𝑄ሶ = 𝑚ሶ ∗ Δh
Specific humidity
Specific humidity stays put, but relative humidity changes
Dry Bulb Temperature
Air becomes cooler.
Cooling and Dehumidification
t≤dp
Power needed 𝑄ሶ = 𝑚ሶ ∗ Δh
Specific humidity
Specific humidity changes.
Dry Bulb Temperature
Air becomes cooler.
Sources of heat inside buildings
Lighting
Equipment
Qsolar
Energy equilibrium applies, i.e. + Qfabric + Qpeople + Qlighting + Qequipment + Qventilation = 0
More temperature definitions • The mean radiant temperature (MRT) = the uniform temperature of an imaginary enclosure in which the radiant heat transfer from the human body is equal to the radiant heat transfer in the actual non-uniform enclosure. • Operative temperature = Uniform temperature of an imaginary black enclosure in which an occupant would
exchange the same amount of heat by radiation and convection as in actual non-uniform environment.
Source: http://www.ides-edu.eu/wp-content/uploads/2013/04/2-thermal-comfort.pdf
Thermal comfort •
People feel good within a certain
boundary of operative temperature and Dehumidify and reheat if necessary
Heating only
Cooling only
this is in turn translated in a certain
space in the psychrometric chart. •
This space is objectively defined.
•
But statistics help us find a common space.
•
Statistics are applied to people’s voting using a predefined scale of comfort.
Heating + Humidify Humidify
Cooling + Humidify
Thermoregulatory system • Humans are endothermic organizations, i.e. heat needed for vital needs stems from metabolic functions
• Humans are homeothermic organizations(or warm-blooded), i.e. body temperature is kept within certain bounds • Human body uses homeostasis (i.e. preservation of relatively constant conditions), a highly complex control
system which takes place in the brain area called hypothalamus
Thermoregulatory system • Homeostasis caters for preserving a stable body temperature, through energy homeostasis, i.e. energy balancing, by • adjusting metabolism i.e. the set of life-sustaining chemical transformations within the cells of living organisms • inaugurating positive/negative loop mechanisms (Positive feedback is a process that occurs in a feedback
loop in which the effects of a small disturbance on a system include an increase in the magnitude of the perturbation. Negative is the opposite)
6 factors of thermal comfort Metabolic rate
Clothing
RH
Air temperature
Air velocity
Mean radiant temperature
Metabolic rate • Increased work leads to increased heat production → type of activity influences heat produced by the human body and is proportional to heart rate • Metabolic rate = Energy/time = power
• Expressed as W/m2, i.e. power per surface area of the body (as per EN ISO 8996 “average” individual is 30 years-old, 70kg weight man of 1,8m2 and 60 kg weight woman of 1,6m2) • Additional unit used met = 58,15 W/m2
Metabolic rate • EN ISO 8996 defines methodology of calculating or measuring metabolic rate.
• Practically occupancy loads are taken from national/EU standard tables that define load per building space. • In such cases it is important to remember that loads are expressed also in W/m2, but m2 usually is building area. • Work can also be expressed in W/m2 or met units. For common light work is usually accounted as being 0.
• Metabolic rate influences evaporation (skin, respiration), thus adjusting for latent load.
Metabolic rate Metabolic Rate [W/m2]
Metabolic Rate [met]
Seated, Relaxed
58
1.0
Shopping
93
1.6
Domestic work
116
2.0
Shivering
200
3.4
Activity
Source: EN ISO 8996:2004
Clothing principle
Outer environment
Clothing layers
Layer of still warmed fluid heated by human body Clothing adjusts: • Heat radiated • Heat convected by passing of the air though garments • Evaporation cooling as sweat passes through clothing fibers
Clothing
Source: EN ISO 9920:2009
Clothing • Clothing insulation (Icl) is the means of maintaining this still warm layer.
• As insulation is expressed in thermal resistance units, i.e. m2K/W or clo=0,155 m2K/W • Evaporation cooling resistance (Re) provided is proportional to clothing permeability (material specific),
approached by permeability index (im). • As per EN ISO 9920 Re = f(im, Icl).
Clothing Icl 2 [m K/W]
Icl [clo]
Panties, T-shirt, shorts, light socks, sandals
0.050
0.30
Underpants, shirt with short sleeves, light trousers, light socks, shoes
0.080
0.50
Panties, shirt, trousers, jacket, socks, shoes
0.155
1
Clothing
Icl continuum [clo]
0.2
Considered as nude
0.5
0.6
1.0
Considered as clothed
Common summertime design parameter
Common wintertime design parameter
Temperatures • Operative temperature is a function of mean radiant temperature (MRT) and air temperature
• MRT considers for heat transferred by radiation and is commonly measured by black globe thermometer • Air temperature considers heat transferred by convection and is measured by typical thermometers
Air velocity • Airflow in spaces is typically turbulent • Turbulent flows enable greater heat transfer rates • But also increased turbulence Turbulent means flow increased discomfort
Source: Wikipedia, "False color image of the far field of a submerged turbulent jet" by C. Fukushima and J. Westerweel, Technical University of Delft, The Netherlands
Both laminar and turbulent flow
Source: Wikimedia, By Instrueforme231 (Own work)
Air velocity
•
Humans show different sensibility on wind direction
•
Human body does not have a specialized
sensing for wind measurement. Wind is indirectly
change
determined
by
temperature
Air velocity • Correlates to convection and evaporation heat transfer
• Difficult to measure accurately • Fluid mechanics & heat transfer calculations are both knowledge and resource demanding • Currently encountered either with simplistic assumptions leading to linear equations or CFD (computational fluid dynamics) based on Navier Stokes equation (e.g. k-ω, k-ε etc)
Humidity • Interacts with thermoregulatory system through: • Gas diffusion • Sweat evaporation
• Humidification of inhaled air • It loosely affects skin temperature • The amount of sweat remaining on the skin is a very good indicator of discomfort
Humidity Measured ether by psychrometer or by hygrometer
Source: EN ISO 7726:2003
Interdependability table Table 1 - Main independent quantities involved in the analysis of the thermal balance between man and the thermal environment Quantities
ta
va
pa
Icl
Rcl
M
W
Air velocity
Absolute humidity of the air (partial pressure of water vapour)
Insulation of clothing
Evaporative resistance of clothing
Metabolism
External work
X
X
Elements in the thermal balance Air temperature
Mean radiant temperature
Internal heat production, M-W X
Heat transfer by radiation, R
Heat transfer by convection, C*
X
Heat losses through evaporation: - evaporation from the skin, E - evaporation by respiration, Eres Convection by respiration, Cres
X
X
X
X
X
X X
X X X
* Heat transfer by convection is also influenced by body movements. The resultant air velocity at skin level is called relative air velocity (var). Heat conduction (surface temperature) has only a limited influence on the thermal heat balance. Source: EN ISO 7726:2003
Some food for thought Arabs in thawb
Source: Wikipedia, "Dishdasha" by Mary Paulose from Muscat, Oman Assorted Arabs.
American workers
Spare fisherman
Farmer in Venezuela
Source: Wikipedia, "Civilian Conservation Corps at an experimental farm in Beltsville, Maryland - NARA 195831" by Unknown or not provided - U.S. National Archives and Records Administration.
Source: Wikipedia, "Chasseur sous-marin et son équipement" by Calcineur Own work.
Source: Wikipedia, "Campesino Venezolano, Edo. Yaracuy crop" by The Photographer - Own work
Adaptation • Previous analysis pre-assumed that individuals act passively on environmental parameters.
• Is this the case or: • When you feel hot you open the window?
• When you feel cold you wear your wool shirt? • Isn’t adaptation the cornerstone for our evolutionary straggling?
Adaptation • Thermoregulatory system is controlled by homeostasis system that produces stimuli.
• Thus, adaptation defined as: the gradual decrease of the organism’s response to repeated exposure to a stimulus, involving all the actions
that make them better suited to survive in such an environment
Adaptation Adaptive opportunity
Thermal discomfort
Thermal discomfort
Adaptive opportunity
Temperature
Thermal neutrality
Thermal discomfort Good
Low
Inexistent Time
Adapted from: Baker and Standeven, 1996
Adaptation Field studies and the adaptive model Adaptive model of thermal comfort “If a change occurs in the thermal environment which tends to produce discomfort, people will respond in ways that tend to restore their comfort.”
(Humphreys, 1997).
Adaptation The adaptive model
ASHRAE RP 885
In buildings with HVAC systems, the comfort temperature adjust to EN ISO 7730 model.
In buildings without mechanical systems, the occupants adapt themselves in a way that EN ISO 7730 does not predict. Dear et al.
Adaptation Adaptation to Indoor Climate The “adaptive” hypothesis
The three components of adaptation to indoor climate
Habituation (psychological adaptation changing expectations)
Adjustment (behavioural/technological changes to heat-balance)
Acclimatization (long-term physiological adaptation to climate)
ASHRAE RP 884
Adaptation The adaptive model The types of action which can be taken to adapt to the indoor climate are:
– Modifying the internal heat generation: this can be achieved unconsciously with raised muscular tension or, in a more extreme situation, the shivering reflex, or consciously, for instance through jumping about in the cold to increase metabolic heat or having a siesta in the warm to reduce it. – Modifying the rate of body heat loss: achieved unconsciously through vasoregulation or sweating: consciously by such actions as changing ones clothing, cuddling up or by taking a cooling drink.
– Modifying the thermal environment: through lighting a fire, opening a window, or in the longer term by insulating the loft or moving house. – Selecting a different environment: within a room by moving closer to the fire or catching the breeze from a window, between rooms in the same house with different temperatures, or by moving house or visiting a friend.
Adaptation strategies Adaptation
Physiological
Behavioral
Genetic
Personal
Acclimatization
Technological
Cultural
Psychological
Reference
Genetic • Change in natural characteristics
• Long term
A Tibetan family Source: Wikipedia, "Sherpa" by Original uploader was Gac at it.wikipedia
Source: Mother nature network
Acclimatization • Habituation (stop in responding to a stimulus which is no longer biologically relevant)
• Metabolic adaptations • Insulative adaptations
Source: Ultimate everest
Behavioral • Most common type of adaptation • Personal (e.g. clothing, warm/chill drinks) • Technological (e.g. turn air condition on/off)
• Cultural (e.g. siesta) • But also contextually rearranging the above: • Reactive (personal adjustment - e.g. it got hot so I revise my clothing) • Interactive (change the circumstances)
Source: Discovering antartica
Psychological • Naturalness (free of artificiality)
• Expectations (how environment should be) • Experience • Short term (memory related) • Long term (schemata in mind related) • Time of exposure (e.g. getting out of a warm car to enter a building in winter)
• Perceived control (control over a source of discomfort) • Environmental stimulation
Flip-side of adaptive opportunity (i.e, the lack of...) The flip-side of adaptive opportunity (i.e, the lack of...), is the analysis of constraints to thermal control. These constraints may be gathered under five main headings (Nicol and Humphreys 1972, Humphreys 1994a): a) Constraints due to climate.
b) Economic constraints. c) Constraints due to social custom or regulation. d) Constraints due to task or occupation.
e) Constraints due to design.
Adaptive thermal comfort model ASHRAE 55:2013
Indoor operative temperature, Toc, (ºC)
Portugal
Average outdoor temperature in Lisbon (12ºC; 23ºC)
Toc = 17,8 + 0,31T m
21
90% acceptability limits 80% acceptability limits
Mean monthly outdoor air temperature, Tm, (ºC)
Global vs local comfort Solar irradiation
air
Imagine a space within thermal comfort boundaries. • Under your perception between Mr. Black, Mr. Green and Mr. Red, who is supposed to feel most comfortable?
Global vs local comfort • Thus local discomfort consists of exposing parts of body to conditions thermally uncomfortable.
Evaluating thermal environment
=
Global comfort
+
Local comfort
Radiant asymmetry
•
Radiant temperature asymmetry leads to
discomfort •
Warm ceilings and cold windows cause
greater discomfort than cold ceilings and warm walls Source: Wikipedia, By Ernst Vikne (Watching the fireplace)
Vertical air temperature differences • Unpleasant to be warm around head and cold around feet
• Temperature is measured at ankle and neck
hot
cold
Draught air • Most common complaint
• Discomfort depends on air velocity and turbulence
Floor • Depends on floor’s conductivity, floor’s thermal mass and footwear • Difference in conductivity and heat capacity makes cork floors feel warm and marble floors feel cold • Normal footwear makes floor influence minor • Bathroom is an exemption since walking on bare feet is the norm.
Source: Wikipedia, "Fire Walking (1234969885)" by Aidan Jones from Oxford, U.K. - Fire Walking
Natural ventilation •
Correlates to psychological adaptation, i.e. Naturalness, Environmental stimulation
•
Research is converging that natural ventilation makes individual feel more thermally comfortable
•
Depends on outside air velocity (impossible to control outside air, hard to predict, may change as surroundings change)
•
Natural sometimes also mean “natural” air born noise thus a thermally comfortable environment may not be comfortable.
•
Sometimes difficult to implement (e.g. renovation projects)
Adaptive thermal comfort model
Use of natural ventilation strategies 30
Temperature (ºC)
Thermal Comfort interval with a breeze (natural ventilation)
Thermal Comfort interval
20
10
6h
12h
18h
24h
6h
Adapted from: Jim Lambert, Natural Ventilation – capabilities and limitations (comfort and energy efficiency in domestic dwellings), ATA Melbourne Branch presentation, April 2008
Age • As people get older: • Metabolic rate probably falls • Sweating normally reduces
• Thermoregulation becomes harder • But apart from physical also psyco-socio-economical parameters are influenced: • Income tends to decrease • Usually spend more time indoors • Perception of what is cold and hot may change
Gender • Females tend to be more prone to express thermal discomfort than males
• Females are expected to have higher thermo-neutral temperature • Differences are attribute to: • Body fat • Surface to mass ratio • Regulatory hormones
• Clothing and clothing distribution across body
Temperature changes over time • Changes of temperature within a day
• Temperature changes from day to day • Seasonal changes in temperature
Correlation to climate change
Source: Wikipedia, "NSFmonsoonsandclimatesince200AD" by U.S. Government, National Science Foundation (NSF)
Dynasties may fall and rise, but desire for thermal comfort remains unchanged.
Correlation to climate change
Source: Wikipedia , "Mauna Loa Carbon Dioxide-en" by © Sémhur / Wikimedia Commons.
Correlation to climate change
Temperature range Health dangerous temperatures Discomfort temperatures Comfort temperatures
Thermal comfort and productivity • Many researches have shown a positive correlation in business environment between lowering temperature during cooling period and increase in productivity. • 10-12 year old students have shown to have an improved performance by increasing ventilation rate and
lowering temperature. Ventilation rate had a positive impact of 8-14%, while cooling 2-4%.
Source: Thermco, 2009
What is the “discomfort cost”? • In 2000 Fisk* estimated that for the U.S. improved indoor environment could: • Save 6-14 b$/a from reduced respiratory disease • Save 2-4 b$/a from reduced allergies & asthma • Save 10-30 b$/a from reduced building syndrome symptoms • Generate extra 20-160 b$/a due to improved personnel performance
• Nicol et.al.** claim that UK medical treatment cost due to poor housing is 2,5b₤/a out of which 700m₤/a stem from poor energy efficiency/fuel poverty.
*Fisk W., REVIEW OF HEALTH AND PRODUCTIVITY GAINS FROM BETTER IEQ, Proceedings of Healthy Buildings 2000 Vol. 4 **Nicol, S., Roys, M., Davidson, M., Summers, C., Ormandy, D., Ambrose, P., Quantifying the Cost of Poor Housing. IHS BRE Press, Watford, 2010.
Heat stress • Associated with the heat balance between human body and environment: it shows the load a human may be exposed; • Mild heat stress may cause discomfort or deterioration of performance;
• Above tolerated temperatures, heat related illness arise.
Thermal Comfort Assessment Thermal Comfort assessment procedures overview Monitoring and evaluation Empirical approach (surveys) Analytical approach Thermal comfort measurements. Sensors and equipment Practical session with equipment
Thermal Comfort Assessment Evaluation of the thermal environment
Talking to and interviewing people Observation → subjective judgement
Qualitative
Thermal Comfort Evaluation
Carry out measurements → Objective assessment
Quantitative
Thermal Comfort Assessment Evaluation of the thermal environment Validating the Thermal Environment Validation Methods In order to determine the thermal environments’ ability to meet the defined criteria there are two methods that can be implemented (ASHRAE 55): •
statistically determine occupant satisfaction through the evaluation of survey results.
•
technically establish comfort conditions through the analysis of environment variables.
Thermal Comfort Assessment Measuring thermal comfort A simple way of estimating the level of thermal comfort in a workplace or home is to ask the workers or inhabitants. If the percentage of workers/inhabitants dissatisfied with the thermal environment is above a certain level it is necessary to take actions. The use of a thermal comfort checklist helps to identify whether there may be a risk of thermal discomfort to the occupants of a room.
Thermal comfort checklist
Thermal Comfort Assessment
Factor
Assessing thermal comfort
Air temperature
Read the descriptions for each thermal comfort factor, and tick the appropriate box.
YES
Does the temperature in the workplace change a lot during hot or cold seasonal variations?
Radiant temperature
Humidity
Air movement
If two or more ‘YES’ boxes are ticked there may be a risk of thermal discomfort and it is necessary to carry out a more detailed assessment.
Description Does the air feel warm or hot? Does the temperature in the workplace fluctuate during a normal working day?
Metabolic rate Changes to the environment What your think
Is there a heat source in the environment? Is there any equipment that produces steam? Is the workplace affected by external weather conditions? Are you wearing clothes or protection equipment that is vapour impermeable? Do you complain that the air is too dry? Do you complain that the air is humid? Is cold or warm air blowing directly into the workspace? Are you or your colleagues complaining of draught? Is work rate moderate to intensive in warm or hot conditions? Are you or your colleagues sedentary in cool or cold environments? Can you make individual alterations to your clothing in response to the thermal environment? Do your think that there is a thermal comfort problem?
Adapted from: http://www.hse.gog.uk/temperature/thermal/measuringthermalcomfort.pdf
Thermal Comfort Assessment Subjective evaluations Questionnaires
https://www.educate-sustainability.eu/kb/sites/www.educate-sustainability.eu.portal/files/OCCUPANT%20COMFORT%20SURVEY%20QUESTIONNAIRE.pdf
Thermal Comfort Assessment Empirical approach (surveys) Survey Occupants The occupants’ survey require a survey check sheet to be provided by the team responsible for validating the thermal environment of the space. The sheet shall have, as a minimum, the following data for the occupant to fill in: • Occupants name, date & time; • Approximate outside air temperature; • Clear sky/ Overcast (if applicable); • Seasonal conditions; • Occupant’s clothing; • Occupant’s activity level; • Applicable equipment; • General thermal comfort level; • Occupant’s location. In addition to the occupant’s data, space should be provided for the surveyor to: • number the survey; • summarize the results; and • sign his/her name.
Thermal Comfort Assessment Empirical approach (surveys)
Source: ASHRAE 55:2013
Thermal Comfort Assessment Empirical approach (surveys) EN 15251:2007 - Methodologies for subjective evaluations Subjective questionnaires can be used to evaluate the indoor environment. Subjective scales are presented to the occupants at fixed time intervals (daily, weekly, monthly, etc.).
The questionnaires should be filled out during middle morning or middle afternoon. Not just after arrival or after a lunch break. The results can be presented as average values and/or distributions.
Source: EN 15251:2007
Thermal Comfort Assessment Empirical approach (surveys) Example of a Questionnaire (Based on ASHRAE 55 and EN15251)
Evaluation of the thermal environment
At the design stage the thermal environment may be evaluated by calculations.
Simple hand calculations and computer models and software of buildings and systems are available for this purpose (see Training Module 2.4 section 6.2). Temperature[ºC] 35 Occupation period
Heating and Cooling Energy Needs [kW/h] 8 Occupation period
7
30 Comfort zone
6
25
5
20
4 15
3
10
2
5 0 0:00
1 3:00
5:00
21st Feb -Ext 3rd Jun - Int
7:00
9:00
11:00
13:00
15:00
21st Feb - Int Heating needs [kW/h]
17:00
19:00
21:00
0 23:00
Hour 3rd Jun - Ext Cooling needs [kW/h]
Evaluation of the thermal environment
In existing buildings the thermal environment may be evaluated based on measurements conducted during building operations.
Full scale laboratory testing may provide a more controlled validation.
http://www.healthyheating.com/Built -to-code.htm#.VRwRR_zF_R8
IR survey
Evaluation of the thermal environment Measurement positions Location of measurements
Measurements shall be made in occupied zones of the building at locations where the occupants are known to or are expected to spend their time. Locations might be workstation or seating areas, depending on the function of the space.
www.testo.org/en/home/products/comfort_and _indoor_air_quality/iaq_and_comfort_level.jsp
Occupied rooms → measurements at a representative sample of occupant locations spread throughout the occupied zone. Unoccupied rooms → make a good faith estimate of the most significant future occupant locations within the room and make appropriate measurements. www.testo.org/en/home/products/comfort_and _indoor_air_quality/iaq_and_comfort_level.jsp
Evaluation of the thermal environment
Measurement positions
Location of measurements If occupancy distribution cannot be estimated, then the measurement locations shall be: a) in the center of the room or zone; b) 1.0 m inward from the center of each of the room's walls; c) 1.0 m inward from the center of the largest window for exterior walls with windows.
1m
1m 1m
Evaluation of the thermal environment
Measurement positions Height above floor of measurements
- 1.1 m (ta, va)
- 1.7 m (ta, va)
- 1.1 m (H, pa, ∆tpr) - 0.6 m (H, pa, ∆tpr)
- 0.1 m (ta, va) - 0.1 m (ta, va)
http://www.blowtex-educair.it/
Evaluation of the thermal environment Measuring Conditions To determine the effectiveness of the building system at providing the environmental conditions specified in the ASHRAE 55 Standard, measurements shall be made under the following conditions: • Heating period (winter conditions) → measurements shall be made when the indooroutdoor temperature difference is not less than 50% of the difference used for design and with cloudy to partly cloudy sky conditions. If these sky conditions are rare and not representative of the sky conditions used for design, then sky conditions representative of design conditions are acceptable. • Cooling period (summer conditions) → measurements shall be made when the outdoorindoor temperature difference and humidity difference are not less than 50% of the differences used for design and with clear to partly cloudy sky conditions. If these sky conditions are rare and not representative of the sky conditions used for design, then sky conditions representative of design conditions are acceptable. • Test interior zones of large buildings → measurements shall be made with the zone loaded to at least 50% of the design load for at least one complete cycle of the HVAC system, if not proportionally controlled. Simulation of heat generated by occupants is recommended.
Evaluation of the thermal environment Mechanical Equipment Operating Conditions To determine appropriate corrective actions following the use of ASHRAE 55 Standard to analyse the environment, the following operations of the mechanical system should be measured concurrently with the environmental data: •
Air supply rate into the space being measured;
•
Room/supply air temperature differential;
•
Type and location of room diffuser or air outlet;
•
Discharge air speed;
•
Perimeter heat type, location and status;
•
Return grille location and size;
•
Type of air supply system;
•
Surface temperatures of heated or cooled surfaces;
•
Water supply and return temperatures of hydronic systems.
Evaluation of the thermal environment Validating the Thermal Environment
Define Criteria After the definition of the comfort criteria, the validation team will evaluate the system’s ability to meet and maintain the desired comfort level(s). The comfort criteria definition must outline at least the following: • Temperature (air, radiant, surface); • Humidity; • Air speed.
The environmental conditions must be specified as well to ensure measurements taken correspond correctly to the design parameters. https://www.dantecdynamics.com/e-shop
Environmental conditions required are, but are not limited to: • Outdoor temperature design conditions; • Outdoor humidity design conditions; • Clothing (seasonal); • Activity expected.
Evaluation of the thermal environment Validating the Thermal Environment
Documentation The validation also involves ensuring a thoroughly documented process. The process must be well documented and turned over to the design engineer and the owner
for approval and for their records. When surveying the occupants of a building the survey method must be developed, written, and
turned over, with the sample survey sheets to the design engineer and the owner for review and approval. At the completion of the survey, the survey sheets and analysis of the data shall be turned over to the design engineer and the owner for review and sign-off of the validation process.
Evaluation of the thermal environment Long-term evaluation of the general thermal comfort conditions In order to evaluate the comfort conditions over time (season, year), a summation of parameters must be made based on data measured in real buildings or dynamic computer simulations. EN ISO 7730 Annex H lists five methods, each of which can be used for that purpose: Method A: Calculate the number or percentage of hours during the hours the building is occupied, the PMV or the operative temperature is outside a specified range. Method B: The time during which the actual operative temperature exceeds the specified range during the occupied hours is weighted with a factor which is a function of how many degrees the range has been exceeded. Method C: The time during which the actual PMV exceeds the comfort boundaries is weighted with a factor which is a function of the PPD. Method D: The average PPD over time during the occupied hours is calculated. Method E: The PPD over time during the occupied hours is summed.
Evaluation of the thermal environment EN 15251:2007 - Inspections and measurement of the indoor environment in existing buildings Measurements shall be made where occupants are known to spend most of their time and under representative weather condition of cold and warm season.
For the winter (heating season) measurements at or below mean outside temperatures for the 3 coldest months of the year. For the summer (cooling season) measurements at or above statistic average outside temperatures for the 3 warmest months of the year with clear sky.
The measurement period for all measured parameters should be long enough to be representative, for example 10 days. Air temperature in a room can be used in long term measurements and corrected for large hot or cold surfaces to estimate the operative temperature of the room.
Evaluation of the thermal environment EN 15251:2007 - Long term evaluation of the general thermal comfort conditions
According to EN 15251 to evaluate the comfort conditions over time (season, year) a summation of parameters must be made based on data measured in real buildings or dynamic computer simulations. EN 15251 Annex F lists the methods, which can be used for that purpose: Method A: Percentage outside the range - Calculate the number or percentage of occupied hours (those during which the building is occupied) when the PMV or the operative temperature is outside a specified range.
Method B: Degree hours criteria - The time during which the actual operative temperature exceeds the specified range during the occupied hours is weighted by a factor which is a function depending on by how many degrees, the range has been exceeded. Method C: PPD weighted criteria - The time during which the actual PMV exceeds the comfort boundaries is weighted by a factor which is a function of the PPD.
Equipment and methods Measuring instruments Measured quantities Main independent quantities involved in the analysis of the thermal balance between man and the thermal environment Quantities _
ta
tr
va
pa
Icl
Rcl
Air temperature
Mean radiant temperature
Air velocity
Absolute humidity of the air (partial pressure of water vapour)
Insulation of clothing
Evaporative resistance of clothing
Elements in the thermal balance
Internal heat production, M-W Heat transfer by radiation, R Heat transfer by convection, C*
X X
Heat losses through evaporation: - evaporation from the skin, E - evaporation by respiration, Eres
Convection by respiration, Cres
W
Metabolism
External work
X
X
X X
X
X
M
X
X X
X
X
X
* Heat transfer by convection is also influenced by body movements. The resultant air velocity at skin level is called relative air velocity (var). Heat conduction (surface temperature) has only a limited influence on the thermal heat balance.
Source: EN ISO 7726
http://www.testolimited.com/testo-480high-end-vac-measuring-instrument
Equipment and methods Types of temperature sensor
a) Expansion thermometers: 1) liquid expansion thermometer (mercury);
2) solid expansion thermometer. b) Electrical thermometers:
1) variable resistance thermometer • platinum resistor; • thermistor; 2) thermometer based on the generation of an electromotive force (thermocouple). c) Thermom-anometers (variation in the pressure of a liquid as a function of temperature).
Equipment and methods Precautions to be taken when using a temperature probe Reduction of the effect of radiation Care should be taken to prevent the probe from being subjected to radiation from neighbouring heat sources. Means of reducing the effect of radiation on the probe :
a) Reduction of the emission factor of the sensor; b) Reduction in the difference in temperature between the sensor and the adjacent walls. c) Increasing the coefficient of heat transfer by convection.
Certain devices use the three means of protection simultaneously, which results in small measuring errors.
http://www.deltaohm.com/
Equipment and methods The mean radiant temperature is the uniform temperature of an imaginary enclosure in which radiant heat transfer from the human body is equal to the radiant heat transfer in the actual non-uniform enclosure. The mean radiant temperature is defined in relation to the human body.
The mean radiant temperature can be measured by instruments which allow the generally heterogeneous radiation from the walls of an actual enclosure to be "integrated" into a mean value. The black globe thermometer is a device frequently used in order to derive an approximate value of the mean radiant temperature from the observed simultaneous values of the globe temperature, tg, and the temperature and the velocity of the air surrounding the globe.
The spherical shape of the globe thermometer can give a reasonable approximation of the shape of the body in the case of a seated person. An ellipsoid-shaped sensor gives a closer approximation to the human shape both in the upright position and the seated position.
www.alphaomegaelectronics.com
Equipment and methods
Source: ISO 7726
Method for calculation of mean radiant temperature Calculation from the temperature of the surrounding surfaces
The mean radiant temperature can be calculated from • the surface temperature of the surrounding surfaces; • the angle factor between a person and the surrounding surfaces, a function of the shape, the size and the relative positions of the surface in relation to the person. As most building materials have a high emissivity (e), it is possible to disregard the reflection i.e. to assume that all the surfaces in the room are black.
Mean value of angle factor between a seated person and a vertical rectangle (above or below his centre) when the person is rotated around a vertical axis. (To be used when the location but not the orientation of the person is known).
Mean value of angle factor between a seated person and a horizontal rectangle (on the ceiling or on the floor) when the person is rotated around a vertical axis. (To be used when the location but not the orientation of the person is known.)
Equipment and methods Method for calculation of mean radiant temperature Calculation from the temperature of the surrounding surfaces The angle factors (Fp-n) can also be calculated from the equation:
Where:
Source: ISO 7726
Fmax
A
B
C
Seated Person Vertical surfaces: Wall, Window
0.18
1.216
0.169
0.717
Seated Person Horizontal surfaces: Floor, Ceiling
0.116
1.396
0.130
0.951
0.080
0.055
Standing Person Vertical surfaces: Wall, Window
0.120
1.242
0.167
0.616
0.082
0.051
0.116
1.595
0.128
1.226
0.046
0.044
Standing Person Horizontal surfaces: Floor, Ceiling
D 0.087
E 0.052
Equipment and methods
Projected area factors
Method for calculation of mean radiant temperature Calculation from the plane radiant temperature
The mean radiant temperature may be calculated from: • the plane radiant temperature, tpr, in six directions; • the projected area factors for a person in the same six directions.
The mean radiant temperature can be calculated by multiplying the six measured values by the relevant projection factors given in the table adding the resultant data and dividing the result by the sum of the projected area factors. Where the orientation of the person is not fixed, the average of the Right/Left and Front/Back projected area factors is used.
Left/right
Front/bac k
Standing
Person Ellipsoid Sphere
0.,08 0.08 0.25
0.23 0.28 0.25
0.35 0.28 0.25
Seated
Person Ellipsoid Sphere
0.18 0.18 0.25
0.22 0.22 0.25
0.30 0.28 0.25
Source: EN ISO 7726
The projected area factors for a seated or standing person are given in the table for the six directions: up (1), down (2), left (3), right (4), front (5), back (6).
Up/down
Equipment and methods The plane radiant temperature and radiant temperature asymmetry can be measured using : • a net radiometer; • a heated sensor consisting of a reflective disc, and an absorbing disc;
With a net radiometer it is possible to determine the plane radiant temperature from the net radiation exchanged between the environment and the surface element and the surface temperature of the radiometer. A radiometer with a sensor consisting of a reflective disc (polished) and an absorbent disc (painted black) can also be used.
http://www.deltaohm.com
www.kippzonen.com
Equipment and methods Method for calculation of plane radiant temperature The plane radiant temperature can be calculated from: •
the surface temperature of the surrounding surfaces;
•
the angle factor between a small plane element and the surrounding surfaces, a function of the shape, the size and the relative position of the surface in relation to a person.
The radiant temperature asymmetry is estimated as the difference between the plane radiant
temperature in two opposite directions. As most building materials have a high emittance (e), it is possible to disregard the reflections, i.e. to
assume that all the surfaces in the room are black. Analytical formula relating to the calculation of the Analytical relating to the calculation of the as shape factor value in the case of asurface small plane element The planeformula radiant temperature is calculated the mean of the temperatures shape factor in the case of a small plane element parallel to a rectangular surface weighted according to the magnitude of the respective angle factors. perpendicular to a rectangular surface Source: ISO 7726
Equipment and methods Method for calculation of plane radiant temperature
Chart for the calculation of the shape factor in the case of a small plane element perpendicular to a rectangular surface Source: ISO 7726
Chart for the calculation of the shape factor in the case of a small plane element parallel to a rectangular surface
Equipment and methods The absolute humidity can be determined: •
•
Directly: -
dew-point instruments;
-
electrolytic instruments; or
Indirectly by the simultaneously:
measurement
of
several
-
relative humidity and temperature of the air;
-
psychrometric wet temperature; and
-
temperature of the air.
quantities
http://www.dpi.nsw.gov.au/agriculture/h orticulture/greenhouse/structures/evapcooling
http://www.deltaohm.com/
Equipment and methods Measurement of the absolute humidity using psychrometry
Description and principle of operation A psychrometer consists of two thermometers and a device to ensure ventilation of the thermometers at a minimum air velocity. The first thermometer is an ordinary thermometer indicating the air temperature, ta, the "dry" temperature of the air. The latter consists of a thermometer surrounded by a wet wick generally made from close-meshed cotton. The end of the wick lies in a container of water.
Equipment and methods Direct determination of the characteristics of humid air using a psychometric chart
thermo-hygrometric
The main characteristics of humid air are usually grouped together in a chart known as a psychometric chart. The coordinates of this chart are as follows: • on the x-axis → the air temperature, ta (ºC); • on the y-axis → the partial pressure of water vapour, pa, of the air (kPa).
Psychrometric chart Source: ISO 7726
Equipment and methods The air velocity is a quantity defined by its magnitude and direction. The quantity to be considered in the case of thermal environments is the speed of the air, i.e. the magnitude of the velocity vector of the flow at the measuring point considered. The following factors must be considered for accurate velocity measurements: a) the calibration of the instrument; b) the response time of the sensor and the instrument; c) the measuring period. Types of anemometers https://www.dantecdynamics.com/e-shop The air velocity, Va, can be determined: • either by the use of an omnidirectional probe which is sensitive to the magnitude of the velocity whatever its direction (hot-sphere sensor); • or by the use of three directional sensors which allow the components of the air velocity to be measured along three perpendicular axis (cosine law).
In practice it is very difficult to measure accurately in one direction.
Equipment and methods The surface temperature can be measured by the method given in EN ISO 7726 Annex F, including: •
contact thermometer, where the sensor is in direct contact with the surface.
•
infrared sensor, where the radiant heat flux from the surface is measured and converted to a temperature. This may be influenced by the emissivity of surface.
http://www.deltaohm.com
Equipment and methods Characteristics of measuring instruments Characteristics of instruments for measuring the basic quantities Characteristics of measuring instruments – Air temperature (ta) Class C (Comfort)
Class S (thermal stress)
Measuring Accuracy range
Response time (90%)
10ºC to 40ºC
The shortest -40ºC to possible. Value +120ºC to be specified as characteristic of the measuring instrument.
Source: EN ISO 7726
Measuring range
Accuracy
Response time (90%) The shortest possible. Value to be specified as characteristic of the measuring instrument.
Comments The air temperature sensor shall be effectively protected from any effects of the thermal radiation coming from hot or cold Wall. Na indication of the mean value over a period of 1 min is also desirable
Equipment and methods Characteristics of measuring instruments Characteristics of instruments for measuring the basic quantities
Class C (Comfort)
Class S (thermal stress)
Measuring range
Accuracy
Response time (90%)
Measuring range
10ºC to 40ºC
Required: ± 2ºC Desirable: ± 0.2ºC
The shortest possible. Value to be specified as characteristic of the measuring instrument.
-40ºC to +150ºC
These levels are difficult or even impossible to achieve in certain cases with the equipment normally available. When they cannot be achieved, indicate the actual measuring precision.
Source: EN ISO 7726
Accuracy
Response time (90%)
Comments
The shortest possible. Value to be specified as characteristic of the measuring instrument.
When the measurement is carried out with a black sphere, the inaccuracy relating to the mean radiant temperature can be as high as ± 5ºC for class C and ± 20ºC for class S according to the environment and the inaccuracy for Va, ta and tg.
Equipment and methods Characteristics of measuring instruments Characteristics of instruments for measuring the basic quantities Characteristics of measuring instruments – Plane radiant temperature (tpr) Class C (Comfort) Measuring Accuracy range
Class S (thermal stress) Response time (90%) The shortest possible.
0ºC to 50ºC
Value to be specified as characteristic of the measuring instrument.
Source: EN ISO 7726
Measuring range 0ºC to 200ºC
Accuracy
Response time (90%) The shortest possible. Value to be specified as characteristic of the measuring instrument.
Comments
Equipment and methods Characteristics of measuring instruments
Characteristics of instruments for measuring the basic quantities Characteristics of measuring instruments – Air Velocity (Va) Class C (Comfort) Measuring Accuracy range
0.05 m/s to 1.0 m/s
Required: ± (0.05 + 0.05Va) m/s
Class S (thermal stress) Response time (90%)
Measuring range
Accuracy
Response time (90%)
Required: 0.5 s
0.2 m/s to 20.0 m/s
Required: ± (0.1 + 0.05Va) m/s
The shortest possible. Value to be specified as characteristic of the measuring instrument.
Desirable: 0.2 s
Desirable: ± (0.02 + 0.07Va) m/s
Desirable: ± (0.05 + 0.05Va) m/s
These levels shall be guaranteed whatever the direction of flow within a solid angle (:) = 3 sr
These levels shall be guaranteed whatever the direction of flow within a solid angle (:) = 3 sr
Source: EN ISO 7726
For measuring the degree of turbulence a small response time is needed.
Comments Except in the case of a unidirectional air current, the air velocity sensor shall measure the velocity whatever the direction of the air. An indication of the mean value and standard deviation for a period of 3 min is also desirable.
Equipment and methods Characteristics of measuring instruments
Characteristics of instruments for measuring the basic quantities Characteristics of measuring instruments – Absolute humidity expressed as partial pressure of water vapour (pa) Class C (Comfort)
Measuring range
Accuracy
Class S (thermal stress)
Response time (90%)
Measuring range
The shortest 0.5 kPa to possible. Value 6.0 kPa to be specified as characteristic of the measuring instrument.
0.5 kPa to 3.0 kPa
Source: EN ISO 7726
Accuracy
Response time (90%) The shortest possible. Value to be specified as characteristic of the measuring instrument.
Comments
Equipment and methods Characteristics of measuring instruments Characteristics of instruments for measuring the basic quantities Characteristics of measuring instruments – Surface temperature (ts) Class C (Comfort) Measuring Accuracy range 0ºC to 50ºC
Required: ± 1ºC Desirable: ± 0.5ºC
Class S (thermal stress) Response time (90%)
Measuring range
The shortest -40ºC to possible. Value +120ºC to be specified as characteristic of the measuring instrument.
Accuracy Required: < -10ºC: ± [1+0.05(-ts10)] -10ºC to 50ºC: ± 1ºC > 50ºC: ± [1+0.05(ts50)]
Desirable: required accuracy / 2
Source: EN ISO 7726
Response time (90%) The shortest possible. Value to be specified as characteristic of the measuring instrument.
Comments
Equipment and methods Characteristics of measuring instruments for measuring the basic quantities The standard environmental conditions specified shall be used as a reference except where this contradicts the principle for measuring the quantities under consideration. Standard environmental conditions for the determinations of time constants of sensors Quantities of the standard environment Measurement of the response time of sensors for
ta
Air temperature
= ta
Mean radiant temperature
pa
va
Any
< 0.15 m/s
Any
< 0.15 m/s
Absolute humidity
= 20ºC
= ta
Air velocity
= 20ºC
= ta
Any
Plane radiant temperature
= 20ºC
= ta
Any
< 0.15 m/s
Surface temperature
= 20ºC
= ta
Any
< 0.15 m/s
Source: EN ISO 7726
To be specified according to the measuring method
Equipment and methods Specifications relating to measuring methods The methods for measuring the physical characteristics of the environment shall take account of the fact that these characteristics vary in location and time. The thermal environment may vary with the horizontal location, and then account has to be taken of how long a time a person is working at the different locations.
The environment may also vary in the vertical direction.
Equipment and methods Specifications relating to measuring methods Specifications relating to variations in the physical quantities within the space surrounding the subject When the environment is too heterogeneous, the physical quantities shall be measured at several locations at or around the subject and account taken of the partial results obtained in order to determine the mean value of the quantities to be considered in assessing the comfort or the thermal stress. Previous analyses of the thermal stress of the work places being studied or of work places of a similar type may provide information which is of interest in determining whether certain of the quantities are distributed in a homogeneous way.
In the case of poorly defined rooms or work places consider only a limited zone of occupancy where the criteria of comfort or thermal stress shall be respected. In case of dispute in the interpretation of data, measurements carried out presuming the environment to be heterogeneous shall be used as a reference.
Equipment and methods Specifications relating to measuring methods Specifications relating to variations in the physical quantities within the space surrounding the subject The sensors shall be placed at the heights where the person normally carries out his activity. Measuring heights for the physical quantities of an environment
Location of the sensors
Weighting coefficients for measurements for calculation mean values Homogeneous environment Class C
Class S
Head level
Abdomen level
1
Ankle level
1
Heterogeneous environment
Recommended heights (guidance )
Class C
Class S
Sitting
Standing
1
1
1.1 m
1.7 m
1
2
0.6 m
1.1 m
1
1
0.1 m
0.1 m
Plane radiant temperature, mean radiant temperature and absolute humidity are normally only measured at the centre height. Source: EN ISO 7726
Class C (Comfort)
Equipment and methods Specifications methods
relating
to
measuring
Class S (thermal stress)
Measuri Accuracy ng range
Response time (90%)
10ºC to 40ºC
The shortest -40ºC to possible. +120ºC Value to be specified as characteristi c of the measuring instrument.
Specifications relating to the variations in the physical quantities with time An environment is said to be stationary in
Measurin Accuracy g range
The shortest possible. Value to be specified as characteristi c of the measuring instrument.
relation to the subject when the physical quantities used to describe the level of
exposure are practically independent of the
Response time (90%)
Comments
The air temperature sensor shall be effectively protected from any effects of the thermal radiation coming from hot or cold Wall. Na indication of the mean value over a period of 1 min is also desirable
Class C (comfort) Factor x
Class S (thermal stress) Factor x
Air temperature
3
4
Mean radiant temperature
2
2
temporal value do not exceed the values
Radiant temperature asymmetry
2
3
obtained by multiplying the required measuring
Mean air velocity
2
3
Vapour pressure
2
3
Elements in the thermal balance
time, i.e. for instance when the fluctuations in
these parameters in relation to their mean
accuracy by the corresponding factor X. Source: EN ISO 7726
Note: Deviation between each individual quantity and their mean value shall be less than that obtained multiplying the required measuring accuracy by the appropriate factor x listed here.
Equipment and methods Operative temperature (to) is defined as the uniform temperature of an enclosure in which an occupant would exchange the same amount of heat by radiation plus convection as in the existing non-uniform environment.
ℎ𝑐 . 𝑡𝑎 + ℎ𝑟 . 𝑡𝑟ҧ 𝑡𝑜 = ℎ𝑐 + ℎ𝑟 Where: ta – air temperature 𝑡𝑟ҧ – mean radiant temperature hc – heat-transfer coefficient by convection hc – heat-transfer coefficient by radiation. In general: hr = 4,9 w/m2k hc = 2,9 w/m2k If : - surfaces with very different temperatures - hr = 𝑡𝑟ҧ ; - high air velocities (var >0.2 m/s) - hc = (10. var ) 1/2.
Assessment procedures overview
Working procedure: 1. 2. 3. 4. 5. 6. 7.
Identification of the problem, which causes complaints. What is the reason? Identification of values that will support the assumption. Taking measurements. Evaluation of data obtained. Making conclusion and draft of measures to solve detected problems. Final report. http://www.healthyheating.com/Ther mal-Comfort-Survey/Thermalcomfort-survey.htm#.VR0uBfzF_R8
Assessment procedures overview Complete plans, descriptions, component literature, and operation and maintenance instructions for the building systems should be provided and maintained.
https://www.energystar.gov/index.cfm?c=next_generation.ng_thermal_enclosure_sys
Assessment procedures overview The information should include, but not be limited to, building system design specifications
and design intent as follows: 1. The design criteria of the system in terms of indoor temperature and humidity,
including any tolerance or range, based on stated design outdoor ambient conditions and total indoor loads, should be stated. Values assumed for comfort parameters,
including clothing and metabolic rate, used in calculation of design temperatures, should be clearly stated.
2. The system input or output capacities necessary to attain the design indoor conditions at design outdoor ambient conditions should be stated, as well as the full
input or output capacities of the system as supplied and installed. 3. The limitations of the system to control the environment of the zone (s) should be
stated whether based on temperature, humidity, ventilation, time of week, time of day, or seasonal criteria.
Assessment procedures overview The information should include, but not be limited to, building system design specifications and design intent as follows: 4. The overall space supplied by the system should be shown in a plan view layout, with individual zones within it identified. All registers or terminal units should be shown and identified with type, flow, or radiant value. 5. Significant structural and decor items should be shown and identified if they affect indoor comfort. Notes should be provided to identify which areas within a space, and what locations relative to registers, terminal units, relief grills, and control sensors should not be obstructed as this would negatively affect indoor comfort. 6. Areas within any zone that lie outside the comfort control areas, where people should not be permanently located, should be identified.
Assessment procedures overview The information should include, but not be limited to, building system design specifications and design intent as follows: 7. Locations of all occupant adjustable controls should be identified, and each should be provided with a legend describing what zone(s) it controls, what function(s) it controls, how it is to be adjusted, the range of effect it can have, and the recommended setting for various times of day, season, or occupancy load. 8. If more than one comfort level is available for any zone(s), they should be identified as A, B, C etc., with A being the narrowest range (highest comfort), and the specifications as above should be provided for each, along with the relative seasonal energy usage for each at 80 % of design ambient.
Assessment procedures overview The information should include, but not be limited to, building system design specifications and design intent as follows: 9. A control schematic should be provided in block diagram with sensors, adjustable controls, and actuators accurately identified for each zone. If zone control systems are independent but identical, one diagram is sufficient if identified for which zones it applies. If zones are interdependent or inter-active, their control diagram
should be shown in total on one block diagram with the point(s) of interconnection identified.
10. The general maintenance, operation and performance of the building systems should be stated, followed by more specific comments on the maintenance and operation of the automatic controls and manually adjustable controls, and the response of the system to each. Where necessary, specific seasonal settings of manual controls should be stated, as also major system changeovers that are required to be performed
by a professional service agency should be identified.
Assessment procedures overview The information should include, but not be limited to, building system design specifications and design intent as follows: 11. Specific limits in the adjustment of manual controls should be stated.
Recommendations for seasonal setting on these should be stated along with the degree of manual change that should be made at any one time, and the waiting time
between adjustments, in trying to fine tune the system. A maintenance and inspection schedule for all thermal environmental related building systems
should be provided. 12. Assumed electrical load for lighting and equipment in occupied spaces (including
diversity considerations) used in HVAC load calculations should be documented, along with any other significant thermal and moisture loads assumed in HVAC load
calculations and any other assumptions upon which HVAC and control design is based.
Thermal Comfort Predictive Models Standards EN ISO 7730:2005
EN 15251:2007 ASHRAE 55:2010
Thermal Comfort Predictive Models Standards EN ISO 7726:2001 - Ergonomics of the thermal environment - Instruments and methods for measuring physical quantities; EN ISO 7243:1989 - Hot environments - Estimation of the heat stress on working man, based on the WBGT-index (wet bulb globe temperature); ISO 7933:2004 - Ergonomics of the thermal environment - Analytical determination and interpretation of heat stress using calculation of the predicted heat strain; ISO 11079:2007 - Ergonomics of the thermal environment - Determination and interpretation of cold stress when using required clothing insulation (IREQ) and local cooling effects.
Air Velocity
Clothing Insulation
Metabolic Rate
Mean Radiant Temperature
Air Temperature
Relative Humidity
Thermal Comfort Predictive Models
EN ISO 7730:2005 Air Temperature
Relative Humidity
Thermal Comfort Predictive Models
Clothing Insulation
Ergonomics of the thermal environment
comfort using calculation of the PMV and PPD indices and local thermal comfort criteria Air Velocity
Metabolic Rate
Mean Radiant Temperature
Analytical determination and interpretation of thermal
Thermal Comfort Predictive Models EN ISO 7730:2005 Presents methods for predicting the general thermal sensation and degree of discomfort (thermal dissatisfaction) of people exposed to moderate thermal environments.
Also specifies how to predict the percentage dissatisfied owing to local discomfort parameters.
http://sustainabilityworkshop.autodesk.com/buildings/controls-lighting-and-daylighting
Thermal Comfort Predictive Models EN ISO 7730:2005 A human being's thermal sensation is mainly related to the thermal balance of his or her body as a
whole.
physical activity clothing • PMV (predicted mean vote) estimated or measured
• PPD (predicted percentage of dissatisfied)
air temperature mean radiant temperature air velocity air humidity
• Local criteria
thermal
comfort
Thermal Comfort Predictive Models EN ISO 7730:2005 PMV Seven-point thermal sensation scale: + 3 → Hot + 2 → Warm + 1 → Slightly warm
0 → Neutral − 1 → Slightly cool − 2 → Cool − 3 → Cold
Thermal Comfort Predictive Models EN ISO 7730:2005
Thermal Comfort Predictive Models EN ISO 7730:2005 Where:
𝑀 is the metabolic rate (W/𝑚2 ); 𝑊 is the effective mechanical power (W/𝑚2 );
𝐼𝑐𝑙 is the clothing insulation (𝑚2 ⋅K/W); 𝑓𝑐𝑙 is the clothing surface area factor;
𝑡𝑎 is the air temperature (°C); 𝑡𝑟ҧ is the mean radiant temperature (°C);
𝑣𝑎𝑟 is the relative air velocity (m/s); 𝑝𝑎 is the water vapour partial pressure (Pa); ℎ𝑐 is the convective heat transfer coefficient [W/(𝑚2 ⋅ K)]; 𝑡𝑐𝑙 is the clothing surface temperature (°C).
Thermal Comfort Predictive Models EN ISO 7730:2005 The PMV index should be used only for values of PMV between −2 and +2, and when the six main parameters are within the following intervals: M - 46 W/m2 to 232 W/m2 (0,8 met to 4 met); Icl - 0 m2 ⋅ K/W to 0,310 m2⋅K/W (0 clo to 2 clo); ta - 10 °C to 30 °C; tr - 10 °C to 40 °C;
var - 0 m/s to 1 m/s; pa - 0 Pa to 2 700 Pa. 1 metabolic unit = 1 met = 58,2 W/m2;
1 clothing unit = 1 clo = 0,155 m2 ⋅ °C/W.
Thermal Comfort Predictive Models EN ISO 7730:2005 100%
Predicted percentage dissatisfied (PPD)
90%
With the PMV value determined, calculate the PPD: 𝑃𝑃𝐷 = 100 − 95 ∗ exp(−0.03353 ∗ 𝑃𝑀𝑉 4 − 0.2179 ∗ 𝑃𝑀𝑉 2 )
PPD
80% 70% 60% 50% 40%
Where: PMV - predicted mean vote PPD - predicted percentage dissatisfied (%) The
PPD
predicts
the
number
of
thermally
dissatisfied persons among a large group of people.
30% 20% 10% 0% -3
-2
-1
0 PMV
-3
-2
-1
0
Cold
Cool
slightly cool
Neutral
The rest of the group will feel thermally neutral,
1
2
3
+1
+2
+3
slightly warm
Warm
Hot
T = Tair - Tair comfortable
slightly warm or slightly cool. -8º
-6
-4
-2
0º
+2
+4
+6
+8º
Thermal Comfort Predictive Models EN ISO 7730:2005
Local thermal discomfort The PMV and PPD express warm and cold discomfort for the body as a whole. Thermal dissatisfaction can also be caused by unwanted cooling or heating of one particular part of the body → local discomfort. The most common local discomfort factors are: • draught (local cooling of the body caused by air movement); • radiant temperature asymmetry (cold or warm surfaces); • vertical air temperature difference (between the head and ankles); and • cold or warm floors.
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Thermal Comfort Predictive Models EN ISO 7730:2005 Local thermal discomfort Draught The discomfort due to draught may be expressed as the percentage of people predicted to be bothered by draught. The draught rate (DR): 𝐷𝑅 = 34 − 𝑡𝑎.𝐼 . 𝑣ҧ𝑎,𝐼 − 0.05
0.62
. 0.37. 𝑣ҧ𝑎,𝐼 . 𝑇𝑢 + 3.14
𝐹𝑜𝑟 𝑣ҧ𝑎,𝐼 < 0.05 𝑚/𝑠 𝑢𝑠𝑒 𝑣ҧ𝑎,𝐼 = 0.05 𝑚/𝑠 For DR > 100% use DR=100%
Where: ta,I - local air temperature, in degrees Celsius, 20 °C to 26 °C; 𝑣ҧ𝑎,𝐼 - local mean air velocity, in metres per second, < 0,5 m/s; Tu - local turbulence intensity, in percent, 10 % to 60 % (if unknown, 40% may be used). The model applies to people at light, mainly sedentary activity with a thermal sensation for the whole body close to neutral and for prediction of draught at the neck. At the level of arms and feet, the model could overestimate the predicted draught rate. The sensation of draught is lower at activities higher than sedentary (> 1,2 met) and for people feeling warmer than neutral.
Thermal Comfort Predictive Models EN ISO 7730:2005 Local thermal discomfort Vertical air temperature difference
Local thermal discomfort
Warm and cool floors
25 oC
19 oC
PD - percentage dissatisfied (%) ta,v - vertical air temperature difference between head and feet (°C)
Local discomfort caused by vertical air temperature difference, when the temperature increases upwards
PD tf
- percentage dissatisfied (%) - floor temperature (°C)
Local thermal discomfort caused by warm or cold floors
Thermal Comfort Predictive Models Local thermal discomfort
Radiant asymmetry Warm ceiling
Cool wall
Cool ceiling Warm wall
PD - percentage dissatisfied (%) tpr - radiant temperature asymmetry (°C)
Local thermal discomfort caused by radiant temperature asymmetry
Source: EN 7730:2005
Thermal Comfort Predictive Models EN ISO 7730:2005 Categories of thermal environment The desired thermal environment for a space may be selected from among the three categories, A, B and C. All the criteria should be satisfied simultaneously for each category. Categories of thermal environment Thermal state of the body as a whole
Local discomfort PD (%)
Category PPD (%)
PMV
DR (%)
caused by vertical air temperature difference
warm or cool floor
radiant asymmetry
A