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Sem 2 bs1 ventitation 2
- 1. VENTILATION QSB 1714 Prepared by:Lim T. S.
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- 3. Thermal Comfort Thermalcomfort is defined in British Standard BS EN ISO 7730 as: ‘that condition of mind which expresses satisfaction with the thermal environment.’ So the term ‘thermal comfort’ describes a person’s psychological state of mind and is usually referred to in terms of whether someone is feeling too hot or too cold.
- 4. Thermal Comfort Thermalcomfort is very difficult to define because you need to take into account a range of environmental and personal factors when deciding what will make people feel comfortable. Even people who are in the same room can feel significant temperature differences due to their metabolic rates, which makes it very hard to find an optimal temperature for everyone in a given location. The best that you can realistically hope to achieve is a thermal environment that satisfies the majority of people in the workplace, or put more simply, ‘reasonable comfort’.
- 5. Thermal comfortis a term used by the American Society of Heating, Refrigerating and Air- Conditioning Engineers, an international body. It is defined as the state of mind in humans that expresses satisfaction with the surrounding environment (ANSI/ASHRAE Standard 55). 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. Thermal Comfort
- 6. Thermal comfortis affected by heat conduction, convection, radiation, and evaporative heat loss. Thermal comfort is maintained when the heat generated by human metabolism is allowed to dissipate, thus maintaining thermal equilibrium with the surroundings. It has been long recognised that the sensation of feeling hot or cold is not just dependent on air temperature alone. Thermal Comfort
- 7. Thermal discomforthas been known to lead to Sick Building Syndrome symptoms. The combination of high temperature and high relative humidity serves to reduce thermal comfort and indoor air quality. The occurrence of symptoms increased much more with raised indoor temperatures in the winter than in the summer due to the larger difference created between indoor and outdoor temperatures. Importance of thermal comfort
- 8. Thermal Comfort What affectthermal comfort? Personal factors (health, psychology, sociology & situational factors) Activity levels Insulative clothing Air temperature Mean radiant temperature Air movement/velocity (see wind chill factor) Relative humidity (see also perspiration)
- 9. Each personhas a different metabolic rate, and these rates can fluctuate when a person is performing certain activities, or under certain environmental conditions. Level of activity influences the level of heat generated. In high activity the temperature rises and the more heat you will give off. Typical heat output of an adult male
- 10. The amountof clothing that we wear generally depends on the season and affects our thermal comfort. Clothing is measured in a scale called clo value. During cold weather, layers of insulating clothing can help keep a person warm. At the same time, if the person is doing a large amount of physical activity, lots of clothing layers can prevent heat loss and possibly lead to overheating. Activity level is compared to being seated quietly, such as in a classroom. This standard amount of insulation required to keep a resting person warm in a windless room at 70 °F (21.1 °C) is equal to one clo.
- 11. Environmental Comfort Factors Theconditions that maintain the thermal balance in a building are: Air temperature (dry bulb – deg C) Humidity of the air (%) Air speed (m per sec) Radiant conditions These factors are controllable through design – a passive system should control all four factors; – an active (HVAC) system is expected to control the first three (with “architecture” controlling the fourth)
- 12. When we adjusta thermostat, we are setting a goal for a comfort air temperature.
- 13. …and the levelof humidity at that temperature. Relative humidity creates the perception of an extremely dry or extremely damp indoor environment. This can then play a part in the perceived temperature and their thermal comfort. The recommended level of indoor humidity is in the range of 30-60%.
- 14. and the temperature*of the wall, window, ceiling, and floor surfaces in the room * This condition is called the “mean radiant temperature”
- 15. To feel good,a range of combinations create a comfort field in which: The air is not too humid Air speeds remain within established limits The difference between radiant and air temperature remains small The difference of the radiant temperature in different directions (between your body and adjacent surfaces) remains small. Room air temperature between head and feet is small The air is clean
- 16. Optimal thermal comfortrequires the heat loss of the human body to be in BALANCE with its heat production. This is similar to the relationship between an activity (exercising, skiing…) and clothes - our second skin.
- 17. And our home…. …whichwe might think of as our third “skin”.
- 18. What are thequalities that assure we are comfortable in our homes?
- 19. The ability toprovide thermal comfort is one of the most important functions of a building. not too hot, not too cold
- 20. Comfort in building Good building is not only about avoiding problems, it should also be about creating positively pleasurable and healthy living places. Comfort in building is about the physical environment in its totality.
- 21. Comfort in building Human beings operate and feel better when they are at temperatures which are comfortable. It is now well understood that in the workplace, accidents increase as temperatures go outside the zone of 16 to 24°C. However temperature is also strongly linked to humidity levels as regards comfort. In the section on health, controlling humidity and temperature was seen as a method of controlling pollutants . Interestingly the levels of humidity and temperature which are most healthy are also the most comfortable. There is no conflict between health and comfort.
- 22. Maintaining this comfortfield is the domain of these two important building systems: BUILDING ENVELOPE Which includes the walls, floors, and roof or ceilings that enclose the building, and any penetrations of that enclosure for doors, windows, chimneys, vents, etc. plus the accumulated air leakage created by gaps in the structure MECHANICAL SYSTEMS That provide supplemental heating, sometimes cooling, and any controlled ventilation.
- 23. Shortcomings in thebuilding envelope often require us to tolerate conditions outside the comfort field. Buildings that are leaky, drafty, and minimally insulated, with average windows, variation in temperature between ceiling and floor, and cold surrounding surfaces are likely to be experienced as uncomfortable …this is typical of MOST buildings!
- 24. We seek controlover these conditions thru the use of mechanical systems like boilers and furnaces.
- 25. To overcome ourdiscomfort we may rely (at a cost) on additional fans, heaters, humidifiers, etc. to establish a local comfort zone. …or just wear more clothes
- 26. Comfort design inbuilding What would you consider in design to maintain temperature in buildings? The resistance of a material to the passage of heat and the thermal conductivity of the material in passing the heat along are the basics of understanding of maintaining a steady temperature and a comfortable thermal indoor environment. In order to maintain a comfortable room temperature the building must be provided with as much heat as is lost through ventilation.
- 27. Comfort design inbuilding Comfortable temperature for humans is provided by balancing the heat lost through conduction and ventilation through the fabric with similar heat. Optimum temperature will depend on material used , type of construction, orientation of the building and degree of exposure to the rain and wind. What will the loss of heat in buildings depend on? Materials used Type of construction Orientation of the building in relation to the sun Degree of exposure to rain and wind
- 28. These are thebuilding design strategies and effects that we rely on to create the conditions that assure thermal comfort.
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- 30. Causes of IndoorAir Quality Problem Temperature and/or Humidity Too much glare Inadequate fresh air Lead to carbon dioxide (CO2) buildup Normal outdoor CO2 Level is 350 ppm Indoor CO2 level can be 600-800 ppm > 1000ppm CO2 levels –Tired/sleepness Cal/OSHA permissible exposure limit for CO2 is 5000 ppm.
- 31. Sources of IndoorPollutants Base on Specific Building Combustion activity Furniture Chemical Building materials Food Water Smoking activity Outdoor air pollution
- 32. Control of indoorpollutant methods include: 1. remove source of pollution 2. provide local extract at pollution sources 3. provide sufficient general ventilation to dilute and remove the pollution 4. purify internal air
- 33. Introduction of Chemicals& Contaminants into the Building Old food – Forgotten lunches/snacks Building Remodeling – Adhesives, Paints Select Low volatile/low toxicity products Schedule work on weekends/after hours Allow remodeled area to off-gas prior to re-occupation Temporarily relocate employees
- 34. Introduction of Chemicals& Contaminants into the Building Building air inlet – Auto exhaust Cleaners UCOP Uses green seal cleaning supplies Non-Toxic Not a skin sensitizer Does not contain substance which contribute to poor indoor air quality If using a cleaner – be aware of how your actions may impact your co- workers
- 35. Introduction of Chemicals& Contaminants into the Building Printer/Copying Machines Can generate particulate and ozone Ozone –eye & respiratory irriation Do not place in room with poor ventilation Do not point printer exhaust at individuals
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- 37. Passive Stack Ventilation(PSV) Combines with trickle ventilation through window frames.
- 38. The simple vertical(or as near vertical as possible) ducts from kitchen and bathroom to ridge vents or a roof terminal.
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- 42. One optionto provide domestic ventilation is the use of a passive stack (PSV) system. This uses a combination of the air flowing over the roof and the natural buoyancy of warm moist air to lift the moist, stale air from the kitchen, bathroom, etc up ducting to the roof ridge level where it escapes into the atmosphere.
- 43. Fresh air isdrawn into the building through the trickle vents in the windows and doors etc. Without the need for any electric fans or control, PSV system are energy efficient. The amount of ventilation achieved depends largely on the amount of movement of the external air and the external air temperature.
- 44. Factors Affecting Ventilation& Wind Forces Include: Average wind speed Prevailing wind direction Seasonal and daily variation in wind speed and direction Local obstructing objects, such as nearby buildings and trees Position and characteristic of openings through which air flows; and Distribution of surface pressure coefficients for the wind. Natural ventilation systems are often designed for wind speeds of half the average seasonal velocity because from climatic analysis there are very few places where wind speed falls below half the average velocity for many hours in a year.
- 45. Guidelines for naturalventilation A natural ventilation system should be effective regardless of wind direction and there must be adequate ventilation even when the wind does not blow from the prevailing direction; Inlet and outlet openings should not be obstructed by nearby objects; windows should be located in opposing pressure zone since this usually will increase ventilation rate; A certain vertical distance should be kept between openings for temperature to produce stack effect; Openings at the same level and near to the ceiling should be avoided since much of the air flow may bypass the occupied zone; Architectural elements like wingwalls, parapets and overhangs may be used to promote air flow into the building;
- 46. Guidelines for naturalventilation Topography, landscaping, and surrounding buildings should be used to redirect airflow and give maximum exposure to breeze; In hot, humid climates, air velocities should be maximized in the occupied zones for bodily cooling; To admit wind air flow, the long facade of the building and the door and window opening should be oriented with respect to the prevailing wind direction; If possible, window openings should be accessible to and operable by occupants; Vertical shafts and open staircases may be used to increase and generate stack effects; Opening in the vicinity of the neutral pressure level may be reduced since they are less effective for the thermally induced ventilation;
- 47. Effects of naturalventilation of thermal comfort Many buildings use a HVAC (Heating Ventilation Air Conditioning) unit to control their thermal environment. Recently, with the current energy and financial situation, new methods for indoor temperature control are being used. One of these is natural ventilation.
- 48. Effects of naturalventilation of thermal comfort This process can make the controlled indoor air temperature more susceptible to the outdoor weather, and during the seasonal months the temperatures inside can become too extreme. During the summer months, the temperature inside can rise too high and cause the need for open windows and fans to be used. In contrast, the winter months could call for more insulation and layered clothing to deal with the less than ideal temperatures.
- 49. Barriers to theApplication of Natural Ventilation Barriers during building operations Safety concerns Noise from outdoor Dust and air pollution Solar shading covering the openings Draught prevention Knowledge of the users about how to take the best advantage of natural ventilation
- 50. Barriers to theApplication of Natural Ventilation Barriers during building design Building and fire regulations Need for acoustic protection Difficult to predict pattern of use Devices for shading, privacy and daylighting may hamper the free flow of air Problem with automatic controls in openings Lack of suitable, reliable design tools Other barriers Impact on architectural and envelope design Fluctuation of the indoor conditions Design a naturally ventilated building requires more work but could reduce mechanical system (design fee on a fixed percentage of system’s cost) Increase risk for designers Lack of suitable standards
- 51. Indoor Air QualityCouncil-USA The IAQ Council offers certifications in five disciplines related to indoor air quality: Microbial Consulting and Investigation Council-certified Microbial Consultant (CMC) Council-certified Microbial Investigator (CMI) Microbial Remediation Council-certified Microbial Remediation Supervisor (CMRS) Council-certified Microbial Remediator (CMR) Indoor Air Quality Administration Council-certified Indoor Air Quality Manager (CIAQM) Council-certified Microbial Claims Adjuster (CMCA)
- 52. Indoor Air QualityCouncil-USA Indoor Environmental Consulting and Investigation Council-certified Indoor Environmental Consultant (CIEC) Council-certified Indoor Environmentalist (CIE) Residential Mold Inspection Council-certified Residential Mold Inspector (CRMI)
- 53. Malaysian Approach Green BuildingIndex (GBI) The Green Building Index (GBI) is Malaysia’s industry recognized green rating tool for buildings to promote sustainability in the built environments and raise awareness among Developers, Architects, Engineers, Planners, Designers, Contractors and the Public about environmental issues and our responsibility to the future generations.
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