Ventilation is the deliberate introduction of ambient air into space and is primarily used to control indoor air quality by diluting and removing indoor pollutants; it can also be used for thermal comfort or dehumidification purposes. Proper ambient air recognition will help achieve the desired level of indoor comfort although the size of the ideal comfort level varies from individual to individual.
Intentional introduction of subaerial air may be categorized as mechanical ventilation, or natural ventilation. Mechanical ventilation uses the fan to move the subaerial airflow into the building. This can be achieved by pressure (in the case of positive pressure buildings), or by depressurization (in the case of exhaust ventilation systems). Many mechanically-ventilated buildings use a combination of both, with ventilation integrated into the HVAC system. Natural ventilation is the deliberate passive flow of intentional air into the building through planned openings (such as lattices, doors, and windows). Natural ventilation does not require a mechanical system to move subaerial air, it is entirely dependent on passive physical phenomena, such as diffusion, wind pressure, or stack effect. The mixed mode ventilation system uses both mechanical and natural processes. Mechanical and natural components can be used together with each other or separately at different times of the day or season of the year. Since natural components can be affected by unpredictable environmental conditions, they may not always provide the right amount of ventilation. In this case, the mechanical system can be used to add or regulate the naturally driven flow.
In many cases, ventilation for indoor air quality simultaneously is advantageous to control thermal comfort. At this time, it can be useful to increase the ventilation level beyond the minimum required for indoor air quality. Two examples include an air side economizer strategy and pre-cooling ventilation. In other cases, ventilation for indoor air quality contributes to the need - and energy use by - mechanical heating and refrigeration equipment. In hot and humid climates, dehumidification of air vents can be an energy-intensive process.
Ventilation should be considered for its connection with "ventilation" for equipment and incinerators such as water heaters, furnaces, boilers, and wood stoves. Most importantly, the design of building ventilation should be careful to avoid backdraft of combustion products from "naturally" disposed equipment to the occupied space. This problem is more important in new buildings with more airtight envelopes. To avoid danger, many modern combustion appliances use "direct ventilation" that attracts direct combustion air from outside, not from the indoor environment.
Natural ventilation can also be achieved through the use of windows that can be run, this has largely been removed from most of the current architectural building as the mechanical system continues to operate. The current United States strategy for building ventilation is to rely solely on mechanical ventilation. In Europe designers have experimented with design solutions that will allow for natural ventilation with minimal mechanical disturbance. These techniques include: the layout of the building, the construction of the facade, and the materials used to complete the inside. European designers have also switched back to the use of operating windows to solve indoor air quality problems. "In the United States, the removal of operating windows is one of the biggest disadvantages in contemporary architecture.".
Video Ventilation (architecture)
Ventilation category
- Mechanical ventilation refers to any system that uses mechanical means, such as a fan, to introduce subaerial air into space. These include positive pressure vents, exhaust ventilation, and a balanced system that uses supply and exhaust ventilation.
- Natural ventilation refers to a deliberately designed passive method for introducing subaerial to space without the use of a mechanical system.
- Mixed ventilation system (or hybrid hybrid ) uses natural and mechanical processes.
- Infiltration is the uncontrolled flow of air from outside into the room through leaks (unplanned openings) in the building envelope. When building designs depend on deep infiltration driven by the environment to maintain indoor air quality, this stream has been referred to as adventitious ventilation.
Maps Ventilation (architecture)
Standard vent level
The level of ventilation, for building CII, usually expressed by the subaerial air volumetric flow discharge, is introduced into the building. The typical unit used is cubic feet per minute (CFM) or liters per second (L/s). The level of ventilation may also be expressed on a per person or per unit of floor area, such as CFM/p or CFM/ftÃ,², or as hourly air change (ACH).
Standard for residential buildings
For residential buildings, which are largely dependent on infiltration to meet their ventilation needs, the size of the general ventilation rate is the rate of air change (or hourly air change): the rate of ventilation per hour divided by the volume of space ( I or ACH , unit 1/h). During the winter, ACH can range from 0.50-0.41 in dotted homes up to 1.11-1.47 in an air-sealed house.
ASHRAE now recommends the level of ventilation depending on floor area, as revised against standard 62-2001, where minimum ACH is 0.35, but not less than 15 CFM/person (7.1 L/s/person). In 2003, the standard was changed to 3 CFM/100 sq. Ft. (15 l/s/100 sq. M.) Plus 7.5 CFM/person (3.5 L/s/person).
Standard for commercial buildings
Ventilation rate procedure
Ventilation Level Procedure is a level based on the standard and determines the level at which air vents should be sent to space and various ways to condition the air. Air quality is assessed (via CO 2 measurements) and ventilation levels are lowered mathematically using constants. Indoor Air Quality Procedures use one or more guidelines for specific specific acceptable indoor airborne contaminant concentrations but do not prescribe ventilation levels or air treatment methods. It discusses quantitative and subjective evaluations, and is based on the Ventilation Level Procedure. It also contributes potential contaminants that may not have measurable limits, or that there are no unregulated boundaries (such as formaldehyde offgassing of carpets and furniture).
History and development of ventilation level standards
In 1973, in response to the oil crisis and conservation concerns of 1973, ASHRAE Standard 62-73 and 62-81) reduced the required ventilation from 10 CFM (4.76 L/S) per person to 5 CFM (2.37 L)/S) per person. This is found to be a contributing factor to sick development syndrome.In certain applications, such as submarines, pressure aircraft, and spacecraft, air vents are also needed to provide oxygen, and to liquefy carbon dioxide to survive. Submarine batteries also release hydrogen gas, which must also be ventilated for health and safety. In a pressurized and orderly environment, ventilation is required to control fire that may occur, as fire can lose oxygen.
ANSI/ASHRAE (Standard 62-89) speculates that "the criterion of convenience (odor) is likely to be met if the ventilation level is set so that 1,000 ppm CO 2 is not exceeded" while the OSHA has set a limit of 5000 ppm over 8 hour.
Ventilation guidelines are based on the minimum ventilation level required to maintain acceptable levels of bioeffluents. Carbon dioxide is used as a reference point, because the highest emission gas at a constant value is 0.005 L/s. The mass balance equation is:
Q = G/(C i - C a )
- Q = laju ventilasi (L/s)
- G = CO 2 rasio generasi
- C i = CO indoor yang dapat diterima 2 konsentrasi
- C a = konsentrasi CO 2 ambien
Ventilating space with fresh air aims to avoid "bad air". The study of what was a bad air date back to the 1600s, when Mayow scientists studied animal asphyxia in a limited bottle. The toxic components of air were then identified as carbon dioxide (CO2), by Lavoisier in the late 1700s, initiating a debate about the nature of "bad air" that humans perceived as stuffy or unpleasant. The initial hypothesis included excess CO2 concentration and oxygen depletion. However, in the late 1800s, scientists thought biological contamination, not oxygen or CO2, as the main component of unacceptable indoor air. However, it was recorded in early 1872 that CO2 concentrations are closely related to perceived air quality.
The first estimate of the minimum ventilation level was developed by Tredgold in 1836. This was followed by subsequent research on the topic by Billings in 1886 and Flugge in 1905. Recommendations from Billings and Flugge were incorporated into a number of building codes from the 1900-1920s , and published as an industry standard by ASHVE (ASHRAE's predecessor) in 1914.
The study proceeded to various thermal comfort effects, oxygen, carbon dioxide, and biological contaminants. The study was conducted with human subjects controlled test chambers. Two studies, published between 1909 and 1911, show that carbon dioxide is not an offensive component. Subjects remain satisfied in rooms with high CO2 levels, provided the room stays cool. (Furthermore, it has been determined that CO2, in fact, is hazardous at concentrations above 50,000 ppm)
ASHVE began a strong research effort in 1919. In 1935, ASHVE funded the research conducted by Lemberg, Brandt, and Morse - again using human subjects in the test chamber - suggesting the main component of "bad air" was the smell, felt by the nerves human smell.. The human response to odor is found to be logarithmic to the concentration of contaminants, and associated with temperature. At lower and more convenient temperatures, lower ventilation levels are satisfactory. The 1936 study of the human test chamber by Yaglou, Riley, and Coggins summarizes most of these efforts, taking into account the smell, volume of rooms, the age of passengers, the effects of cooling equipment, and the implications of the air being recirculated, providing guidance for ventilation levels. The Yaglou research was validated, and adopted into industry standards, beginning with the ASA code in 1946. From this research base, ASHRAE (after replacing ASHVE) developed space with space recommendations, and published it as ASHRAE Standard 62-1975: Ventilation for air quality in an acceptable room.
As more architecture incorporates mechanical ventilation, the cost of outdoor air ventilation is under supervision. In cold climates, warm, moist, or dusty, it is better to minimize ventilation with the outside air to save energy, cost, or filtering. This criticism (eg Tiller) led ASHRAE to reduce outdoor ventilation levels in 1981, especially in non-smoking areas. But subsequent research by Fanger, W. Cain, and Janssen validate the Yaglou model.
ASHRAE continues to publish recommendations of space-by-space ventilation levels, decided by the industry experts' consensus committee. The modern descendants of ASHRAE standard 62-1975 are ASHRAE Standard 62.1, for non-residential spaces, and ASHRAE 62.2 for shelter.
In 2004, the calculation method was revised to include occupant-based contamination components and the region-based contamination component. Both of these components are additive, to achieve overall ventilation level. The change was made to recognize that densely populated areas are sometimes too hot (leading to energy and higher costs) using a per-person methodology.
Work-Based Ventilation Rates , ANSI/ASHRAE Standard 62.1-2004
Room-based ventilation level , ANSI/ASHRAE Standard 62.1-2004
The addition of occupant-based and area-based ventilation levels found in the above table often results in significant rate reductions compared to the previous standard. This is compensated in other parts of the standard that require that the minimum amount of air is actually delivered to the respirator zone of the individual occupant at any time. The total intake air intake from the ventilation system (in a variable multi-zone air volume system (VAV)) may therefore be similar to the airflow required by the 1989 standard. From 1999 to 2010, there was a lot of application protocol development for ventilation levels. This progress discusses the occupied and process-based ventilation levels, the effectiveness of room ventilation, and the effectiveness of the ventilation system
Natural ventilation strategy
A building design that promotes occupant health and wellness requires a clear understanding of the ways ventilation airflows interact with, melt, move or introduce pollutants in occupied space. Although ventilation is an integral component to maintaining good indoor air quality, it may not satisfy itself. In scenarios where outdoor pollution will degrade indoor air quality, other treatment devices such as screening may also be needed. In a kitchen ventilation system, or for laboratory laboratory cabinets, effective effluent catch design can be more important than the large amount of ventilation in the room. More generally, the way the air distribution system causes ventilation to flow in and out of space affects the ability for a certain level of ventilation to remove internally generated pollutants. The system's ability to eliminate pollution is described as "the effectiveness of ventilation". However, the overall impact of ventilation on indoor air quality may depend on more complex factors such as pollution sources, and the ways in which air activity and flow interact to influence occupant exposure.
The architectural techniques and features used for building ventilation and structure naturally include, but are not limited to:
- Operable window
- Pressurized air pump
- Night cleaning vent
- Window classification and ventilated roof windows
- Building orientation
- Wind catches faÃÆ'§ades
Natural ventilation
Natural ventilation harnesses the natural forces available to supply and remove air in enclosed spaces. There are three types of natural ventilation that occur in the building: wind-driven ventilation, pressure-driven flow, and stack vents. The pressure generated by the 'pile effect' depends on the buoyancy of hot or rising air. Wind vents are driven depending on the prevailing wind force to pull and push air through enclosed spaces as well as through violations in building envelopes. Seoul University Professor Wonjun Kwon recently discovered a new way to distribute a large indoor space. The "air pump" system uses internal and outdoor pressure to push air out of the structure. (see Infiltration (HVAC)).
Almost all historic buildings are naturally ventilated. This technique was generally abandoned in larger US buildings during the late 20th century as the use of air conditioners became wider. However, with the advent of Advanced Performance Simulation (BPS) software, improved Building Automation Systems (BAS), Leadership design requirements in Energy and Environmental Design (LEED), and improved window manufacturing techniques; Natural ventilation has made a resurgence in commercial buildings both globally and across the US.
The benefits of natural ventilation include:
- Indoor air quality improvement (IAQ)
- Energy savings
- GHG emissions reductions
- Occupant control
- Reduced occupant disease associated with Sick Building Syndrome
- Increased worker productivity
Mechanical ventilation strategy
Building mechanical vents and structures can be achieved using the following techniques:
- House-intact ventilation
- Mixing vents
- Displacement Ventilation
- Specific subaerial air supply
Ventilation controlled by request (DCV)
Ventilation controlled by need ( DCV , also known as Demand Control Ventilation) makes it possible to maintain air quality while saving energy. ASHRAE has stipulated that: "This is consistent with a ventilation level procedure that requires controls to be allowed to be used to reduce total external air supply during a less occupancy period." In DCV systems, CO 2 sensors control the amount of ventilation. During peak occupancy, the CO 2 level rises, and the system adjusts to provide the same amount of outside air as that would be used by the rate-vent procedure. However, when less space is occupied, CO 2 levels are reduced, and the system reduces ventilation to save energy. DCV is an established practice, and is required in high residential spaces by building energy standards such as ASHRAE 90.1.
Private ventilation
Personal ventilation is an air distribution strategy that allows an individual to control the amount of ventilation received. This approach provides fresh air more directly to the respiratory zone and aims to improve the quality of air inhaled. Private ventilation provides a much higher ventilation effectiveness than conventional mixing ventilation systems by removing pollution from the respiratory zone by far less air volume. Beyond improving the quality of air benefits, this strategy can also improve the thermal comfort of the occupants, the perceived air quality, and overall satisfaction with the indoor environment. Individual preferences for temperature and air movement are not the same, and the traditional approach to homogeneous environmental control fails to achieve high occupant satisfaction. Techniques such as private ventilation facilitate the control of a more diverse thermal environment that can increase thermal satisfaction for most residents.
Local exhaust ventilation
Local exhaust ventilation addresses the problem of avoiding indoor air contamination by certain high emission sources by capturing airborne contaminants before they spread to the environment. These may include moisture control, lavatory bioeffluent control, solvent vapor from industrial processes, and dust from wood and metal work machinery. Air can run out through a pressed hood or through the use of a fan and suppress a certain area The local exhaust system consists of 5 basic parts
- Cap captures contaminants at source
- Channels for air transport
- Air purifier that removes/minimizes contaminants
- Fans who move the air through the system
- The exhaust pile through which the contaminated air is dumped
In the UK, the use of LEV systems has regulations defined by the Health and Safety Executive (HSE) called Harmful Substances Control for Health (CoSHH). Under CoSHH, legislation is established to protect LEV system users by ensuring that all equipment is tested at least every 14 months to ensure the LEV system performs adequately. All parts of the system should be examined visually and tested thoroughly and where every part is found to be defective, the inspector must issue a red label to identify the defective part and the problem.
The owner of the LEV system must then repair the damaged or replaced parts before the system can be used.
Ventilation and burning
Combustion (eg, fireplace, gas heater, candle, oil lamp, etc.) Consume oxygen while generating carbon dioxide and other unhealthy gases and fumes, requiring ventilation air. The open chimney promotes infiltration (ie natural ventilation) due to negative pressure changes caused by the floating and warm air coming out through the chimney. Warm air is usually replaced by heavier and cooler air.
Ventilation in the structure is also required to remove moisture generated by respiration, combustion, and cooking, and to remove odors. If moisture is allowed to accumulate, moisture can damage structures, insulations, or finishes. When operating, air conditioning usually removes excessive moisture from the air. Dehumidifiers may also be appropriate to remove air humidity.
Smoking and ventilation
ASHRAE Standard 62 states that air expelled from areas with environmental tobacco smoke should not be re-circulated into ETS-free air. Space with ETS requires more ventilation to achieve air quality similar to non-smoking environments.
The amount of ventilation in the ETS area is the same as the total area ETS plus the sum of V, where:
V = DSD ÃÆ'â € "VA ÃÆ'â €" A/60E
- V = recommended extra flow rate in CFM (L/s)
- DSD = design of cigarette density (estimated number of cigarettes smoked per hour per unit area)
- VA = volume of ventilation air per cigarette for the room being designed (ft 3 /cig)
- E = effectiveness of contaminant removal
History
The primitive ventilation system is found on the archaeological site Plo'nik (belonging to Vin? Culture) in Serbia and built into an early copper smelting furnace. The stove, built on the outside of the workshop, features an air vent like a ground pipe with hundreds of tiny holes in it and a prototype chimney to ensure air gets into the furnace to feed the fire and smoke out safely.
The development of forced ventilation was triggered by a general belief in the late 18th and early 19th centuries in the theory of miasma diseases, in which stagnant 'air' was thought to spread the disease. The initial method of ventilation is the use of fire ventilation near air vents that will forcibly cause air in the building to circulate. British engineer John Theophilus Desaguliers gave an early example of this, when he installed fire vents in the air jar on the roof of the House of Commons. Beginning with Covent Garden Theater, gas-burning chandeliers on the ceiling are often designed specifically to perform the role of ventilation.
Mechanical system
A more sophisticated system involving the use of mechanical equipment for air circulation was developed in the mid-19th century. The basic bellows system was applied to Newgate Prison ventilation and outer buildings, by engineer Stephen Hales in the mid-1700s. The problem with these early devices is that they require constant human labor to operate. David Boswell Reid was called to testify before the Parliamentary committee on the proposed architectural design for the new House of Commons, after a long burning in a fire in 1834. In January 1840 Reid was appointed by a committee for the House of Lords dealing with the construction of a replacement Building Parliament. The post is in the capacity of the ventilation engineer, basically; and with his creation there began a series of long battles between Reid and Charles Barry, the architect.
Reid recommends installing a highly sophisticated ventilation system in the new Home. The design has air drawn into the basement, where it will undergo heating or cooling. Then it will rise into space through thousands of small holes drilled to the floor, and will be extracted through the ceiling by special ventilation fire in large piles.
Reid's reputation was made by his work in Westminster. He was assigned to an air quality survey in 1837 by Leeds and Selby Railway in their tunnels. The steam generators built for the Niger expedition of 1841 are equipped with a ventilation system based on Reid's Westminster model. Air dried, filtered and passed through the charcoal. Reid's ventilation method is also applied more fully to St. George's Hall, Liverpool, where architect, Harvey Lonsdale Elmes, asked Reid to be involved in ventilation design. Reid considers this the only building in which the system is actually implemented.
Fans
With the emergence of practical steam power, fans can finally be used for ventilation. Reid installed four steam-powered fans at St George's Hospital ceiling in Liverpool, so the pressure generated by fans would force air into and through the vents on the ceiling. Reid's pioneering work provides the basis for a ventilation system to this day. He is remembered as the "Reid the Ventilator" in the twenty-first century in energy efficiency discussions, by Lord Wade of Chorlton.
Problem
- In a hot, humid climate, unconditioned air vents will channel approximately one pound of water per day for each cfm of outdoor air per day, an annual average. It's very humid, and can cause serious moisture and mold problems in the room.
- The efficiency of ventilation is determined by design and layout, and depends on the placement and proximity of the diffusers and return air channels. If they are located close together, the air supply can be mixed with musty air, reduce the efficiency of the HVAC system, and create air quality problems.
- System imbalances occur when the HVAC system components are not adjusted or properly installed, and can create pressure differentials (too much air circulation makes the concept or air circulation too little to create stagnancy).
- Cross-contamination occurs when pressure differentials occur, forcing contaminated air from one zone to the non-contaminated zone. This often involves an unwanted odor or VOC.
- The re-entry of exhaust air occurs when the drainage and fresh air intake are too close, or the prevailing wind changes the exhaust pattern, or by infiltration between intake and exhaust airflow.
- The entry of contaminated subaerial air through the inlet stream will result in indoor air contamination. There are various contaminated air sources, ranging from industrial waste to VOCs being suspended by nearby construction works.
See also
- Architectural techniques
- Environmental tobacco smoke
- Mechanical engineering
- Sick building syndrome
- Solar chimney
- Windcatcher
- Acid Cupboard
- Biological safety
- Dilution vents
- Room air distribution
- Heat recovery vents
External links
- Publication of Air Infiltration & amp; Ventilation Center (AIVC): http://www.aivc.org/resources/publications
- Publications of the International Energy Agency (IEA) Project on Energy Building and Community (EBC) Project related to ventilation project-attachment:
- EBC Appendix 9 Minimum Ventilation Level
- EBC Annex 18 Request Controlled Ventilation System
- EBC Enclosure 26 Energy Saving Ventilation from Large Box
- EBC Annex 27 Evalutation and Demonstration of Domestic Ventilation Systems
- EBC Annex 35 Control Strategies for Hybrid Ventilation in New and Enhanced Office Building (HYBVENT)
- EBC Annex 62 Ventilative Cooling
References and notes
Source of the article : Wikipedia
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