Ventilation in architecture, the procedure of replacing or changing the existing open space in any place with fresh air to provide the area with high indoor air quality. It is critical to the comfort of the space, the process of changing stale air with fresh air. As a matter of important factor in architecture it is the introduction of the external air from outdoor to indoor, it helps in maintaining the air quality, displacing indoor pollutants, thermal comfort, control impurities, stops condensation, reduces temperatures. The process of introduction of outdoor air intentionally can be grouped as natural ventilation or mechanical ventilation. The beneficiary of ventilation is the control of comfort inside, also to increase the air quality and rate of ventilation beyond the average required.
Revolving around the major aspect of design is ventilation as it plays a major role. Various categories of ventilation applied in the process are Natural ventilation, Mechanical ventilation, Hybrid ventilation (mixed mode ventilation), Adventitious ventilation (infiltration). Some sustainable design methods used for the passive building designs are architecture forms, evaporate cooling, night cooling, shading, thermal mass, vegetation.
“Indoor air quality (IAQ) is a term which refers to the air quality within and around buildings and structures. IAQ is known to affect the health, comfort and well-being of building occupants. Poor indoor air quality has been linked to Sick Building Syndrome, reduced productivity and impaired learning in schools.”
Natural ventilation, the passive method of designing intentionally for the establishment of subaerial to the area or space without the usage of mechanical components and systems. This intentional passive flow of external air into the space by planned and designed openings achieve natural ventilation without any system to move the air, lying totally on the physical phenomena of wind flow, wind pressure, diffusion, wind direction, stack effect. The design holding planned architectural features like opening of windows, doors brings in the air flow. Use of operable windows is the main design aspect in achieving natural air into the space, the design strategy for ventilating buildings include techniques of facade construction, building layout, interior finishes with minimal mechanical interference. Major benefits lying under the design process of natural ventilation are lowering building construction costs and building operating costs. The use of natural ventilation distinctly establishes a commitment to sustainable green practices, reduced mechanical dependence and the creation of a more natural, environmentally friendly occupant experience. Categorization of this ventilation divides itself into two mechanisms, one being wind driven cross ventilation and the other being buoyancy driven stack ventilation. “Wind-driven (or wind-induced) cross ventilation, where pressure differences between one side of the building and the other draw air in on the high pressure side and draw it out on the low pressure side” and “Buoyancy-driven stack ventilation (the stack effect), where cooler air enters the building at low level, is heated by occupants, equipment, heating systems and so on, becomes less dense and so more buoyant and rises through the building to be ventilated to the outside at the top.”
The design process here is extremely complex as the interaction between the two mechanisms as well as the complex geometries of the buildings and the distribution of openings need a specialist analysis with specific software revolving around fluid dynamics. It is also be influenced by the behavior of the occupant in the place. For this reason it can be beneficial to automate natural ventilation systems, or to provide training for occupants. It is necessary then to monitor behavior to make sure that the systems continue to be operated as intended. Naturally ventilated buildings are called “breathing buildings” as it is the element of green and sustainable architecture. The concept of natural ventilation lies in driving force, ventilation principle and characteristic element. Designing a naturally ventilated building is more difficult than that of designing a similar but mechanically ventilated building structure. An interdisciplinary approach from the early stages of design process is mandatory for achieving successful natural ventilation concepts.
“Mechanical ventilation, the process of introducing subaerial air by any system with the usage of mechanical means such as a fan, including positive pressure ventilation, exhaust ventilation, and balanced systems that use both supply and exhaust ventilation.” Mechanical devices such as fan is used to drive the flow of the external air into the building space accomplished by pressurization or by depressurization. Many ventilated structures by mechanical system use a combination of both, with the ventilation being unified into the HVAC system. By the usage of techniques like mixing ventilation, dedicated subaerial air supply, whole-house ventilation, displacement ventilation mechanical ventilation of structures can be achieved. Certain strategies of mechanical ventilation helping in the design planning of the building involves Demand-controlled ventilation, Local exhaust ventilation and Personalized ventilation. Heating, humidity control and cooling are included in mechanical ventilation.
Hybrid ventilation, the ventilation system incorporating both mechanical and natural ventilation processes also said to be the mixed mode ventilation. The components of both natural and mechanical are used in conjunction with each other in the design or also used separately at different times of the day or different seasons of the year. Since the natural ventilation component can be affected by unpredictable environmental conditions it may not always provide an appropriate amount of ventilation. In this case, mechanical systems may be used to supplement or to regulate the naturally driven flow. There are various principles in hybrid ventilation such as natural and mechanical ventilation, fan-assisted natural ventilation and stack-and-wind assisted mechanical ventilation. A pragmatic approach by the architect towards the design process is a simplest strategy to provide design solution that is neither entirely natural nor entirely mechanical.
Infiltration is the uncontrolled flow of air from outdoors to indoors through leaks (unplanned openings) in a building envelope. When a building design relies on environmentally driven circumstantial infiltration to maintain indoor air quality, this flow has been referred to as adventitious ventilation. Infiltration occurs mainly in winter when the air outside is colder and heavier than the air inside. It depends on wind velocity, wind direction and the air-tightness of the building envelope. In the case of high-rise building the stack effect also causes infiltration.
Being the key aspect of architecture, different ventilation system holds different uses to various types of buildings. Taking in account during the design process, architect should plan at the early stages of design the various architectural features of a building at the concept stage, how ventilation responds to the indoor space. The deliverables that has to be taken in account by the designer is the site analysis and site orientation for proper designing of the ventilation system, thus ventilation plays a major role in architecture design as the feel of the space, the comfort zone, the need of respiration and thermal effects for the living of the human being and importance of ventilation in different types of buildings are widely seen.