and
passive ventilation techniques. Heavy masonry walls, small exterior windows, and a narrow walled garden oriented N-S shade the house, preventing heat gain. The house opens onto a central
atrium with an
impluvium (open to the sky); the
evaporative cooling of the water causes a
cross-draft from atrium to garden. Primitive ventilation systems were found at the
Pločnik archeological site (belonging to the
Vinča culture) in Serbia and were built into early copper smelting furnaces. The furnace, built on the outside of the workshop, featured earthen pipe-like air vents with hundreds of tiny holes in them and a prototype chimney to ensure air goes into the furnace to feed the fire and smoke comes out safely.
Passive ventilation and
passive cooling systems were widely written about around the Mediterranean by Classical times. Both heat and cooling sources, such as fountains and subterranean heat reservoirs, were used to drive air circulation, and buildings were designed to encourage or exclude drafts, according to climate and function. Public bathhouses were often particularly sophisticated in their heating and cooling.
Icehouses are some millennia old and were part of a well-developed ice industry by classical times. The development of forced ventilation was spurred by the common belief in the late 18th and early 19th century in the
miasma theory of
disease, where stagnant 'airs' were thought to spread illness. An early method of ventilation was the use of a ventilating fire near an air vent which would forcibly cause the air in the building to circulate. English engineer
John Theophilus Desaguliers provided an early example of this when he installed ventilating fires in the air tubes on the roof of the
House of Commons. Starting with the
Covent Garden Theatre, gas burning
chandeliers on the ceiling were often specially designed to perform a ventilating role.
Mechanical systems A more sophisticated system involving the use of mechanical equipment to circulate the air was developed in the mid-19th century. A basic system of
bellows was put in place to ventilate
Newgate Prison and outlying buildings, by the engineer
Stephen Hales in the mid-1700s. The problem with these early devices was that they required constant human labor to operate.
David Boswell Reid was called to testify before a Parliamentary committee on proposed architectural designs for the new
House of Commons, after the old one burned down in a fire in 1834. In January 1840 Reid was appointed by the committee for the
House of Lords dealing with the construction of the replacement for the Houses of Parliament. The post was in the capacity of ventilation engineer, in effect; and with its creation there began a long series of quarrels between Reid and
Charles Barry, the architect. Reid advocated the installation of a very advanced ventilation system in the new House. His design had air being drawn into an underground chamber, where it would undergo either heating or cooling. It would then ascend into the chamber through thousands of small holes drilled into the floor, and would be extracted through the ceiling by a special ventilation fire within a great stack. Reid's reputation was made by his work in Westminster. He was commissioned for an
air quality survey in 1837 by the
Leeds and Selby Railway in their tunnel. The steam vessels built for the
Niger expedition of 1841 were fitted with ventilation systems based on Reid's Westminster model. Air was dried, filtered and passed over charcoal. Reid's ventilation method was also applied more fully to
St. George's Hall, Liverpool, where the architect,
Harvey Lonsdale Elmes, requested that Reid should be involved in ventilation design. Reid considered this the only building in which his system was completely carried out.
Fans With the advent of practical
steam power,
ceiling fans could finally be used for ventilation. Reid installed four steam-powered fans in the ceiling of
St George's Hospital in
Liverpool, so that the pressure produced by the fans would force the incoming air upward and through vents in the ceiling. Reid's pioneering work provides the basis for ventilation systems to this day.
History and development of ventilation rate standards Ventilating a space with fresh air aims to avoid "bad air". The study of what constitutes bad air dates back to the 1600s when the scientist Mayow studied
asphyxia of animals in confined bottles. The poisonous component of air was later identified as carbon dioxide (), by Lavoisier in the very late 1700s, starting a debate as to the nature of "bad air" which humans perceive to be stuffy or unpleasant. Early hypotheses included excess concentrations of and
oxygen depletion. However, by the late 1800s, scientists thought biological contamination, not oxygen or , was the primary component of unacceptable indoor air. However, it was noted as early as 1872 that concentration closely correlates to perceived air quality. The first estimate of minimum ventilation rates was developed by Tredgold in 1836. This was followed by subsequent studies on the topic by Billings in 1886 and Flugge in 1905. The recommendations of Billings and Flugge were incorporated into numerous building codes from 1900–the 1920s and published as an industry standard by ASHVE (the predecessor to
ASHRAE) in 1914. ASHVE began a robust research effort in 1919. By 1935, ASHVE-funded research conducted by Lemberg, Brandt, and Morse – again using human subjects in test chambers – suggested the primary component of "bad air" was an odor, perceived by the human olfactory nerves. Human response to odor was found to be logarithmic to contaminant concentrations, and related to temperature. At lower, more comfortable temperatures, lower ventilation rates were satisfactory. A 1936 human test chamber study by Yaglou, Riley, and Coggins culminated much of this effort, considering odor, room volume, occupant age, cooling equipment effects, and recirculated air implications, which guided ventilation rates. The Yagle research has been validated, and adopted into industry standards, beginning with the ASA code in 1946. From this research base,
ASHRAE (having replaced ASHVE) developed space-by-space recommendations, and published them as ASHRAE Standard 62-1975: Ventilation for acceptable indoor air quality. As more architecture incorporated mechanical ventilation, the cost of outdoor air ventilation came under some scrutiny. In 1973, in response to the
1973 oil crisis and conservation concerns, ASHRAE Standards 62-73 and 62–81) reduced required ventilation from 10 CFM (4.76 L/s) per person to 5 CFM (2.37 L/s) per person. In cold, warm, humid, or dusty climates, it is preferable to minimize ventilation with outdoor air to conserve energy, cost, or filtration. This critique (e.g. Tiller) led ASHRAE to reduce outdoor ventilation rates in 1981, particularly in non-smoking areas. However subsequent research by Fanger, W. Cain, and Janssen validated the Yagle model. The reduced ventilation rates were found to be a contributing factor to
sick building syndrome. The 1989 ASHRAE standard (Standard 62–89) states that appropriate ventilation guidelines are 20 CFM (9.2 L/s) per person in an office building, and 15 CFM (7.1 L/s) per person for schools, while 2004 Standard 62.1-2004 has lower recommendations again (see tables below). ANSI/ASHRAE (Standard 62–89) speculated that "comfort (odor) criteria are likely to be satisfied if the ventilation rate is set so that 1,000 ppm CO2 is not exceeded" while OSHA has set a limit of 5000 ppm over 8 hours. ASHRAE continues to publish space-by-space ventilation rate recommendations, which are decided by a consensus committee of industry experts. The modern descendants of ASHRAE standard 62-1975 are ASHRAE Standard 62.1, for non-residential spaces, and ASHRAE 62.2 for residences. In 2004, the calculation method was revised to include both an occupant-based contamination component and an area–based contamination component. These two components are additive, to arrive at an overall ventilation rate. The change was made to recognize that densely populated areas were sometimes overventilated (leading to higher energy and cost) using a per-person methodology.
Occupant Based Ventilation Rates, == Problems ==