Ventilation – Air, Ventilator, Energy

Ensures a healthy and comfortable environment in energy-efficient homes.

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Natural ventilation, spot ventilation, and whole-house ventilation are the three types of ventilation.

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Ventilation occurs when air flows through cracks and small holes in a house uncontrollably. In the past, air leakage diluted pollutants enough to keep indoor air quality adequate. These days, we are sealing those cracks and holes to make our homes more energy-efficient, and to maintain a healthy indoor environment, ventilation is essential. By opening windows and doors, you can let in natural ventilation, but many people keep their homes closed up all year long because they use central heating and cooling systems.

It is impossible to rely on natural ventilation to ventilate a house evenly because it is unpredictable and uncontrollable. Airtightness, outdoor temperatures, wind, and other factors all contribute to natural ventilation. Some homes may not have enough natural ventilation to remove pollutants in mild weather. An unair-sealed home will be drafty, uncomfortable, and expensive to heat and cool, especially during windy or extreme weather.

Spot Ventilation

Natural ventilation and whole-house ventilation are more efficient with spot ventilation, which removes air pollution and moisture at their source. Localized ventilation is provided by exhaust fans, such as those used in kitchens and bathrooms. In bathrooms or kitchens, ASHRAE recommends an intermittent or continuous ventilation rate of 50 or 20 cubic feet per minute.

This is called ventilation.

Fresh air is supplied to an area by purposeful (intentional) ventilation, while stale air is removed. The system can be natural or mechanical.

As well as intentional ventilation, exfiltration and infiltration of air in a building are inevitable. An air leak can occur accidentally or unintentionally through cracks and gaps in a building envelope. Exfiltration refers to the loss of air from enclosed spaces. Infiltration depends on the porosity of the building shell and the wind and temperature forces. Openings and vents built into a building as part of ventilation design can also result in unintentional air flow when the pressures acting across such openings are determined by weather conditions rather than mechanically induced driving forces. Besides increasing the amount of air entering a building, air infiltration can also change the intended air flow pattern, affecting overall comfort and indoor air quality. Additionally, infiltration can lead to inferior performance, excessive energy consumption, insufficient heating (or cooling), and drastic reduction in heat recovery. Measures are available to limit infiltration losses.

A substantial amount of air leaks from the seams and joints of ventilation, heating, and air conditioning circulation ducts. When ducting passes through unconditioned spaces, significant energy loss may occur. According to a study performed in the United States in 2005, 10%–30% of conditioned air escapes from central air conditioning ducts (Modera, 2005). Through these openings, pollutants may also be drawn into the building. To reduce duct leakage, some countries have adopted ductwork airtightness standards.

Air recirculation: Air recirculation is frequently used in commercial buildings to provide for thermal conditioning. Recirculated air is usually filtered for dust removal but, since oxygen is not replenished and metabolic pollutants are not removed, recirculation should not usually be considered as contributing towards ventilation need.

It is necessary to ventilate in order to provide oxygen for metabolism and to dilute metabolic pollutants (carbon dioxide and odour). The device is also used to ensure good indoor air quality by diluting and removing other pollutants emitted within a space, but it should not be used in place of proper pollution source control. Aside from providing oxygen for combustion appliances, ventilation is also used for cooling. Ventilation contributes significantly to the comfort and health of building occupants.

Since ventilation plays a significant role in COVID-19, the AIVC board decided at their last (online) meeting in September 2020 to launch a project to collect, discuss, and disseminate information about ventilation and airtightness.

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