In old buildings, leaks in doors and windows served as fans. Over time, systems of chimneys and ducts were created using the principle of physics that escaping warm air causes an inflow of new, but also cold, air. Currently, mechanical ventilation with heat recovery is being used more and more often, but many facilities still use gravity ventilation. How does gravity ventilation work? What is gravity ventilation and what challenges does it pose?
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How gravity ventilation works
Each of us has had the opportunity to notice what happens to the air in a room when we open a window. This is even more visible when tenants or users smoke nicotine. Cigarette smoke rises upwards, and when the window is opened, it escapes through the upper part of the window opening. This is because convention, i.e. the movement of air caused by the difference in its pressure and density . Warmer air is less dense, which causes it to rise. It is immediately replaced by heavier air, which in this case is cool.
This simple principle was used to create ventilation systems based on ducts and vents. Of course, to For the phenomenon of convention to exist at all, a basic condition must be met. Air exchange should take place simultaneously in both directions. All it takes is a clogged air inlet or outlet and the convention will end. To clarify, it is worth recalling that the so-called sequence is actually a misleading concept. Warm and stale air is not sucked out, but pushed out by new, fresh and cool air. To facilitate replacement, chimneys are equipped with vertical ventilation ducts . The tightness of the system is also extremely important, so it is good to use proven methods when using elements of the highest quality.
The advantage of this solution is that gravity ventilation does not require additional power supply forcing air movement. The disadvantage, however, is the loss associated with the removal of heat resulting from heating the premises.
The lack of an electromechanical device that would support gravity ventilation makes it suitable for use in places at risk of explosion. An example of such a solution are boiler rooms with boilers in which the combustion chamber is open.
Why may gravity ventilation not work?
The most common reason for disruption of the convention process is that one of the channels is clogged. We remind you that gas exchange must take place at the same time. A clogged vent immediately cuts off the outflow and thus blocks the access of subsequent batches of fresh air. Another phenomenon is the so-called reverse string. It involves returning stale air from the ventilation grids back into the apartment. What causes reverse thrust?
The cause is a distortion of proportions. In other words, there is too little fresh air to displace the used air. This may happen, for example, if there are too few channels or inlet holes. You should also check the cleanliness of the grilles, where dust, grease and various types of dust accumulate. By the way, it should be noted that it should be used ventilation grilles with a mat that effectively protects the apartment against airborne impurities entering the interior or duct.
Another cause of reverse draft is an incorrect temperature difference outside and inside the building. The effect is visible in the summer, when the exhaust duct becomes the supply duct, as a result of which pollutants and unpleasant odors from the kitchen and bathrooms spread throughout the apartment.
Advantages of gravity ventilation:
Maintenance-free operation;
No power supply supporting air exchange;
Ventilation does not emit noise;
Low operating costs.
Unfortunately, the disadvantage is heat loss, which increases heating costs.
Ventilation at the Onninen wholesaler
Where to locate the supply and exhaust ducts?
The arrangement of supply and exhaust ducts of gravity ventilation is as important as its cleanliness. Exhaust ducts should be located in rooms where moisture and unpleasant odors naturally accumulate.
Such places include:
Kitchens;
bathrooms;
Toilets;
Laundries;
Rooms without windows (wardrobes, closets).
Ventilation ducts should be located on each floor (two-level apartments). If a fireplace is used, the room in which it is located must be equipped with a supply and exhaust opening. This is to prevent the accumulation of carbon monoxide (carbon monoxide).
Gravity ventilation is still a widely used solution and it will certainly be a long time before everyone switches to mechanical ventilation with heat recovery. The basis for the effectiveness of this type of ventilation is its cleanliness and the quality of the elements from which it is made. It is good to remember this before starting the renovation and replacement of old channels.
It is also worth using professional knowledge , thanks to which not only the ventilation, but also the entire house will function trouble-free for many years. We invite you to read other articles.