Vent stack. Drainage of air through a ventilation chimney

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Ventilation chimneys are a gravitational ventilation system through which air can be exchanged in apartments, houses, public spaces or workplaces. They are most often made of ventilation blocks distinguished by their high fire resistance.

In all residential, commercial and public spaces there should be adequate ventilation. Thanks to ventilation chimneys, “used” air can be carried away from the interiors outside the building. There may even be several ventilation ducts in a single chimney. Their number and arrangement, as well as where the inlets leading to them will be located, is determined by the architect. No corrections and changes should be implemented on our own.

Inlets to ventilation chimneys should be located in the kitchen, bathroom, toilet, boiler room, attics and rooms without windows. The ventilation duct is located inside the house, just inside an exterior or interior wall. If the ventilation duct meets an exterior wall or runs through an unheated room, it must be insulated. Only then will ensure adequate draught.

The most important rules for the construction of ventilation chimneys

The ventilation duct should be erected on the foundation. It is worth remembering that a longer duct provides better draught. On pitched roofs covered with non-flammable or flame-retardant material, a chimney should be erected, the top of which reaches a minimum of 0.3 m above the surface of the slope. At the same time, the chimney must be at least 1 meter away from the slope. In turn, roofs that are covered with flammable materials should have a chimney extending more than half a meter above the ridge.

For houses made of wood, the ventilation chimney can be self-supporting, that is, not connected to the structural walls. If the draught in the chimney turns out to be insufficient, it is sufficient to equip the duct outlets with chimney caps, which will act as additional elements to increase the draught. We can then also use chimney caps with low-pressure mounting foam.

When designing and installing ventilation chimneys, we should still remember a few rules:

  • The walls in the center of the ventilation duct must be as smooth as possible, because only then they will not resist the flowing air.
  • The minimum angle of deviation from the vertical can be thirty degrees.
  • The surfaces inside the ventilation ducts are not plastered.
  • In unheated rooms, the walls of the ventilation chimney should be insulated.
  • Inlets to ventilation chimneys should not be placed above 15 cm from the ceiling. They are equipped with protection in the form of louvered grilles. Pay attention to whether the grilles have adjustable capacity.

What materials should ventilation chimneys be made of?

Ventilation chimneys can be built of solid bricks – silicate mortar bricks or ceramic bricks. Instead, we should avoid slotted bricks – trusses and hollow bricks. It is also worth paying attention to special ventilation hollow bricks, among which we can distinguish ceramic hollow bricks, silicate hollow bricks and those made of lightweight expanded concrete. Ceramic hollow bricks require brickwork. Silicate and expanded concrete blocks do not require bricklaying.

main photo:

Peter Bowers

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