The lift in a block of flats is not just a means of getting from floor to floor – it is part of the building's pressure system. Loopshore's measurements and research show that the lift shaft and the movement of the lift can affect pressure differences and indoor air quality, especially when the building's ventilation is out of balance.
The lift shaft acts like a chimney
The lift shaft runs the full height of the building and often behaves like a vertical flue. When indoor air is warmer than outdoor air, it rises up the shaft and can cause:
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Negative pressure in the lower parts of the building
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Positive pressure in the upper parts
This phenomenon is called the stack effect. Its strength depends on the outdoor temperature, the airtightness of the building and the balance of the ventilation.
Lift movement causes momentary pressure pulses
When a lift moves, it acts like a piston: it pushes or pulls air along with it. When it stops at a floor, it can cause brief positive pressure above it and negative pressure below. These changes are short-lived, but they can be transmitted to the stairwell through small gaps, especially if the lift is located next to a flat.
Interaction between the lift shaft and the stairwell
In modern buildings, the lift shaft and the stairwell are usually separate fire compartments with no shared ventilation. Interaction can still occur, however, if there are air leaks in the structures or the ventilation is out of balance. In that case, air can pass from the lift shaft into the stairwell or the flats.
Airtightness and ventilation are decisive
Pressure differences are particularly affected by:
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The airtightness of the building and its spaces
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The balance between supply and extract airflows
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Weather conditions (temperature, wind)
If the ventilation is not working properly or the supply of replacement air is inadequate, uncontrolled airflows develop. These can lead to excessive negative pressure in the flats, and polluted air can also find its way in via the lift shaft or the stairwell.
Impact on living comfort and indoor air
Although the lift shaft itself is not usually a source of indoor air pollutants, it can act as a pathway if the pressure difference draws air from the wrong place. This can increase odour problems, draughts and even moisture risks. Properly adjusted ventilation, airtight structures and a well-designed pressure profile are effective in preventing these problems.
Conclusion
The effect of lifts on pressure differences is real, but manageable. Ventilation design and maintenance are key to ensuring that the stack effect and phenomena in the lift shaft do not impair indoor air quality.
Loopshore helps make invisible pressure differences visible – and fixable.