The Principles of Natural Ventilation...

The Stack Effect

In a completely sealed enclosure, thermal differences between the inside and outside will result in a pressure difference because warm air is less dense than cold air. Therefore when there is an opening air will flow across the Roof terminals boundary to equalise the pressure.

During the heating season the warmer indoor air rises up through the building and escapes at the top through ventilation openings (or Roof terminals). The rising warm air reduces the pressure in the base of the building, forcing cold air to infiltrate through either open doors, windows, or ventilation openings. During the cooling season, the stack effect is reversed*.

Passivent

The Wind Effect

The force of the wind is driven down into the room or space below and, having a greater density than the internal air, this cooler incoming air flows down to floor level, whilst the less dense, warmer internal air rises and exits through the passive or active stack quadrants as a form of displacement ventilation.

As the wind changes direction at Roof top level the system quadrants also change their function to continually provide the incoming air and extract stale air from the building.

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More about Passivent

Comparison with market leaders Monodraft/passivent. Naturalvent roof and wall ventilators have been designed to compete with market leaders Monodraft and passivent. Monodraft were the originators of natural ventilation in the U.K. shortly followed by passivent. Monodraft only produce Roof terminals but now include solar fans in their range but no acoustic solutions.

passivent have a range of roof and wall terminals but no solar fans or light tubes. Naturalvent a division of TEK Limited have an extensive range of Roof terminals with insulated and thermally broken dampers and inbuilt attenuation for both passive and active mode.

Naturalvents wall units differ from passivent incorporating thermally broken insulated dampers with 100% seal and low, medium, or high attenuation, validated by SRI Laboratories.

Unlike Monodraft and passivent or Midtherm, Nautralvent have solar fans, light tubes , controls, roof curb construction and in-house fitting as part of our standard package. Please ring to discuss your project.

You may wish to visit our other sites Naturalvent, Air-Tek, Tek Limited, Natural- Shade, Tek Acoustics, covering natural ventilation, light tubes, solar fans, grilles, diffusers, displacement systems, solar shading, attenuators, acoustics and louvres, louvre screens, louvred doors and system design.