The most common Air Intake

Wall vents

If the room does not have an attic, you cannot design for diffuse ceiling. The normal design is wall vents, but also the more expensive roof vent is a possibility.

Wall vents are placed in a wall typically an outer wall and in pig houses with 0.2 meter from the top of the vent to the ceiling. The ceiling must be smooth and without obstacles as light boxes disturbing the distribution of the air. The ceiling must comply to this minimum 70 % of the throw of air.

A wide room must have differential opening of the vent. Running at minimum ventilation the air flow is small, the aperture of the vents are even smaller, because the air speed in the vent is at maximum because of the cold air. These small apertures are very inefficient and cannot throw the air halfway into the room.

To overcome this challenge a fraction of the vents are fully closed at low ventilation forcing the air to pass the less opened vents, which then have to be correspondingly more open. This advanced inlet control can be mechanical or electrical; the latter has the maximum adjustability.

VengSystem tends to place the wall vents in two heights and with an actuator for each row. The modular control system makes it easy to delay the opening of the vents in the lower row, and to progress the opening of the vents in the upper row.

A ventilation system with wall vents has to be adjusted to get the right negative pressure curve. The cold season is preferable and smoke machines must be available. VengSystem’s control system has all the necessary tools to create and maintain the optimal negative pressure at all working points.
The negative pressure also expresses the weakness with this system. You may need 30 Pa at minimum falling to 10 Pa at maximum.

This put demands to the room, leakages cannot be tolerated as air is bypassed and comes in without any control. The air jets get weaker and the room is poor ventilated.

Compared with diffuse ceiling the negative pressure around minimum ventilation is at its lowest, increasing as ventilation increases.

In addition a system with wall vents is very sensitive to the wind, as wind builds a positive pressure at the windside and a negative pressure at the lee side.

It helps to fit wind baffles to shelter for the direct wind pressure, but the positive pressure at the wall cannot be compensated. You must accept that the air inside moves as the wind blows. Consider having bushes growing up around the farm as windbreakers.

Positively the system with wall vents is good at emergency ventilation. Also positive that heating of the attic by the sun is no theme although the air is heated by the sun at the sunny side of the wall, which is comparable with a good attic design.

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