What is this?

In the petrochemical industry, cabinet rooms require positive pressure ventilation, with few doors and windows, and there are also requirements regarding air volume. The cabinet room is equipped with an air conditioning system for supplying air, and to facilitate airflow management, the airflow may be exhausted in the manner shown in the diagram.

The studs are part of the roof’s lightning protection system; those that are white are for ventilation – they must be ventilation openings in the insulation layer

It looks like an exhaust port. Why is there so much? Who has the correct answer?

This post was last edited by hesonchang214 on 2018-10-17 at 11:14. For ordinary roof insulation layers made using materials such as cement cinder or cement vermiculite, which require wet construction methods, vent holes must be installed; however, this is not necessary when polystyrene boards are used for insulation. Vent holes should always remain in place. The vent holes are designed to remove moisture from the insulation material. The air (moisture) present in the insulation can cause damage to the roof due to expansion, so it cannot be removed and sealed after a certain period of time. The regulation for installing roof exhaust pipes is to install one exhaust pipe every 36 or 25 square meters; these exhaust pipes can be made of PVC pipes with elbows.

The roof ventilation system falls within the field of roof moisture-proof ventilation technology. In the construction of roof systems, roof vent holes are used to remove water from the slope layer promptly. They are widely employed in roof construction to ensure that water in the slope layer is drained in a timely manner, preventing water beneath the waterproof layer from evaporating due to high temperatures and thus causing the waterproof layer to bulge and get damaged. According to item 7 of clause 4.4.2 of the Technical Code for Roof Engineering GB50345-2012, for closed insulation layers or membrane roofs where insulation and drying are difficult, vapor discharge measures should be adopted. Function of roof vent holes: Roof vent channels are primarily used to release moisture vapor from beneath the insulated roof. If the insulation layer and finishing layer are not dry enough or it is difficult to dry them, ventilation channels should be provided when laying the membrane to allow moisture beneath the membrane layer to escape. This type of roofing system is known as a vented roof. If exhaust vents are not provided, the moisture from the insulation and finishing layers gets trapped beneath the membrane waterproofing layer. When temperatures are high, especially during hot summers, this moisture evaporates and causes the volume to expand, leading to bulging of the membrane. This in turn results in cracks and damage to the membrane waterproofing layer, causing leaks in the roof.

Separation joints should be provided in the leveling layer on top of the insulation layer; the width of these joints is 40 mm, and they should be filled with stones. The spacing between such joints, both vertically and horizontally, should be around 6 meters. An exhaust vent should be installed every 36 square meters of roof area, and these vents must be made waterproof. The exhaust ducts should run vertically and horizontally, and they should be connected to exhaust openings that lead to the atmosphere; these exhaust openings can be located beneath the eaves or at the intersections of the vertical and horizontal exhaust ducts. A vent pipe should be installed at the exhaust outlet; this vent pipe shall be placed on the structural layer. Vent holes should be provided in the pipe walls that pass through the insulation layer. The end of the pipe serving as a vapor passage should be inserted into the bottom of the vent pipe and connected to it. Its lower end should be firmly welded or connected to the roof structure, while its upper end should be at least 250 mm above the roof surface. The height of the exhaust opening should be aligned with the direction of the vent cap.