Ventilation Systems

Integrated Allweather Natural Ventilation

Client: An industrial workshop
Location: Lombardy region, Italy
Aim: Allweather natural ventilation and natural evacuation of smoke and heat
Kind of project: Design and realization of an integrated system
Description: Natural ventilation is currently a particularly appropriate solution for creating comfort even in environments that lie at the limits of traditional applications (production areas, storage areas, large public spaces).


This is a natural ventilation system Bovema Italia created for an industrial workshop that is a leader in the production of flanges for the petrochemical sector. The company had to build a brand new, completely automatized warehouse for intensive storage (more than 80% overall volume) of steel products, and therefore needed to reduce humidity to a minimum in order to avoid damaging oxidation processes.

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The building’s large scale (40 x 34 meters at the base; 16 meters tall) rendered traditional air conditioning and cooling, including through forced ventilation, unachievable; while it amounted to an advantage for anyone attempting to induce convective motion in the air.

For this reason, the solution Bovema proposed was based on a completely natural ventilation system that could take advantage of convective movement in order to guarantee air recirculation. This recirculation continues even in the event of wind or rain, thanks to the company’s “allweather” (solution, which enables aerators on the roof to continuing working under any and all weather conditions.

Another interesting aspect of this proposal was its high level of integration. The system, in addition to cooling the air and removing humidity, also satisfies regulatory requirements concerning fireproofing and the evacuation and expulsion of smoke and heat.

External and Internal Environments

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Compared to a forced ventilation or air conditioning system, natural ventilation is far more interconnected with surrounding conditions. For this reason, Bovema’s study had to contextualize the project with respect to outside weather conditions, as well as take into consideration variables like prevailing wind directions and average temperatures in both winter and summer.

In this specific case, the building is located in mountain foothills, not far from a river and within a verdant valley, therefore an environment with a significant evaporation-transpiration rate. This is the kind of natural context that generally tends to have high humidity levels.

Using the system of thermodynamic calculations created by Bovema International, this data was analyzed in light of ulterior input including the kind of structure, its layout and intended use, as well as the organization of machinery and instruments inside the building. The responses provided by the calculation model were evaluated in terms of efficiency and benefit for the system as a whole in order to determine the best sizes for the rooftop aerators and grille intakes at the base of the edifice.

System characteristics and performance

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The solution Bovema proposed, bearing in mind a reasonable compromise between efficiency in the natural ventilation system and the economic feasibility of the entire project, called for air temperatures of 30° Celsius in summer with the warehouse at 70% capacity, with overall air extraction of roughly 32,500 m3/h (5.3 exchanges/h), corresponding to an extraction strength – experimentally calculated – equal to roughly 81 thermal kW. By integrated the central blade opening with the evacuator, the system’s performance further improved to 8.27 exchanges/h and an extraction strength of 127 thermal kW.

In order to achieve this level of performance the project called for installation of 8 allweather aerators on the roof, and 14 aeration grilles with mobile blades measuring 2,000 x 1,000 mm. Both components were modified to render the system more efficient: the aerator brings the added benefits of ulterior “good weather” ventilation to the allweather ventilation system, thanks to a central system of blade openings that make it possible to increase the quantity of air circulating, while the grille on the perimeter can close in order to keep rainwater from entering during times of rain with side winds superior to 3m/s. All these devices are controlled by a weather-sensitive unit that regulates opening and closing in the event of wind, rain and snow in order to always obtain the maximum results possible.

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Furthermore, the system Bovema proposed is modular, meaning that the client can adjust the ventilating capabilities of the system at a later date by inserting new aerators on the rooftop.

Modularity is another advantage that Bovema’s natural ventilation systems can offer, added to the fact that they function where forced ventilation and air conditioning fail, can work under any weather conditions (ognitempo, or “allweather” solutions), help conserve energy, guarantee results and even integrate additional solutions (fireproof and ventilation).