Industrial ventilation sizing errors

Technical guide: Sizing mistakes to avoid for a perfect warehouse climate

An inadequately sized ventilation system doesn’t just cause discomfort. It also leads to downtime, health risks for workers, anduncontrolled energy costs. Yet ventilation design is still often based on rough estimates, when it actually requires precise data and a rigorous calculation method.

Why a sizing error is a serious problem

A warehouse is not a static container. It is a dynamic environment where heat, humidity, dust, gases, and, in many sectors, animals or machinery sensitive to temperature variations coexist.

If the air flow is insufficient, humidity and pollutants stagnate, exposing personnel to real risks and the company to regulatory non-compliance. If the system is oversized, it consumes more electricity than necessary and produces noise that affects working conditions. In both cases, the actual cost is higher than what appears on the bill.

The goal is not to install the most powerful fan available, but to find the correct operating point for that specific warehouse.

Parameters you cannot ignore when calculating air exchange rates

There is no one-size-fits-all formula. Each warehouse has its own characteristics that determine the necessary air exchange rate.

The first parameteris the actual volume of the space. Simply multiplying the floor area isn’t enough, as the height of the structure completely changes the picture. In warehouses with shed roofs or exposed beams, it’s essential to measure the actual volume.

The second factoris the intended use. A poultry farm requires a much higher number of air changes per hour than a logistics warehouse. An abrasive powder processing plant has completely different needs than adairy. There are no universal tables, design data is required.

The third, and often overlooked, factor is air density. The performance figures indicated in fan catalogs are calculated at standard conditions, i.e., +20°C at sea level. If your warehouse is located at a high altitude or if the exhaust air is very hot, the density will change. Ignoring this figure means undersizing the system right from the spreadsheet.

For this reason, it’s useful to distinguish between volumetric flow rate and normalized flow rate. The value you need is the one that takes into account actual operating conditions, not the raw data from the catalog.

The characteristic curve and the duty point

Every fan has a characteristic curve that correlates flow rate and pressure. Proper design means matching this curve with the actual system resistance, i.e., the pressure drops generated by ducts, filters, and any obstructions to airflow.

If the duty point falls too far to the left of the curve, efficiency drops and noise increases. If it falls too far to the right, the motor risks overheating. Choosing the right size, such as between EWD 26″, 31″, or 37″, helps you achieve the maximum efficiency for your application.

Another costly mistake is not checking the fan’s moment of inertia against themotor‘s starting capacity. If the value exceeds the maximum allowed, the motor won’t start properly, and in some cases, the windings burn out on the first try.

Thermal stratification, the invisible problem

Thermal stratification is one of the most underestimated phenomena when sizing warehouse systems. Heat tends to rise and accumulate in the upper areas of the structure, leaving work areas cold in the winter and overheated in the summer due to radiation from the roof.

ACF seriescirculators are designed to break down this stratification. Their cylindrical shape generates a cone of collimated air that passes through the layers and forces the heat to be redistributed evenly, with measurable effects on the efficiency of heating in the winter and cooling in the summer.

For theroof fansare designed to manage heat at the top and allow accumulated hot air to be evacuated. Above 60°C, heat-dissipating fans or adequate insulation are required toprotect motorsand mechanical transmissions.

Axial or centrifugal, when to choose

Using the wrong type of fan is one of the most commontechnical errors, and often stems from an incomplete understanding of the installation conditions.

Axial fansare designed to move large airflows with low pressure drops. They are the correct choice for general ventilation, warehouse cooling, and extraction in environments with low aerodynamic resistance.

Centrifugal fans, on the other hand, are necessary when air must travel through long ducts, pass through heavy filters, or overcome high pressures, such as in dust extraction systems or fume extraction from industrial processes. Where resistance is high, an axial fan lacks the static pressure to maintain the required flow rate.

The difference is not in absolute performance, but in the field. Application. Choosing the wrong type means having a system that doesn’t reach design conditions, even if it’s technically functional.

What to do before choosing a fan

So, before selecting any machine, you need three things:

• the actual volume of the building and its intended use
• the system’s pressure drops, including all flow obstacles
• the actual operating conditions of temperature and altitude.

Without this data, any choice is an approximation. With this data, the choice becomes a matter of engineering. If you prefer, you can start with atechnical analysisof your system, orcontact usdirectly.