Incorporating optional ventilation features such as louvers, exhaust fans and ridge vents into your metal building design prevents moisture build-up and promotes good indoor air quality. And facilitating better airflow can even reduce operating expenses over the lifetime of your building by minimizing heating and cooling needs.

How ventilation works

To understand your ventilation needs, it is important to first understand the basics of how ventilation works and why that is important to the performance of your building and the health of its occupants.

Ventilation systems facilitate the flow of fresh, ambient air flow into and throughout the building, while also allowing excess heat, moisture and fumes a means of escape. Oftentimes, ventilation systems are designed to allow for cross-ventilation. A louver or powered supply fan placed lower in the wall brings air into your building. As fresh air comes in, warmer air will rise toward the roof and exit through a corresponding ridge vent or exhaust fan within the roof.

Adequate air circulation allows excess moisture, heat and fumes to be displaced by fresh air and maintains a comfortable, cool atmosphere inside the building. This is vital to the long-term health and performance of any metal building system, especially in the wake of mounting energy code requirements.

Insulation and thermal envelopes for metal buildings are becoming more efficient at preventing the transmission of heat, air and moisture through the walls and roof of your building. While beneficial to reducing the energy needs of your building, weathertight envelopes inhibit air flow and can trap unwanted moisture, fumes and heat on the inside of your building. Ventilation allows these elements to escape without compromising the thermal efficiency of your building.

In fact, insulation and ventilation can work together to maintain a comfortable, safe environment inside your building. Insulation with a vapor barrier reduces ventilation needs. In turn, proper ventilation further reduces moisture levels, preventing corrosion of the roof and wall panels and condensation forming in the insulation. And by maintaining a more consistent temperature inside your building, the ventilation system lessens the thermal expansion and contraction of your building’s metal components — which can prematurely wear down panels and fasteners.

How much ventilation does my building require?

The commonly used rule of thumb is to have a 1 square foot vent opening for every 150 square feet of roof — to determine the roof area of your building, click here. But no rule of thumb can account for all the factors that go into a building’s design and the best way to ventilate your building will depend on factors such as the building size, its intended use and the humidity levels in your area.

To serve the needs of different buildings, there are two general categories of ventilation systems: Passive (unpowered) and mechanical (powered). Both are designed to promote healthy circulation of air throughout your metal building system and prevent condensation, corrosion, ice damming and poor indoor air quality.

Passive ventilation systems —consisting of unpowered louvers and ridge vents— tend to be preferable due to their energy efficiency, lower initial cost and near-zero operating costs. But for applications such as manufacturing or livestock barns or in areas of high humidity, more air circulation may be required than can be supported by a passive system. In such cases, passive louvers can be replaced with supply fans, and ridge vents with exhaust fans, to maximize air flow and ensure optimal conditions inside the building.

A smaller building located in a dry climate, for example, may require just one louver and one ridge vent to facilitate proper ventilation. But larger buildings —especially ones housing livestock, storing harsh chemicals or facilitating complex industrial processes— may require an elaborate mechanical ventilation system designed precisely to the airflow needs of the application.

Your metal building consultant will work with you to design the most cost-effective solution to meet your building’s specific ventilation needs. But you will consider much more than ventilation when you purchase a metal building. To learn other key factors you need to weigh and glean valuable insight into how to maximize the long-term value of your steel building purchase, check out our guide to capturing savings with a metal building. You will learn how simple ideas can save owners thousands in operating costs over the lifetime of your building. Download the guide today.