Proper Metal Building Ventilation: The Basics to Keeping Non-Conditioned Spaces Cool and Dry
When it comes to non-conditioned buildings—think garages, barns, carports, workshops, and storage units—two of the most important performance goals are to keep the air temperatures low and the interior dry. Whether you’re storing tools or simply working inside, no one wants to step into a sweltering, damp space. That’s where a proper metal building ventilation strategy makes all the difference.
Air Temps vs Surface Temps
There are a various things that can affect the air temperature inside of a non-conditioned building, but typically there are two main factors: the amount of heat entering the structure (heat gain) and the amount of airflow passing through (ventilation). While these two things are independent of one another, when they are controlled and working together, they make the biggest impact on making the building cooler and more comfortable.
Before diving into how to ventilate, let’s talk about the science behind heat in a building. There are two types of heat you deal with in a metal structure:
Air Temperature – The temperature of the air you feel when you walk into the building.
Surface Temperature – How hot the actual surfaces inside the building feel (walls, ceiling, storage boxes, etc.).
These are related, but they’re not the same. You can reduce surface temperatures by installing a radiant barrier, like BlueTex™ foil insulation, which reflects radiant heat away from the interior. Meanwhile, ventilation helps reduce air temperature by allowing heat to escape.
When surface and air temperatures are managed together, you create a dramatically more comfortable and functional space.
Gaps for Airflow
Ideally you want to give the air in your structure a free, clear path to flow around the foil installation. Air movement is important for regulating air temperatures and also for keeping the building dry (i.e. preventing any condensation from forming). Just like opening windows on a breezy day cools a house, letting air move inside your building helps reduce heat and moisture.
If you install radiant barrier foil insulation in your metal building, it’s crucial to leave small gaps for air to flow around the foil. This doesn’t reduce the effectiveness of the insulation—it actually enhances it. Think of it like wearing breathable fabric on a hot day: you stay cooler because air can circulate.
By leaving some gaps in the installation, air can easily move around the foil – in other words, proper ventilation can take place. The hot air in the building will travel the path of least resistance to make its way out of your building. When you install BlueTex™ with the proper air gaps, it allows for maximum ventilation between the roof and the foil and it also gives you the benefit of full coverage.
Basic Metal Building Ventilation Tips
Here’s a quick checklist for improving air movement in your non-conditioned metal structure:
- In vented buildings that are not being heated/cooled at all, choose perforated radiant barrier foil.
- Ensure intake vents are low (e.g. eaves or soffits) and exhaust vents are high (e.g. ridge or roof vents).
- Keep foil or insulation clear of vent openings by 3–6 inches.
- Make sure vent paths are unobstructed and clean. Don’t block venting with foil, or other insulation materials.
- Seal any conditioned areas inside the building up, air tight.
Ventilation & Moisture: Why It’s Not Just About Heat
The key to managing moisture in a metal building is proper ventilation in the areas that are vented and proper air sealing in the conditioned areas (when applicable). To be proactive toward these potential problems, it’s important to keep your building both cool and dry.
High humidity is the hidden enemy of metal buildings. Moisture inside can lead to condensation, rust, mold, and structural damage. The key to avoiding this is—again—proper ventilation. When warm air inside the building hits a cooler metal surface (like an uninsulated roof), condensation can form. This is especially common overnight or during seasonal temperature swings.
Ventilation helps manage moisture by letting water vapor escape before it condenses. That’s why perforated radiant barriers like our BlueTex™ Foil Only materials are ideal for vented spaces—the tiny holes allow moisture vapor to pass through, keeping your structure dry and healthy.
The idea behind ventilation is quite simple – don’t over complicate it. You need intake vents and exhaust vents; intake should occur at the bottom of the roof and exhaust vents should occur at the top since this is in line with natural airflow (warm air will naturally rise). This natural flow allows for moisture to freely move about and eventually diffuse. Incidentally, this is why radiant barrier is perforated and why you should always use a perforated product in a vented space. The perforations in the foil are tiny pinholes that allow water vapor molecules to pass through. This is exactly what you want: moisture moving freely to contribute to an overall dry building space.
Do I Need More Ventilation?
How much ventilation do you actually need? You certainly want adequate ventilation, but more is not always better. It’s not about flooding the building with vents—it’s about balance. Ideally, you want a 1:1 ratio of intake to exhaust; from our experience, most buildings have plenty of roof vents and not enough low intake vents. Without enough intake, your exhaust vents can become intake vents, disrupting natural airflow. This prevents hot air from escaping properly and can trap moisture where you don’t want it.
Having good ventilation helps to reduce the air temperature, while having a radiant barrier helps reduce the surface temperatures. This is why radiant barrier combined with proper ventilation works to make your building more comfortable and energy efficient.
If you have several points of exit for the air, but not enough intake vents, then some of those outtake vents can actually turn into intake vents, completely disrupting the natural cycle of airflow. Air always travels the path of least resistance so by mixing exhaust vents, you can actually have the strongest vents dominate as the outtake and all other vents will become a point of air intake. Best Practice: Let air in at the bottom, and out at the top. Air naturally wants to rise as it warms, so working with this flow (instead of against it) makes your building perform better.
What Should You Expect from Proper Ventilation?
If your non-conditioned building is vented properly and lined with a radiant barrier, it’s reasonable to expect the interior temperature to be within 10–15°F of the outdoor temperature on a hot day. That’s a huge improvement compared to a metal box that can bake at 120°F+ without insulation or airflow.
A well-ventilated, radiant barrier–lined metal building not only feels better—it performs better. You’ll reduce heat stress on stored items, avoid moisture damage, and create a space that’s easier to work in or enjoy.
At BlueTex™, we’re all about helping you get the most out of your metal building. Pairing radiant barrier insulation with proper metal building ventilation gives you the best shot at a cooler, drier, more efficient structure—without breaking the bank or your back.
Check out our full range of metal building insulation products, or contact us for personalized advice on how to make your building more comfortable year-round.
