Natural Ventilation in Underground Buildings

One of the benefits of an underground building is a fairly stable temperature that doesn’t need thick insulation. But you need an efficient ventilation system to get the most out of it. Natural ventilation is one of the options available, but will it be suitable for underground buildings?

Natural ventilation for underground buildings may seem complicated and impractical. But with the right location and condition, it will work really well. If you want to get the most out of this system, you also need to consider the external climatic condition, moisture and heat transfer, and pollutants.

All of these are crucial to make a natural ventilation system work well for an underground building. Stick around because we’ll share everything that you need to know about it in great detail. We’ll also compare it with another ventilation system that many people use for underground buildings.

Underground Buildings With Natural Ventilation: Considerations

Natural ventilation is one of the first things that people consider when it comes to underground buildings. After all, it’s easy to set up and won’t cost as much to install, operate, and maintain. However, having one may not be as straightforward as it seems; there are a lot of things that you need to consider, including the following:

External Climatic Conditions

Underground temperature remains relatively constant throughout the year, but it may not be the case if you decide to use natural ventilation. Since it relies on external climatic conditions to regulate the temperature, it’ll make the underground facility slightly more susceptible to weather. Instead of enjoying consistent temperatures, you’ll have a slightly colder winter and warmer summer.

Like natural ventilation for houses, it’s more advisable for areas that don’t get drastic temperature changes. Fluctuations in temperature can be very challenging to control if you rely on natural ventilation. You have to be very careful because it can significantly affect your level of comfort.

Moisture Transfer

Unlike conventional buildings, underground buildings deal with much higher humidity. It can even go higher during summer, making it easier for mold, mildew, and fungus to grow. Aside from this, too much air moisture can cause various health issues and may even affect furniture and electronics. High humidity can also cause corrosion and damage to the building and equipment.

Natural ventilation may help with moisture transfer, but it’s usually not enough. It would be best if you have a better system dedicated to humidity control. Still, you have to plan for both systems and ensure that they work coherently to effectively facilitate moisture transfer.

Harmful Microorganisms

Since underground buildings typically have a more humid environment than the surface, you’ll have to pay close attention to microorganisms. Fungi, viruses, and bacteria are more common in damp places and can easily contaminate the building.

You need an efficient natural ventilation system that doesn’t only work in regulating temperature but also prevents the transmission of pathogens. Well-designed ventilation is also one of the best ways to prevent the contamination of other rooms.

Unstable Heat Transfer

Natural ventilation means that air flows from the surface through an underground tunnel into the building. This process can make the air exchange more complicated, making heat transfer a bit more unstable. There are several things that you need to consider when building natural ventilation for an underground building, including the following:

  • Tunnel shape: each shape has a different effect on heat transfer, depending on surface and soil condition. So, to keep it stable, it would be best to, at least, consider using various shapes.
  • Tunnel size: it determines the amount of airflow that you can get from your natural ventilation system. The more air you get, the easier it’ll be to control humidity, temperature, and more.
  • Mass transfer: managing condensation and evaporation are common in every building, but it’s even more important in underground buildings because of the lack of ventilation.


Pollutants exist in almost every environment, but it’s even more crucial for underground buildings. Higher amounts of pollutants underground, such as TVOC, carbon monoxide, and radon, make it more important to have adequate ventilation. 

You have to consider all of these compounds before deciding the shape, size, and mechanism you’ll use for natural ventilation. These compounds have a massive impact on the quality of life that you can expect from the building, so you have to get it under control.

Smoke Control

When a fire starts, does the building have enough ventilation to control smoke? If there’s not enough ventilation in the building, fumes can quickly increase the temperature, making it harder to extinguish the fire. Aside from this, insufficient combustions can also occur if the building lacks ventilation.

It’s one of the most important things that you need to consider, especially for underground buildings, because they already lack entrance and exit points that people can use during a fire. Lack of natural ventilation can only make it even more dangerous.


If you have natural ventilation systems for an underground building, it’ll run through several meters of soil, making it more challenging for maintenance. It’s significant because an effective ventilation system needs regular and proper maintenance. Without it, your ventilation may not work as you intend and could end up causing various problems, including health, comfort, and safety.

It would be best to get a professional to maintain natural ventilation because it can be too complicated. These systems have several moving parts, each with the potential to make your system less effective or efficient.

Natural Ventilation vs. Mechanical Ventilation

Despite all the considerations that you need to make for natural ventilation in underground buildings, it’s still an excellent option because of the advantages that it can provide. Here are some of the advantages that you can get from a natural ventilation system that you wouldn’t from mechanical ventilation:

Stack Effect

The stack effect is the core principle of natural ventilation. It takes advantage of the fact that hot air is lighter than cold air, forcing the lower levels to cool down while pushing hot air out of the building. The same concept is applied in every structure with natural ventilation, but it works better for underground buildings.

Unlike mechanical ventilation, occupants don’t have to do anything to control air movement in a natural ventilation system. It always moves the same way—hot air goes up, cold air goes down. It will remain independent of any mechanical system within the building.

Energy Consumption

More and more people opt for natural ventilation because it doesn’t need electricity to work. The airflow may be inconsistent and less effective than mechanical ventilation when it comes to controlling the temperature. Still, it’s the only one that can help you reduce the building’s carbon emissions and the actual cost of operation.


Since natural ventilation doesn’t rely on mechanical equipment and energy to run, it’s a highly sustainable system. Sure, there are some considerations that you have to make before you can install natural ventilation. Still, if it passes everything, you don’t have to worry about its sustainability in the long run.


Both natural and mechanical ventilation requires regular maintenance to keep them efficient. However, natural ventilation doesn’t require as much for it to work properly. Despite the several working parts in an effective natural ventilation system, you can easily maintain all of them, which ultimately reduces the overall cost of using it over mechanical.


Despite the problems that you may encounter with underground buildings, there’s still a growing interest in it over the years. Natural ventilation is one solution that can address many of the things that prevent people from having one, but it may not be as straightforward we think.

Installing natural ventilation in underground buildings may be complicated with all the factors you need to consider. However, it’s also one of the few solutions that can solve many of the disadvantages you may get from underground buildings.


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