How To Properly Vent A Crawl Space

If you’re searching for the perfect living space for yourself and your family, it is crucial to consider several factors.

Other than the infrastructure, age, and durability of the property, many new-age homeowners have started to pay close attention to the aspect of crawl space ventilation.

At the same time, many struggle to implement a smart ventilation plan for crawl spaces and know nothing about its importance. 

If you are one of them, this guide is just for you! Continue reading if you want to know everything about crawl space ventilation and how you can go about it. 

What is Crawl Space Ventilation?

Crawl space ventilation refers to the airflow mechanism in the shallow area, usually found under the first floor or the building roof.

Generally, the crawl space is meant to access everything related to the house’s wiring and plumbing. It is crucial to consider how well this particular space is vented if you want to get your hands on an ideal home.

All in all, the smartest way to ensure proper airflow and a rigid system that maintains the functionality of your home is the placement of a reliable crawl space ventilation mechanism.

Unfortunately, many traditional house owners end up underestimating the effects crawl spaces have on their homes. The impact of improper crawl space ventilation plays a significant role in making living uncomfortable and challenging. 

While it is true that the crawl space is an area that you might visit only once or twice a year, it is imperative to keep the area in good shape. If you fail to take care of your crawl space, the value of your house may reduce, and the safety of your humble abode might get negatively affected as well. 

If you wonder why homebuyers are now only interested in buying houses with properly vented crawl spaces, so they do not have to worry about mold growth and other structural problems such as weak foundations. 

Therefore, the proper functioning of your home relies heavily on how properly you ventilate your crawl space. 

How Crawl Space Ventilation Works?

The whole idea of crawl space ventilation is based on driving off moisture from your home. That is why you will find crawl space-type foundations in climates that are warm and moist. 

To avoid moisture accumulation that can adversely harm your home’s framework, you can raise the structure slightly off the ground. This way, you can also properly ventilate your crawl space as you will have plenty of room. 

Light, heat, and airflow are the best weapons against fighting moisture. However, the penetration of light and heat is arduous in shallow areas or under the ground. So, when you ensure that the airflow in your crawl space is efficient, you make your home safe from any destruction caused by moisture. 

When architects are designing crawl spaces, they keep the factor of ventilation a priority. If not, moisture alone can bring down the building in a short period, as it weakens the base foundation of buildings. 

Other than that, it is also responsible for a myriad of other problems such as wood rot, growth of different strains of mold, and mildew. If these issues are left unabated, you should get ready for a significant dent in your bank account, as you will need a lot of reconstruction.

Is Crawl Space Ventilation Necessary?

The answer to this question is a big fat, yes! Like many, you might not think much about your crawl space vents, but it is high time that you do! They are a critical part of your home for many reasons. 

Besides keeping your house well-ventilated, crawl spaces are also responsible for running other systems, such as plumbing, within your home smoothly. Most importantly, an excellent space ventilation mechanism helps build an efficient air circulation system for the entire house.

If the airflow in your crawl space is not generous, it is at great risk of falling victim to vicious mold growth. Poorly vented crawl spaces significantly impact the insulation, flooring, and drywall in the upper portion of your home. 

On top of that, mold also indicates the presence of other dangerous threats to the foundation of your house, such as insects, including termites, and other animals like rodents. Problems like these can make living hard and highly uncomfortable. 

However, suppose your crawl spaces are ventilated with the right approach, such as well-calculated openings and the use of the right vapor-barrier covering material. In that case, you do not have to worry about the presence of mold, insects, and structural damage in your home. 

Crawl Space Vents; Open or Closed?

You can opt for both types of vents, depending on the temperature of your surroundings. Usually, people prefer open crawl space vents during the summer and closed ones when the temperature drops. 

In summer, the humidity in the air spikes up, which means there are high chances that moisture may accumulate in crawl spaces. People go for open crawl space vents to reduce the damaging consequences of moisture penetration in floors and walls. 

On the contrary, in winters, the air is much drier. That is why homeowners close down their crawl space vents to minimize the chances of pipe freezing. It is critical to keep such things into consideration, so you do not have to ring the plumber when tragedy strikes on the wiring and plumbing system of your home. 

How to Calculate Crawl Space Ventilation?

To make things less complicated for homeowners, there are specified building codes that make the calculation of crawl space ventilation easier. If you want to determine the size of your crawl space accurately, you can refer to the following mathematical technique: 

The minimum net area of ventilation opening should be equal to or slightly greater than 1 square foot for every 150 square feet of your crawl space or under-floor space area.

If you stick to this calculation, you will face no problem getting accurate measurements for your crawl space ventilation. 

What Happens if your Attic is not Vented?

In homes where there is no proper ventilation and insulation in the attic, heat finds its way inside and causes immense destruction. As hot air is highly-saturated with moisture, it seeps into the building walls, resulting in several structural problems. Therefore, any water hanging out in the attic is nothing short of a bad idea. 

Moisture accumulation in crawl spaces and attics causes condensation to build up that can be hazardous for your roof and roofing materials. Not only will there be wiring problems, but the plumbing system of your house will suffer as well. 

When to Ventilate your Crawl Space?

Experts suggest that crawl spaces should be ventilated at all times, regardless of the weather. However, people should keep good airflow in crawl spaces higher in their priorities list during the summers.

Why? Because warmer air tends to carry a higher ratio of water molecules than cooler air, leading to greater chances of moisture accumulation in homes when the external temperature is high. 

Crawl Space Ventilation Requirements

All the crucial requirements for state-of-the-art crawl space ventilation are listed in the International Residential Code (IRC). The outline includes rules and regulations that ensure the health and safety of every inhabitant in the house. The following are some important terms of IRC: 

1) There should be at least 1 sq. ft. of a venting area (preferably screened) for every 150 sq. ft. of area. 

2) Owners should cover the ground of their crawl spaces with any vapor-resistant material approved by the IRC. 

3) Every building corner must have at least one vent opening that will allow maximum airflow. 

How Much Does it Cost to Ventilate Crawl Space?

In many countries, the average cost to ventilate crawl spaces ranges from $3,000 to $8,000. The price can go from $3 to $7 per square foot of the space, to be more exact. If you choose the right crawl space ventilation service provider, you can get vapor barrier installation within this budget. 

Things to Consider Before Ventilating Crawl Space

The International Residential Code provides everything that homeowners need to know about crawl space ventilation. From information about the vented surface’s net area to the material that you can use to ensure maximum airflow in your crawl space, all can be found in the guidelines issued by the IRC.

So, before you decide to go ahead with a ventilation plan, make sure you go through IRC’s terms and conditions. 

The vent opening size is considered one of the crucial aspects of an accurate crawl space ventilation system. According to IRC, they should be at least one square foot in size. Additional rules that concern crawl space ventilation are explained thoroughly in the section: Crawl space ventilation requirements. 

How To Properly Vent A Crawl Space

Ventilation of your crawl space is no rocket science, but it requires time and patience to get accustomed to it. You can opt for several options that depend on the foundation and building type.

Traditionally, you will see many people venting their crawl spaces to the outdoors. However, a new procedure called encapsulation is the new favorite among modern homeowners. 

In encapsulation, the walls, ceilings, and floors are covered with plastic sheets to minimize moisture accumulation.

Not only is it much cheaper than other crawl space ventilation procedures, but it is also great for ensuring energy efficiency. So, if you want to give this a try, we say you go for encapsulation. 


Now that you know everything required to ventilate your crawl spaces properly, you should start working on it right away if you haven’t already.

Lastly, do not forget to refer to the IRC guidelines before designing the ventilation plan for your crawl space, as it is always smart to be safe rather than sorry.