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How to Vent a Crawl Space (Step By Step)

How to Vent a Crawl Space (Step By Step)

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A crawl space is a hallowed area beneath a given building. It’s typically about 3 feet in height, so a person can only crawl in it, hence the name.

A crawl space is needed for installing various systems that can take place inside a building. This includes HVAC units, piping systems, plumbing systems, and electrical wiring.

The problem is that crawl space humidity can greatly affect the systems installed within it as well as the entire structure of the house. A high level of humidity can cause mold growth, while a low level can weaken the wood and lead to various health problems.

This leads us to today’s question; how to vent a crawl space? We’ve prepared a complete guide for you on how to vent a crawl space, so stick around!

How to Install Crawl Space Vents

Crawl space vents, also known as foundation vents, are important for getting rid of the humidity and moisture inside your crawl space. They allow the air to circulate more efficiently underneath your house.

The following steps will guide you through the process of installing crawl space vents:

Step 1: Determine How Many Vents You Need

The general rule of thumb for venting a crawl space is to install one vent for each 8-10 feet of the foundation wall.

Most building codes require a single square foot of ventilation for every 150 square feet of crawl space. On the other hand, automatic foundation vents only contain 50 inches of net-free area.

This basically means that, for automatic foundation vents, you’ll need to install one vent per 50 square feet of crawl space.

Step 2: Getting the Dimensions of the Vent

Most foundation vents are 9 inches by 18 inches. However, you need to find the rough opening dimensions of the vent package.

Step 3: Determine the Position of the Crawl Space Vent

Grab the rough opening dimension and transfer it to the foundation wall where you’ll be drilling. Typically, you want to place the vent right beneath the still plate.

Then, place a 4-foot level across the top of the vent and level the vent against the wall. Next, go inside the crawl space and check if there are any wires or plumbing behind the location you’ve chosen for the vent.

Step 4: Drill Through the Foundation Wall

Before we proceed with this step, you must note that this process is tough, time-consuming, and shouldn’t be attempted by a beginner.

With that said, if you have no experience in using rotary hammers and drilling, you must contact a professional to do it for you. You should also wear protective gear all the time.

For this step, you’ll need a half-inch masonry bit. It should be at least 10 inches long to be able to drill all the way through the foundation wall.

Put on your safety equipment and start drilling holes as close together as possible. After drilling holes all the way through the lines of the vent frame, get rid of the masonry chunks inside.

Finally, if you come across a rebar, you can cut through it using a reciprocating saw fitted with a metal cutting blade.

Step 5: Installing the Foundation Vent

First, you’ll need to insert the frame of the foundation vent inside the opening from the outside. Place the vent in the hole with the louvers angled downward.

Next, depending on the manufacturer’s installation instructions, you’ll need to secure the vent from the inside.

Typically, you’ll find a plate that fits from the inside and contains clips or holes for screws or long bolts. Make sure to tighten any screws or bolts.

You can use caulk to fill any openings around the vent.

Why Is It Important to Install a Crawl Space Vent?

Crawl spaces can become humid and have high levels of moisture, which makes them perfect places for mold to grow.

Crawl space vents help circulate fresh air around your house in order to prevent damage to the wood and metal in your home. Additionally, foundation vents allow the excess moisture in your crawl space to escape to the outside.

During warm summer months, the air will be able to circulate freely, and moisture won’t build up inside your crawl space.

How Do Crawl Space Vents Work?

When warm air within a given home rises, the vents draw in air from the outside and allow the moisture to escape.

Without venting, moisture will build up inside. And without fresh air, the humidity level will spike up, which results in the growth of mold and mildew.

How to Maintain a Crawl Space Vent?

Crawl space vents need to be cleaned on a regular basis as they can get dirty and eventually become clogged. It’s recommended that you wash and vacuum the vents to get rid of built-up dust and debris.

You also should regularly inspect the vents for any broken parts. What’s more, rodents and insects can get inside through any small opening in your vent, and that can lead to infestations.

Is Crawl Space Encapsulation Better Than Foundation Vents?

The answer is yes. Crawl space encapsulation is much safer and more efficient than normal venting. However, it’s an expensive method, and it can only be installed by a professional.

On the other hand, crawl space vents are relatively cheap and can be easily installed by someone who has a basic background of using heavy tools.

Frequently Asked Questions

Do you still have a question in mind? Here are some frequently asked questions regarding our topic for today.

How much does it cost to vent a crawl space?

Installing foundation vents is relatively cheap. The installation process can cost you anywhere from $15 to $200.

On the other hand, installing a crawl space encapsulation system, which is a way to completely seal your crawl space and prevent moisture, can cost around $1,500-$15,000.

Foundation vents are both efficient and inexpensive. That’s why they were and still are a popular solution for keeping your crawl space dry.

How high should crawl space vents be?

The height of the foundation vent depends on the height of the 2-by-12 joist between the two subfloor joists.

Standard joists are usually 11 inches high, with the space between them measuring about 14.5 inches.

Can bad ventilation cause structural damage?

Bad ventilation can lead to excessive levels of moisture and humidity in your crawl space. Moisture can cause many dangerous problems like mold and wood rot.

So, to avoid damage, your crawl space should always be dry, and the humidity level should be around 40-50%.

Final Thoughts

Your crawl space needs to be vented to avoid having built-up moisture and humidity, as mold and mildew tend to grow in these conditions.

Foundation vents allow excess moisture to escape. Additionally, they let fresh air inside that circulates through the house.

If you’re wondering how to vent a crawl space, simply follow the above-listed steps. If you don’t have enough experience with rotary hammers and drilling, it’s best to hire a professional to do it for you.

Stay safe!


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