3 Issues Caused by Crawl Space Vents

Crawl spaces have been a cause of headaches for many years. While they are an important structural component of homes, crawl spaces aren’t the most practical areas. Homeowners mostly ignore them for this reason. This isn’t always the wisest decision.

According to building codes from the 1950s, it became common practice to ventilate these areas. Back then it was thought that crawl space ventilation would reduce moisture below the home. Since moisture is the number one cause of problems in crawl spaces, this sounded like a great idea. Unfortunately, it wasn’t.

Fast forward 40 years and new research shows that vents actually make it easier for humidity to get inside a crawl space. Today, building a new crawl space with vents doesn’t happen as often, but homeowners with older homes are feeling the effects of this outdated design today.

We’re going to look at why ventilation really harms a crawl space—and what you should do instead.

Problems Caused by Open Crawl Space Vents

Although crawl space ventilation does sometimes improve air circulation, it still leaves your crawl space exposed to outside moisture, especially in humid states like Alabama or Tennessee. If your crawl space has open vents, you’re home is more likely to suffer from the following crawl space problems.

1. High Humidity and Water Damage

Open vents in a home’s crawl space draw in humid air from the outside. Once inside, the humid air cools down and produces condensation. Water droplets form on surfaces in your crawl space including wooden support beams, floor joists, air vents, and electric wiring. High crawl space humidity leads to several issues:

Mold growth: breaks down the home’s structure, causes musty odors, and poses health risks
Wood rot: fungal growth that feeds exclusively on wooden structures, leading to weaker home stability
Pests: bugs and rodents are drawn to dark, humid crawl spaces because they provide shelter and warmth

Controlling humidity levels is essential to avoid these issues. But there are bigger problems brewing because of open vents as well. High humidity is usually just the starting point.

2. Sagging Floors

Crawl space vents introduce humid air under your home. Excessive moisture is problematic because it is easily absorbed by wooden structures, such as the floor joists. Over time, this causes the wood to soften and rot, weakening its structural integrity.

This degradation often manifests as sagging or uneven floors inside the home. Thus, open crawl space vents indirectly contribute to sagging floors and damage the overall structural integrity of your home.

3. Increased Energy Bills

Much like other crawl space problem signs, humid air is the root cause behind this issue. When humid air gets into your crawl space, the warm air rises into your home and causes your air conditioning to work harder. However, open vents can also raise energy bills in the winter.

In winter, these vents allow cold air to seep into the crawl space, which can make the floors cold. Your heating system then needs to work harder to maintain a comfortable temperature inside the house, again increasing your energy consumption and bills.

Alternative Crawl Space Ventilation

Since crawl space ventilation allows humid air to get below your home, you need an alternative that actively stops water in its tracks.

That’s where crawl space encapsulation comes in.

Crawl space encapsulation is a bit like giving your home a protective layer, a sort of ‘raincoat’ against the elements. This process involves installing various water managements systems below your home.

Working together, these systems create a controlled environment below your home that keeps water out and stops humid air from coming in through vents:

Vapor barrier: prevents ground moisture from seeping into the crawl space.
Dehumidifier: maintains optimal humidity levels.
Crawl space drainage: directs water out of the crawl space.
Thermal insulation: reduces energy costs and creates a comfortable home environment.
Crawl space sump pump: actively monitors and removes standing water below the home.

Work With AFS to Keep Humidity and Moisture Out

Crawl space vents, while originally designed with good intentions, lead to a variety of issues for homeowners.

They invite outside air and humidity into your home, creating the potential for moisture buildup, mold growth, and structural damage, including sagging floors. They also increase your energy bills by making heating and cooling systems work harder.

However, there are solutions available. Implementing methods like crawl space encapsulation provides an effective fix for these problems. AFS has the expert team and industry-leading resources to install encapsulation in your crawl space.

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Ted Dryce

Content Writer

Ted is an SEO Content Writer who has been with Groundworks since 2021. He’s covered home repair topics ranging from crawl space encapsulation to regional soil conditions. When he’s not working, Ted is performing improv comedy and working on his own creative projects.