Why Crawl Space Vents Exist and Why They're Outdated

If you live in an older home around the GTA, there’s a good chance your crawl space has vents. These small metal grates were once considered essential for protecting homes from moisture. But today, we know they can actually do more harm than good.

Let’s take a closer look at why crawl space vents were added in the first place and why it’s now better to seal them up.

Why Vents Were Installed in the First Place

Back in the mid-1900s, builders believed that allowing outside air to pass through a crawl space would help keep it dry. The idea was that fresh air would move through the space and prevent moisture buildup, mold, and rot.

It sounded good in theory, but in practice, it simply doesn't work.

What Really Happens With Crawl Space Vents

Instead of drying out the crawl space, vents often invite moisture in. During warmer months, humid outdoor air enters the crawl space and condenses on cooler surfaces like pipes and ductwork. This creates the perfect conditions for:

• Mold and mildew
• Rotting wood and structural damage
• Unwanted pests
• Poor indoor air quality

In winter, vents let cold air inside, which can freeze pipes and cause cold, uncomfortable floors above the crawl space.

Open Crawl Spaces Waste Energy

Most people don’t realize that the air in your crawl space moves up into your home. This process, known as the stack effect, means that whatever is in your crawl space eventually ends up in your living space. Damp air, odors, and even allergens can travel through your floors.

This also leads to higher energy use. In the winter, your heating system works harder to warm your home. In the summer, your cooling system struggles to keep it cool. All of this adds up to higher utility bills.

The Modern Solution: Seal and Encapsulate

Today’s building science clearly shows that crawl spaces should be sealed and encapsulated. A proper encapsulation system includes:

• Sealing or covering all vents
• Installing a thick vapor barrier along the floor and walls
• Adding insulation and a dehumidifier when necessary

At Basement Systems Toronto, we use CleanSpace® vent covers as part of our full encapsulation solution. These covers are airtight, durable, and help keep outdoor air and moisture out. The result is better comfort, improved energy efficiency, and a healthier home environment.

Contact Us for a Free Inspection

If your crawl space still has open vents, it’s time to update your home with a modern, proven solution.
Reach out to Basement Systems Toronto today by calling 1-289-212-8986 or fill out our online form to schedule your free crawl space inspection and get a personalized plan that fits your home’s needs.

A drier, cleaner, and more efficient home starts with a sealed crawl space.