The Case Against Basement and Crawl Space Ventilation

Open Crawl Space Vents

For far too many years, homeowners in throughout New Hampshire and Greater Boston have tried to use outside air to dry out their humid basements and crawl spaces. Fans are placed in basement windows, some blowing air inside the home, other basement fans designed to blow air outside. In many areas of the country, crawl space vents have been built into building codes, and while those are changing, the conventional "wisdom" is that if outside air is allowed to pass through the space, it will keep the space dry. Basement Systems of New Hampshire has the solutions you need for a dry basement in crawl space. We provide FREE dry crawl space or basement estimates, call or contact us by e-mail today!

Ask yourself these three questions:

1. Who is paying to condition to air I'm blowing out of my basement?
2. When it's raining or humid outside, how dry can that air keep my basement?
3. If venting crawl spaces works, why are they still rotting and growing mold?

To put it simply: Venting basements and crawl spaces does not work.

Problem 1: Vented Basements and Crawl Spaces Mean Money out the Window

Drafty Crawl Space Door

Except on the most pleasant days, you won't want the air outside your home to be the same temperature as the air inside. You pay a lot of money to cool your summer air and heat your air in the winter. If you have a fan in your basement that pulls air from that home and sends it outside, then the air that you paid to condition is literally going out the window. Even if that fan is energy-efficient, this method cannot effectively dry your basement.

If you have a vented crawl space and do not seal the vents in the winter, then you're inviting cold winter air into your home. As the cold air enters, it will immediately cool down all warm things in your crawl space, including heating ducts, hot water pipes, water heaters, and furnaces. While these utilities are working harder to maintain their temperature, the cold will rise upwards, cooling your floorboards and creating an uncomfortable, drafty home.

Problem 2: The Air You Vent Your Home with is Not Dry

A Grated Basement Window Opening in Boston that was Eventually Sealed off After Leaking with Rainwater

If it's raining outside, how dry will the air in your basement or crawl space be? Not very, you can count on that.

And during a NH or MA summer, when hot, humid air is pulled into the basement or crawl space, it's brought into below-grade space. This subterranean space cools this summer air, causing it to cool, and forcing its relative humidity level to rise dramatically. For each degree the air is cooled, its relative humidity will rise approximately 2.2%. Once the air's relative humidity rises past 100%, the excess moisture will be deposited on all cold surfaces in the crawl space, including wood, metal, and other organic materials. That's not creating a drier home.

Additionally, allowing humid air into your home in the summer will significantly affect your home's cooling efficiency. Air thick with humidity is harder for air conditioning units to cool, as part of the cooling system's job is to dehumidify the air. That's why air conditioners drip. More humidity means more work for the system, and more money for you to spend.

Problem 3: Venting Crawl Spaces Leads to Rot, Mold and Structural Issues

Crawl Space Walls Stained with Years of Flooding and Moisture

If crawl space vents worked, wouldn't the crawl space be dry?

Crawl space rot is a serious problem, and its repercussions can affect the entire home. Crawl spaces with rotting beams and wood will begin to sag, leading to dipping, uneven floors upstairs. Installing crawl space jacks will temporarily aid in supporting and reinforcing the structure, but sooner or later, the rot must be stopped to maintain structural integrity in the home.

Additionally, because air moves upwards in the home as it warms, leaving out the attic and upper levels, some of the air in your home is pulled up through the basement and crawl space. If there is allergenic mold spores and dust mite waste in these spaces-- even when it's growing behind your drywall-- it will join the air in your home.

Crawl space vents are also openings in your home that are very close to the ground. This leaves an open invitation for a wide variety of pests to come in and feast on your rotting wood, including termites, carpenter ants, and mice. Other creatures, such as snakes, spiders, and beetles, will also find this to be a comfortable home.

How to Properly Dry a Basement and Crawl Space

Basement With Vapor Barrier on Walls and Floor and Airtight Windows
An Encapsulated Crawl Space with Sealed Vents

Refer to the trinity of healthy below-grade spaces: Vapor Barriers, Dehumidification, and Inorganic Materials.

First, seal off all vents and close all windows. Then, install a plastic vapor barrier on the walls and floors in the basement or crawl space to keep moisture from passing through the concrete and entering into the space. Once the space is sealed, dehumidify the area to pull any remaining moisture from the space and to keep the area dry. If you're finishing the basement, follow up by using as many inorganic, waterproof materials as possible.

Additionally, new vinyl basement windows are important, as they can keep drafts and leaking water from the space. And if you want to install an extra bonus, installing covered basement window wells can keep cold air away from the glass basement windows while also reflecting in valuable natural sunlight to cheer up the space.

A dry basement and/or crawl space means a healthier, more comfortable home. You'll save a ton of money on your home in energy-efficiency, and your home will be protected from structural damage due to mold and rot.

Basement Systems of New Hampshire wants to help you create a dry basement and crawl space environment. If you live around Greater Boston or in New Hampshire, call or e-mail us today for a FREE dry crawl space or basement estimate!

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