Skip to Main Content
FRS Logo Truck

Open Crawl Space Vents

Crawl space vents have many drawbacks so it’s advisable that you seal yours and encapsulate your crawl space.

Get a Free Estimate

Most of the older homes in Missouri have open crawl space vents. Back when these homes were built, homeowners installed open crawl space vents to dry out the crawl space and promote ventilation in line with codes that were first adopted in the 1950s. Fast forward and building experts are questioning their usefulness. 

Like any curious homeowner, you might also be asking yourself whether open crawl space vents help control moisture. And what about their impact on the structural integrity of the foundation? Read on to learn more about the dangers of open crawl space vents and what can be done about them. 

open vents

The Dangers of Open Crawl Space Vents 

Builders historically installed crawl space vents to allow for air circulation and prevent mold. The problem is that the crawl space is located under the house where the earth is cool throughout the year. Typical indoor ventilation that works for the house simply doesn’t work for the crawl space. 

Left unsealed, open vents introduce humid air into the crawl space, which sets the stage for numerous problems that can lower the quality of indoor air and comfort levels in your home. Some of the problems you might experience include: 

Mold and Rot 

Because of its continental climate, Missouri is generally humid. Outside air can sweep into the crawl space through the vents, bringing with it moisture. This moisture will soak into the porous construction materials used on your home, like fiberglass insulation and wood. Considering the dark nature of the crawl space, it’s only a matter of time before mold starts to grow on the wooden construction materials it houses. If not mitigated, the mold and rot could cause serious structural damage to the foundation. 

Insulation Damage 

A humid environment in the crawl space damages fiberglass in two ways: by infecting it with mold and saturating it with moisture, which can lead to sagging over time. Substances like dyes and resins within fiberglass support the growth of mold. Fiberglass often has a paper backing, which also supports mold growth. Also, when the fiberglass gets soaked up with water, it will get heavy and eventually sag and fall to the ground. 

Rodent and Pest Infestation 

Homeowners across Missouri fight their fair share of rodents and pests. Mice, ants, rodents, termites, and even spiders invade crawl spaces, depending on the time of year. Unfortunately, open crawl space vents only make the problem worse. A low-light environment filled with rot, mold, and damaged fiberglass is heaven for pests that get in through the vents. Rodents nestle in the fiberglass, breeding, dying, and visiting your kitchen for snacks. Wood-destroying pests love the damp environment as well. 

Increased Energy Consumption 

The crawl space is home to utilities, ducts, and pipes that cannot be allowed to freeze. When cold winter air enters the crawl space through the open vents, it forces the utility systems to work harder, leading to increased energy use and higher monthly bills. However, it can also freeze pipes, causing them to burst. 

The Stack Effect 

The main reason why open crawl space vents fail is the stack effect, which is the movement of air due to thermal differences. 

As warm air rises in the house, it creates a vacuum in the lower levels of the home. This creates a pressure difference that allows outside air to move into the bottom floors during the winter and the cycle continues. 

The stack effect is reversed during the summer when warm air enters the upper floors of the house and creates a draft downstairs. 

If the crawl space is filled with allergens like mold spores, dander, dust mite waste, and musty odors, you can be sure they’ll float into your living space and compromise the quality of indoor air. 

Humidity from the crawl space adds to your utility systems’ workload while the cool air cools the floorboards, making your home drafty and uncomfortable. 

Sealing the Crawl Space Vents Makes a Difference 

Crawl space ventilation is a great idea and does promote a healthy home if it’s combined with conditioning the air. With all the dangers of open crawl space vents, sealing the crawl space goes a long way in protecting your family. Unfortunately, it won’t address any moisture issues you may already have. 

Foundation Recovery Systems uses a comprehensive waterproofing approach that includes: 

  • Addressing water and moisture issues – Installing an interior drainage system to address consistent water issues along the foundation and crawl space and draining away any standing water or groundwater. 
  • Encapsulation – Sealing off the crawl space with a vapor barrier and vent covers so there are no air gaps. 
  • Dehumidification – Installing a crawl space dehumidifier to manage humidity levels throughout the year. 

Get the Job Done Right 

The certified inspectors and installers at Foundation Recovery Systems are experienced in crawl spaces, foundations, and basement repairs. We understand that homeowners have unique needs and may sometimes require a personalized service with their crawl space. Contact us today to discuss your crawl space needs and get a free inspection and repair quote

Foundation Recovery Systems Service Map

Our Service Areas

Des Moines Location

2401 SE Creekview Dr.
Ankeny, IA 50021

Kansas City Location

7280 NW 87th Terrace, Suite C-210
Kansas City, MO 64153
(816) 774-1539

Lee's Summit Location

211 SE State Route 150
Lee's Summit, MO 64082
(816) 774-1539

Moberly Location

1401 US-24
Moberly, MO 65270
(660) 202-8662

Springfield Location
1820 N Barnes Ave
Springfield, MO 65803
(417) 612-8286
St. Louis Location

1625 Larkin Williams rd.
Fenton, MO 63026
(314) 207-9995