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May 22, 2023

Venting after the rain

What’s the solution to keeping your crawl space dry in an area deluged with rain

What's the solution to keeping your crawl space dry in an area deluged with rain and floodwater?

There is no one simple solution, when you talk to insulation and moisture-control experts.

"Every house is different, it depends on the soil," says Chris Brown with Four Seasons Insulation in Gloucester.

"You have to look at the house and determine what you need."

There are some simple steps you can take to guard against groundwater moving into your crawl space.

First, get gutters on your house and keep them clean. Opt for the extra large gutters and downspouts, which are better at catching heavy downpours, particularly on steep roofs. Run underground drains for your downspouts, taking water away from the house so it empties into a spot where it drains quickly. But, be a good neighbor and keep that extra water from running into the yard next to you.

Make sure soil around your house is graded away from your foundation. The guideline is 6 inches of slope for every 10 feet. Consider creating a graveled swale at your side property lines to take care of some of that runoff water. Trench down about 8 to 12 inches, fill with 6 to 8 inches of gravel and top fill with soil. This area gives water an immediate place to drop and filter into the surrounding soil – it's a simplified French drain that can be used wherever water tends to stand.

Under your house, check to see if any ductwork there is insulated. If not, get it wrapped to prevent air leaks and condensation; if you are getting new ductwork, consider the kind with insulation already installed.

Cover your crawl space dirt floor with a minimum 6-mil poly vapor barrier, overlapping all seams about one foot. Run the plastic to the edges of the cinderblock walls, according to moisture-control experts and the national Energy and Environmental Building Association.

Outdoors, check to see if water coming from the drain line on your air-conditioning unit is dripping toward your foundation. If it is, use plastic plumbing pipe to extend and redirect that line so water flows away from the foundation.

Make sure your irrigation system is not causing your ground to become too saturated.

Keep shrubs at least 3 to 5 feet away from your house so you get good air circulation around the perimeter of your structure. Eliminating too much shade over your home's roof can also help. If you still have too much moisture in your crawl space, you need to take extra precautions. Check with your building codes office about any regulations that may govern what you want to do, and hire a licensed electrician for any wiring you need.

For years, humidity- or time-controlled fans placed under a vented house have been the recommended way to help dry a too-wet crawl space. Now, experts say these fans draw in moist, humid air, possibly adding to the problem.

A fan, however, may be the route some homeowners choose to take. A simple box fan can be purchased economically to stimulate air circulation under a crawl space, but make sure its electrical source is suitable for that application.

Specialized companies such as Crawl Space Door Systems in Virginia Beach offer no-rust PVC plastic-framed fans that range in size from 10 to 24 inches, making them conducive to all types of crawl-space sizes. Each fan is constructed so it sits on a side pedestal to keep it from toppling.

In addition, the company provides PVC-plastic foundation access doors with screens or fans and above/below ground vents.

There are, however, newer methods that may give you better results.

One such method is called the "conditioned crawl space." Essentially, you close up the crawl space by sealing the foundation vents with blocks of foam or clear acrylic cut to fit those spaces. Foam blocks, about 2 inches thick, are glued onto the interior sides of the cinderblock walls. Heavy 6-mil plastic is placed 100 percent over the dirt floor and up the wall a few inches.

Steve Tetreault of Insulpro home insulation services in James City County and Robert Criner of Criner Construction in York County both recommend conditioned crawl spaces.

"It's the only way to go," says Tetreault.

His new home in New Kent County is done just that way. He put 6-mil poly over the ground, sprayed 2-inch-thick polyurethane foam on the 5-foot-high walls and put no vents in the foundation.

Once you seal up the crawl space, you can go one step further – use a dehumidifier to remove any moisture, which is the method Criner prefers.

"Then you know the moisture is gone," he says.

Or, you can actually heat and cool the area with a heat duct coming from your main system. Either way, the cost is nominal, according to people who advocate it.

You also can seal up your foundation and equip it with a fan that sucks in dry air from the home's living space. Tetreault does these jobs, using special radon fans that continually draw crawl- space air to the outdoors.

Homeowners in flood zones can seal their foundation vents differently, using the FEMA-compliant FloodVent by Smart Vent Inc. The foam-insulated vent remains closed until the floodwater raises its "float" mechanism, allowing the vent to open so water enters and exits.

The company also sells an automatic foundation vent that opens when it's hot and closes when it's cold; it, too, reacts to floodwater. Each U.S.-made, no-rust stainless steel vent costs $180 and provides coverage for 200 square feet of enclosed area.

If you choose to vent your crawl space and want to bypass fans, you can use interior drain systems provided by companies such as B-Dry Waterproofing and Foundation Repair in Richmond and JES Construction in Chesapeake. Essentially, the systems are French drains installed around the inside perimeter of your foundation. Cost runs about $20 to $30 per linear foot; the drains empty by natural gravity or with a sump pump if the grade of your soil is not sufficient.

"I’ve seen some tremendous results with these drains," says Mike Hall, a moisture-control specialist with Colonial Exterminating Co. in Newport News.

Before jumping to any of these solutions, experts recommend you first think the problem through and try the obvious solutions first.

If you get stumped, look for a good consultant.

But, never ignore excessive dampness in your house, they say.

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