Conditioned Crawlspace Nashville

Crawlspaces are fundamentally a bad idea, the way they are currently constructed. In the old days, log cabins were built on piers with a pretty much open crawlspace. Now we almost close them, install plumbing and air conditioning ducts, and trap the moisture inside. This results in mold growth, cupping wood floors, moldy smells, and sometimes structural damage. So what do we do with a crawlspace?

A quote from Bruce Lee comes to mind, “No way is THE way”. There are many solutions, depending on your budget, your environmental goals, and the unique conditions in your crawlspace. A guaranteed way to condition your crawlspace is installing a high quality vapor barrier will solve the problem,  but it can be expensive. Sometimes installing powered foundation vents will solve the problem, but the intake air in Tennessee in the summer is hot and humid, which can make the humid crawlspace worse. Sometimes powered foundation vents are installed with the make-up air coming from the living space air via a hole in the floor, but then you are losing expensive conditioned air from your house and it may not make a big enough difference to solve the humidity problem .

A closed system is the most controllable environment. A closed crawlspace system includes all solutions which have closed or non-existent foundation vents. The ground in most crawlspaces will allow some humidity and earth gases unless it is sealed in a vapor-proof manner. This includes water proof seams, a mechanically fastened wall and pier membrane, and a floor membrane which has a low enough permeance rating to prevent radon and other earth gases from penetrating. If a high water table is a possibility, a sump pump, positive drain and a french and/or field drain should be installed.

A word about a recent variation on conditioned crawlspaces. Sometimes the crawlspace is closed, a high quality vapor barrier is installed, and the supply duct has a dryer vent flapper installed on the HVAC system to blow into the crawlspace and positively pressurize the crawlspace. Seems like a good idea at first, but there are some potential problems. Nature seeks an equilibrium. Where is the area of least resistance to air pressure and radon gases when you positively pressurize a crawlspace? Could it be the dryer vent flapper in the air ducts, which introduces the crawlspace air to the lungs of your home or building. Hmmm.? Something to consider.

So, to make a short story long, the absolutely most controlled and reliable crawlspace solution is to seal the foundation vents, install a high quality, low-permeance vapor barrier, and install a dehumidifier. This makes the crawlspace a semi-interior space, seals out the earth gases, and maintains a pressure-neutral condition. The downside is, a commercial dehumidifier is expensive, and expensive to operate. And one thing you can count on is, equipment will eventually break. So, like any equipment, it must be monitored and inspected semi-annually, or at least annually.

We have developed a low-cost way to condition a crawl space which works in crawlspaces that need just a little help. We go ahead and seal all the points of air infiltration, install a high-quality vapor barrier with water-proof seam tape and mechanically sealed to the perimeter walls, but then we install a system which exhausts air from underneath the vapor barrier to the outside. This keeps the humidity, earth gases, and wet earth odors from entering the crawlspace. The make-up air comes from the inevitable pin holes in the vapor barrier, drawing in the crawl space air into the area under the vapor barrier, then exhausts it outside. This results in a slightly depressurized crawlspace, relative to the house, which keeps the crawlspace air from contaminating the air inside the home. The exhaust fan is much cheaper and more reliable compared to a dehumidifier so the total project and maintenance cost is lower. The downside is, sometimes it is not enough to fix the problem. However, we recommend and install a remote monitor in the crawlspace to let you know if it is effective. If not, you can always install a dehumidifier to guarantee the climate control in the crawlspace without needing to remove the exhaust fan. In fact, it is recommended in our Extreme Makeovers. So, if your crawlspace needs just a little help, you might want to try this option first. If it works, you saved lots of money and maintenance. If not, it is still a good way to phase in the ultimate solution.

 To schedule an inspection and get an estimate which matches your budget, goals and specific situation, call 615-412-0172.