actually dump even more humidity in the crawlspace in the form of warm damp air. Think about it, when is the humidity highest? In the early morning when dew is ont eh ground... is that the type of air you want to vent your crawlspace with? If air is being blown out then you will have makeup air coming in from outside. Also, humidity can get really high on hot humid days. The powered vent starts blowing humid air out and the makeup air is coming form outside where it is hot and humid and that hot humid air enters a cool damp crawlspace and you get mass condensation.

And actually somebody does know what is best as there is 12 years of research to back up the info. The problem is you end up hearing from a list of people that know what they know and know nothing about actual studies and data. Check out www.crawlspaces.org to see real actual scientific information based on actual research from actual scientist and energy specialist and not from contractors with no real knowledge of tempurature and humidity control based on dew points and specific humidity in a vented crawlspace.

Bottom line, dont give up, the info is out there and only confusing if you just ask random people and not the right people. Like asking your doctor about financial advice or you financial advisor about a heart transplant.

are hearing about sealed crawlspaces and then assuming just closing the vents will have the same effect. Some homes do fine with open vents and others will have massive problems with open vents but that does not mean simply closing the vents will resolve the problems. Allot more goes into sealing a crawlwpace than just closing the vents.

If you have never had condensation problems or mold problems then keep on doing what you are doing. It only takes minor changes in the environment of the crawlspace to cause humidity and condensation problems. and that new "minor" change you have been advised about may do more harm than good. Every home is different and a wall vented crawlspace is an uncontrolled environment subject to the whims of nature and your unique surroundings/conditions.

Many homes are being built over "Sealed Crawlspaces" due to the problems that many homes have with open vents. This is now a controlled environment and no longer is dpendant on conditions outside the home. The existing vents in your home have two purposes: 1. to control humidity (Which they sometime help and in other homes they actually hurt by allowing in hot humid air that then condensates on any cool surfaces). and 2. they allow for fresh air to keep levels of radon, mold spores, gases from decomposing materials in the soil, gases from building materials, and other air contaminants from getting to high levels not only in the crawlspace but then causing air quality issues in the home. So the advise to just close the vents and hope for the best can actually have unintended consequenses. My advice is to keep on doing what you are doing if you are certian that you have not had any issues down there. The best advise I can give for a wall vented dirt crawlsapce is you keep them open as designed and close the vents in the winter only when or there is an expected extended cold snap to avoid freezing pipes and to help with keeping the home warm. Your home was built with vents so use them as long as they as they work as intended.

dehumidifier but use your own HVAC system to condition. Your HVAC system is a dehumidifier and the best you can buy but will work all year and actually reduce your electric bill if done correctly. A dehumidifier will only run in the most humid months and will increase your maintenance and energy use cost.

The vent fans in the faoundation vent is a BAD idea as it will run when the humidity is high but that will actually pump in (If it is blowing air out there has to be makeup air and that usually comes from outside) even more warm humid air or cold damp morning air that will then increase the condensation on your ducts and other cool surfaces. Go to www.crawlspaces.org to see the results of a 12 year field study on this. Just make sure you work with a good company that understands the use of the HVAC system to condition the air so you get the right amount of metered air in the crawlspace (not too much or too little).

Just closing the vents and adding a dehumidifier is an energy waste and will not allow for fresh air ventilation and can cause an air quality problem in the home. The moisture is mainly coming from humidity from the foundation vents adn not the ground.

trails in the crawlspace to get an idea of where to start.

supplied conditioned air from the HVAC helps with energy use, pest control, air quality, etc...

cause condensation on cool surfaces. IF your crawlspace is very low and cool then the vents ARE the problem.

cannot be seen through the spray on foam. Scraping that stuff off to repair small areas means a HUGE expense to find someone that will come back out to reapply it. No one wants to mobilize a huge spray foam rig just for a small patch job :( Seal the crawlspace and use conditioned air and you can insulate the walls over the concrete instead. Much better option for the long haul and energy.

maticulously maintained. Grading to move water away is the best bet and where this is not practicle a french drain INSIDE the crawlspace last much longer and does not get clogged with mud and debris over time.