Please Enlighten Me With What To Do With My Crawl Space Vents. (home, mold)

[J. Trent Hicks]

Listen to "sacredgrooves" and go to www.crawlspaces.org and decide for yourself.

Our area of the country is unique. In order to make an informed decision you should consider all information and science that is available.

We spend a lot of time in crawl spaces correcting all types of problems; mostly created by builders and homeowners who do not understand the science or the special climates outside and inside the crawlspace in the Southeast.

Advanced Energy has the science to support their recommendations on structures right here in our area. Their work has proven invaluable for our business!

[TuborgP]

Originally Posted by TuborgP

I have been convinced to be of the leave them open year round thread. I have read and discussed and the insurance answer seems to be leave them open. But I understand the two schools of thought are sure they are right. When I sold my old house up North I had to have Radon Abatement done. The guy who did it was like a guru of Radon Abatement and had published on the topic. He told me when I got here to leave them open year round as a constant air flow was important to prevent a number of buildups in your crawl space including mold.

As I went back and reviewed a few things I believe he told me the same thing that SacredGrooves said which was to close them. He was professionally trained and taught Radon Abatement. What really threw me off was when I got here was that everyone said the opposite.

[hula]

Ours are very old and need to be replaced. The door handles are broke and a couple are barely open. The frame around the vents seem to be cemented in place. Any ideas who to contact for replacement or if I want to do it myself how the heck to get them out of the cement? Thanks!

[sacredgrooves]

Originally Posted by hula

Ours are very old and need to be replaced. The door handles are broke and a couple are barely open. The frame around the vents seem to be cemented in place. Any ideas who to contact for replacement or if I want to do it myself how the heck to get them out of the cement? Thanks!

You can buy a sheet of polystyrene foam insulation, cut to size, install in the vent cavity of the foundation wall and seal with a bead of expanding foam or construction adhesive. Much cheaper and less labor, plus the benefit of permanently closed foundation vents.
All these inspectors making recommendations to keep them open or that they are a must need to get out of the 1980's. Mold/mildew propogates with moisture. Our humid summer air is filled with moisture. Do the math. If you have moisture issues with closed vents, then you have grading issues or insufficient vapor barrier installed.

I know I came across a little stern in my posts on this subject, but this misinformation needs to be rectified. In the long run, the more people that know the right way to handle this, the easier my job will be when writing reports on crawlspace conditions lol.

[Charlton Dude]

Originally Posted by sacredgrooves

You can buy a sheet of polystyrene foam insulation, cut to size, install in the vent cavity of the foundation wall and seal with a bead of expanding foam or construction adhesive. Much cheaper and less labor, plus the benefit of permanently closed foundation vents.
All these inspectors making recommendations to keep them open or that they are a must need to get out of the 1980's. Mold/mildew propogates with moisture. Our humid summer air is filled with moisture. Do the math. If you have moisture issues with closed vents, then you have grading issues or insufficient vapor barrier installed.

I know I came across a little stern in my posts on this subject, but this misinformation needs to be rectified. In the long run, the more people that know the right way to handle this, the easier my job will be when writing reports on crawlspace conditions lol.

I appreciate your info. I am still waffling a bit after reading the sealed crawlspace info. It seems that in order to close the vents, you really need to have a complete closed crawlspace system that blocks ALL air. The vapor barrier needs to be attached to the walls and you may need a dehumidifier. I am not sure I want to close off the vents, while some air/moisture still gets in there. I know it is old school to leave them open, but it seems like most people don't have issues with moisture that have left them open. Am I right or wrong? I would hate to do the new school method of closing them, to find out later it was an issue in itself.

[Poggly Woggly]

Originally Posted by Charlton Dude

I AM SO CONFUSED!!!

It is confusing isn't it Old school and common sense lean towards opening them up, but I'll try to keep and open mind. All crawl spaces are different, and what's good for one may not be as good for another....just my thinking

[KGRW]

Leave them open year round. Circulating air in a crawlspce is never really a bad thing. Otherwise, you risk greater issues like mildew and mold.

[sacredgrooves]

Originally Posted by Charlton Dude

I appreciate your info. I am still waffling a bit after reading the sealed crawlspace info. It seems that in order to close the vents, you really need to have a complete closed crawlspace system that blocks ALL air. The vapor barrier needs to be attached to the walls and you may need a dehumidifier. I am not sure I want to close off the vents, while some air/moisture still gets in there. I know it is old school to leave them open, but it seems like most people don't have issues with moisture that have left them open. Am I right or wrong? I would hate to do the new school method of closing them, to find out later it was an issue in itself.

Most people never need a sealed crawlspace. They are nice, but overkill. My father for instance, who is a builder/engineer/inspector had some moisture issues under his house. He closed the vents, put in a $150 dehumidifier, and installed a vapor barrier 100% coverage (not really necessary to bring it up the walls/piers but it certainly does not hurt either). Problem solved for roughly $200 and a few hours of labor.
If your vents remain open, and your crawlspace is dry as bone don't worry about it. I would guesstimate 35% of the houses I am under fit that description. It is the other 65% that need to be proactive. Like I mentioned, this is a cheap fix in most cases. First, figure out where moisture is getting in. It only happens three ways; migration from the ground - vapor barrier, intrusion at the foundation walls (porous by the way) re-grade/add gutters, humid air - close vents. The humid air condenses on objects with a lower dewpoint such as ductwork, cold water supply lines, air handler, the wood structural members, insulation, etc. Think of it this way....what happens to a cold glass of iced tea when you set it outside in the summer? It sweats. What happens when open foundation vents bring in hot humid summer air?

In the summer, I am in several a week that are akin to a rainforest environment. Handle the grading, barrier and close them. If any moisture was to intrude after those steps are taken, the dehumidifier makes quick work of it.

[goat1of2]

Originally Posted by sacredgrooves

First, figure out where moisture is getting in. It only happens three ways; migration from the ground - vapor barrier, intrusion at the foundation walls (porous by the way) re-grade/add gutters, humid air - close vents. ok:

What about hydrostatic pressure? Doesn't some water get into the crawlspace soils no matter *how well* you've waterproofed, guttered, and graded? Especially during monsoon season. Not every crawlspace has the headspace to fit a dehumidifier under there! Then what?

Yup, I'm still in the 1980s....having a very hard time believing that closing those vents is a good thing. I'll work on it, though! Luckily (I guess), our 1937 house has very few foundation vents. We were going to invent a system of fans to ventilate and dry out the soil, but maybe now I have an excuse not to do all that.

[TuborgP]

Originally Posted by sacredgrooves

Most people never need a sealed crawlspace. They are nice, but overkill. My father for instance, who is a builder/engineer/inspector had some moisture issues under his house. He closed the vents, put in a $150 dehumidifier, and installed a vapor barrier 100% coverage (not really necessary to bring it up the walls/piers but it certainly does not hurt either). Problem solved for roughly $200 and a few hours of labor.
If your vents remain open, and your crawlspace is dry as bone don't worry about it. I would guesstimate 35% of the houses I am under fit that description. It is the other 65% that need to be proactive. Like I mentioned, this is a cheap fix in most cases. First, figure out where moisture is getting in. It only happens three ways; migration from the ground - vapor barrier, intrusion at the foundation walls (porous by the way) re-grade/add gutters, humid air - close vents. The humid air condenses on objects with a lower dewpoint such as ductwork, cold water supply lines, air handler, the wood structural members, insulation, etc. Think of it this way....what happens to a cold glass of iced tea when you set it outside in the summer? It sweats. What happens when open foundation vents bring in hot humid summer air?

In the summer, I am in several a week that are akin to a rainforest environment. Handle the grading, barrier and close them. If any moisture was to intrude after those steps are taken, the dehumidifier makes quick work of it.

That is the answer I was looking for. That's why I asked if other factors like grading and how high the vents are etc played a role. Mine is a tall crawl space and is bone dry. I have neighbors who have had drainage issues and have had standing water etc. Also if you block the vents with landscaping or with those metal things to keep water out you are half way there to closing them anyway.