I have a ranch house with a half basement and half crawl space. In the far wall of the crawl space there are two vents to the outside. They have a sliding partition on them allowing them to be opened or closed. My question is when should they be opened and when should they be closed. I am guessing winter/summer, but don't know which. Thanks in advance.

 

They should be closed all the time

 

Then why is the house built with them?

 

IF you have a vapor barrier on the ground, then you can close them. If you do NOT, then they MUST be open to allow moisture to evaporate.

Since the home was built with them, there is probably no vapor barrier, and they are required by code when no vapor barrier is installed.

Will you save anything on energy one way or the other? Probalby not.

 

I bought my ranch style home several years ago. I has foundation vents all around the foundation. When I bought the house it had "vapor barriers" placed throughout the crawl space. I discovered the vapor barriers (thick sheets of plastic allegedly for the purpose of preventing ground moisture from seeping upwards and into the floor joists and flooring), had layers, almost like shallow ponds of condensed water, which had accumulated on top of them. The moisture underneath the house had condensed and was on top of all that plastic. All kinds of creatures (bugs, rats, snakes, etc.) were also thriving underneath the "vapor barrier." No good!!!

Since I'm a sort of do-it-yourselfer, I proceeded to remove all that nasty wet plastic sheeting, plus a lot of debris which the construction crews had left under there ( broken bricks, planks, bottles, cans, lunch bags, cigarette wrappers, etc.) I pulled everything out of there, and raked and cleaned the entire crawl space so that it was "clean as a whistle." I also screened the crawl space entrances to allow more wind and air to blow through and underneath the house.

Now, the whole thing is dry as a bone. I keep all the vents open all the time. In the winter when cold air is coming in through the open vents, it probably does cause the floor to be colder and jack up the heating bill a little. But the crawl space is clean and dry and ventilated. And termites don't like fresh, dry air.

So I keep my vents open all the time. But it all depends on what part of the country you live in I suppose, as well as the kind of soil one's house is built on. But in my case, I don't care what the "experts" say about moisture control -- I think that vapor barrier mess is a bunch of nonsense (they just want to sell you some). Because of the accumulated water on top of the plastic vapor barrier, my crawl space used to look like a lake.

 

I have had vents on every house I have owned (Ohio, Florida and Arkansas) and have opened the vents in the Spring and Summer and closed them in the winter. The humidity level in Spring and Summer caused even the joists to drip. Opening the vents and letting air flow through stopped this. In the winter, I do not want cold air blowing across my water lines or floor so I close them and have had no bad effect.

 

Ill go the other way . Close them all up and seal the crawlspace. We have had to go in and clean to may up where they had and used the vents under the home. Yes it has to be done right.

Go
http://aboutsavingheat.com/crawlspace.html

 

That website describes a home in which there is no insulation in the floor joists.
Never seen one of those except in homes built pre-1940's and without central heat/air.

 

That is the way we do all homes with a crawl space. Also put small registers in the duct and a return down there. The whole thing works as a heat sink. In test homes that they have ran. This way came out with about a 12% lower fuel bill.
Now if like a room is out over the ground and on blocks or post like. Then its all open under it The floor is like a outside wall to us. Then siding on the under side Insulation in the joist paper to the room V/B poly then the floor.

ED