Crawlspace Ventilation Suggestions

Hello

I have a 38-year old 2-BR Ranch in New Jersey on a crawlspace with a concrete floor that has a sump pump. I have addressed a lot of drainage issues and the crawl does not accumulate water.

The house has an attached one-car garage that runs the length of one gable end and does not have access from the living space. The garage was unfinished when I bought the house 11 years ago - open to the attic, but had fire-rated sheetrock on the wall it shared with the living space. I am beginning the process of insulating and installing sheetrock on the remaining three walls and the ceiling.

The crawl has four vents - two are on the gable end opposite the garage which vent directly to the outside and two open up into the garage space.

So, the two vents to the garage have limited use for promoting airflow and will be completely useless once the garage is sealed. I also would like to seal off the vents to the garage to keep out the occasional musty odors (will be using the garage as a home gym). I recognize that would only leave two vents, on the same wall (no cross-ventliation) for an approximately 1000 sf crawl space.

I've got the same issue with the fungus on my floor joists as is described in this thread: http://www.doityourself.com/forum/ba...nto-attic.html, although I have R-13 insulation between the joists, and I'd like to take some steps to ensure adequate ventilation to at least mitigate the issue somewhat.

I was thinking about running a chase up to the attic for at least one of the garage-side vents, but after I read the thread mentioned above, I realize that's not the best solution.

I was also thinking about adding a ventilation fan to one of the outside vents, but I'm concerned that the single remaining open vent would then not provide enough airflow into the crawl.

I was also considering ducting at least one of the garage vents up through the attic, possibly with a ventilation fan there, and either out to the roof or through a soffit vent. This would pull the air from the open vents on the other gable end up and out through the duct.

I know that there is a lot of debate about whether or not to vent or seal a crawl and I'm choosing to vent, so I'd appreciate any feedback anyone might have about my ideas, or any other ideas that might work.

Thanks in advance.

 

I would think the vents from the garage wouldn't pass code so I'd close them off anyway as long as there was the possibility of an engine running in there.

What kind of issue would it be to cut a couple new vents in near that end of the house to replace the two you've lost?

 

Attached garage requires ceiling drywall or attic separation drywall to contain a fire. No vents from garage to attic or house crawlspace. FHA used to vent high/low on opposites walls (not house) of garage to exhaust fumes, check local AHJ for sure. I agree with Mitch, add some vents to get required per code. Links if you need them...

Gary

 

Thanks for the replies.

The crawlspace ends at the garage, and there's a set of old concrete steps under the deck which would be at the back corner of the crawl. 16' of the back corner is the deck so it would mean cutting the vent in from inside the crawl, next to the concrete steps, under the deck, in order to be as close to the corner as possible.

Opposite that on the front of the house is a half-brick facade, with a bit of a raised flower in front bed which probably comes to about the sill plate.

Could put a vent in both cases but I'd rather let the next owner go through that hassle (don't plan on staying here more than 5 years). Probably the reason they put them where they are in the first place.

My idea was to create a chase using metal studs or similar and covered with fire-rated sheetrock to run the duct from the crawlspace vent to the garage, intruding into the garage space along the common wall but sealed off complete from both the garage and the living space, and the chase would exit in the attic. So the chase would be completely surrounded by fire-rated rock. The garage ceiling will be rocked, also. Not sure if that makes a difference?

Also, my furnace is in the garage (@ 16" off floor on block) and ducts up through the attic; would that not be up to code, or are you only saying open ducts that move air from one space to the other?

Thanks again!

 

It's hard to envision this since we can't see it but what you're proposing sounds like an awful lot of work. Plus, the whole idea of the vents is to move air and the attic is not really a source of moving air unless it's well ventilated - is yours?

Additionally, there may be code issues but I'm not the person to address that.