crawlspace foundation vent question

[mcga]

I have read here that many recommend blocking off foundation vents and I have read the referenced research as to why this si a good idea.

My question is, is this still advisable when furnaces are in the crawlspace? I have 2 units in my crawlspace. One day, during winter when my vents were closed off, I wen tinto the crawlspace and I couldn't breath! I assumed that the furnaces had used all of the available oxygen. It was very strange. I have a CO detector down there, so I assumed it wasn't that affecting the air.

Any thoughts appreciated!

[Ed Imeduc]

Not sure what you have here. :confused:
Yes we close up all vent holes in a crawel space summer and winter. seal it, walls have insulation on them and a 6 mil poly down on the ground.Also put registers in the duct work and return down there. You say you have a carbon monoxide tester down there . How about a tester for propane and Methane sewer gas. If you have AC on the units where does the drain go and do they have traps in them. Ok then we have Radon next did you do any test for that?????? Lots ifs ifs or could bes here.


ED ;)

[mcga]

The registers in the crawl space are to provide constant fresh air down there?
I never considered that. In fact, Ive spent a great deal of time sealing the returns down there so they wouldnt introduce the dirt and dust down there into the house

The ac drains go into those small squarish motorized pump, draining up and outside (through the foundation vents, by the way!

[Ed Imeduc]

Drains ok then. yes open the registers down there and the return air. This is to help warm the floor and the whole thing works as a big heat sink for you. Should be a filter there in the furnace .That will stop any dirt there. How about Radon test?????


ED ;)

[mcga]

I will get a radon kit today. How many registers do I need and where?

[Ed Imeduc]

Dont know your duct lay out???? Most of the time we just put in like a 2 1/4"X12" near each end of the trunk line and a 6"X10" in the cold air drop. Now this air has to go through the air filter.

ED :coffee:

[mcga]

Thanks Ed! I know I wasn't specific enough on the layout. I have 3 trunk lines (these are the runs which the room registers come off, right) and 2 cold air deops (these are the return runs?)You are saying put the trunk registers at the very end of the runs, and the cold air drop runs anywhere (in front of filter, of course - couldnt be any othere way I guess)? Thanks big help.

Now I just need to figure out why the crawlspce has a smal river running through it when it rains!

[Ed Imeduc]

Now I just need to figure out why the crawlspce has a smal river running through it when it rains!
Start out side ground slope away from the home. Gutters on the home. Down spouts get water away from the home. Drain all around the outside of the footing. 6 mil poly down on ground and up the walls some. Over lap 2' tape all seams.
The registers for down there go into the main trunk line. not just a register run. Just near the end of the trunk line.

ED ;)

[Grady]

Before you get too carried away you should check with local code officials.
Some areas (like mine for example) require crawl spaces to be ventilated. Here they will bust a contractor in a heartbeat for not having enough ventilation. Codes just don't seem to make much sense on some things. Crawl spaces have to be vented yet they want basements sealed as tight as a drum. :wall: