Originally Posted By: Steven Smith
This post was automatically imported from our archived forum.
I was asked to cut some vents in the wood near the corners of a house that is having problems with Wood Destroying Organisms. Generally this went fine. But I have discovered something that, frankly, I am not sure just what it is.
CRAWL SPACE ISSUE:
On one side of the crawlspace, for the full run of a furnace duct, someone has nailed a piece of tin under the farthest most floor joists. They have run a round furnace duct, which does hook to the furnace (which is barely out of the crawlspace in an attached basement) under this tin. Then, just in from the corner..where I put a vent...they have the furnace duct cut up into the piece of tin. It is like a 'tin chamber" with a single duct going into it
I cannot figure out what this is ???? The tin is just tacked below these two joists. Looking into the chamber, to the sides are the joists, above is wood floor boards.
If it is a cold air return, it is sucking in, and recirculating, air from a very unhealthy environment: Musty odor, with Anabiid Beetle, carpenter ant, termite frass, and excessive moisture, no vapor barrier adding to the smell and bad biology. With my new vent hole there, fresher, but colder, air would be getting in, I guess.
If it is for hot air, then it is a weird one because the duct, where it cuts through the tin chamber does not ever go up into the floor of the house. It would dump the hot air only into the "tin chamber."
It was my luck, as it is nearly impossible to get in the crawlspace, that I happened to place my vent hole exactly at the end of this "tin chamber." No tin was cut, but a wood piece was removed at the end of it, so the vent hole opens this odd tin chamber to the outdoors.
I am not sure what to do here? (1) forget about the vent at this location and carefully patch the hole; (2) Call in a furnace professional to figure out what in the world is going on; (3) leave the vent where I put it.
Anyone with experience, who can give me any advise on what this appears to be would be of help. It's because I have not yet been able to get in the room for, or run the furnace, that I do not know if it is a hot air or cold air duct.
The furnace is probably about 25 years old and runs on oil.
Thanks for any suggestions.