I recently (5 months ago) had construction done in house, old plaster walls taken down on first floor of 2 story detached colonial home, then insulated and sheetrocked. The odor I am questioning has been occurring really since the work has been completed. I called in the local gas company, my plumber and even the fire department. With the equipment they used, they said there is no sign of a gas leak. The odor is very similar to gas but since I ruled out gas as a possible source, I am left to wonder what it is and where it is coming from. The odor only occurs when either a. it is windy outside or b. when the back kitchen patio door is open and a breeze comes through the kitchen into the dining room. The odor is mostly confined to the foyer area next to the dining room (seems like the odor initiates in the foyer and is kickstarted by some cross wind). Opening the front door at the foyer does not help matters. The odor just gets stronger. My theory: the wall between the foyer and the dining room, which was one of the walls sheetrocked had 4 plumbing pipes inside it. Could it be that during the sheetrock process, a nail or nails punctured/cracked one of the pipes, possibly the vent pipe and every time a breeze comes through, an odor from the pipe comes through the wall at the base? Or maybe the vent pipe (which is also one of the 4 pipes) is clogged? I can't get to the roof without calling someone in but I see the vent pipe from street level and it has no cover/cap on it. Honestly, I have never given that pipe protruding from the roof a second thought until now. I'd hate to open up the wall but I think I don't have a choice. I don't want to get my family sick from this odor. If my front and back door are closed, there is no odor whatsoever. I purchased a first alert CO/methane gas detecter from first alert and have it plugged in the foyer area, the alarm has not gone off. Suggestions?

I recently (5 months ago) had construction done in house, old plaster walls taken down on first floor of 2 story detatched colonial home, then insulated and sheetrocked. The odor I am questioning has been occurring really since the work has been completed. I called in the local gas company, my plumber and even the fire department. With the equipment they used, they said there is no sign of a gas leak. The odor is very similar to gas but since I ruled out gas as a possible source, I am left to wonder what it is and where it is coming from. The odor only occurs when either a. it is windy outside or b. when the back kitchen patio door is open and a breeze comes thru the kitchen into the dining room. The odor is mostly confined to the foyer area next to the dining room (seems like the odor initiates in the foyer and is kickstarted by some cross wind). Opening the front door at the foyer does not help matters. The odor just gets stronger. My theory: the wall between the foyer and the dining room, which was one of the walls sheetrocked had 4 plumbing pipes inside it. Could it be that during the sheetrock process, a nail or nails punctured/cracked one of the pipes, possibly the vent pipe and every time a breeze comes thru, an odor from the pipe comes thru the wall at the base? or maybe the vent pipe (which is also one of the 4 pipes) is clogged? I can't get to the roof without calling someone in but I see the vent pipe from street level and it has no cover/cap on it. Honestly, I have never given that pipe protruding from the roof a second thought until now. I'd hate to open up the wall but I think I dont have a choice. I dont want to get my family sick from this odor. If my front and back door are closed, there is no odor whatsoever. I purchased a first alert CO/methane gas detecter from first alert and have it plugged in the foyer area, the alarm has not gone off. Suggestions?

Sounds like it might be sewer gas as you suspect... and as you suspected.. it won't trip those type of sensors. Vent pipes rarely ever have caps over them.

If it was clogged you would likely see problems with sinks, toilet or tub draining... have you noticed a change in that recently?

Now someone else is going to have to offer up ideas on proving that or how to find it without the obvious mess it would entail. Because I have no ideas.

I agree ]with Smoothy. Sure sounds like sewer gas, Has this been a ongoing problem or did it just start. They do make vent caps, (see image) but it sounds to me like a crack in a vent or as pipe left open on construction. To check it out ask your plumber if he has never done a smoke test. Good luck, Tom