Draft source?


My house has a short (15') interior wall between two bathrooms. The ends are up against two closets. All the pipes and septic stack are in the wall. The bottom rests on a concrete slab and the top is up against the ceiling. The attic is filled with about 8" of pink bats for insulation.
Recently, I had to open a 8" hole in the closet on one end of the wall just above the floor. There was a fairly strong cool draft coming out of the hole. My guess was that the draft was outside air temperature, but I can't figure how outside air was getting in.
The draft must be coming down from the attic. There are a few places where electric cables go through into the wall. However, I can't believe there is enough space around them to admit the amount of air I was feeling.
Any guesses? Thanks.
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Stubby wrote:

You don't wan't to say why you are cutting a hole in a closet wall. It is outside air from the attic. It is common for there to be a draft above a partition wall. They are sometimes framed in a way that creates a kind of chimmey effect. Even a gap between studs can cause the effect. Many installers make no special effort to prevent a draft in that area. If you go up in the attic and uncover the bats in that area above the partition you will see what I mean.
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Lawrence wrote:

I am not cutting. I already cut the hole looking for a leak in the shower plumbing. That has since been resolved.
It

This draft is coming down from the attic. Chimneys usually carry heat up.
Even a gap between studs can cause

I don't understand. The studs are on standard 16" centers.
Many installers make no special effort to prevent a draft

What would they do?
If you go up in the attic and uncover the bats in that

I will. And I intend to buy a smoke gun so I can see where the air is flowing. My bet is that once I close up my hole, the air flow will stop. But I still want to know how it is getting in!
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Even a gap between studs can cause it.

The partition wall is at a right angle to the other walls. This would create the gap where the two walls meet.

Foam or caulk the gap where the draft is. Stuff glass into any irregular cavities created by the partition.

It is getting in through the attic. All attics have vents which allows cold air to come in. This is part of of a properly designed attic.
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Lawrence wrote:

Now I understand. I believe there is drywall with taped joints on the ends of the interiors wall in question.

Right. The attic is outside (the insulation envelope of the house). I'm trying to find where the outside air is getting into the interior wall. Improper joints with the walls it butts into is your suggestion, but I want to check around pipes and wires.
Thanks for the help.
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