One difference between a winter jacket and most other jackets are the armpit vents. These are zippered (or sometimes velcro or snap) openings under the arm of an outer shell jacket to help control how warm you are. Getting too hot can be dangerous, since eventually you sweat and cool through evapouration.

Here is a picture of a typical ski jacket arm vent:

Armpit vents are basically in-seam zipper pockets. Since there aren't many tutorials on how to do an armpit vents or in-seam zipper pockets, I thought I would share how I made mine.

As you can see from the picture above, the armpit vent can go up the body of the jacket and into the sleeve seam. I could not do this with my jacket, since my side seams and sleeve seams do not match. So, I only added the armpit vent to my bodice pieces.

Step 1: Make a Box

Before sewing the side seams, draw a box where you want the zipper opening to be. I am adding the zipper to by side back piece. Again, as my sleeve seams don't match, I am doing this before I add sleeves.






One side of the box is along the seam allowance. The other side is 3/8" into the body (or however wide you want it to be). The top and bottom are how long I want the opening to be.

Step 2: Attach One Side of the Zipper

Pin and sew the zipper along the line that is 3/8" in towards the body. Make sure the zipper is facing down. Luckily, as my zipper tape is about 3/8" wide, I was able to match it up with the seam allowance edge for easy alignment.


Step 3: Clip the Seam Allowance

Clip at into the far corners of the box - don't go too far!



Step 4: Make Vent Linings

Instead of a pocket lining, create a mesh lining. I added a facing in my main fabric to prevent the mesh from getting caught in the zipper.


You will need two of these for each vent.

Step 5: Add One Mesh Lining Piece

This is the tricky part - sew the lining piece to the side of the zipper you just sewed. Make sure you are sewing into the zipper facing only. You can match up the side of the lining with the side of the zipper. And don't worry about sewing far from the zipper teeth - this is just to hold it in place.


It should look like this, once you have sewn it:


The 'right side' of the mesh lining is on the inside of the zipper.

Step 6: Topstitch the Vent

Fold down the zipper and the mesh lining into place. The mesh lining should be ironed so that it folds near, but not on, the zipper teeth. Topstitch around the top, side, and bottom of the zipper.


Note: Don't worry too much if you have crooked topstitching (I always find it hard with my tiny zipper foot) - this part will be covered and no one will ever look there.

The inside should look like this:


Step 7:  Add Second Mesh Lining

Sew the second mesh lining to the zipper. Again, make sure you are only sewing onto the zipper facing.


Step 8: Make Vent Flaps and Attach

This step is optional, but it will hide your zipper (and any crooked topstitching) from view and shield it from the wind.


My flaps are curved on one end and will be held down by the sleeve seam on the other end. If you are making flaps that start on the body and end on the sleeve, you will probably want to make both ends curved and add a piece or two of velcro to keep them closed when you are not using your vent.

Baste the flap into place inside the seam allowance. Make sure that both mesh lining pieces are folded into the body and that you do not sew into them.


Step 9: Sew Side Seams

Now, as if the vents weren't even there, sew the side seams together. Again, just make sure not to sew into the mesh linings (note: a piece of tape can help you with keeping it out of the way).


It's starting to look really good!

Step 10: Topstitch the Side Seam

Press the side seam away from the side that has the vent flap. Iron mesh lining piece that hasn't been topstitched yet so that it folds near, but not on, the zipper teeth. Tape back each mesh lining so they are pointed in opposite directions.


Topstitch the side seam. I now have something that looks like this:


Step 11: Sew the Mesh Linings Together

Pin and sew the mesh linings together in an arc shape. Starting just above one zipper end, sew from one side seam edge out to about 1" from the zipper. Continue along and the sew back into the side seam above the other zipper end. Make sure you are only sewing into the mesh lining pieces. Trim excess.


Note: Before the step, I went back and made the facings of my mesh linings smaller. There were about 5/8" to 3/4" wide - this seemed too big. I shortened them to 1/2", which works better. I didn't want the facings to block out my mesh lining.

Step 12: Sew Vent to Jacket Lining

This step comes later when I sew my lining to my jacket. The opening in my jacket lining will be sewn to the facings in the mesh vent linings.

For now, this is what my armpit vent looks like with my sleeves attached:

vent open

vent closed

Considering this is the first time I've done this, I'm pretty happy with the results. My winter jacket is coming along nicely. Now, I think I could even make my own motorcycle jacket (they have vents, too). But, I really should finish this jacket. Winter is here and it's about -20'C (-4'F) today.