Like many things in tailoring, when it comes to wearing and choosing jacket vents, there is no real right and wrong and above all, decisions as to which you wear should be informed by personal preference. There are however some home-truths which may help to inform this decision, and when a few days ago I read an article universally championing double-vents, I thought it might be time for me to offer readers the other side of the coin as it were. Twin rear vents today are everywhere around us, both in the bespoke and ready-to-wear realms, and they are both a sensibly practical and stylish decision when it comes to fitting a jacket - no doubt about it. Furthermore, from the perspective of a menswear retailer, double-vents will be more likely to fit more body shapes, because they can often allow for more freedom of movement in the jacket itself. This does not mean however that the single vent should be snubbed, nor that double-vents should be considered universally preferable.
Chittleborough & Morgan's immaculate double-vents. This is exactly how they should sit. Image from chittleboroughandmorgan.tumblr.com
As a general rule, a single rear vent will better suit men with either large seats, or a significantly curving spine. Conversely, a double-vent will often serve to highlight a large seat, sitting in a square flap over the protrusion (a problem I often have to battle with myself) rather than disguising it as the clean central slit of a single-rear vent will. This is a hugely useful thing to bear in mind if you're either paranoid about the size of your seat, or if you struggle to find a jacket off-the-peg which sits in harmony with the curvature of your spine. Furthermore, twin rear vents have a tendency to fly-away from the seat of the wearer if the back and hips of the coat are too slim. If you like a modern, slim or Neapolitan Pitti Uomo-style fit to your tailoring, a single rear vent might actually keep the back of you looking cleaner and more slim than you'd think. Furthermore, single rear vent will often suit a man who has to settle for overly-roomy off-the-peg jackets, because a single rear vent most easily allows for excess cloth to be removed from jackets simply by altering the jacket through the centre back seam. This is often well worth doing by the way, because the great danger of a single rear vented jacket is that if its loose, the vent will highlight as opposed to disguise any lack of shape running through the spine of the coat.
A cool, skinny modern suit doing its thing at Pitti Uomo - complete with a gaping double vent.
Having said all this, its worth perhaps bearing in mind that if you're wearing vents, the way in which they need to sit will depend firstly upon which type of vent you're wearing. A twin rear vent needs to be cut wide enough to sit and extend over either side of your seat, right from the edge of each hip. Without some space to sit and drape properly, the vents will simply misbehave. Likewise, a single rear vent needs excess cloth built into the rear part of the jacket's skirt on each side, to prevent the skirt from sitting too tightly, pulling outwards over each hip, and producing a gaping vent which cannot sit cleanly. There's a similar reason why you'll only find single breasted overcoats, and again its a practical one. Having a vent in a long garment allows for the wearer to move more freely, and for the length skirt of the coat to fall cleanly around the legs, for the wearer to sit, stride, stretch and so forth. A twin-pleated overcoat will almost over-address this issue, offering two many breaks between the panels of the coat, looking ungainly and impractical. Furthermore, more often than not an overcoat with double-vents will misbehave in the wind in a way a singled vented garment will not.
Dapper, perfectly sitting single rear vents at work. Note how fullness is built into the rear of each side of the jacket's skirt at the side to allow enough room around the seat for the vent to sit cleanly.
Having written these guidelines, I suspect that many will disagree, but I was taught these guidelines both through extensive personal experience, and through discussion with a number of tailors, so don't just take my word for it. If you want a cleaner jacket shape around your seat, or more shape through your spine, try a single rear vent and have it tweaked if needs be - it might just solve a persistent tailoring problem.
Sartorial authority Mr. Simon Crompton wearing another exquisitely shaped Chittleborough & Morgan suit. This is how a suit should look through the spine when shaped well. Image from Permanent Style.
I've been wanting to produce a series offering handy guides on many of the commonly overlooked or misunderstood aspects of tailored dress for some time, but between producing industry focused features and offering insights into worthwhile brands there never seems to be the time! For this reason, I'm going to make this a long-running, relaxed series of features, offering some nuggets of style advice and tailoring science simply as and when there's a moment in the schedule. Next-up will be a piece on understanding drape, stay tuned.