how should a wind shirt fit. How do you layer one?

I don't think there is any just one right answer to this, think it depends more on your particular needs, preferences, average climate conditions, etc.

Personally, i do a lot of trail hiking with minimal bushwhacking, and since i live in and primarily hike in central to western part of VA where there aren't a lot of extremes (except for maybe heat), i like an oversized windshirt that gives me more flexibility with how much i can layer under it, more freedom of movement, and more innate aeration if i want or need it (by reducing layers, leaving the bottom more loose, etc).

If i did a lot of bushwhacking, or mountaineering, i would probably want a more slim fitting windshirt to minimize damage to same, for one example.

Whatever works for you. Some (or a lot) of this stuff is relative and variable.

Edit: just adding that one of the more specific reasons of why i have an oversized windshirt is so that i can put it over my puffy insulation jacket to preserve same from damage. Not that i hike in it, but since the shells are a bit fragile, and i'm cheap, i want to preserve it for a long time and since i actually do more "bushwhacking" usually when camped, than when actually hiking, well makes sense for me.

I find I like different fits for different activities.

I generally like a slim/trim fit as most of the time the wind doesn't bother me to much and I don't like excess material bunching up, ruffling, etc. So, I generally were a small/medium when I am not expecting low temps and will be wearing an insulating layer.

However, I agree with Justin about using the windshirt to protect an insulating layer. Generally, I always try to find decent windshirts on clearance or sale and am usually able to find them for under $30. However, my insulating layer is usually in the $100 range, so if there is any chance of damage to those layers, I go with a large/xlarge layer as it is far easier on the pocket book to replace the windshirt than the insulation layer.

Another thing to consider (and this will vary from person to person). I've found an oversized windshirt protects slightly better from the wind. Since it is not as form fitting and allows more air between the layers, it buffers more of the wind.

I got a pertex wind shirt on sale for $40 and layer it over a 200 weight polartec fleece I purchased on clearance for $10 at Gander Mountain.

I like this system better than my montbell thermawrap I payed double that for. Fleece is much warmer in the wet than anything except the perpetually wet soggy wool options that weigh a ton and pack no better.

Years of sailing on cold wet open deck boats taught me to wear fleece and I still believe in good polartec fleece today. Wet, warm, compressed, it won't let you down 500 washes later.

I wear my wind shirt one size up, giving me room to layer any combo of fleece and puffy vest I want under it.

I size it to fit over my seasonal insulation layer.
If I'm not wearing any insulation layer, then I don't mind if it's a little oversized.
I aim for a relatively close fit over the insulation, but not tight.

I got mine tight like you did.

My question to everyone else:

If you wear a baselayer and a windshirt on a cool weather hike, and it gets colder, can you wear your insulation layer over the windshirt and still get the benefit?

"I'm 6'2" 190 lbs." Given that size, I'd think a M is too small. I'm 6-2, 165, wear a base and large R1 hoodie and fleece vest under a x-large Golite Ether.Can comfortably wear into 20sF while active.No restriction of movement.

"I might be able to get it over a 200 weight fleece if it was trim fit, but it would be a tight squeeze." That would be a deal breaker for me. I hate restricted garments.

For something like a Houdini, I prefer just enough room for a baselayer and 300 weight fleece or equivalent. There's no huge downside to a roomier cut, just personal preference. The Houdini fabric is particular is very loud in the wind, and a trim fit is nice in high winds, on a bike, and so forth. Also as noted a bit less likely to snag on shrubbery.

I have a deep-winter specific windshell which is roomier, and will fit over anything I might have along except my monster down parka.

David, just curious but what do you use for your deep winter windshell?

Sounds like you need to go up a size to get full utility from it. I subscribe to the theory that a loose fit aids ventilation via a "bellows effect." In camp, it would be good to have a loose enough fit to get a light down or polyfill vest under. On the trail and walking hard, it would have to be really cold to wear more than a Cap2 or light Power Dry long sleeve base layer under.

Layering? A windshirt is the outer wrapper, blocking heat-robbing wind and light precip, while remaining breathable. I wear mine with a base layer, adding a Power Stretch vest or hoody. In some ways a windshirt is just a shirt; in other ways it is part of a deconstructed jacket that you can wear the parts in any combination that suits the moment.

In cold past the base/mid/windshirt combo, it's time to get out a big puffy layer. You could wear a puffy vest on top of your windshirt combo— not the most effective I think, but it works for trail breaks without a costume change.

Max- Im answer to your question, I think the effectiveness of an insultating layer over the windshirt depends on how wind-resistant the insultaing layer is. If it blocks the wind well it works well, but then the windshirt's pretty much superfluous. If your insulation doesn't block the wind, then it doesn't do a lot of good and you'd be better off putting it on under the windshirt.

All winter I've been wearing two Ibex layers (t-shirt and Zehpyr) under a Houdini, adjusting the hood and vips to ventilate quite a bit. If it gets cold (usually only when above tree-line or resting) I'll go to a rain shell with pit zips, nano puff, or down jacket over the Houdini. It works well for me; but my Houdini is large enough that i could easily fit at least a nano puff under it if I weren't so damn lazy.

Havent' had a windshirt during the summer before. I'm sure whent it warms up a little there will be plenty of discussion about that!

"If you wear a baselayer and a windshirt on a cool weather hike, and it gets colder, can you wear your insulation layer over the windshirt and still get the benefit?"

Yes, but if it gets really windy the heat trapped in your outer insulation layer will get blown away. You won't feel the wind but you will feel colder every time it starts blowing.
For around camp you can put a puffy over a windshirt and it works fine.
However, in cold and really windy weather it can be nice to have a windshirt that goes over your puffy so you can be protected when you walk away from your shelter to do stuff like getting water, adjusting guy lines, collecting firewood, ect.

I use it as my outer most hiking layer. The only exception is my down sweater. I put that on over my wind shirt. I try never to hike in my down so it doesn't need protection.

Like David I prefer the slim fit and will eventually get a roomier fit for deep winter layering. I particularly like this set up because it's much less hassle to throw on a mid layer over a wispy windshirt than it is to remove the windshirt, keep it from flying away, put on a mid layer, than negotiate putting on a flapping windshirt in a stiff wind. I lose more heat fussing around in one spot than just putting on insulation and moving around again.

I've found that under or over insulating layers there's minimal difference in warmth with a wind shirt for 3 season hiking. If it does indeed get that cold, my rain shell goes over everything and then the windshirt location becomes negligible.

Justin, my winter shell is an older Patagonia Essenshell anorak with a coyote fur ruff (http://bedrockandparadox.com/2012/11/01/ruff-ruff/).

The Essenshell is supposedly made of an epic treated fabric, but I've not found the DWR to be all that great. On the other hand it does breath well and provides just enough wind resistance. Given that I don't bring this out unless it will be consistently in the single digits water resistance is not such a big deal.

Thr fur ruff is a key part of it, as is the fit. I bought a size large (here on the swap) and took in the sides and arms a bit. The torso and arms are thus very long to seal out drafts, and the torso is just roomy enough for all the right layers.

Loki, I'm 6'2.5" and 175 (on a good day) and all my Patagonia stuff is size large (for the most part).
Of course how things fit is a personal matter- I don't like skin tight clothing, not even my baselayers. My stuff isn't baggy, I would say it fits "casual" and comfortable.

I wear my size large Houdini over my Nanopuff, or similar sized insulation. I also have a XL Houdini to fit over thicker layers like my down sweater.

To also answer Max's question I will wear the L under my insulation also depending on the weather and temperature. If I was wearing the windshirt while hiking and got to camp I would probably just put my MB inner over my windshirt, unless the wind was really blowing then I would put the inner under (that sounded funny).

David, where did you get the Coyote ruff? They don't let us harvest those animals he in the city.

I made the ruff myself. Lots of trappers here in Montana only too willing to sell a pelt. Lots of places online as well. One pelt would easily do two ruffs.

I usually buy an extra large even though I could get by with a large or a medium.

My reasons are:

(1) I get long sleeves that protect my hands from sun, bugs and cold.

(2) A big loose fit allows me to wear the windbreaker for sun and bug protection in warm weather with nothing underneath. I find a loose fit cooler than a tight fitting garment.

(3) I can layer to my hearts content, including putting closed cell foam vests or ponchos underneath it.

(4) Big loose clothing is easy to put on and take off.

(5) It keeps the women away from me when I'm on the trail.

Thanks for the reply back David. That's quite an interesting wind jacket, especially the coyote fur ruff part.