Windshirts, sometimes called windbreakers or wind-shells are one of the most versatile pieces of clothing you can use. A simple, unlined windshirt can ounce per ounce provide more warmth than many other clothing items because wind speeds up convection cooling significantly. In many cases a light wind shirt over an appropriate weight base layer is all you need to keep comfortable when active. Furthermore a good wind shirt can keep you comfortable in a light drizzle when a full rain shell would be too much. Windshirts can protect you from many biting insects. Finally, wind shirts also slow evaporation a bit (they are not perfectly breathable) which moderates flash-off cooling. Ideally you want slight air permeability to maximize breathability while still providing protection from convection cooling.
I often use a Montbell Tachyon wind shirt. It weights less than two ounces and compresses down to around the size of a cliff bar. I have an amazing light, breathable, and unfortunately expensive ArcTeryx Norvan SL Trail running rain jacket that I sometimes use instead of a wind shirt when I am minimizing what I carry and need full protection from the rain.
Classic windshirts are ultra-light, ultra-breathable unlined nylon or polyester jackets which block the wind while being highly breathable. I am particularly fond of windshirts with hoods and full zippers such as the Arc Teryx Squamish, Patagonia Houdini, and Montane LightSpeed. There are also a number of nice pull over and/or hoodless windshirts such as the Montane JetStream, Outdoor Research Ion (Quantum model), or RAB Quantum Wind Top.
Softshells can be a good alternative to wind shirts. They tend to be more air permeable and more durable than a classic wind shirt. This makes them great for high energy activities and/or when engaged in activities that are hard on clothing like climbing. My two favorite kinds of soft shells are:
- Stretch woven soft shells. Super breathable with great mobility. The Black Diamond Alpine Start and the Outdoor Research Ferrosi are great example of this sort of shell.
- Classic Soft-shell which combine a wind and water resistant shell with a wicking inner layer are excellent in colder conditions. Think of this as a lined wind shirt. The Rab Vapour Rise is my favorite version of this sort of jackets
Some people use rain gear for wind protection. In warmer weather, most rain gear is not sufficiently breathable and tends to retain more heat than a light rain shell. The result is that they block the wind well, but the wearer will often overheat and get wet from sweat. A counter point is that if you either manage you activity level and/or are in cool weather so rain shells might work.
There was a nice discussion about breathability, CFM and wind shirts windproofness, breathability, and air permeability on a BPL forum. Most people can’t perceive wind if a material is CFM of <=5.
Low Cost: The cheapest solution is a cheap nylon windbreaker found at Target, Walmart, etc. Treat with DWR after-market product.