The following information is what I’ve learned and gathered from years of running and riding outdoors through the winter months. Let me apologize up front for stating only the general case. I like to keep this as simple and as readable as possible.

The basic equation is your body generates heat and your clothing helps retain it. The key is finding the steady-state balance where your clothes release the same amount of heat your body is generating, keeping you warm but not letting you overheat.

Convection (Wind) Heat Loss

• Convection heat loss is less of a concern for runners except in very windy conditions. Nonetheless, male runners should consider windblock briefs.
• Cyclists are more susceptible to convection heat loss because of their higher speeds. Off road cyclists generally experience less convection heat loss due to their lower speeds and the trees and rolling terrain that block or slow the wind.
• There are many windblocking clothing materials on the market including nylon and Windstopper. These should be your outermost layer where possible.
• Windblocking materials tend to be less stretchable (hence their baggy fit) and don’t breath well despite the marketing banter. The better clothing has venting, e.g. back draft flaps and pit-zips.
• One often overlooked clothing feature is a wind flap on the backside of jacket zippers.
• Cyclists primarily require their windblocking on the front of their clothes.
• Windblocking head gear greatly decreases your ability to hear, which may pose a safety issue in urban settings.