Cycling in the rain doesn't have to be so bad!
Thanks to innovations in fabric technology; and advances in garment design and construction, bicycle apparel manufacturers now have the ability to produce rain specific clothing that keeps cyclists dry and comfortable even in the heaviest of downpours.
What is the difference?
Water Resistant refers to fabrics that repel water naturally because they are woven so tightly that individual water droplets are to large too pass through the weave of the fabric. Water resistant fabrics are not "waterproof", and will soak through in heavy or consistent rain fall.
Water Repellent refers to fabrics that have a coating or finish applied to the outside face of the fabric that repels, but is not impervious to water. Water repellent fabrics work very well for light rains, or drizzels, but they are not "waterproof" and are not used to manufacture technical cycling rain apparel.
Waterproof refers to fabrics that are impervious to water. Being "waterproof" means that moisture does not pass through the fabric... rain does not come in, and sweat does not go out.
Cyclists generate so much heat and sweat during a ride, that in order to stay dry on the inside, and the outside; cycling specific rain gear must be able to "wick moisture" and "breath" in addition to being "waterproof".
Garment Construction and Fabric Technology
To be truly "waterproof", a garment must be made from a "waterproof" fabric and have sealed, or taped seams so that rain does not leak in through the small perforations made by sewing needles during the construction of the garment. Sealing and taping seams takes special equipment and extra time. As such, it adds substantially to the cost of the garment, but is the only way to ensure that the garment will be completely waterproof even in the heaviest of downpours. For further information on specific garment design and construction, click on Rain Jackets, Rain Capes, Rain Pants, Gaiters.
Waterproof Breathable Fabrics
"Waterproof" fabrics refer to fabrics that are impervious to water. Being "waterproof" means that moisture does not pass through the fabric... rain does not come in, and sweat does not go out. A cyclist generates so much heat and sweat during a ride; that the only way to stay dry inside and out, is to have a garment that is made of a fabric that is not only "waterproof", but has the ability to "wick moisture" and "breath". Breathability and moisture management are obtained through fabric construction, and/or garment design.
Breathability and Moisture Management
Staying dry is not just about preventing rain from getting in, it’s also about letting sweat out. In order to stay dry on the inside, cycling rain gear must be designed to allow water vapor to escape. All waterproof breathable fabrics use some type of fabric technology to help increase the transfer of moisture vapour away from the skin to the outside of the fabric in an effort to keep skin dry during heavy aerobic activity. But, even the most breathable waterproof fabrics can’t keep up with the rate of moisture evaporation from human skin. As such, in addition to being made from a waterproof breathable fabric, most cycling specific rain gear will also be designed to "vent" air.
Breathability through Venting
Vents are designed to allow air to come into the garment, keeping the cyclist from overheating. A vent can be as simple as a mesh panel, or as detailed as a specially designed zipped or Velcro® vent which allows a cyclist to adjust body temperature by opening and closing the vent as needed. The cost of a garment will be greatly affected by the number and type of vents that the garment has. Simple mesh panels that can not be opened and closed, let air in, but also are not designed to keep water out. More sophisticated (and expensive) vents allow air in, but are also designed to keep water out.
Breathability through Fabric Technology
Waterproof fabrics fall into three main categories:
1. "PVC, or Poly Vinyls"
2. "Coated Fabrics"
3. "Laminated Fabrics"
"Microporous" film laminates
"Hydrophilic" film coatings
PVC or "Poly Vinyls":
These fabrics are completely waterproof, but they have no ability to wick moisture or breath without the addition of exterior vents or mesh panels. PVC's are generally used in the less expensive garments with limited design features such as waterproof venting.
All coated fabrics have an outer layer, or "face" fabric that is usually made of nylon or polyester. The main function of the face fabric is to provide a durable outer shell. To make the face fabric waterproof, the inside of the fabric is coated with a protective moisture barrier.
Fabrics that are coated with a "microporus coating" have the ability to breath, because the moisture barrier has pours. The size of the pours are small enough to prevent water droplets (rain) from penetrating the face fabric, but large enough to allow water vapor (sweat) to escape, making these fabrics waterproof and breathable.
The latest generation of coated fabrics applies the waterproof coating to each individual fabric fiber rather than the entire face of the fabric. When the fabric is woven using these coated fibers the fabric has naturally created pockets of air that facilitate the venting of water vapor.
Laminated fabrics have an outer layer, or "face" fabric that is usually made of nylon or polyester. The main function of the face fabric is to provide a durable outer shell. To make the face fabric waterproof, the inside of the fabric is laminated to a "microporus membrane". The membrane contains millions of microscopic pores, each large enough to enable moisture vapour (sweat) to pass through, but small enough to prevent water droplets (rain) from getting in.
There are different types of laminates:
2- ply Laminate refers to an outer shell fabric that is laminated to a waterproof micro-porous membrane.
3 PLY LAMINATE
3- ply Laminate refers to a 2-ply laminate that has an additional lining layer that protects the fabric and disperses moisture over a large surface so that moisture is absorbed and transferred away from the body.
4 PLY LAMINATE
4-ply Laminate is the same as a 3-ply laminate with an additional hydrophilic coating applied to the micro-porous polyurethane membrane.
Outside Air Temperature Can Effect the Breathability of a Waterproof Fabric
Breathability of a particular fabric is also a function of temperature differential (Delta T). When the environment on the inside of the jacket is warmer than the environment on the outside, a driving force is created. The greater the Delta T, the greater the driving force, and therefore the more breathable the fabric. In simpler terms, waterproof breathable fabrics do not breath as well in warmer temperatures, and will not be as functional as they are in colder weather. If you are looking for cycling specific rain gear to be worn in hot humid climates you may want to consider a basic cycling rain cape and a pair of cycling sandals. For more information on cycling rain capes click here! For information on cycling sandals click here!
The Breathability of a Waterproof Fabric is Dependent on it's Resistance to Evaportaive Heat Transfer (RET)
Even when the Delta T and weather conditions are identical, different waterproof fabrics can have different levels of breathability due to their "RET" Resistance to Evaporative Heat Transfer.
The lower the RET rating of a particular fabric, the higher the breathability.
"Hydrophilic" means "water loving". "Hydrophilic" coatings and "Hydrophillic" membranes rely on the chemical and molecular properties of water molecules to push perspiration away from the body to the external face of the fabric where the moisture can evaporate.