We had record rainfall in July and it is looking like this fall will be pretty wet too. If you have lived in Juneau for a while you might have noticed that Juneauites don't shy away from the rain. Getting out in the rain is a fact of life and a necessity if you want to stay sane during the dark wet months. Choosing the right rain gear is key to making your wet outdoor adventures a success, but deciding which type of jacket has the right combination of breathability and water repellent properties can be confusing.
The level of water resistance and breathability that is right for you depends on the activities that you have planned for your outerwear. If you are standing in the rain fishing, then you would want something that is PVC coated and 100% waterproof (eg. Grundens, Guy Cotton and some Helly Hansen). A PVC coated raincoat is completely waterproof, and may be the ideal garment for standing in a downpour, but if you tried to hike or ski in it, you'd be wet in no time from your own perspiration. So if you are hiking up Mt. Jumbo on a typical fall day then you will want something that has a high waterproof rating (over 10,000mm), and also a high breathability rating (over 10,000g).
Waterproofing for outdoor gear is usually reported in millimeters (mm) or psi (pounds per square inch).
Manufacturers use pressure to determine how much water will pass through a fabric. If you look on the comparison chart you will notice water resistance listed in millimeters (mm). This number comes from placing a square tube with inner dimensions of 1" x 1" over a piece of test fabric. Water is then added to the tube and the height (in mm) that the water reaches before it begins to leak through is measured. The higher the number, the more waterproof the fabric. The mm rating measures the height of the water while the psi rating measures the pressure the water exerts. To convert from mm into psi, divide by 704; to convert from psi to mm, multiply by 704.
Breathability is normally expressed in terms of how many grams (g) of water vapor can pass through a square meter (m) of the fabric from the inside to the outside in a 24 hour period. In the case of a 20k (20,000 g) fabric, this would be 20,000 grams. The larger the number, the more breathable the fabric. Many Rain coats also offer pit and side zips to help increase the breathability of a jacket. When using a coated rain jacket, aim for a larger size which would allow for some air movement around the torso and up the sleeves.
Technical gear is usually waterproofed with an exterior coating (DWR) and a multi-layer laminate fabric.
We carry many jackets that have either Gore-tex, eVent
waterproof membrane which is actually laminated together with another fabric layer for increased durability and to help wick moisture through the membrane and out. Laminate construction usually offers superior breathability and durability but requires some care to maintain its full waterproof/breathable capability.
The reason these jackets appear to lose their ability to shed water over time is because the DWR (Durable Water Repellent) coating which was applied at the factory has worn off. DWR is a polymer applied to the outside of outerwear which makes water bead on the surface instead of soaking through. Once the DWR coating has worn off dust and oils may block the Gore-tex layer causing water to seep in. Washing your waterproof garments with detergent and fabric softener can also clog the pores of the fabric. The remedy is to clean the jacket in a tech-wash solution and then reapply the DWR coating. NAO carries Nikwax products for both processes for down, laminates, shoes, tents, etc, so don't give up on your old Gore-tex jacket until you have tried washing and recoating it. Always check the manufacturer's care label before washing or drying your waterproof gear, as extreme heat will damage most garments.