The insulation layer can actually be a couple of layers and its purpose is to provide additional warmth when the base and mid layer pieces are not warm enough for conditions. (See Part Three of this series for an explanation of base and mid layers). Insulating layers retain body heat by creating a layer of still or dead air around the body while still allowing perspiration to escape. Pockets of still air decrease the heat exchange between the body and the outside world. Synthetic fabric such as fleece is usually a good choice because it traps heat but doesn’t hold moisture. Moisture is deadly when the temperature drops or when you slow down your pace. The key to a good layering system is to let moisture out but not in. (Except by drinking of course).
Insulating layers should be warm, lightweight and as non-bulky as possible. They should also breathe well to let sweat and body heat escape. Choose garments that are easy to slip on and off since you’ll change the insulating layers as you heat up and cool down.
The three most commonly recommended insulating materials are:
Wool: Wool is a great natural insulator. It’s available in knickers, pants, long-sleeve shirts, pullovers, sweaters and jackets. Wool insulates even when wet but can take a long time to dry and can be very bulky/heavy.
Goose Down: Down is a great insulating material and some garments pack down small. It’s hot though, and usually overkill for most hiking outings during the summer.
Fleece: This material consists of polyesters that are treated in a way that makes the fibers stand up and trap air between the fibers. This trapped air forms the protective layer of still air forming the main insulation. These popular man-made synthetic materials come in a wide variety of styles and thickness and combine a few characteristics that make them ideal insulators.
First, they retain pockets of still air that insulates and prevents body heat loss as mentioned above. Additionally, the treated polyesters have almost the same moisture-transporting qualities as base layers. Therefore, they transport moisture to the outer layer and dry very quickly. This makes them comfortable, warm (even when wet), fast drying and lightweight (half as heavy as wool). Fleece products are available in shirts, pants, vests, jackets, pullovers and sweaters. We recommend a nice mid-weight fleece pullover or jacket for our hiking tours.
Some of the more expensive garments also provide wind protection with built in wind/weather liners built right into the material. Gore Wind stopper is one of the popular brand names found on many wind-resistant fleece garments.
Get out the magnifying glass. Here’s a closer inspection of the different types of fleece.
Basic Fleece is mostly made out of polyesters. Check this out: The Patagonia company actually spins new synthetic fibers from old soda bottles! The polyester fabric is then sent to an enormous fleece mill and passed through a ‘napping’ machine. This machine doesn’t make you fall asleep however. The machine picks out and rakes up the fabric loops on one side, creating a fabric with a tight solid weave on one side and a fluffy air-retaining surface at the other side.
This is a very common, single-sided Fleece that has undergone more ‘napping. ‘ Ahh, we could all use more naps. Pile is also a much thicker, open fabric.
Join us next time for Part Five of our series: Rain Gear. As always, please contact Ryder-Walker if you have any questions. We look forward to hearing from you.