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IN A WORLD OF YOUR OWN
- MEC's Guide To
Layering
Layering
clothing is the most versatile way to adapt to a varied range of
environmental conditions. If
you're too cold, too hot, or too wet, it's hard to enjoy the outdoors. Away from climate-controlled buildings, your safety as well
as your comfort can depend on suitable clothing.
Your internal body systems try to maintain a thin layer of warm
(30° to 33°C.), still air around you - your very own microclimate.
If the surrounding environment was constant and your life was
devoid of activity, this personal atmosphere would be all you'd ever need.
However, once you step outdoors into heat, cold, precipitation and
wind, you throw your microclimate out of whack.
Your physical activity and/or the weather can create conditions too
extreme for the body's mechanisms to deal with on their own.
Wearing a series of layers allows you to maintain an optimum
microclimate during periods of physical exertion and rest.
You can anticipate changes and fine-tune your microclimate by
shedding layers before you get too hot or by adding layers before you
start cooling down.
INNER
LAYER
More
commonly called underwear, this layer transports moisture, usually in the
form of sweat, away from the skin and disperses it to the next layer where
it can evaporate. This
process is often advertised as wicking.
Moisture transport is important because water is a very good heat
conductor. A wet garment
against your skin can draw heat away from your body twenty-five times
faster than a dry one. Even
in conditions above freezing, this rapid heat loss can cause a dangerous
drop in your body's core temperature, leading to hypothermia.
Synthetics such as polypropylene and polyester are now the most
popular materials for inner layer garments.
Synthetics are non-allergenic, light, and strong.
Unlike natural fibres, synthetics absorb very little water.
These quick-drying garments reduce the risk of conductive heat
loss. Synthetic underwear is
available in light, medium and heavy weights.
Lightweight underwear best is for sustained activity where moisture
transport is paramount. For
more variable activity levels, midweight layers offer a balance of wicking
and insulation value. Heavyweight
underwear is best when temperatures are very low.
The inner layer should fit snugly but not so tightly as to restrict
blood circulation or body movement, though lighter layers are generally
worn closer fitting than heavier weight layers.
The
distinction between inner layers and mid layers can become pretty blurred,
as heavier inner layers are worn as light sweaters or jackets, and lighter
mid layers are worn alone next to the skin in warmer conditions.
Don't get hung up on definitions.
Wear the combination that provides the right insulation and
moisture transport.
MID
LAYER
The
mid layer provides additional insulation and continues the transport of
moisture towards the outer surface of your clothing.
To slow heat loss, this layer must retain the warmth generated by
your body. Wool and
synthetics work well for this because the structure of their fibres
creates small air spaces that trap warm air. Synthetics are superior for
moisture management because they absorb little water, allowing faster
evaporation. Wool absorbs up
to thirty percent of its own weight in water, leaving it heavy and
difficult to dry. Synthetic
fleece/pile garments (pants, jackets, pullovers and vests), as well as
being lightweight, are very durable and require less care than wool.
Additional features such as pit zippers and full-length front
zippers add to versatility, though they increase weight and price.
As with the inner layer, this layer should be snug but not
constricting. If it's too loose, it leaves unnecessary space your body
must warm up, and allows warm air to flush out of the garment when you
move.
OUTER
LAYER
After
all the effort you put into creating the perfect environment, you don't
want it blown away by wind or washed away by rain or snow. The outer layer, often called a shell garment, protects your
microclimate from the elements. It
should also allow air to circulate and excess moisture to escape.
Choose the outer layer on the basis of what you plan to do, where
you plan to do it and what you plan to spend.
Waterproof/breathable garments, incorporating Gore-Tex®, Entrant®
or similar technologies are hugely popular in the backcountry.
They are wind and waterproof, and comfortable over a wide range
of conditions since they allow much of the wearer's perspiration vapour to
escape. Waterproof/breathable garments "breathe" best when
they are kept clean, and when the outside environment is less humid than
the garment interior. When you are active, your body can produce more
water vapour than any fabric can expel.
The result can be a build-up of moisture on the inside, leaving you
wet, clammy and cold. Strip
off a layer or open any ventilation zippers before this happens to
minimize discomfort. In cold but dry conditions, a wind shell of an uncoated,
non-waterproof fabric will be less sweaty than a waterproof/breathable
garment. Wind shells have
varying degrees of water resistance (not waterproofness). During high aerobic activities, you may find that your heat
output would dry mild precipitation off the surface of wind wear as you
go.
For
conditions of steady precipitation and high humidity, a waterproof
(coated) rain jacket may be your most satisfactory outer layer.
Non-breathable rainwear is not recommended for below freezing
temperatures, however -the condensation inside the garment can be clammy
and even dangerous.
HEAD
PROTECTION
It
has been estimated that up to fifty percent of a person's total heat loss
can occur through the head. This
is because the head, as a rather important extremity, draws a hefty share
of the body's blood to keep warm and functional.
Schoolyard insults notwithstanding, no-one's head has much fat. Without this natural insulation, your head acts like a
radiator, letting heat escape. The rest of your body system must then use
additional energy to re-warm the circulating blood.
A good wool or fleece hat will not only slow heat loss through your
head, it will also make your hands and feet feel warmer because of the
improved circulation. Don't
overlook full-face balaclavas and neck tubes for really harsh conditions.
HANDS
AND FEET
To
keep your head and torso warm in cold conditions, your body reduces blood
flow to the hands and feet. These extremities do not generate much heat on
their own, so some sort of protection is needed. Materials and
construction being otherwise equal, a mitten is warmer than a glove, since
the mitten has less surface area to radiate heat away. The disadvantage of
mittens is a loss of dexterity. Gloves are good for activities that
require independent finger control, such tying knots, but arc less
efficient for keeping your hands warm.
A layering system consisting of a thin wool or synthetic glove for
some warmth and moisture transport, an insulating mitten and a
non-insulated
shell mitten for outer protection will give you a wide range of
temperature control and manual dexterity.
Wool
and wool blends are still the dominant choice for socks, offering a good
balance of moisture management, insulation and cushioning. The addition of
a polypropylene liner sock will speed up moisture transport from the feet
to the outer wool layer. Socks should fit snugly.
If too tight, they may restrict circulation.
If too loose, they can slip or bunch up, creating pressure spots
leading to blisters.
Mountain
Equipment Co-op is a member owned and directed consumer
co-operative. www.mec.ca
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