Dress for Winter
OverviewStudents will dress for winter while explaining the purpose and function behind each layer. Throughout the lesson, students will learn and incorporate vocabulary terms related to heat transfer. At the completion of the lesson, students will be able to explain the different clothing layers and make reasonable choices for dressing in winter conditions.
- Students will be able to choose appropriate clothing for outside winter activities.
- Students will identify the 3 clothing layers needed for outdoor winter activities and explain why each layer is necessary.
- Students will be able to define the terms conduction, radiation, respiration, evaporation and convection, citing specific examples in Grand Teton National Park.
BackgroundWinters are long and cold in Jackson Hole. The first heavy snows fall by November 1 and continue through April; snow and frost are possible any month. At park headquarters, snowfall can average 14 feet in a season. In the mountains, snowfall can average 33 feet. Between winter storms the days are sunny and the nights are frigid. From December through February the average high temperature is 28°F and the average low temperature is 2°F with lows as low as -30°F.
Heat is lost from the body in five ways. It is radiated from the body in the form of infrared radiation. It is lost through convection as the air immediately adjacent to the body is warmed and then disturbed by wind. It is similarly lost through respiration as cool air is taken into the lungs, warmed and then exhaled. Heat loss also occurs by conduction when the body comes in direct contact with some cooler surface, such as the ground, cold pots, snow, rocks, etc. And finally, heat is lost when moisture on the body's surface evaporates - an exothermic chemical reaction. Because an active snowshoer, skier, or hiker can sweat four to six liters of perspiration in a day, evaporative heat loss has special implications for clothing selection. In order to prevent radiation and conduction, some clothing articles must be capable of providing the wearer with "insulation," a thermal barrier of trapped dead air space that conducts heat away from the body as slowly as possible. Because the body and outdoor elements are continuously exposing insulating clothing to moisture, it is a valuable asset for clothing to insulate even when it is wet.
MaterialsMaterials will be brought in by the teacher prior to the lesson. The materials will mostly consist of synthetic, down and wool clothing layers for outside recreation. The clothing should be consistent for a layering system that would be appropriate for winter travel in the Tetons.
Synthetic clothing layers for upper and lower body - the materials will visually demonstrate the purpose and function of each layer. Each layer will build upon and compliment the previous layer.
Synthetic/wool outer body pieces - gloves, hat, boots. These materials will visually demonstrate their function.
- At the beginning of the activity, come in dressed for a winter day. As your introduction progresses, take off each item of clothing one at a time and set the articles on a table for the students to look at. Ask them to consider the layers that you're removing, and to think about why you chose to wear them --- what advantages or disadvantages might they have? Encourage the students to look, feel, and maybe even smell the clothes. Then, bring out a duffle bag or backpack stuffed with all different clothing articles (some good and bad for winter) and explain that you're going to prepare someone to dress for a winter's day! Ask for two volunteers. Choose two volunteers to stand in front of the class, and make sure they're comfortable getting dressed up. Then one at a time, have the remaining students come up and pull out articles of clothing from the bag and decide whether each item is appropriate for winter dress or not. (Make sure to have cotton jeans, a baseball cap, a goofy t-shirt, thin ankle socks, flip flops, and some other impractical articles in the duffle bag.) As the students discover layers, have them dress one student in the appropriate layers, and the other student in the inappropriate layers. By the end of it all, you should have one student who is prepared for a winter's day, and the other student providing comic relief to the lesson
- At the beginning of the lesson, define the five ways in which people can lose body heat, making sure to write (or have a student write) the words/definitions in a visible place. Then emphasize that the most basic rule in dressing for winter is layering as it helps with 3 important outcomes: 1) Keeping moisture away from the skin 2) Creating insulation to help keep the body core warm 3) Protecting against the "elements" - wind, snow, rain, etc.
- Inner layers of clothing should be of materials that "wick" moisture away from the skin. (For a demonstration, you could fill the bottom of a drinking glass with a small amount of water to represent sweat on your skin. Then stand a strip of wool or candle wick in the glass touching the water to show students the idea of moving water from the bottom of the glass to the material; this is "wicking"). Finally, all layers of clothing should dry rapidly, preferably from body heat alone. Compare wool, polypropylene, capilene, and thermax. Describe advantages and disadvantages of each. Pass the materials around and have students feel and smell them. Emphasize the structure and the feel of the materials. This is also a good place to discuss cotton and why it is not a prominent component of outdoor clothing (i.e. it actually absorbs water into the individual fibers, causing the fabric to stay wet for a long time). Ask the students to assess which of the five way(s) their dressed-up peers might lose heat, if they were wearing only the inner layers outside.
- For the middle layers, compare the basic types of insulation used in outdoor clothing: down, polarguard, holofil, qualofil, and thinsulate. It's best if you can have at least two different parkas so the students can feel the differences between them for themselves. Middle insulating layers should "breathe" easily, meaning that they allow for airflow. Ask the students to assess which of the five way(s) their dressed-up peers might lose heat, if they were wearing only the inner and the middle layers outside.
- Protective layers of outer clothing should repel precipitation so that it does not soak through to the inner layers. These must also stop the wind to protect the wearer from convection heat loss, and allow ventilation to minimize evaporative heat loss. Explain the basic types of nylon: taffeta, lycra, rips-stop, and cordura. Discuss its tight weave and wind resistance, as well as its inability to absorb water into the fibers of the cloth. Explain Goretex and describe its advantages and disadvantages. Discuss the difference between water resistant and water proof. Ask the students to assess which of the five way(s) their dressed-up peers might lose heat, if they were wearing the inner, middle and protective layers outside.
- Hands and Feet! Gloves and/or mittens protect your hands from being cold – this is especially useful when participating in snow sports. A lot of body heat escapes through the hands just as it does through the head. Another area to keep warm is your feet. A pair of wool socks or polypropylene will keep feet warm even if they get wet. Again - stay away from cotton. And of course, make sure you have a pair of good winter boots!
- Bring out the hats and scarves! Certain basic essentials are just as important as a warm jacket and a pair of snowpants. Sixty percent of your body heat escapes through your head if you are not wearing a hat. It is an essential in the winter (not a ball cap but a lightweight wool or fleece will do fine). Add a scarf.
- Eyes/Vision and Skin! On a sunny day (and even cloudy days), wear sun glasses. They protect your eyes from the sun's UV rays that penetrate even in the winter and can be especially reflective off of snow. The sun also can affect the skin, so sunscreen is an important consideration.
- Dressing in layers allows you to add or subtract articles of clothing depending on the weather, temperatures, and your level of activity. When you go to the mountains, remember that weather conditions close to home are generally very different from conditions in the mountains. For every 1,000 feet of elevation gain, the temperature drops 3.5 degrees Fahrenheit.
- When the duffle bag or backpack is finally empty, compare and contrast your two student models; one student is expertly prepared to be outside on a winter day, and the other… well… might be a little embarrassed about his/her fashion sense, and is definitely NOT ready to be outside. Talk about the possibility of carrying extra layers in daypack too, in case a layer gets wet, lost or ruined. It's always good to be prepared. Thank your student models and other participants, and return the dress up layers to the duffle bag.
Assessment-Students will list and describe the five main means by which we lose heat from our bodies in the winter.
-Students will list and describe the three main clothing layers and each of their respective functions.
-Students will be able to discuss/explain winter weather, and factors for consideration when dressing for outdoor activities in Grand Teton National Park.
Park ConnectionsThe lesson relates outdoor preparedness to the dramatic winter weather of Grand Teton National Park. In order to safely enjoy and explore the outdoors, students need to have the understanding that clothing can wick, insulate, and transfer heat energy.
ExtensionsThe teacher could wear or demonstrate with a wet synthetic sock and a cotton sock and record the temperature and/or time it takes each one to dry.
You could have the student models (while dressed in all their layers) step outside for 30 seconds and come back inside to report their experience to the class.
Depending on the group size and the materials available, the facilitator could bring in many different duffle bags and have the students break into small groups to dress up their classmates.
*Winter adaptation extension – Students could compare/contrast the inability of people to adapt to winter and our subsequent need to layer our clothing, to the abilities of other animals in Grand Teton National Park that cope with winter by growing thicker coats, hibernating, migrating, etc.
Additional Resources-Weather data chart listed on the Grand Teton National Park website.
-Stories of winter survival/ranger rescues in the park during the winter.