Insulation from sweaters and booties differs
Yesterday, I talked about keeping your feet warm at frigid temperatures. In today’s post, let’s talk about booties and sweaters to create ageless style and stay warm when the Polar Vortex extends south.
A winter sweater of one climate region fails in another
Sweaters are a fall/winter essential in all cold climate regions. But not every sweater works for every climate region. A cotton cable knit sweater is a great way to create a winter look down in California or anywhere a long the coast of the Gulf of Mexico. However, this sweater would be unsuitable for wet, humid just above the freezing point weather of Washington state, the blizzards in the Midwest, Canada, Alaska or even the East Coast. In these climates, cashmere, wool, silk and qivuit (musk ox under wool), or any blend of them are much better.
Cotton sweaters are for warm/hot climate region winters
The physical properties of the yarns are the reason. Cotton absorbs water, i.e. sweat. It is comfortable to wear in hot climates as it breathes, and is slow to dry. Thus, one gets some wanted cooling on a hot summer day. However, the slowness in drying means in a cold climate that the body sweat may even freeze. Cotton rarely gets electrostatic, which happens to many fabric in cold dry continental climate like in Central Canada or Interior Alaska.
Insulation is key in winters of cold climates
A key factor for winter clothing in general is the thermal conductivity. This term refers to the heat transfer by molecules. You know this physical phenomenon very well, when you own an iron pan with iron handle. Even though the handle isn’t in contact with the heat source, it gets hot by exactly this thermal conduction.
In case of your feet or body, which are both warmer than the cold ground or ambient air, the body heat flows to the colder ground or air. Thus, you need a fabric that a low rate of heat conduction across the fabric, i.e. a low thermal conductivity. In other words, the fabric provides high thermal insulation from the cold.
Examples of good and bad insulators in apparel
Fabrics with low thermal conductivity are all kinds of wool with qivuit being the best. Rubber has a high thermal conductivity. Thus, rubber booties without insole are not a good idea at below freezing temperatures. Norwegian wool felt booties are great at temperatures in the negative digits (less than -18oC).
In general as a material, thermal conductivity of cotton, wool and fleece are 0.168-0.184, 0.04-0.07, and 0.035 W/(m·K), respectively. This means you stay warm in the fleece longer than in wool than in cotton.
The knit/weave also plays a role
Of course, the thickness and tightness of a fabric play a role. A single jersey cotton fabric with a surface density of 1 gram per square centimeter (g/m2; 0.23 oz per square inch) has a thermal conductivity of 0.035 W/(m·K). The thermal conductivity of interlock and 1×1 rib cotton fabrics is higher than that of cotton jersey. This is due to the fact that air is a bad conductor and as the fabric gets tighter the space and amount of “air pores” goes down. The thermal conductivity of polyester single jersey at same density as that of the cotton jersey is 0.032 W/(m·K). This means one is better off with a polyester sweater in cold climate than with a cotton sweater of same tightness of the knit. Again, when the knit gets tighter the thermal conductivity goes up as the pore spcae for still air goes down. The thermal conductivity of wool felts with about 1 g/m2 is about 0.094 W/(m·K). Norwegian booties are made from that.
Sweaters that I wear in winter
Now to my sweaters that suit me well from when we have “warm weather” due to Chinook, to frigid cold when cold air builds over the Interior and northwestern Canada (to get ready to bring a cold snap to southern Canada and the northern US). 😉 I wear the cotton sweater at temperatures around the freezing point. Doing so works in the dry continental, calm wind climate of the Interior. I wear my wool sweaters (e.g. Fair Isle sweater, Irish cable knit sweater) when temperatures get below -10F (-17.2o. When temperatures plump below -20F (-28.9o) nothing helps any better than layers, layers and even more layers.
It wasn’t really cold yet, up here in the Interior. Thus, I had not to wear any cozy sweaters and booties in my 17th winter yet. 😉 Therefore, I compiled a slide show of how I styled my sweaters last winter.
Ageless Style Linkup – sweaters and booties
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Photos of me: G. Kramm
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