In this post in our thermoneutrality series we will be covering the role that clothing plays in influencing our thermal comfort, describing CLO Values, and covering the problem of clothing differences in determining ideal office temperatures.
The Importance of Clothing
As we know from our previous thermoneutrality posts. The human body is constantly generating heat, in turn leading it to need to expel excess heat in warmer environments and conserve heat in colder environments.
In these situations clothing serves as an invaluable tool for facilitating these tasks. Prior to the invention and adoption of clothing we, as a species, were limited to environments wherein it neither reached too hot temperatures (causing us to overheat) or too cold environments (wherein our bodies would not be able to maintain its internal temperature and suffer from hypothermia). However, with the development of clothing we were able to overcome these challenges and gradually spread across the globe.
In addition to the heat regulating function of clothing, clothing also serves as a critical improvement of our hygienic environment, protecting us from pathogens and minor injuries, in turn decreasing average mortality.
Clothing over time also has had a significant impact on our cultural development, with certain clothing types coming to display social status, individuality, cultural associations, as well as religious orientation. However, in this post we will be focusing primarily on Clothing’s role in regulating our thermal comfort.
Form Fits Function
Clothing in respect to managing our thermal comfort is generally designed to accomplish one of two tasks. It either helps to reduce or increase heat loss depending on the circumstance.
In a hot desert environment there is a constant risk of not being able to expel excess heat leading to heatstroke or severe dehydration. To prevent this, clothing developed in these regions serves to maximize heat loss via convective and evaporative cooling, while minimizing heat gain via conduction and/or radiation.
Clothing accomplishes this through being loose fitting, made of a porous material such as linen/cloth, being light in color and also covering the majority of ones body.
Why Wear Loose Clothing?
It helps us get rid of excess heat!
Wearing loose clothing allows for an increased rate of air movement in the space between one’s clothing and skin, in turn increasing heat loss through convective heat transfer and evaporative cooling.
Why should clothing be made of a porous material?
A major way that we regulate our temperature is through evaporative cooling, whereby we sweat and that sweat absorbs some of our bodies heat in order to evaporate. By wearing porous clothing we allow this now relatively saturated air to easily diffuse outwards allowing for constant evaporative cooling to take place. In contrast, if we wore none porous clothing after a point the air close to our skin may become too saturated with water and reduce the effectiveness of evaporative cooling.
Why is it best to cover the majority of the body and wear lighter colors?
The reason is to minimize radiative heat gain. Our bodies are extremely effective at absorbing heat via radiation. This means that in hot environments we can easily take on too much heat. Through covering the majority of our body we reduce the surface area of our skin which is exposed to the environment and thus reduce the amount radiated out to our surroundings. As for wearing a lighter color, lighter colors such as white often have lower emissivities meaning that they both radiate and absorb less radiative heat then darker colors such as black! These are all the major reasons how clothing in hot desert environments developed in the way that it did!
In Cold Environments Heat Preservation is The Name of The Game
Clothing in cold environments is largely designed for the purpose of heat retention. Our bodies are constantly generating heat and when wearing the correct clothing this heat is sufficient to keep us warm and comfortable even in the coldest of environments. However, in order to accomplish this the clothing being worn has to be able to minimize heat loss via convection, conduction, and evaporation. This is done by wearing clothing that is thick, made from highly insulated material, and is either form fitting or forms a closed system with very few gaps for air to get in.
In the above picture you can see an example of a highly effective form of winter clothing the snow suit. This snow suit checks all the boxes, covering the majority of the body, being quite thick, being made out of insulated material, and being mostly sealed.
Winter clothing greatly benefits from having a certain thickness and insulation since these things serve to reduce the speed at which heat transfers from the inner layer(facing our bodies) to the outer layer. For very cold environments this is usually accomplished by using a non porous material such as nylon along with an insulative lightweight spacious material such as down stuffing. Down stuffing is usually an intermediary layer in certain winter clothing consisting of duck or goose plumage. Prior to down stuffing animal furs and wool coats where the common alternatives. However, due to their heavy weight and after a certain point questionable origin, the most popular choice for winter clothing became those using the lighter and easily sourced down stuffing.
Minimize Radiative Heat Loss
The need for clothing to cover the majority of our bodies is due to our bodies being so effective at radiating. Have too much skin exposed in cold environments and your surroundings will quickly suck as much heat as it can from you due to the large temperature difference. Covering the majority of one’s also helps reduce heat loss to the air via convection(when the clothing isn’t extremely loose), especially if one is wearing tight clothing that forms a solid seal on the openings(cuff,ankle,neck). So now hopefully you know a bit more of the science behind why people always tell you to cover up in winter!
Not surprisingly it should be quite clear not that the form of clothing development to fit it’s function. Next we will go over a common tool for defining a piece of clothing’s insulation value specifically its Clo Value.
What is Clo?
A Clo is a unit used to define the amount of thermal insulation a piece of clothing provides. CLO values are usually used for scientific modeling and/or testing since it allows the scientist to be able to assign an attributable value to people’s clothing in order to allow for more accurate modeling and assessment of specific comfort scenarios.
1 CLO is equal to an insulative value of .155 w/m2k and is about the amount of clothing needed for a seated individual to feel comfortable at 21C/71F with an air humidity of less than 50%. Below you can find an example chart showing some common clothing items and their respective Clo values.
Although CLO values are mostly used for scientific purposes it can still help us make informed decisions about how we engage with our environment.
Clo, Office Space, and Rethinking Set Temperatures
As stated in the previous section a Clo of 1 relates to the temperature needed for an individual to feel comfortable at 71C or at most 50% humidity. However, this is also for someone in a business suit! Nowadays the majority of us aren’t walkin around in suits so the environment wherein we feel comfortable will also differ greatly. This can be seen most acutely in office spaces where there is often a near constant struggle for controlling the thermostat set temperature, owing in large part to differences in dress.
In more corporate environments the men may be expected to wear suits versus the women wearing dresses. This already leads to a large discrepancy amongst these two groups. The women may need a temperature that is 2-4C greater than the men to feel comfortable owing just to the difference in dress! But, that doesn’t mean we should abolish office dress codes since when you completely remove the dress code in can become even more complicated with there existing a “comfort gap” of 6+C solely dependent on everyone’s difference in clothing!
Maybe it would be more appropriate to either focus on giving individuals control of their own space with very reactive heating/cooling solutions, allowing them to set their own set temperature, or make sure that office designs incorporate a range of thermal environments giving its occupants the choice to match their working area to their thermal needs.
In this modern age there is no longer any excuse to just blindly accept the one size fits all approach for setting the temperature in an office building, it not only fails to deliver a positive result for the majority of people but also wastes a massive amount of energy.
Now hopefully you’ve learned how clothing affects our thermoneutrality, how it is defined, and some practical applications. In our next post in our thermoneutrality series we will be focusing on Humidity!