What do glass beer bottles, stainless steel bottles, and polar bear hair have in common?
Yes, they are all great insulators, but the reason why may surprise you!
What is Insulation?
To learn what makes a great insulator let’s first look at exactly what insulation is. There are many kinds of insulation – thermal, sound, electrical, etc. For our purposes, we’re going to talk about thermal insulation, which reduces heat transfer between objects by either reflecting thermal radiation or decreasing thermal conduction and convection from one object to the other (more on this in a moment). In basic terms, thermal insulation is what keeps your coffee hot in an insulated mug and your hands warm in gloves.
Types of Heat Transfer
A common misconception is that insulation keeps cold out, when in fact the function of insulation is to reduce the transfer of heat, which means it keeps heat in. Heat energy will transfer to nearby objects of lower temperature, which you can feel happening as hot coffee is poured into your coffee mug, unless the transfer is slowed or stopped by a thermal insulator.
To understand what makes a great thermal insulator, you’ll need to understand the three methods of heat transfer: Conduction, Convection, and Radiation.
Conduction: The process by which heat is transferred from an area of greater kinetic energy (higher temperature) to an area of lower kinetic energy (lower temperature), e.g. touching a hot handle. Occurs through physical contact and is the most common form of heat transfer.
Convection: The process by which a gas or liquid is heated and then travels away from the source, e.g. feeling the hot air above a boiling pot.
Radiation: The process of heat transfer through electromagnetic waves, e.g. heat from the sun.
The job of a thermal insulator is to reduce the heat transfer – either keeping the intended object hot or cold. A great example of a thermal insulator is a stainless steel water bottle, which keeps cold drinks cool and hot drinks hot – all in the same device! But here’s the perplexing part – stainless steel isn’t a good thermal insulator – in fact, it’s a better conductor.
Superior Glove spoke to Paul Faucher, a principal engineer at NOVO Engineering, to get to the bottom of this mystery.
“The stainless steel water bottle is such an interesting example because a lot of people don’t realize that it isn’t the stainless steel providing the insulation – it’s a vacuum,” explained Faucher. “The stainless steel bottle is actually two bottles – one on top of the other with a small space in between. This space is void of air and actually creates a vacuum – it is this vacuum that provides the insulation.”
Faucher went on to explain that a vacuum is one of the best known insulators, but that air itself is also an excellent insulator and a main contributor to the insulating properties of items such as oven mitts and fiberglass insulation. It is the air pockets within these materials that slow down heat transfer much more than the materials themselves.
“NASA actually uses air pockets to help keep space shuttles from burning up upon re-entry to Earth.”
Thermal Insulators for Fabrics
When it comes to thermal insulators for fabrics, the struggle for manufacturers has always been size vs. efficacy. The bulkier the glove or garment, the better the insulating properties, but the more uncomfortable it is for the person wearing it.
“Insulation for your clothes works much the same as for your home – an insulating fabric is woven together with plenty of space for air. Using hollow fabrics and loosely weaving them together is the best way to insulate clothing, but much like home insulation, this creates a bulky material that isn’t always practical for the wearer,” explained Adam Bahret, Owner and Lead Engineer of Apex Ridge, a product reliability engineering consulting firm.
“Items like glass and ceramic make fantastic insulators when broken down into fibers and woven into a fabric,” explains Bahret. “One of the biggest challenges for insulating fabrics designed to keep heat energy in is how to produce those insulating properties without massive bulk. Fabrics like Thinsulate® have successfully overcome this challenge by providing great insulation in a thin fabric.”
One of the most creative, yet effective, forms of insulation Bahret has ever run into involved an ingenious way to insulate homes in third world countries. The idea is incredibly simple but works extremely well. Glass beer bottles are used to build a wall and held together by mortar. The hollowness and round shape of the bottles makes them excellent thermal insulators while the transparency of the bottles lets in plenty of natural light. It makes for a functional, cost-effective way to build an insulated home.
The Future of Insulation
What will insulation look like in the future? Will new materials be discovered that will drastically change how insulating clothes are made and worn? Paul Faucher thinks so.
In fact, Faucher believes the future of insulation is already here – it’s just too expensive.
“In the future, I think you’ll see new micro-tube and micro-sphere insulators based on the technology used to manufacture carbon nanotubes (microtubes). These will be used to provide desired insulating properties in thin, wearable fabrics, films, and even molded parts,” predicts Faucher.
“Microtubes are microscopically small and excellent insulators due to their hollowness, which traps air. They work a lot like down feathers, which are also hollow, to insulate heat energy. As anyone with a down jacket knows, the insulating properties are excellent. The microtubes take this insulation a step further given their microscopic size, allowing for less bulk and better heat-retaining capabilities.”
The price of microtube technology still makes it unpractical for consumer purposes. As the price comes down, he believes we’ll see more and more of this technology employed in insulating fabrics.
Is a microtube glove in the works for Superior Glove? You’ll have to wait and see!
The Puzzle of the Glass Bottle, Stainless Steel Bottle, and Polar Bear Hair
We’ve finally come back to our original puzzle – what do all these items have in common that makes them such great insulators? If you read the article and didn’t skip right to the bottom, then you already know that it is the hollowness of both bottles that provides their superior insulating properties. Air, a poor conductor and good insulator, is trapped in the hollowness of the glass bottle, while stainless steel bottles go a step further by creating a vacuum to slow heat energy.
But what about the polar bear hair?
Similar to down feathers, polar bear hair is actually hollow. This hollow center traps air and insulates the polar bear from the extreme cold of the Artic. This must be why they always look so happy in the freezing cold!
Looking for gloves to keep your hands nicely insulated this winter? Check out our line of winter gloves!
Thank you to Paul Faucher of NOVO Engineering and Adam Bahret of Apex Ridge for their contributions to this article.
Paul Faucher is a principal engineer at NOVO Engineering, a consulting firm that provides comprehensive hardware and software development engineering services from concept through pilot manufacturing. Faucher has a versatile background in mechanical engineering and physics. He received his BSME from San Diego State University and has over 25 years of engineering experience.
Adam Bahret is the Founder, Owner, and Lead Engineer of Apex Ridge, an engineering consulting firm specializing in reliability engineering for product development with clients including Google, Boeing, Amazon Robotics, and Hyundai. Bahret is a mechanical and electrical systems reliability expert with over 20 years of experience in product development. He received his MS in Mechanical Engineering from Northeastern University and is an ASQ nationally certified reliability engineer as well as a member of IEEE.