Before many of the contemporary advances in technology, heat management boiled down to building things out of thick layers of non-conductive materials. Parkas and fire jackets were packages stuffed with insulation. Fire walls were made of metal or concrete, and heat-resistant walls were just thicker than others.
Heat reflection entered the market as a result of NASA experimentation for use with the space programs. This is why the most recognizable consumer example of the technology is called a “space blanket.” A regular blanket works by reducing the emission of temperature from a warm object (a human body) to a cold object (the night air). Space blankets accomplish the same thing despite being thinner than a paper towel by reflecting the heat of a warm body back toward the body, resulting in significantly less warmth emitted out into the night air.
Those aluminum metallized thin film blankets are just one example of heat-reflective fabrics, and an older-tech example at that. Over the intervening half-century since the invention of space blankets, Sigma and other leading companies have developed a variety of other types of heat reflective fabric:
- Aluminium foil - fabric laminates
- Metallized thin film - fabric laminates
- Direct-metallized fabrics (non-laminates)
Although virtually every application of heat reflective fabrics works via the same process as those space blankets, the applications are incredibly diverse. More than one major industry needs to protect things from becoming too hot, too cold, or both. For example…
If a layperson has seen reflective fabrics in action outside a space blanket or a winter coat, this is the most likely place. Aluminum foil laminated to high-strength fabrics were common in the 80s as “radiant barrier” applications were catching on. The aluminum was installed either under the roof or on the attic floor to reflect out the incoming heat in warm climates and reflect back in the heat in cold climates, saving homeowners money.
In 2010, after contractors were electrocuted installing aluminum foil in an attic with poor wiring, and when many aluminum foil products failed to meet changes to radiant barrier fire standards, foil - fabric laminate manufacturers moved over to an aluminum film (like Mylar) laminated to the high-strength fabric. These products were only slightly less reflective than their aluminum foil counterparts (95% vs. 97%) and were not as electrically conductive (4+ ohms per sq), and much more fire safe (0 flame spread). Unfortunately, the lamination from plastic film to plastic fabric wasn’t always as strong a bond over time, and many products started delaminating. In 2011, Sigma Technologies developed a direct metalized (no-lamination) high strength radiant barrier that could match the performance of the laminates. The result is a product that improves the insulation of the home, while both safe and long-lasting.
Vehicles are especially problematic from a heat containment standpoint because they must (a) hold up to higher temperature differences and (b) be thin and light. Heat-reflective fabrics allow for more densely-packed insulation components. Aircraft often typically uses reflective shades over the windows to prevent heat build-up, similar to the sun-shade you put in your car windshield on a hot day. These single or multi-layered reflective curtains protect against both incoming infrared heat (reflecting 97%) and harmful UV rays (reflecting 92%). Additionally, small aircraft, like corporate jets, tend to develop cold floors due to their small size and the temperatures at high altitudes. Multi-layer fabrics consisting of layers of foil and felt are installed in the floor. These foil laminate products can maintain a 42F temperature differential in just a fraction of an inch.
Metalized fabrics are at the center of countless other aerospace applications, some of which are “out of this world”. Multi-layer insulating fabrics comprised of metalized films or foils and open (often ceramic) fibers have been in place from as far back as the Saturn V rocket launch in 1967 to as recently as 2015’s SpaceX Falcon 9. The film/foil and fabric laminates here are used for heat shield for reentry into Earth’s atmosphere. By using heat reflective fabrics to insulate, these manufacturers minimize the thickness and the weight of their insulation without sacrificing performance.
Tents and Shelters
This category is an extrapolation on the space blanket idea that brought heat reflective fabrics into the public eye. The same heat reflection that makes a space blanket useful allows for lighter tents in temperate climates, and the building of tents useful in desert, jungle, arctic/antarctic and other extreme conditions.
For example, the inflatable and portable shelters made by HDT Global and used by the US Military when operating in desert environments include an inner lining of a low emissivity "radiant barrier" fabric. Suspended between the outer shell fabric and the inner “ceiling”, the heat reflective fabric is able to face an air space on both sides for maximum efficiency. A single layer of heat reflective fabric installed this way is able to reflect the incoming infrared radiant heat by about 95%, reducing the temperature by 20-30 degrees F. This makes a dramatic difference in comfort, with a corresponding increase in soldier health and morale. Heat reflective technology is also preferred here because reducing weight and thickness of the overall portable shelters is key. Using several inches of fiberglass or foam, as would be used for a permanent building, simply isn't an option.
Engineering modern electronics, construction environments or industrial/governmental installations requires engineering for heat transfer. These needs range from low-cost building insulation, to miniaturization of sensitive components, to shielding rooms or equipment from exterior temperatures. A layer of heat-reflective fabric can mean significant savings while minimizing space when compared to other materials.
The small motor in a hot tub is designed to heat the water to and maintain it at 104F. Since the motor shares a small space with pipes, pumps and other equipment, smaller is better. In addition to filling the cavity with fiberglass or foam, a heat reflective fabric (usually aluminum or copper) is installed behind the wall paneling to reflect the heat back in and not allow the heat to emit out, which greatly improves the energy efficiency of the hot tub. Hot tub manufacturers, like MAAX Spas, that use a heat reflective fabric can realize an energy savings of 25% to 35% more energy efficient than the guidelines set by the state of California in 2014.
The most advanced technologies in the world still need to travel from point A to point B before the client takes delivery, and that travel happens most often in a delivery truck, cargo plane, or shipping container. Heat and cold-sensitive cargos must ship in packaging that protects them from extreme temperatures.
Lining the sides of a refrigerated shipping container with a heat reflective fabric protects the contents, and allow energy-efficient maintenance of temperatures anywhere between -30C and 40C. Lining the sides of a box or bag for individual food packages allows them to stay frozen for a 2-day ship time. In either application, heat reflective fabrics offer the unique ability to prevent approximately 95% to 97% of the infrared heat from entering container and warming the contents. Additionally, heat reflective fabrics take up considerably less space and weight than other insulation solutions.
Firefighters, field biologists, astronauts and industrial workers all work in environments beyond the normal human range of temperature tolerance. Using a heat reflective fabric, a Fire Approach Suit can withstand temperatures up to 200 F, and a Fire Proximity Suit can withstand temperatures of 500F. Aluminum foil laminates and metallized aluminum thin films are the industry standard for these types of garments, and no major manufacturer makes them without the reflectors