Evolution of thermal insulation from antiquity to the present day
It is often said that PUF insulation is the most reliable method of insulating pipes. There is a lot of evidence to confirm it: from ease of installation, to low thermal conductivity and long life compared to similar products, etc.
In this article we provide a historic outlook on the advantages of polyurethane foam, so that you can decide what’s best for yourself: using 19th century thermal insulation or PUF?
Introduction
There was a time when thermal insulation was not a separate field of construction science, because there was no need to use additional materials for ensuring insulation.
Ancient people already had to insulate their shelters. The main reason was to protect themselves from wild animals, natural disasters and poor weather (hot summers and cold winters).
A brief history of thermal insulation
Period | Reasons of change | Change | Insulating material |
---|---|---|---|
before 7000 BC | nomadic life | clothing materials | animal skin, fur, wool |
7000 BC to 1870 AD | sedentary life | robust materials, plant fiber | earth, wood, bricks, straw, algae, reeds |
1870—1950 | industrial revolution, heat loss calculation |
first natural insulation products;
introduction of brickwork;
first products made of artificial insulating materials
|
cane, cork, linen, cellulose insulation;
lime-ash and hollow bricks;
asbestos, mineral wool, foam glass, perlite
|
1950—2000 | widespread use of plastics | widespread use of artificial materials, emergence of foams, natural materials are no longer used | polystyrene, polyurethane, polyester, polyethylene, phenol, formaldehyde |
2000 — present day | CO2 emissions deplete fossil fuel reserves, climate change, global warming | experiments with new materials | transparent thermal insulation, nanocellular insulation, vacuum insulation panels |
Natural materials
For thousands of years indigenous peoples of tropical regions used straw or cane to build their shelters. In the 12th and 13th centuries, Northern Europeans built straw houses with straw roofs 60 to 80 cm thick.
The first thermal insulating cork panels were manufactured by processing natural materials at the end of the 19th century. They were cheap but absorbed too much water.
An insulating product made of woodwool was manufactured in Austria in 1908 using magnesite and cement as an adhesive. The products had a major flaw — they were flammable.
In the early 20th century, cane panels with bitumen coatings emerged; however, they did not become widespread due to their flammability and poor quality.
The first attempts at making linen panels for roof insulation were made in the USA. Finally, around 1910, the first products were put on the market.
Simonton straw house in Nebraska, 1908
Artificial materials
Besides natural products, a number of artificial materials were designed during the industrial revolution. They had many advantages in contrast with natural materials: long life, resistance to fire and water.
Non-organic products
Asbestos is a fibrous mineral whose advantages (fire resistance, high tensile strength) have been known since ancient times. Asbestos was used in the manufacturing industry to insulate pipes, steam engines, boilers and chimneys. However, it was banned in many countries because of its hazardous properties.
Mineral wool was invented in 1840. Mineral wool raw material (limestone, basalt) was melted in gas-heated ovens at 1500-1600 °C. Then, fine intertwined fibers 6 to 10 µm were formed using a high-speed spinning wheel. At this step, binding material (phenol-formaldehyde resin, oil emulsion) was added to form the insulating coating.
Asbestos mining in 1876
John Player patented a process for obtaining thermal insulation made of mineral wool
Foam glass
In the 1930s, as many as three technologies to produce foam glass were patented. A mixture of finely dispersed powdered glass and calcium carbonate (CaCO3) was taken as a blowing agent, heated to 850 ˚C, and then cooled in steel molds.
Foam glass products were light-weight, rigid, resistant to fire, water, rodents and insects, therefore easy to use as a new insulating material.
Brickwork elements
The late 19th — early 20th century was a period of experimenting with bricks. For example, Bischweiler’s brick, hollow on the one side, and filled with ash on the other, was introduced.
In 1918 a Swedish architect Johan Axel Eriksson began his studies to develop fireproof brick. In 1923 he patented a method for manufacturing foam concrete blocks.
Workers of the Yxhults Stenhuggeri foam concrete plant
Granulated insulator
Slag was used as insulation for flat roofs and slab structures in the 19th century. Since the 1930s using slag was allowed only in combination with appropriate ventilation.
Expanded perlite was invented in the 1930s in the USA. Its cellular structure prevents heat transfer, while improving fire resistance and reducing weight.
Expanded clay has been produced since 1918. Crushed slate was heated to 1000-1200 °C in a rotating kiln. High temperature makes the grain surface soft, and organic particles are burned. Gases make the grains expand by 4-5 times, while the pores that ensure the thermal insulating properties of expanding clay, are left inside.
Foam materials
The emergence of foam materials (polystyrene foam and polyurethane foam) revolutionized the market of insulating materials in the 1940s and 1950s. After the oil crisis of the 1970s, their spread accelerated, and today they account for about 90-95% of the total production of thermal insulation materials.
During the Second World War polyurethane foam was used as a coating for airplanes, but the final breakthrough was achieved in the 1950s, when polyisocyanate production became possible. The first commercially available insulating foam polyurethane panel was produced in 1954.
Otto Bayer with the foam polyurethane he invented
Conclusions
A variety of new products have been launched since the 1950s. Some of them are also categorized as foam materials, but it is too early to evaluate their efficiency.
Today, polyurethane foam is the most modern, yet tried and tested thermal insulating material. Across the world, pipelines with mineral wool or other old-fashioned insulation are being replaced with new PUF-insulated pipes.
We estimate that polyurethane foam will remain widespread in the nearest decades until a more reliable and durable coating emerges.