Thermal insulation is a cornerstone of policies aimed at reducing the high energy consumption for heating and cooling buildings. ¹ In many industrialized countries, building energy regulations require new and existing buildings to have insulated walls, floors, and roofs, as well as double- or triple-glazed windows. In cold weather, insulation slows down the heat loss from the interior to the exterior, reducing the energy use of the heating system. In hot weather, insulation delays the transfer of heat from the outside to the inside, thereby reducing the energy consumption of the air conditioning system.

Modern insulation methods involve the permanent addition of non-structural materials with high thermal resistance, such as fiberglass, cellulose, or mineral wool, to the building surfaces. Viewed in a historical context, this approach is unusual and stems from a shift in architectural style. ² Preindustrial buildings often didn’t require extra insulation because they had a significant amount of thermal mass, which acts as a buffer to outside temperature fluctuations. Additionally, the building materials themselves could have high thermal resistance.

Viewed in a historical context, modern insulation methods are unusual and stem from a shift in architectural style.

For example, in the 12th and 13th centuries, Northern Europeans built thatched houses with straw roofs that were 60-80 cm thick. Walls were often built of clay and straw, which provided excellent levels of both thermal mass and thermal resistance. ³ In contrast, modern buildings are frequently steel and concrete structures that have very little thermal mass. Consequently, they are very sensitive to outside temperature fluctuations.

Furthermore, preindustrial buildings had few and small windows, which were often unglazed and closed only by sliding shutters at night. ⁴ On the other side, modern buildings have large glass surfaces, which results in significant heat losses in winter and high solar heat gain in summer.

In hot climates, buildings were also designed for maximal ventilation, for example, through the use of courtyards and building orientation. ⁵ By contrast, modern buildings often resemble one another, regardless of the local climate. All this results in high energy use for heating and cooling, so we add insulation and double-pane windows, especially since the oil crises of the 1970s.

Permanent versus Removable Insulation

A return to vernacular buildings, which maintain interiors at a comfortable temperature through architectural design rather than energy-intensive technical installations, could significantly reduce energy consumption for heating and cooling. However, it’s not a short-term solution: it would require a large amount of time, money, and energy to replace the existing building stock.

Fortunately, history offers an alternative solution that can be deployed more quickly and with fewer resources: textiles. Before the Industrial Revolution, people added a temporary layer of textile insulation to either the interior or the exterior of a building, depending on the climate and the season. In cold weather, walls, floors, roofs, windows, doors, and furniture were insulated with drapery and carpetry. In hot weather, windows, doors, facades, roofs, courtyards, and streets were shaded by awnings and toldos.

Removable insulation can achieve significant energy savings with much more flexibility than permanently enclosed insulation materials. Because modern insulation methods require construction permits and structural interventions to a building, they are expensive, time-consuming, and only accessible to home owners. Furthermore, modern insulation methods are ill-suited for older buildings, in which case they are often not financially and energetically sustainable. ⁶⁷

People can often install removable insulation without obtaining building permits or hiring professionals, making it an affordable do-it-yourself solution within reach of everyone.

In contrast, removable textile insulation is suitable for both new and existing buildings, as well as for renters and owners alike. People can often install removable insulation without obtaining building permits or hiring professionals, making it an affordable do-it-yourself solution within reach of everyone. Removable insulation can be applied quickly and without causing a nuisance to residents and neighbors.

For cooling, textiles have another advantage. Airtight buildings with a permanent insulation layer may overheat dramatically if the electric cooling system fails during a heatwave. ⁸ In contrast, awnings and toldos can keep interiors comfortable independent of an electricity supply.

Winter: Carpets and Curtains

Historically, the use of removable textile layers followed different approaches depending on the climate. In cold regions, for example, in large parts of Europe, people installed various textile “devices” on the interior building surfaces to increase thermal comfort. Some of these, such as curtains and carpets, can still be found in modern interiors, although not to the same extent as they were used in earlier times.

For example, carpets were not only laid on floors but also hung on walls (“wall carpets” or “wall hangings”), draped over tables (“table mats”), and used on other furniture. Likewise, thick curtains were hung in front of windows but also doors (“portières”) or door openings and mounted around beds (“bed canopies” or “bed hangings”). ^{9101112131415} In some regions, people suspended thick fabrics, such as duvets and quilts, from the ceiling during the winter months. ¹⁶¹⁷

These “home fabrics” were usually made of natural wool, still one of the best-performing insulation materials. ¹⁸ The thermal resistance of wool remains the same whether it’s permanently enclosed in building surfaces or hung in front or laid on top of them. Floor carpets and wall hangings thus slowed down the heat transfer from the inside to the outside of the building, just like modern insulation methods do. Likewise, a set of wool curtains 2-3 cm thick gave a single-glazed window the insulation value of a modern double-glazed window. ¹⁹

Before the 18th century, Europeans imported oriental carpets but only used them on walls and furniture because they considered them too precious to walk on.

The production of wool rugs and carpets by flat weaving and, later, by knotting dates back to at least the early centuries AD in the Middle East, Central Asia, and the Far East. However, wool floor carpets only became commonplace in Europe around the 18th century, when carpet production was mechanized. Before that time, Europeans imported oriental carpets but only used them on walls and furniture because they considered them too precious to walk on. For floor insulation, they used animal skins, loose straws, or “rush mats” made from grasses. ^1112132021

Home textiles also stopped draughts coming in through cracks in building surfaces and window and door frames. ⁹ That is the reason why window curtains evolved to open from both sides. Two-sided curtains can be open, providing daylight and a view while stopping draughts that enter through the poorly sealed joints between the wall and window frame. ¹⁰¹¹

Two-sided curtains can be open, providing daylight and a view while stopping draughts that enter through the poorly sealed joints between the wall and window frame.

During winter, thick and heavy curtains could shield a space from the cold air coming in everytime someone opened the door. Such “portières” can still be found in the entrances of historical public buildings or cafés, but they were common in family dwellings as well. ¹⁰¹¹¹⁶

Fabrics also increased comfort in ways that modern insulation methods cannot. Floor carpets slowed down the conductive heat transfer from the feet to the cold floor, while table mats brought arms and hands in contact with a warmer surface. Duvets hanging from the ceiling, bed hangings, and table mats all accumulated heat from the human body or another heat source in a smaller space. ¹⁶¹⁷

Upholstered Chairs, Wainscoted Walls

Textiles could also be combined with woodwork to the same effect. For example, the folding screen was a work of tapestry and carpentry that blocked draughts and reflected radiant heat from a fireplace. ⁹ Upholstered chairs, which appeared at the end of the 1600s, had a cushion encased in the covering material and were padded with feathers, wool, horsehair, down, or rags. ¹² They provided a softer seating surface but also reduced the conductive heat loss from the body to the furniture. ⁹ Pillows also contributed to thermal comfort.

Some decorative devices, consisting of wood or plaster, fulfilled similar functions to textiles. For example, molding stopped draughts and was used to cover joints between walls and floors (baseboards), ceilings (crown moldings), and doors and windows (casings). ⁹²² Some houses had wooden partitions hinged to the ceiling that were let down in winter to concentrate warmth around the fireplace. ²³

Molding stopped draughts and was used to cover joints between walls and floors, ceilings, and doors and windows.

Wainscoting was a type of oak or pine wood paneling typically installed over a wall’s lower portion, a practice that dates back to the late Middle Ages. ⁹¹²²⁴ Such wooden paneling could also be upholstered, further increasing its thermal insulation value. Interior shutters could replace curtains. Box beds were closed on all sides by panels of wood, substituting for bed hangings.

Unfortunately, there is very little academic research on the potential energy savings of home textiles and similar devices, whether used alone or in combination with permanent insulation. There is a handful of older studies that calculate the insulation values of floor or wall carpets, but none examine the combined effects of interior fabrics and other decorative elements. ²⁵

Summer: Awnings

The home textiles described above were primarily used to improve thermal comfort in cold weather. The exception is the window curtain, which not only keeps heat indoors during winter but can also keep solar heat out in summer, resulting in a cooler environment. ²⁶ However, for cooling purposes, window textiles are much more effectively used on the building’s exterior in the form of an “awning,” which blocks solar heat before it enters through the glazing. ²⁷

In Europe, both window curtains and awnings only emerged in the 16th and 17th centuries, when glass became affordable enough to allow for larger areas of glazing. ¹⁰¹²²⁰ As mentioned, larger windows complicate the heating and cooling of buildings. Still, they also have advantages: they provide free solar heat in winter, increase natural ventilation, offer a better view, and allow for daylight throughout the year. ²²⁶²⁸

Window curtains and awnings - the latter usually made of canvas - can reconcile all these concerns. For example, an awning can block solar gain in the summer while keeping the window open for ventilation and continuing to provide a view and lighting. ²⁹ In the 19th and early 20th centuries, European and North American cities were dressed in awnings. Several skyscrapers in New York City and Chicago originally had them, too. ³⁰

In the 19th and early 20th centuries, European and North American cities were dressed in awnings.

However, awnings and air conditioning can be combined, resulting in a significant decrease in energy consumption. Several studies show that awnings can reduce the energy use of air conditioning systems by one-third to more than one-half of the total, yielding energy savings that surpass those of more expensive double-pane or low-emissivity glazing (which is designed to block UV rays). ^{831323334353637} Nowadays, windows are larger than ever, and so awnings can obtain very good results for a relatively small investment.

Summer: Toldos

Outside of Western Europe and North America, the use of exterior “curtains” for cooling predates the use of glass windows by many centuries. For at least 2,000 years in the Middle East and around the Mediterranean, people used textiles not only to shade (unglazed) windows and doors but also roofs, facades, courtyards, and entire streets. Such textile furnishings are known as “toldos” or “sun sails.”

The classical toldo, made from hemp canvas, is a rectangular or triangular, curtain-like awning suspended by sewn-on eyelets on parallel wires. ³⁸ Micro perforations avoid the stagnation of warm air underneath the shading device. ³⁹

In Ancient Rome, sailors assembled large “velaria” to shade amphitheaters. ³⁸⁴⁰³⁹ In Cairo, Egypt, street and courtyard canopies, or toldos, still characterize the cityscape, especially in some historic neighborhoods. ³⁸ European cities with Islamic roots, such as Córdoba, Málaga, Granada, and Seville in Spain, continue to use or have revived the use of street toldos that span entire city streets and districts.

Although toldos have been used predominantly in desert climates, climate change makes them increasingly useful for temperate climate regions as well.

A 2020 study in Cordoba showed that street toldos decrease the temperature of pavement surfaces, building facades, and roofs by up to fifteen degrees Celsius. ³⁹ Collective shading could thus replace individual awnings, but the cooling effect on buildings depends on street orientation. Although toldos have been used predominantly in desert climates, climate change makes them increasingly useful for temperate climate regions as well.

Unlike air-conditioning, awnings and toldos are robust, low-cost, and technically simple solutions within reach of most households and societies. ³⁹ In Egypt, rather than a top-down development initiated by authorities, toldos are made and installed by residents in a demonstration of an architectural bottom-up movement supported by a local industry of expertise and craftsmanship. ³⁸

Covered Streets

The boundary between removable and permanent insulation is not rigid on the outside, either. For example, louvered wooden shutters or architectural interventions such as recessed windows and covered galleries can replace awnings and toldos. ⁴¹

Residential streets in Islamic cities could be either partially covered by cantilevered buildings or totally by additional living spaces. Shopping streets were often completely covered, either heavily by perforated vaults, semi-heavily by high parapet walls and double-pitched roofs, or lightly by thick planks and reeds. ⁴¹

Trees can also serve as awnings and toldos. Deciduous trees shade buildings and streets in summer while allowing the sun to pass through in winter. However, trees take decades to grow and need water as well, which is often scarce in the regions where toldos have been used traditionally.

Textile Architecture: Tents

In all the examples above, textiles form an additional “soft” architectural layer, either on the inside or the outside of “hard” architectural building surfaces. However, the soft architectural layer can also stand on its own. In many parts of the world, rather than living in permanent structures made of wood, stone, mud, brick, or other materials, people inhabited lightweight, portable structures that they made almost entirely of textiles: tents. The tent’s velum serves as a curtain, wall carpet, and awning all at once - there is no hard building surface in between.

The tent’s velum serves as a curtain, wall carpet, and awning all at once - there is no hard building surface in between.

As an academic discipline, architectural history has largely ignored textile architecture, which arose among nomadic peoples or so-called “barbarians” outside the governed, “civilized” world. ⁴⁰⁴² However, tents were as widespread as permanent buildings. They were the preferred shelter when two often related conditions prevailed: a lack of building materials and a need for mobility. Nomadic pastoralists utilized portable architecture across vast stretches of Eurasia, North Africa, and North America until relatively recently, and some still do. ⁴⁰

One can still make strong arguments for the tent, even today, in terms of both sustainability and resilience. First, tents are significantly less resource-intensive to build than permanent structures. Second, permanent buildings need defenses against all types of natural threats, including heat waves, hurricanes, forest fires, flooding, and so on. In contrast, the tent allows you to solve these issues by relocation: you can flee from danger without leaving your home behind. Tents are also safe shelters in the case of an earthquake.

Tents for hot and cold regions

Tents were found in regions subject to extreme heat or cold, demonstrating the versatility and effectiveness of textiles in providing thermal comfort. ⁴⁰ Both the skin-covered conical tent of Northern Eurasia and North America, better known as the “tipi,” and the “kibitka” or felt tent, more popularly known as a “yurt,” were designed for efficient combustion in cold, windy climates. The structures served as a combustion chamber, chimney, and windbreak for the central fire, in addition to functioning as a dwelling. ⁴⁰

In contrast, the “black tent” of the Middle East was designed to keep the heat outside rather than inside. Most closely resembling the tents we still use today, it was a non-skeletal tent with a prestressed velum, tensed in an aerodynamic shape over minimal wood supports. Unlike the mats and leather awnings of the conical tent and kibitka, the woven vellum made from black goat hair was strong enough in tension to be prestressed. ⁴⁰ It absorbed heat while providing shade, and as a result, temperatures inside the black tent could be up to 10-15 degrees Celsius cooler than in the surrounding atmosphere. ⁴

Tipis

Kibitkas

Black tents

Dressing and Undressing the House

In modern buildings, maintaining thermal comfort requires no attention or effort from residents. If it gets colder in winter or hotter in summer, modern heating and cooling systems keep the thermostat-programmed indoor temperature by increasing energy use. In contrast, preindustrial buildings demanded active participation from their inhabitants. It was a common practice to adjust indoor and outdoor textiles according to the time of day, weather, and seasons.

The historical use of removable textile insulation reminds us of the act of dressing and undressing our bodies, which also relies on the weather and the seasons.

The historical use of removable textile insulation reminds us of the act of dressing and undressing our bodies, which also relies on the weather and the seasons. ⁴³ Daily, people opened and closed curtains and awnings depending on the weather and the time of the day. ¹⁰ Street and courtyard toldos were folded together during the night so that the warmth stored in the thermal mass of the pavement and the buildings could radiate to the sky. ³⁵ The same happened during windy weather.

On a seasonal scale, rugs and carpets were rolled up in summer to expose the cold stone floor. Bed hangings made of thick materials, used in wintertime, were replaced by lighter textiles in summer, which allowed people to sleep without the nuisance of insects. ¹¹ In Córdoba and other Spanish cities, street toldos are only installed between May and October. ³⁹

Some people also added temporary winter insulation to the exterior of a structure by piling up a low barrier to cold temperatures along the lowest parts of the walls, especially the wall facing the prevailing wind. For example, in the colonial period in North America, Connecticut houses were often banked with turf, piles of leaves, or, near the coast, with seaweed. Even today, in rural areas of the northern US, bales of hay can be seen piled up around the foundations of frame houses. ⁴

Dressing and Undressing the Tent

Tents also demonstrate the seasonal nature of textiles. In Lapland, the tent cover was traditionally made of birch bark in the summer and reindeer skin in the winter. In the Mongolian and Turkish kibitka, the number of felt layers used to cover the tent frame depended on the outside temperature. During winter, two or three layers of felt may have been added, whereas in summer, the side felts were raised approximately half a meter off the ground to ventilate the interior. Native Americans regulated the intensity of the fire by opening and closing parts of the tent. In summer, they left the tipi partially open to the environment. ⁴⁰

During winter, two or three layers of felt may have been added, whereas in summer, the side felts were raised approximately half a meter off the ground to ventilate the interior.

In black tents, an extra cotton lining, a tent within a tent, could be hung on the inside in winter as insulation against the cold. During the hot season, the tent was left open on all sides. The excellent wind stability of the black tent in strong winds also depended on regular interventions by the inhabitants. Because the open side of the tent faced away from the prevailing wind, a sudden change in wind direction required the residents to remove the front poles to the rear, take down the back wall, and reattach it across the tent’s front. ⁴⁰

Tents could also have external insulation added during cold seasons. Some people surrounded their tents with wattle walls, while others built earthen walls around them or erected stone or mud walls. In Lapland, people sometimes covered the tent sides with snow in winter. ⁴⁰ Some native American tribes piled earth and stones all around the base of their tipis to block cold drafts and add insulation. The practice also helped to anchor the structure against winter winds. ⁴

Privacy, Noise, Aesthetic Pleasure

While keeping people warm or cool, textiles also served other functions, both in permanent buildings and tents. First of all, they helped to mark off areas for private life. ¹⁰ Spaces were separated by curtains, which disrupted sightlines and muffled sounds. ^9101316 Curtains could screen off certain areas dedicated to specific functions that required restricted access. ¹⁴ Bed hangings offered privacy in the absence of a separate bedroom. ¹⁰

Curtains and awnings provided privacy without sacrificing thermal comfort. During summer, a door curtain or awning could prevent outsiders from gazing into the interior when the doors or windows were open, allowing some degree of light and air. Rooms separated by door curtains provided some privacy from other residents while allowing air to move. ¹⁰ Textiles also protected people and their possessions from dust and insects, regulated the lighting of interiors, reduced noise, and made speech richer and more resonant. ¹⁵

Finally, home textiles contributed to the adornment of the spaces in which they were hung, “either in their own right or as a backdrop or frame for the display of objects and persons, thus affording aesthetic pleasure and imparting a sense of solemnity, opulence, warmth, or intimacy, depending on the context.” ¹⁴ Textiles were often the most valuable items on display in an interior, and their quality and variety reflected the standing of their owners. ¹¹¹⁴

Textiles were often the most valuable items on display in an interior, and their quality and variety reflected the standing of their owners.

For example, in most households, wall hangings were made of plain wool, linen, cotton, or leather, while the walls in castles, palaces, and rich houses were adorned with embossed leather hangings or tapestries presenting specific scenes or landscapes - made of silk and wool and intertwined with gold and silver threads to add richness. ¹³⁴⁴

Air-conditioned, Bare-white Interiors

Nowadays, few of us live in buildings with door curtains, bed hangings, or awnings. The abundance of interior decoration gave way to a minimalist, neutral, and often bare-white interior design devoid of textiles. ⁹¹³²⁰ Likewise, we now prefer to build air-conditioned shopping malls instead of buildings with awnings or street markets covered by toldos. Of course, we can only do these things thanks to a seemingly endless stream of fossil fuels. ⁹

Curtains, carpets, awnings, and toldos have their inconveniences and disadvantages. They require attention and manual intervention, need to be cleaned ⁴⁵, and can pose a fire risk unless made of wool or leather. However, the continued burning of fossil fuels has even larger inconveniences and disadvantages, especially in the long term. Textiles could decrease energy use and enhance comfort and livability in all types of buildings. Toldos could span the streets and roofs of entire city districts. History shows that removable textile insulation works.

Unfortunately, building and renovation regulations overlook the thermal insulation properties of carpets, curtains, and other textile devices. You may add as many thick curtains and carpets as you like; however, legislation will still require you to install double- or triple-glazed windows and insulated building surfaces, even though textiles could be just as effective in providing insulation. ⁶

On the outside of the building, awnings may not even be legal. The British Blind and Shutter Association had to fight hard to overturn a ban on awnings by the authorities. ²⁹ And, in case you are considering it, in many countries, it’s forbidden to live in a tent, even if it’s on private property.

Thanks to Louise Morin for the inspiration.

Thanks to Jonas Görgen, Roel Roscam Abbing, and Marie Verdeil for their feedback on an earlier version of this article.