Thermal insulation: its history, from survival instinct to RE2020

Expertise in the service of the building envelope

Thermal insulation is the invisible building shield. The art of controlling heat exchanges between the interior and the exterior, it is the pillar of comfort, sustainability of the building and health of its occupants. Today at the heart of the construction sector's concerns, this discipline is the result of a very long evolution, a thousand-year-old quest by humanity to create a protective cocoon against the elements. It has gone from a survival reflex to a complex science, the rules of which are now enshrined in the most demanding regulations.

How did we go from raw earth walls to vacuum insulation panels? How could a global economic crisis revolutionize the way we build? And why are regulations, often perceived as constraints, actually the greatest driver of innovation and promotion of our heritage ?

To understand this, we must go back in time. This article offers a chronological journey through the history of thermal insulation. We will start from the instinctive foundations and follow the innovations, oversights, and successive realizations. This journey will take us to the contemporary era, where standards such as the RE2020 are no longer content with limiting losses, but aim to transform our buildings into real energy power stations. A story which demonstrates that insulation, much more than a cost, is the safest investment for the future.

The foundations of expertise: a detailed history of thermal insulation

The history of insulation is inseparable from the history of housing. Each era, with its own resources, climate, and knowledge, has contributed its contribution to the edifice of thermal performance, sometimes spectacularly, sometimes ignoring the lessons of the past.

1.1. The age of instinct: survival as the first insulator (prehistory)

The earliest form of insulation was not built, but found. By seeking refuge in caves, prehistoric man benefited from one of the oldest thermal strategies: inertiaThe colossal mass of the rock, with its ability to store heat and release it very slowly, created a stable microclimate, protecting against the bitter cold of winter and the crushing heat of summer.

When man began to build, he replicated this instinct with the means at his disposal. The first huts made of branches were filled with earth, mud, and clods of grass. The principle, even if it was not theorized, was already there: create a thick wall that was as airtight as possible to to trap still airRoofs, often made of thatch or animal skins, also played this crucial role, anticipating by several millennia the functioning of our modern fibrous insulation.

1.2. The Age of Mass and Inertia: The Constructive Wisdom of Antiquity

The great civilizations of Antiquity developed remarkable construction techniques where thermal management was a central concern, although not formalized by science.

• in Egypt: the builders mastered the art of adobe brick, a mixture of Nile silt, sand, and chopped straw. Dried in the sun, these bricks were used to build very thick walls that offered exceptional protection against the desert climate. The thermal inertia kept the interiors cool during the day, as the heat did not have time to penetrate the thickness of the wall before the coolness of the night returned.
• in Greece: architects designed houses with pastas (portico) or peristyle (inner courtyard), often facing south. This design bioclimatic before its time, it was possible to capture the low winter sun to heat the house, while being protected from the high summer sun by the overhanging roof. It was the recognition that orientation and architectural design were acts of insulation in their own right.
• in Rome: The Romans, outstanding engineers, took this logic even further. Their walls, built from opus caementicium (the ancestor of concrete), were of considerable thickness. But their most famous innovation remains the hypocaustThis underfloor heating system, where warm air circulated through a crawl space created by brick piles (pilae), demonstrates an advanced understanding of heat transfer by convection and radiation. They also used the cork, a remarkable natural insulator, for certain specific applications, notably for insulating the roofs of certain villas.

1.3. The Middle Ages and the Renaissance: between tradition and pageantry

During the Middle Ages, the construction of castles and cathedrals perpetuated the legacy of massive construction. Stone walls, which could be several meters thick, guaranteed phenomenal thermal inertia. Openings, for both defensive and thermal reasons, remained modest in size.

Inside, comfort was enhanced by functional additions. The large wall tapestries, especially the greenery, was not just decorative. By creating a gap between it and the wall, it played a crucial role in cutting drafts and breaking the cold radiation of the stone walls, thus increasing the perceived temperature. Similarly, the woodwork which covered the walls of stately homes during the Renaissance created an additional insulating layer while giving a luxurious appearance.

1.4. The great oversight: the industrial revolution and the manufacture of thermal strainers (XNUMXth - XNUMXth century)

The advent of the steam engine, the mass production of new materials like steel, and the development of flat glass radically changed the situation. Construction became faster, lighter, and more economical. But in this race for modernity, ancestral know-how in thermal comfort was largely forgotten.

The walls have become thinner. The large windows single glazing, like those of Haussmannian buildings in Paris, have become an outward sign of wealth, to the detriment of insulation. coal-fired central heating, then fuel oil, became widespread. Its abundance and low cost made poorly insulated housing tolerable, even acceptable. One could simply "turn up the heating" to compensate for losses. It was during this period that buildings were built en masse which are, by design, real "thermal strainers"Insulation was no longer an architectural concern, but a problem that heating power had to solve.

1.5. The rude awakening: the oil shocks and the birth of thermal building (1970s)

Le premier oil shock in 1973, acts as an electroshock. In the context of the "Thirty Glorious Years," a period of growth and abundant and cheap energy, the surge in energy prices reveals the vulnerability of Western economies. Heating buildings, which represents a considerable share of energy consumption, becomes a national economic and strategic issue.

In France, the response was immediate. As early as 1974, the first thermal regulation (RT) was born. Its objective is simple: to slow the energy haemorrhage. For the first time, it imposes an overall coefficient of heat loss, the "G coefficient". This regulation, although modest by current standards, is a revolution. It marks the official birth of building thermal insulation as a regulatory discipline. Manufacturers then massively developed the first industrial insulation materials, such as glass wool, and professionals must learn to integrate them into their projects. Insulation is no longer a luxury, but an obligation.

1.6. The era of programmed performance: the rise of regulations (1980 - 2012)

The following decades were marked by a succession of increasingly demanding thermal regulations, which would permanently structure the construction and renovation market.

• RT 1982, 1988 and 2000: Each new regulation strengthens the requirements. We are gradually moving from an obligation of means to an obligation of results. RT 2000, in particular, introduces performance requirements for each wall of the building (walls, roof, floor, windows), popularizing the concept of a high-performance and homogeneous envelope.
• RT 2005 and the BBC label: a new step is taken with the introduction of the label BBC (Low Consumption Building)The objective is to limit primary energy consumption to 50 kWh/m²/year on average. To achieve this, high-performance insulation and excellent airtightness are essential. What was once a pioneering label will quickly become the norm.
• RT 2012: the generalization of BBC: la RT 2012 makes the BBC label performance level mandatory for all new constructions. Energy consumption (Cepmax) becomes the key indicator. For construction professionals, this requires perfect control of envelope insulation, treatment of thermal bridges and airtightness, validated by a test at the end of the work ("blower door test").

The heart of the matter: an overview of insulation families

The choice of insulation depends on multiple factors: desired performance, budget, installation constraints, and environmental sensitivity. There are four main types.

2.1. Mineral insulators: the essentials

Made from natural raw materials such as volcanic rock (basalt) or sand, they are the most widespread on the market.

• glass wool: Made from sand and recycled glass, it offers excellent value for money. It is lightweight, fireproof, and easy to install.
• rock wool: Made from basalt, it has similar performance to glass wool, with better fire resistance and better acoustic properties.

These materials are appreciated for their efficiency and their controlled cost, but their sensitivity to humidity requires the installation of a vapor to ensure their durability.

2.2. Synthetic insulators: optimized performance

Derived from petrochemicals, these insulators are characterized by very high thermal performance for a low thickness.

• expanded polystyrene (EPS): known for its white beads, it is light, economical and widely used for exterior insulation.
• extruded polystyrene (XPS): denser and more resistant to compression and humidity than EPS, it is ideal for insulating floors and basements.
• polyurethane (PUR): It is one of the most efficient insulators on the market at equal thickness, perfect for situations where space is limited.

Their main disadvantage lies in their fossil origin and their behavior in fire, which requires specific precautions.

2.3. Bio-sourced insulation: the choice of sustainability

These materials, derived from plant or animal biomass, are experiencing remarkable growth, driven by the challenges of sustainable construction.

• wood fiber: presented in dense or semi-rigid panels, it offers excellent thermal insulation (particularly against summer heat) and acoustic insulation.
• cellulose wadding: Made from recycled newspaper, it is often used in bulk for insulating unused attics.
• expanded cork: rot-proof, excellent thermal and acoustic insulator, it is particularly durable.
• hemp, flax, straw: These local and renewable materials are part of a short circuit and low carbon footprint approach.

In addition to their ecological advantages, bio-sourced insulators have an excellent capacity to regulate humidity (hygrothermal), contributing to a healthier indoor climate.

2.4. New generation and specific insulators

• thin reflective insulators: Also called thin reflective products (PMR), they are composed of one or more layers of reflective materials (often aluminum) enclosing intermediate layers (wadding, foam, etc.). Their principle is not to slow down conduction, but to return thermal radiation. Their effectiveness in situ is the subject of debate, and their performance depends crucially on the presence of still air blades on either side.
• aerogels and vacuum insulation panels (VIP): These high-tech products offer performance up to 5 or 10 times higher than traditional insulation. Their very high cost currently reserves them for niche applications where space saving is an absolute priority (renovation of historic monuments, insulation of singular points).

Regulatory peak and its virtues: RE2020 and the vision of sustainable building

After decades focused solely on energy consumption, the Environmental Regulation 2020 (RE2020) mark one profound paradigm shiftIt no longer only targets buildings that consume little energy, but buildings that have a low impact on the planet throughout their lifetime.

3.1. The introduction of the carbon footprint

The big revolution of RE2020 is the taking into account of life cycle assessment (LCA). From now on, we no longer only measure the energy consumed for heating or lighting (Cep), but also the carbon impact of the construction itself (Ic construction). This indicator values ​​bio-sourced materials (such as wood fiber, cellulose wadding or hemp) which store carbon during their growth, and penalizes materials whose production emits a lot of CO₂. Insulation thus becomes a major lever for decarbonization of buildings.

3.2. Summer comfort as a new requirement

In the face of global warming, RE2020 introduces a new indicator: discomfort degree hours (DH). It sets a maximum threshold of hours during which the interior temperature exceeds a certain comfort level in summer. This requirement requires rethinking insulation. It is no longer just a question of protecting against the cold, but also against the heat. Insulators with high inertia or high thermal phase shift, such as dense bio-sourced insulation, are particularly favored because they slow down the penetration of summer heat into the home.

3.3. The bepos objective: towards positive energy buildings

RE2020 pushes the logic of performance to its paroxysm by aiming, in the long term, for positive energy buildings (BEPOS)A BEPOS building is a building which produces more energy (usually via photovoltaic panels or other renewable sources) than it consumes for its operation.

This ambitious goal is absolutely unattainable without a exceptional insulation. Before even thinking about producing energy, we must drastically reduce the need at the source. Thermal insulation therefore constitutes the foundation, the fundamental prerequisite on which any BEPOS strategy is built. A high-performance envelope, with insulation levels well above the regulatory minimum and a total absence of thermal bridges, is the first step in any energy-producing building.

Insulation: a profitable investment and a sustainable way to enhance property value

The history of thermal regulations demonstrates that what begins as a constraint quickly becomes a standard, then a formidable lever for innovation and value. Far from being a simple expense, insulation today represents a one of the most profitable investments and the safest for any property owner.

The main areas concerned are:

• the walls (insulation from the inside or outside),
• the roofs and attics,
• the low floors,
• the exterior carpentry and openings.
   
• direct economic profitability: A well-insulated building consumes very little energy. The initial investment is therefore amortized over the years by the savings made on heating and cooling bills. In a context of continuously rising energy prices, this profitability is only accelerating. In addition, public authorities massively support this work through schemes such as MyPrimeRénov ', L 'zero rate eco-loan (eco-PTZ) or Energy Savings Certificates (ESC), which considerably reduce the initial investment.
   
• an valuation of real estate assets: Energy performance has become a major selection criterion in the real estate market. A property rated A or B on the Energy Performance Diagnosis (DPE) sells or rents more expensively and more quickly than a "thermal sieve" rated F or G. Insulating your property therefore increases its "green value" and make it more attractive. It also protects it from regulatory obsolescence, while increasingly stringent constraints weigh on the most energy-intensive housing.
   
• a gain in comfort and durability: Beyond the financial aspect, good insulation offers unparalleled living comfort, summer and winter. It guarantees a consistent temperature, eliminates cold walls and drafts. In addition, by ensuring good humidity management, it protects the building's structure from pathologies (mold, condensation) and ensures its longevity.

The history of thermal insulation is one of gradual awareness. It has led us from a state of nature where we instinctively protected ourselves, to an age of reason where regulations, driven by crises, require us to build better. RE2020 is not an end in itself, but a decisive step. It establishes insulation as the founding act of any construction or renovation project. For construction professionals, mastering this history and the techniques that result from it is the key to building a real estate portfolio sober, comfortable, durable and valued.