Thermal insulation: managing the building's energy performance

Energy efficiency: why is insulation the foundation of renovation?

On the ground, the reality is simple: a building consumes first because it loses. As long as theenvelope remains permeable to heat exchange energy systems they only compensate for a permanent imbalance.

In a poorly insulated house, the heat The product immediately escapes. walls remain cold, the sensations ofdiscomfort persist, and the consumption increase. Conversely, a high-performance envelope naturally stabilizes the indoor temperature.

It is this logic that places thethermal insulation as the first step of any renovationIt does not improve an existing system, it redefines its needs.

"To isolate is to transform a energy-intensive building in a controlled building.

In this context, thethermal insulation goes beyond the purely technical framework and is part of a dynamic of the market driven by economic and regulatory issues.

Insulation market in France: key figures, trends and opportunities

The French market forthermal insulation is part of a dynamic supported by the public policies for energy renovation, the rising energy costs and regulatory requirements growing. Today, it represents a key structural pillar of the activity of building, particularly in the sector of renovation.

According to data from the sector and theADEME, the market for energy renovation represents several tens of billions of euros per year, a significant portion of which is dedicated to insulation workThese interventions mainly concern the existing park, which constitutes the main deposit ofenergy improvement in France.

The thermal insulation market in France (key data)

Beyond these market dynamics, the performance of theisolation rests primarily on its coherent integration into thebuilding envelope.

Building envelope design: ensuring thermal continuity

The thermal insulation is part of a comprehensive approach called building envelopeThis envelope contains all of the walls in contact with the outside world: walls, roofing, floorsBut also overtures.

In this context, three elements must be considered together:

• thewall insulation
• la exterior carpentry
• la roof covering

On construction sites, malfunctions often appear at the interfaces. high-performance insulation can be compromised by poorly sealed windows. A poorly ventilated roof can degrade a insulating yet effective.

The challenge, therefore, is not only to isolate, but to create a thermal continuity consistent.

Among all the walls to be treated, some areas present more critical issues than others, starting with the roofing.

Roof and attic insulation: stopping the number one source of heat loss

The roof covering is the highest point of the building, and therefore the first place of accumulation of heat. Without effective insulationThis heat escapes quickly.

In old buildings, the roof space are often the main weakness. Theinsulating is insufficient, degraded or absent. Losses are then immediate.

Working on the roof provides quick and noticeable savings. However, this work is not limited to simply adding insulation. It also involves checking:

• the state of the roof covering
• la attic ventilation
• the management ofhumidity

A high-performance insulation requires a sound and consistent roof.

If the roof constitutes the main item of lossThe building's openings also represent sensitive points that should not be overlooked.

Exterior joinery and glazing: optimizing airtightness

Exterior joinery They occupy a strategic position. They provide openings for the building while also constituting thermally sensitive areas.

On the ground, defects are frequent: air infiltrationPoorly performing glazing, degraded seals. These problems generate continuous losses, often invisible but significant.

The replacement of joinery improves the performancebut only if it's part of a comprehensive approach. A high-performance window won't compensate for an uninsulated wall. Conversely, enhanced insulation requires a Appropriate ventilation to avoid disorder.

Performance therefore depends on the balance between the components.

Beyond the openings, the question ofwall insulation remains central and poses a structuring choice between different techniques.

Comparison of ITI vs ITE: which insulation technique should you choose for your construction projects?

The choice between internal thermal insulation (ITI) et external thermal insulation (ETI) constitutes a turning point in a project.

The ITI is often preferred for its simplicity. It allows for rapid intervention without altering the building's exterior appearance. It remains suitable for constrained projects, particularly in partial renovationHowever, it has limitations: reduced surface area, partial treatment of thermal bridges.

The ITE, on the other hand, acts as a continuous envelopeIt eliminates a large part of the thermal bridges and significantly improves the overall performanceIt also allows for the treatment of the facade's appearance. On the other hand, it involves a larger investment and regulatory constraints.

On the ground, the choice depends on:

• of the state of built
• du budget
• constraints oftown planning
• as energy objectives

In global renovationExternal thermal insulation (ETI) is often the most effective solution. However, a well-designed internal thermal insulation (ITI) system remains a relevant answer in many cases.

Regardless of the technical choice made, understanding the loss zones remains essential to guarantee overall effectiveness.

"In a comprehensive renovation, external thermal insulation (ETI) is now the standard solution for achieving a high level of energetic performance. "

Performance and thermal resistance: the critical thresholds to be respected

For insulation to be considered effective — and to be eligible for state aid — it must reach a minimum thermal resistance (R)Expressed in m².K/WThis value measures a wall's ability to resist heat flow. More R The higher the number of layers, the more insulating the material.

Minimum requirements for renovation (Criteria) MyPrimeRénov ' et EEC)

In 2026, to benefit from the financing schemes, the works must comply with the following performance thresholds:

Understanding the relationship between Conductivity (lambda) and Thickness

Actual performance on site depends on the choice ofinsulating. The thermal resistance is calculated according to the following formula:

R = e / λ

e represents thematerial thickness (in meters).

λ (lambda) represents the thermal conductivity of the material.

Note for professionals: To achieve an R-value of 7 in attics, the thickness will vary depending on the material. Where 25 cm of polyurethane (λ = 0,022) may be sufficient; approximately 30 to 35 cm of mineral wool or cellulose wadding (λ = 0,038 to 0,040). This calculation is crucial for determining the footprint of living spaces, particularly in ITI.

Certification and marking: performance guarantees

Beyond the figure announced by the manufacturer, the reliability of a insulating is based on two key certifications:

• Le CE marking : mandatory, it certifies compliance with European standards.
• La ACERMI certification It scientifically validates the thermal characteristics (λ, R) as well as the mechanical behavior and resistance tohumidity (ISOLATED profile).

Diagnosing heat loss: identifying and addressing thermal bridges

heat losses are distributed throughout the entireenvelopeThe roof often remains the most important element, followed by the walls, the ground floors and the joinery.

But beyond the surfaces, it is the junction zones that concentrate the losses. These zones, called thermal bridges, are breaks in the continuity of theisolation.

They appear in particular:

• to the connections walls/floors
• around the overtures
• en roofing

These weaknesses can represent a significant portion of the losses and must be handled with precision.

Insulation materials: thermal performance, bio-based materials and selection criteria

The choice of materials it is not limited to a thermal performanceIt is part of an overall project strategy.

mineral insulators are widely used for their efficiency and cost. synthetic insulation allow for limiting the thickness. biobased materials provide an environmental response and improve the summer comfort.

On the construction site, the choice also depends on:

• du support
• of'humidity
• constraints of pose
• of the Sustainability

Actual performance depends as much on the material as on its Implementation.

Once the technical solutions have been defined, the question of cost becomes a determining factor in decision-making.

Profitability and cost of thermal insulation: calculating energy ROI

The cost of a isolation varies depending on the technique, the surfaces and the complexity of the project. But it cannot be analyzed in isolation.

A high-performance insulation generates sustainable gains:

• decrease in consumption
• improvement of comfort
• valuation of carefully

The right approach is to reason in overall cost, by integrating the energy savings and aids availables.

This overall cost reasoning must be considered in light of the support mechanisms that significantly reduce theInitial investment.

Regulatory framework: RE2020 and current thermal insulation standards

The thermal insulation is now overseen by several regulations which aim to improve the energy performance of buildingsboth in new construction and renovation.

In the new, the RE2020 imposes high levels of performance. It is no longer limited to the energy consumptionbut also incorporates the summer comfort and carbon impactInsulation plays a central role in achieving these objectives, particularly by reducing the energy needs from the design stage.

In renovation projects, the requirements are defined by the thermal regulations for existing buildingsThis standard sets minimum performance levels to be achieved during construction work, particularly in terms of thermal resistance of wallsThese thresholds often determine access to financial help.

In practice, these requirements translate into minimum values ​​that must be respected, for example:

• thermal resistance walls, attics or floors
• performance insulation
• continuity of insulation

In addition to these obligations, there are the criteria for aid (EEC, MyPrimeRenov ') and product standards (ACERMI, DTU), which concretely structure the technical choices and the Implementation On the worksite.

Despite this technical and regulatory framework, some errors persist on construction sites and can compromise the performance expected.

Financing for renovations: guide to available subsidies (MaPrimeRénov', CEE, Éco-PTZ)

The works ofthermal insulation benefit from several public aid in France, which allow for a significant reduction in the cost of operations.

The main devices are:

• MyPrimeRenov '
• Energy saving certificates (EEC)
• Eco-loan at zero interest (eco-PTZ)
• Local aid

Access to this aid requires:

• using a company RGE
• compliance with levels of minimum performance

In practice, these devices guide technical choices and encourage comprehensive renovations.

"The success of a project ofisolation thus relies on the coordinated intervention of several specialist actors. "

Accidents and poor performance: 4 mistakes to avoid on your construction sites

Certain errors regularly recur on the construction sitesThey compromise the overall performance.

The most frequent ones:

• isolate without treating the ventilation
• replace the exterior carpentry without insulating the walls
• neglecting the thermal bridges
• poorly coordinate the interventions

The success of a project depends on a global vision and total controlled execution.

" A partial insulationEven when well executed, it does not allow for achieving the expected performance of a complete energy renovation. "

Site coordination: the key trades involved in insulation

The success of a thermal insulation depends not only on the quality of the materials, but also on the consistency of the interfaces between the different stakeholders. A successful project relies on synergy between thetechnical expertise, the mastery of the building and scientific control.

The actors involved in implementation and prescription

A project toisolation mobilizes an ecosystem of professionals whose missions overlap to guarantee theair tightness and the continuity of theenvelope :

• The Office ofThermal Study (BET) Upstream, he defines the strategy (calculating the coefficient, hygrothermal study). His role is crucial to avoid phenomena of Internal condensation and validate compliance with the RE2020.
   
• L'Insulation Company / Drywall Installer Specialist inITI (Interior Thermal Insulation)He ensures the installation of insulators and the rigorous implementation of vapor barrier membranes.
   
• Le Facade contractor (External Thermal Insulation Trades) : True guarantor of theoverall envelopehe deals with thermal bridges of slabs and ensures thesustainable aesthetics of the building via systems ofexterior insulation under plaster or cladding.
   
• Le Roofer-Zinc Worker His intervention is a priority (the roof accounts for 30% of the losses). He manages the complex interface between theinsulating, the ventilation of the underside and thewater tightness.
   
• Le Carpenter It ensures the building is weatherproof. The performance of an insulated wall is nil if the connections between the window frame and the wall (AEV sealing) are neglected.

An industrial ecosystem geared towards innovation

Behind these field professionals, dense network of manufacturers and industrialists specializing in building envelopes, supplies the market with increasingly technical solutions.

Breakaway fastening systems thermal bridge to biosourced insulation (wood fiber, hemp, straw) via the reflective coatingsInnovation is constant. These players are no longer simply suppliers, but partners who support the industry through... Technical Opinions (CSTB) and specific training to guarantee a implementation in accordance with according to best practices (DTU).

Batipole's opinion: The accident rate Insulating materials rarely originate from the material itself, but almost always from a defect in coordination at the junction points. The designation of a "waterproofing expert"on the construction site is often the key to a successful renovation.

Text written and documented by batipole.com, a media outlet for professionals in the building, housing and real estate sectors.