ROI of textile insulation in tertiary buildings: the energy quick win
The Tertiaire Decree (Éco Énergie Tertiaire) requires tertiary buildings larger than 1,000 m² to reduce their energy consumption by 40% by 2030 and by 60% by 2050, compared to a reference year. Windows account for 10 to 15% of a building's heat loss (source ADEME), and heating represents over 50% of office energy bills. High-density thermal curtains on windows reduce glazed heat loss by 20 to 30%, directly contributing to the regulatory objective, without major works and with an ROI of 2 to 5 years.
This professional guide details the contribution of textile insulation to the objectives of the Tertiaire Decree, the calculation of ROI per m² of window, and a comparison with classic structural solutions (double glazing, wall insulation, HVAC).
The Tertiaire Decree: what it requires from your building
Decree n° 2019-771 of July 23, 2019 (Éco Énergie Tertiaire) applies to any tertiary building larger than 1,000 m²: offices, shops, hotels, nursing homes (EHPAD), educational establishments, healthcare facilities. The deadlines are as follows:
| Deadline | Required reduction | Compared to |
|---|---|---|
| 2030 | -40% | Reference year (2010 or year chosen between 2010-2019) |
| 2040 | -50% | Same |
| 2050 | -60% | Same |
Sanctions: those subject to the decree who do not comply with their obligations are listed on a public register ("name and shame") and face a fine of 1,500 euros per site per year of delay (7,500 euros for legal entities). Beyond the fine, non-compliance affects the rental value and marketability of the building (the "green value" criterion in real estate transactions).
In practice, many building managers look for quick wins to achieve the first reductions (quickly -10 to -15%) before embarking on heavy works (wall insulation, HVAC replacement) which will take 3 to 5 years. This is exactly the role of textile insulation.
Contribution of thermal curtains to the -40% objective
The calculation is based on ADEME data concerning the distribution of heat loss in a tertiary building:
| Heat loss item | Share of losses | Possible reduction with thermal curtain | Contribution to the -40% objective |
|---|---|---|---|
| Roof | 25-30% | 0% (not covered by the curtain) | — |
| Walls | 20-25% | 0% (not covered by the curtain) | — |
| Windows / glazing | 10-15% | 20-30% reduction | 2-4.5% overall reduction |
| Ventilation / air renewal | 20-25% | 0% | — |
| Floors | 7-10% | 0% | — |
| Thermal bridges | 5-10% | 0% | — |
Result: thermal curtains on all windows of a building contribute to a 2 to 4.5% reduction in overall energy consumption. This represents 5 to 11% of the -40% objective. It is not the only solution, but it is an immediate quick win: deployable in 1 to 2 weeks, without major works, without interrupting activity, and with an ROI of 1 to 3 years.
In comparison, wall insulation works (25-30% of the treated building) take 6 to 12 months of construction and pay for themselves in 8 to 15 years. Window replacement (10-15% of the treated building) takes 2 to 6 months and pays for itself in 10 to 25 years. Curtains are the immediate complement while heavy works are planned.
ROI calculation per m² of window
| Parameter | Typical tertiary building (2,000 m², 50 windows) |
|---|---|
| Total glazed surface | 150 m² (50 windows × 3 m² on average) |
| Heat loss through windows | 12% of heating bill (ADEME) |
| Annual heating bill (typical building) | €25,000-40,000/year |
| Annual cost of window heat loss | €3,000-4,800/year |
| Reduction by thermal curtain (20-30%) | €600-1,440/year in savings |
| Curtain investment (50 custom-made windows) | €5,000-12,000 |
| ROI | 3.5 to 8 years (heating only) |
This calculation only takes into account heating savings. By integrating summer air conditioning savings (curtains block 60-80% of solar radiation) and comfort gains (reduction in occupant complaints related to cold near windows), the real ROI is between 2 and 5 years.
Comparison with classic insulation solutions
| Solution | Contribution to the -40% objective | Cost (2,000 m² building) | ROI | Deployment time | Activity disruption |
|---|---|---|---|---|---|
| High-density thermal curtains | 2-4.5% | €5,000-12,000 | 2-5 years | 1-2 weeks | None |
| Double-glazed window replacement | 5-8% | €75,000-200,000 | 10-25 years | 2-6 months | High (noise, dust) |
| Roof insulation | 8-12% | €40,000-80,000 | 5-10 years | 1-3 months | Moderate |
| Exterior wall insulation | 8-12% | €80,000-200,000 | 8-15 years | 3-6 months | High (scaffolding) |
| HVAC replacement | 10-20% | €50,000-150,000 | 5-10 years | 1-3 months | Moderate to high |
The optimal strategy: deploy thermal curtains immediately (quick win, 2-4.5% reduction, rapid ROI) while heavy works (wall insulation, roof, HVAC) are planned and financed. Curtains provide a measurable gain from the first OPERAT declaration (Tertiaire Decree monitoring platform) and demonstrate the company's active approach.
Benefits beyond energy
Occupant comfort
The "cold wall" effect in front of windows is the primary cause of occupant complaints in offices during winter. Thermal curtains eliminate this sensation (up to 7°C gain* between the window and the room). Result: fewer complaints, fewer auxiliary heaters plugged in by employees (who consume 1,000 to 2,000 watts each and sabotage the building's energy performance).
Summer comfort
Large glazed areas in tertiary buildings create a greenhouse effect in summer. Curtains block 60 to 80% of incoming solar radiation, reducing the air conditioning load. In a building with 150 m² of south/west-facing glazing, air conditioning savings can reach 2,000 to 5,000 euros per year. RE2020 strengthens summer comfort requirements in new buildings, but existing buildings do not benefit without intervention.
Sound attenuation
A 620 g/m² curtain attenuates 22 dB* of outdoor noise through windows. In an open-plan office facing the street (55-70 dB of outdoor noise with the window closed), this attenuation significantly improves concentration. Consult our article acoustic curtains for open plan offices for details on the acoustic business case.
Green value of the building
Energy performance directly influences the rental value and market value of tertiary buildings. According to the Observatoire de l'Immobilier Durable (OID), a high-performing building (DPE A-B) rents for 5 to 15% more than an energy-intensive building (DPE D-E). Every energy improvement action, however modest, contributes to the DPE classification and "green value."
How to declare curtains in OPERAT
OPERAT is the ADEME platform where those subject to the Tertiaire Decree declare their consumption and actions. Thermal curtains can be declared in the "consumption reduction actions" category:
- Category: improvement of the building envelope (sub-category: treatment of windows and glazing).
- Description: installation of high-density thermal curtains (density according to specifications, for example 620 g/m²) on [number] windows, estimated reduction of glazed heat loss by 20-30%.
- Justification: purchase invoice, technical specifications of the curtain (density, thermal performance), and ideally before/after consumption readings to quantify the actual gain.
This declaration demonstrates to the administration that the company is taking concrete actions to achieve the -40% objective, even if heavy works are still being planned.
Key takeaways
Textile insulation is the quick win for the Tertiaire Decree. For an investment of 5,000 to 12,000 euros (2,000 m² building, 50 windows), thermal curtains provide an immediate 2 to 4.5% reduction in consumption, an ROI of 2 to 5 years, zero activity disruption, and a documented contribution to the -40% objective for 2030.
For a personalized quote for your tertiary building: request a professional quote. M1 certification available upon request (ERP), custom manufacturing, quote within 24 working hours. For open-plan offices: curtains for offices and open spaces. For hotels: curtains for hotels.
*Data from tests conducted under optimal conditions.
Frequently Asked Questions
Do thermal curtains contribute to the Tertiaire Decree?
Yes. Windows account for 10-15% of a building's heat loss (ADEME). High-density thermal curtains reduce these losses by 20-30%, contributing 2-4.5% to the overall -40% objective. This is a quick win deployable in 1-2 weeks, without major works, while heavy renovations (wall insulation, HVAC) are being planned. The action is declarable in OPERAT.
What is the ROI of thermal curtains in tertiary buildings?
For a 2,000 m² building with 50 windows: investment €5,000-12,000, annual savings €600-1,440 (heating) + €2,000-5,000 (summer air conditioning) = €2,600-6,440/year. ROI: 1 to 5 years depending on the type of glazing and exposure. This is the best ROI among envelope improvement solutions (window replacement: ROI 10-25 years, wall insulation: ROI 8-15 years).
Do thermal curtains replace window insulation?
No, they complement it. Window replacement (high-performance double glazing) reduces glazed heat loss by 50-80%. Curtains reduce it by 20-30%. The two can be combined. The advantage of curtains: they can be deployed immediately (1-2 weeks) without major works, while window replacement is being planned (2-6 months of construction, budget 10 to 40 times higher). Curtains provide an immediate gain that persists even after windows are changed.
How to declare curtains in OPERAT?
In the "building envelope improvement" category, sub-category "treatment of windows and glazing". Attach the purchase invoice, technical specifications (density, thermal performance) and if possible, before/after consumption readings. This declaration shows the administration an active approach towards the -40% objective, even if heavy works are still underway.
Do curtains require fire rating in tertiary buildings?
In tertiary buildings classified as ERP (Public Access Buildings) (type W for offices), M2 classification is mandatory in escape routes (corridors, halls) and rooms larger than 50 m² (article AM 12 b of the decree of June 25, 1980). M1 is mandatory only in enclosed staircases (AM 12 a). For non-ERP offices, the Labor Code (articles R. 4216) applies. M1 certification is available on request from Kurtens for projects that require it.
How long does it take to equip a building with 50 windows?
Quote within 24 working hours, custom manufacturing in 2-3 weeks, installation in 1-2 days (30 minutes per window by the building's technical staff). Total process: 3-4 weeks. No activity interruption, installation possible outside business hours. No minimum order, delivery terms upon quotation.
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