Long-term testing on a green inverted roof: FIW confirms a stable thermal conductivity of 0.032 W/(m·K) for JACKODUR® EVO

This is precisely where a long-term field test comes in: the Research Institute for Thermal Insulation (FIW) in Munich has examined JACKODUR® EVO 300 Standard insulation boards (180 mm thick) after three winter seasons, having previously been installed in a green inverted roof. The laboratory results from the samples show extremely low water absorption, as well as thermal conductivity values within the declared nominal range; the compressive strength was greater than 342 kPa. This sends a strong signal to architects and planners who, when it comes to inverted roofs, need one thing above all else: consistently reliable performance data.

Insulation beneath the substrate and sedum: FIW study following practical application

For the study, the FIW Munich took samples from the green inverted roof of an apartment block in Mettmann. The system design included, amongst other things, a substrate layer (with sedum vegetation), drainage, and a water-permeable separation layer above the insulation.

The aim of the study: To assess the suitability and durability of XPS insulation boards for use in inverted roofs over a period of several years – with a focus on thermal conductivity, compressive strength and moisture content in laboratory tests.

Measurement results at a glance: Low moisture content – thermal conductivity within the specified range – compressive strength exceeds the declared value

The lab results paint a clear picture:

• Very low moisture content in the insulation boards (0.23 to 0.41% by volume, average approx. 0.35% by volume)
• Thermal conductivity values of the damp samples at a maximum of 0.0321 W/(m·K), and thus within the range of the declared nominal value 0.032 W/(m·K)
• Compressive stress at 10% compression in the damp state > 342 kPa

These results clearly demonstrate that JACKODUR® EVO maintains its performance stability in inverted roof systems, not only in theory but also after several years of practical use.

Tino Dannenberg, Product Manager at JACKON Insulation by BEWI, oversaw the study: “With inverted roofs, what counts in the end is not the promise, but the evidence of performance in real-world conditions. Long-term experience can be gained under real-world conditions on site. This is the only way to reliably assess the actual performance of the insulation boards. The fact that the FIW measurements, taken several years after installation in a green inverted roof, fall within the range of our declared λ-value, confirms the product’s quality.”

Separating layer also tested: the roof membrane remains vapour-permeable

Samples were also taken from the vapour-permeable separating layer JACKODUR® filter layer WA and tested for water vapour permeability. Even after a period of use, the measured values remained below the declared sd value of 0.1 m. It is therefore unlikely that vapour diffusion will be impaired due to soiling or ageing.

The system component therefore remains fully functional even after many years. This is an important consideration during the planning stage if green roof structures are to remain low-maintenance and reliable in the long term.

Single-layer construction up to 400 mm: Faster construction process, greater certainty regarding completion dates, assured structural integrity

In addition to consistent performance figures, rapid and reliable installation is a key factor in the project business: single-layer installation up to 400 mm is a clear advantage here, which ultimately pays off in terms of meeting deadlines and keeping costs under control.

Furthermore, in the case of single-layer installation, the formation of a water film between two layers of insulation—as discussed in the context of multi-layer construction—does not occur. This is an important detail in terms of building physics that is significant in inverted roofs.

BBA certification for construction projects with an international dimension

JACKODUR® EVO 300 is BBA-certified in the UK for use as inverted roof insulation (Certificate 21/5944). The British Board of Agrément (BBA) is one of the established, independent testing bodies in the British construction industry. BBA certification is frequently cited in specifications as reliable evidence of suitability, performance and durability, particularly when designers require a clear, external basis for product selection and construction details.

JACKODUR® EVO

As a logical evolution of the established multilayer technology from JACKON Insulation by BEWI, JACKODUR® EVO offers key benefits for designers: the design thermal conductivity value remains consistently at λ = 0.033 W/(m·K) across all thicknesses (up to 400 mm).

This significantly simplifies tendering and documentation: insulation thicknesses can be flexibly varied within a project without changing the lambda value. This creates clarity in component structures and detailed planning.

JACKON Insulation by BEWI adopts an environmentally friendly approach to manufacturing: the cell contents consist of air, and the product is free from HBCD flame retardants as well as propellants containing CFCs, HCFCs or HFCs.
 

Summary

Produkt: JACKODUR® EVO 300 Standard (XPS-Dämmung in Multilayer-Technik produziert)
Anwendungsschwerpunkte: Umkehrdach (bekiest / begrünt), außerdem als Perimeterdämmung, Kelleraußenwanddämmung, Kerndämmung, Dämmung unter Estrich
Dicken: 40 - 400 mm (einlagige Verlegung bis 400 mm)
Wärmeleitfähigkeit: λ_D = 0,032 W/(m·K) (konstant über alle Dicken); Bemessungswert λ = 0,033 W/(m·K)
Druckfestigkeit (deklar.): 300 kPa
Langzeit-Praxischeck durch das FIW, im begrünten Umkehrdach: sehr geringe Wasseraufnahme; Wärmeleitfähigkeit der feuchten Probe max. 0,0321 W/(m·K); Druckspannung bei 10 % Stauchung > 342 kPa (Quelle: Untersuchungsbericht FIW München)

Images for the message

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  Image 1 / 7: The flat roof was constructed as a zero-degree roof. No root penetration of the JACKODUR® WA roof membrane was detected.
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  Image 2 / 7: This is where the samples were taken: the apartment block has an inverted roof structure with a green roof.
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  Image 3 / 7: The green roof is heavily overgrown with moss and small plants.
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  Image 4 / 7:
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  Image 5 / 7: Above the insulation layer are the JACKODUR® WA roof membrane (vapour-permeable and water-repellent), a 20 mm drainage mat with a non-woven backing, and 100 mm of substrate with sedum vegetation.
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  Image 6 / 7: It had rained the night before the removal: at one of the two removal points, standing water was found on the roof waterproofing after the insulation boards had been removed.
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  Image 7 / 7: