FAQs - Frequently asked questions

Can a flat roof survey tell me if my insulation is adequate?

Not necessarily. A visual survey may identify information about the apparent roof build-up, but it cannot reliably confirm the condition, moisture content or thickness of concealed insulation. Where this information is required, further investigation such as core sampling may be necessary. The applicable thermal requirements also depend on factors including the building, the work being undertaken and which Building Regulations provisions apply.

Can I walk on Deck-VQ® vacuum insulation panels?

Yes, this is possible due to the protection layers in high density PIR and the compressive strength of 150 kPa (CS(10\Y)150). Deck-VQ® is suitable for application in flat roofs and terraces, subject to light foot traffic.

As for every type of insulation, we recommend to limit the foot traffic during installation to a minimum and apply the waterproofing as soon as possible after installation. It is best practice to only install the area you are able to insulate AND waterproof in one day.

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Can you drill, nail or saw into a Vacuum Insulation Panel?

No, because these actions will lead to the loss of vacuum in the VIP and reduce the thermal performance by a factor of three*.

Our Deck-VQ® concept offers an optimum protection to prevent most damage on site. (see “What is the difference between Deck-VQ® and a Vacuum Insulation Panel?”).



Our technical services provide guidance and deliver a detailed design for your project.
Do not hesitate to contact us for further information.

*The thermal conductivity of the core material rises to ca. 0,020 W/mK under ambient pressure.

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Do I need an intrusive survey or core samples?

Not every roof survey requires intrusive investigation. If the purpose is to identify visible defects or drainage issues, a visual assessment may be sufficient. However, where the condition of the underlying roof build-up, moisture levels or insulation needs to be established, intrusive investigation may be recommended. The appropriate scope will depend on the condition of the roof and the reason for the survey.

How can I improve the thermal performance of an existing flat roof?

Improving an existing flat roof's thermal performance may involve adding insulation as part of a refurbishment or overlay system, subject to the condition and construction of the existing roof.

The appropriate solution depends on factors such as:

  • Existing roof construction
  • Existing waterproofing
  • Available build-up height
  • Required U-value
  • Moisture and condensation considerations
  • Drainage
  • Existing roof condition
  • Upstands and junctions

Where available space is restricted, high-performance insulation such as vacuum insulation can provide an option for achieving improved thermal performance without requiring the same thickness as some conventional insulation products. Gradient's Deck-VQ® has been used in refurbishment projects where existing roof height and parapet constraints limited the available build-up.

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How do I prevent thermal bridging through a flat roof?

Thermal bridging occurs where heat can flow more readily through part of a building element because of a change in material, geometry or construction.

In a flat roof, thermal bridging can occur around areas such as junctions, penetrations, parapets, rooflights and structural elements.

Good design should aim to maintain continuity of insulation wherever possible and address junctions and details appropriately.

The thermal performance of the complete roof build-up should be assessed rather than considering the insulation product in isolation. Accurate U-value calculations can help determine the thermal performance of the proposed construction. Gradient states that its U-value calculations are based on the relevant calculation methodology, including BS EN ISO 6946 for building elements.

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How is polyurethane ecological?

We do everything we can to reduce CO emissions2, but the core of our insulation products is also truly made of environmentally friendly materials.


Eco-friendly synthetic materials may seem strange to you, but with PU insulation, you will save 400 times more energy than they require for their production in 75 years. In short, a good thing for nature.

Sustainable development takes on its full meaning with Recticel Insulation polyurethane insulation:
not only does polyurethane insulation have a very high thermal performance that does not deteriorate over time, but Recticel Insulation polyurethane insulation also significantly reduces the carbon footprint of the insulation.

The proof by four:

1 - The least energy-intensive of all factory-made insulation is polyurethane insulation.

2 – Thinner and more efficient: With the same thermal performance, Recticel Insulation panels are up to 2 times thinner and 5 times lighter.
This reduces the quantities produced and so does the energy required.®

3 – Less bulky for better efficiency: This means fewer trucks to transport them.

4 – Less heavy: CO emissions2 are considerably reduced.

The ecological impact is controlled at all levels and the environment is better preserved.

We need to consume less energy:


Fossil resources such as oil are practically exhausted.
That is why we are advocating for the rational use of this oil.
In concrete terms: we need to burn less oil and use it to produce PU, the high-performance material of which our insulation materials are made.


Today, 96% of oil is used in the form of fuels.
The remaining 4% is processed into synthetic materials, of which only 0.08% is PU.
This is very unfortunate when you know that PU insulation saves 400 times more energy than it requires for its production.

The RECTICEL group acts at the international level, in all its businesses, for the protection of the environment.

What does “circularity” mean for Gradient’s products and processes?

Circularity means designing products and systems that minimize waste and keep materials in use for as long as possible. At Gradient, this includes responsible sourcing, efficient manufacturing, waste reduction, and developing pathways for recycling or repurposing materials at the end of their life cycle, all aligned with Recticel’s circular economy ambitions.

What does PEFC certification mean for Gradient and the Recticel Group?

PEFC certification ensures that the wood‑based materials we use come from sustainably managed forests. For Gradient, this means our sourcing practices align with strict environmental, social, and ethical standards reinforcing the Recticel Group’s commitment to responsible supply chains and traceable, sustainable raw materials.

What happens if a vacuum insulation panel is damaged?

Damage that penetrates the vacuum insulation panel can cause the vacuum to be lost, reducing its thermal performance.

For this reason, vacuum insulation panels should not be drilled, nailed or sawn.

Gradient specifically states that drilling, nailing or sawing a Vacuum Insulation Panel can cause loss of vacuum and reduce thermal performance. Deck-VQ® incorporates protective high-density PIR layers designed to provide additional protection to the vacuum panel during installation and use.

Installers should follow the manufacturer's installation instructions and avoid activities that could damage the panels.

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