Are thermal calculations done in the same way for all building elements?
Generally speaking, yes - all calculations are done by the 'combined method'. However, ground floors differ slightly from other building elements in the information that is required. If requesting a calculation for a ground floor, please ensure that you provide a floor area and length of the exposed perimeter (i.e. the length of new floor along outside-facing walls). This allows us to calculate a perimeter/area ratio, which is crucial in the floor calculation.
Can a breather membrane be laid directly over insulation boards?
Different breather membrane manufacturers have different guidelines for their products, and these should always be consulted prior to installation. It may be possible to lay the breather membrane on the insulation, but with a counter batten airspace above.
If you would like to discuss application of any specific project, please contact our Technical Services.
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 recess cables into PIR insulation boards?
Cables should not be recessed into the insulation boards. They may be laid between two layers of boards with the cabling oversized to accommodate for an increase in operating temperature. If cables penetrate an insulation layer, PIR will have no detrimental effect on cable sheathing.
Further guidance on the above should be obtained from a qualified electrician.
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
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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.
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.
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.
How thick do I need to insulate?
We recommend that you seek advice from your architect, designer, energy assessor etc. to determine the appropriate insulation thickness. If you already know the desired performance, you can contact our Technical Services team for U-value calculations or look up the required R-value and corresponding thickness in the technical datasheet.
The cleanest energy for heating and cooling, is the energy you do not have to use. That is why we recommend to insulate a flat roof to a higher standard than the minimum requirement. We recommend a minimum of 45 mm Deck-VQ® (Lambda (λ) = 0,009 W/mK) for renovation and 60 mm (Lambda (λ) = 0,008 W/mK) for new build.
Speak with our technical experts
What air gap is required between insulation and breather membrane?
This should be confirmed in the membrane manufacturer's BBA certificate, though 25mm to 50mm is typical.