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 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.
Can tapered insulation be used on an existing flat roof?
Yes. Tapered insulation can be designed for both new and existing roofs.
For refurbishment projects, the existing roof construction should be assessed before a tapered insulation scheme is designed. The survey and design should consider the existing roof dimensions, drainage points, falls, obstructions, roof condition and the proposed new roof build-up.
How is a tapered insulation scheme designed?
A tapered insulation scheme is designed around the geometry and drainage requirements of the individual roof.
The design process should consider factors such as:
- Roof dimensions and geometry
- Drainage outlets and gutters
- Existing falls and backfalls
- Rooflights and other obstructions
- Required insulation performance
- The structural deck
- Waterproofing system
- Required roof build-up
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Upstands and perimeter details
Gradient provides a design service that produces a pre-designed, dimensionally accurate tapered insulation solution with detailed layout drawings.
How should I store Insulation boards?
Our boards are supplied in polythene shrink wrap which is designed for short-term protection only. It is accepted that storing boards indoors is not always possible – when outdoor storage is necessary, boards should be stored clear of the ground, on a level surface, and under cover to protect them from prolonged exposure to moisture or mechanical damage.
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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.
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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.
What is a warm flat roof construction?
A warm flat roof is a roof construction where the insulation is positioned above the structural roof deck, keeping the deck and structure on the warm side of the insulation.
A typical warm roof build-up may include the structural deck, vapour control layer, insulation and waterproofing system. The exact arrangement depends on the roof construction and waterproofing system being used. Warm roof construction can provide continuous insulation across the roof, helping to reduce heat loss and improve the thermal performance of the building. The complete roof build-up should be designed to meet the required thermal, moisture, structural and fire performance criteria.
What is tapered insulation?
Tapered insulation is insulation manufactured or designed with varying thicknesses to create a fall across a flat or low-slope roof.
Rather than using insulation of a constant thickness, a tapered scheme uses different insulation thicknesses to form designed falls that direct rainwater towards outlets, gutters or other drainage points.
Gradient provides bespoke tapered insulation solutions designed around the individual roof geometry, including new and existing roofs.