Can I get a U-value calculated for my flat roofing project?
Absolutely! Please contact our freephone technical helpline on 01543 678777.
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.
Does thicker insulation always provide better thermal performance?
Increasing insulation thickness will generally increase the thermal resistance of the insulation layer, but thickness alone does not determine the thermal performance of a complete roof.
The thermal conductivity of the insulation, the other components within the roof build-up and the construction details all contribute to the final U-value.
Different insulation materials can therefore achieve similar thermal performance at different thicknesses.
This is particularly relevant where roof build-up height is restricted, because high-performance insulation can help achieve a required thermal target without simply increasing the thickness of conventional insulation.
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.
What if I cannot provide all of the information required for thermal calculations of a specific project?
It is possible for us to make certain assumptions when performing a calculation, but this can reduce the accuracy of the final result. Assumptions are routinely made about the types of fixings to be used, but we will always try to inform you if a general figure has been used where more accurate data could affect the calculation result.
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.
What is the difference between a U-value and an R-value?
U-values take into account all elements of a construction, including thermal bridges. They can only be worked out by calculation. The R-value, or thermal resistance, is a measure of the insulation board on its own, dividing the thickness (in metres) by the thermal conductivity (lambda value, W/m.K). The R-value can be used to compare how different thicknesses of products with different lambda values perform comparatively.
What is the difference between U-value, R-value and thermal conductivity?
U-value measures how easily heat passes through a building element such as a roof, wall or floor. It is expressed in W/m²K. A lower U-value generally indicates better thermal performance.
R-value represents the thermal resistance of a material or construction. A higher R-value indicates greater resistance to heat flow.
Thermal conductivity, represented by the Greek letter λ (lambda), describes how readily heat passes through a material. It is expressed in W/mK. A lower lambda value generally indicates a material with better insulating properties.
Importantly, the U-value of a roof is determined by the performance of the complete construction, not simply the lambda value of the insulation product.