Building Envelope Kalzip low U-value roof system

Kalzip low U-value roof system

Proven and highly versatile solution

Kalzip has taken the traditional standing seam roof concept and developed it into an industrially prefabricated system which is quick to install and especially suitable for flat sloping roofs. This sophisticated modular system is not only available in a vast range of shapes, but also offers tried and tested accessories to meet every requirement, including:

  • Roof lights
  • Additional components for the ridge, eave or gable end areas
  • Transparent sheets incl. accessories
  • Soakers, cover strip, seam clamps
  • Walkways
  • Customized solutions

Click the logo above to download the BIM Object for this product.

The Kalzip low U-value roof system is a dual insulation system capable of achieving U-values as low as 0.10 W/m2/K. It has been developed in anticipation of changes to Part L of the Building Regulations in 2010 and beyond – changes that will lead to ever-tightening design limits on thermal performance.

The Code for Sustainable Homes represents current best practice for the construction of residential dwellings and is closely linked to the Building Regulations. It is generally accepted that a similar code will be extended to non-dwellings, driving the way forward to achieving zero carbon buildings by 2019.

The symbiosis of rigid insulation boards with glass mineral fibre layers allows the system to achieve such low U-values giving significantly greater overall thermal resistance compared to that of one single layer of insulation of the same total thickness.

The low U-value system is primarily based on a standard Kalzip standing seam roof build and as such is subject to the same basic set of criteria and properties for materials, finishes, geometries, accessories and components. It is available with four types of roof lining; standard liner; liner-deck; structural metal deck; timber deck.

Sustainable options

The low U-value system can be combined with green roof (Kalzip Nature Roof) technologies.

Curving parameters
Where Kalzip Insulation 23 board is fixed to a curved liner, there are a number of possibilities to accommodate solutions for flat roofs and curved roofs down to a 1.5° radius.

NBS specifications are available on request along with further details on acoustics, fire and thermal efficiency.

System configurations

The Kalzip low U-value system is available with four types of roof lining

Standard liner tray over purlins

1. Inverted liner sheet over purlins

2. Vapour control layer

3. Kalzip Insulation 23

(2400 mm x 1200 mm boards)

4. SFS Iso-Tak fastener system

5. E clips fixed to inverted channel

6. Kalzip Insulation Plus range

7. Kalzip top sheet

Liner-deck spanning
between purlins

Structural metal deck spanning
between rafters

Timber decking

Liner-deck roof system
The liner-deck roof system is a variation
of the standard liner roof system. A higher
structural grade of steel is used to allow
the clip rails to be positioned away
from purlins.
Structural deck roof system
The structural deck roof system is a variation
of the standard liner roof system. A higher
structural grade of steel is used to allow the
clip rails to be positioned away from purlins.

Timber deck roof system
Timber (or SIPS) decking provides a popular
sustainable solution for supporting roof constructions.
Please contact our technical services department for
fastener pull out values.

Kalzip Insulation 23

Kalzip Insulation 23 is a standard component for use in the Kalzip low U-value roof system. It is a high performance rigid polyisocyanurate (PIR) insulation board, introduced to give a second layer of insulation with low thermal conductivity.

Kalzip Insulation 23 is faced on both sides with a low-emissivity which is highly resistant to the transmission of water vapour in accordance with BS 4370-2: 1993.

Kalzip Insulation 23 - physical properties

MaterialAluminium foil-faced polyisocyanurate foam board
Dimensions (mm) 2400 x 1200
Thickness (mm) 25, 30*, 40, 50, 60, 70, 75*, 80, 90, 95, 100, 110, 120, 130, 140
Density (kg/m3) 32
Thermal conductivity (W/m/K) 0.023
Tensile strength (kPa) 60
Compressive strength (kPa) 150
Specific heat capacity 1400
Vapour resistance (MNs/g) > 100 MNs/g

*Non standard product

Kalzip glass quilt insulation

Kalzip’s range of insulation products includes glass mineral wool quilt and rock and glass mineral wool slab with the newly available ECOSE™ Technology. 

At the heart of Kalzip’s insulation products is a full range of Kalzip Insulation Plus materials which are high performance glass quilts offering extremely efficient thermal performance.

Products are fully compliant with the harmonised European Standard BS EN 13162 : 2001, are non-hygroscopic, non combustible to BS 476:Part 4, Class 0 and in accordance with BSI Quality Assurance Standard BE EN ISO 9002.

Seam height mmProfile width mmThickness mm
50 333 0,8/ 0,9/ 1,0/ 1,2
50 429 0,8/ 0,9/ 1,0/ 1,2
65 305 0,8/ 0,9/ 1,0/ 1,2
65 333 0,8/ 0,9/ 1,0/ 1,2
65 400 0,8/ 0,9/ 1,0/ 1,2
65 500 0,8/ 0,9/ 1,0/ 1,2
AF65 333 0,8/ 0,9/ 1,0/ 1,2
AF65 434 0,8/ 0,9/ 1,0/ 1,2
AS65 422 0,8/ 0,9/ 1,0/ 1,2


Curving Kalzip 
The unique formability of Kalzip aluminium profiled sheets enables design and functionality to be combined with technical perfection.  The range of shapes available – convex, concave, elliptically or hyperbolically curved – opens up a whole variety of fascinating options for creating stunning architectural designs.

Kalzip roof sheets can be produced with a convex or concave radius utilising 3 methods; Natural curved, smooth curved and crimp curved.  

Kalzip roof and cladding systems are available in a host of finishes and materials. In addition to aluminium, the system is offered in special finishes like AluPlusZinc or AluPlusPatina as well as standard stucco-embossed finish.

With the very latest surface finishing and processing technology Kalzip offers an almost unlimited choice of colours in a range of effects and finishes.

Colour coated Kalzip aluminium products meet the stringent demands of modern building technology and design with regards to colour fastness, adhesion and resistance against aggressive substances and environments, and are available in a wide variety of standard RAL colours with a choice between high quality polyester or PVdF coatings.

Together with aluminium, Kalzip in stainless steel and copper give even more choice to the discerning architect or planner.


Kalzip profiled sheets are available in three standard pre-coated systems:

  • Polyester coil coated
  • Abrasion resistant coated (ARS)
  • Polyvinylidene flouride (PVdF)
  • HighPerformanceCoating (HPC)

Kalzip profiled sheets are available in a natural and pre-weathered natural and coloured finish:

  • Natural Aluminium in Stucco embossed
  • AluPlusPatina natural Aluminium
  • AluPlusPatina 


AluPlusZinc with the aesthetic appeal of zinc.

Please refer to the Kalzip technical department for further information on low U-value system performance including acoustics, fire and thermal efficiency. NBS specifications are also available on request.


Environmental performance
Kalzip insulation products conserve energy and therefore assist in reducing demand for fuels for the heating and air-conditioning of buildings. As a result they reduce the emission of the major greenhouse gas – CO2.

The core of the PIR based formulation and all Kalzip insulation products are CFC/HCFC free with zero Ozone Depletion Potential (ODP) and a Global Warming Potential (GWP) of less than five.

Durability and recycling
When correctly applied Kalzip Insulation 23 has an indefinite life fully supporting the sustainable credentials of standard Kalzip standing seam systems.  Kalzip insulation products can be reused or recycled at the end of the building’s life. 

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