Zenon in-plane and barrel-vault GRP rooflights are built using different components dependent on the specification. There are two GRP rooflight sheet products available: Zenon Pro and Zenon Evolution. UKCA and CE marked in accordance with BS EN1013 and manufactured to match typical metal, aluminium and fibre cement profiles, Zenon rooflight sheets are ideal for industrial, commercial, or agricultural buildings.

Zenon Pro and Zenon Evolution carry a service life guarantee of 25 and 30 years depending on weight; service life is defined in BS 7543. These guarantees cover durability, serviceability, and structural integrity of the sheet material.

In Hambleside Danelaw’s journey to offer more sustainable options, the Zenon Insulator was developed.  This insulation layer replaces the commonly used polycarbonate layer which sits between the liner and weather sheet.  Compostable at the end of its service life, Insulator won the Queen’s Award for Innovation in 2006 and continues to be a sustainable and high performing component.

Traditional Methods of Rooflight Insulation

The most widely used method to insulate GRP rooflights is by using multiple layers of materials with high transparency. This approach is reasonably effective for uses where moderately improved U-values are required, and a common technique would be to use multi-wall or structured polycarbonate sheet.

Still air pockets are created, and conduction is minimised by using thin-walled sections to inter-connect the walls or layers within the polycarbonate; for each layer is added, there is a penalty in terms of light-transmission due to the cumulative effect of the reflectance of light at each layer. As the number of layers increase, so does the absorption into the increasing mass within the rooflight cavity and the greater the re-radiation of heat through the rooflight as a secondary component of solar gain.

Zenon Insulator

To overcome the problem of achieving a more environmentally conscious product, which still attains low U-value without significantly compromising the light transmission, Hambleside Danelaw developed the unique Zenon Insulator.

Made from cellulose acetate, a recycled wood pulp product, it provides much improved U-values without the penalties of creating multiple layers within the rooflight. It achieves this by trapping and containing the air in small pockets within the rooflight cavity thus significantly inhibiting the convection currents that carry the heat through the rooflight panels to the outside air.

The honeycomb Zenon Insulator core comprises a lightweight, transparent cell structure that is perpendicular to the plane of the rooflight. This requires only a single thin clear film layer to encapsulate the air pockets and has minimal interference with the light transmission. The light entering the cell structure is channelled directly, or by reflectance, into the building creating a better, wider spread of diffused light, irrespective of the angle of incidence of the light.  Insulator also minimises the absorptance and re-radiation of the light energy as heat energy.

The standard thicknesses for insulation layers when using simple structured polycarbonate inserts for both site-assembled rooflight applications for built-up cladding systems, or composite panel rooflights for use with composite cladding systems, are 4mm twin-wall or 10mm four-wall panels.

Zenon Insulator is available for both site-assembled rooflights or composite panel rooflights. There are three standard thicknesses available, 20mm, 40mm and 80mm, depending upon thermal performance requirements. The thermal properties of any rooflight insulation layer should always be considered in conjunction with the U-value of the rooflight outer and liner sheets, and the type of assembly in which they are to be incorporated.

Product FAQs

Is a 10mm 4-wall polycarbonate a better insulation layer than the 4mm twin-wall option?

As an insulant, yes it is, but for the marginal improvement in the heat that is retained by it, the extra layers that both absorb and reflect light mean that the light transmission losses are higher. For some designs, this would be a sound solution, but in many cases the light improvement and lower embodied carbon of the lighter product delivers a better result.

For the best of both worlds, consider the use of Zenon Insulator. This can deliver improved U-values with minimal impact on light transmission, so the best of both worlds.

Why can I not find Zenon Archlight?

Due to customer feedback, Zenon Archlight Barrel Vault Rooflight is now called Zenon Curve to avoid confusion with Zenon Arc Barrel Vault Rooflight.

Why use Zenon Evolution in favour of Zenon Pro when the light transmission is worse?

Zenon Evolution might not always be the best choice for the project, however it brings many benefits. The glass reinforcement comprises continuous strands that run the length and width of the rooflight providing greater levels of tear resistance and greater safety without having to make the rooflight thicker. This means that it can be manufactured to a sharper profile shape to match the metal sheets better, under at the top and over at the bottom. This makes the sealing of the rooflight easier and more reliable.

Due to the increased glass content, the level of light transmission through the Evolution product is less, but the diffusion is greater. Lower levels of light transmission result in lower levels of solar heat gains, therefore greater areas of rooflighting can be used to improve the uniformity of light within the building and avoid areas of shadow.

The stronger thinner product uses less raw materials which reduces the amount of embodied carbon in the product and can also be more cost effective compared to thicker alternatives. Please see FAQs about design considerations, for more information on why specifying rooflights is an important component within building design.

What span can we achieve with your in-plane rooflights?

Span capabilities vary by profile depth and weight of rooflight sheet.  Maximum span recommendations can be found on our product data sheets, which can be emailed to you via our Zenon sales team.

Zenon Arc is a factory-built panel barrel vault rooflight system available in double skin configuration manufactured using either the Zenon Pro or Zenon Evolution type materials and with the choice of two additional ‘Insulator’ upgrade options. It is manufactured to accommodate spans or 1.0m or 1.2m and is extremely quick to install on site.

The rooflight needs to cover an opening more than a metre wide. What are my options?

Some roof sheet profiles are more than 1 metre wide as standard and we have tooling to make many such products. Often the rooflight pattern of an installation can include two or more rooflights adjacent to one another, depending on the daylighting requirements within the building. For other roof types, Barrel Vault Rooflights, available for daylight opening widths of up to 4 metres, may be the best option. Please contact us to discuss your requirements.

What type of rooflight do I need to use in a low pitch/standing seam roof system?

We can supply certain rooflight profiles to match these metal roof profiles, however there are usually strong technical reasons where this is not the best approach, and ‘out-of-plane’ barrel vault systems mounted on kerbs such as Zenon Arc would be a more appropriate solution. Please contact us to discuss your requirements.

What guarantees do Zenon rooflights come with?

Zenon rooflights have either a 25 year or 30 year Service Life Guarantee dependent upon choice of material.  Project specific service life guarantees can be issued for inclusion in O&M manuals upon request. As manufacturers of components fitted into or onto roof assemblies by others, we cannot offer any guarantees on non-fragility as there are too many factors beyond our control.

Have all Zenon rooflights been tested?

Yes. Rooflights must be tested for light, heat and solar transmission properties, together with fire performance. They’re are also tested for non-fragility in a representative assembly of the different construction details required for that system.

What roof pitches are your rooflights suitable for?

In-plane GRP rooflights are not recommended for use in pitches below 4°, although some system manufacturers may allow this, subject to the limits of their system guarantee.  They can also be used as ‘wall lights’ in vertical cladding applications where required.  For roofs with a pitch below 4°, or for some specialised roof systems, kerb-mounted barrel vault rooflights are often the best option. We supply a GRP barrel vault rooflight system, Zenon ArcContact us for further information.

Why are Zenon Rooflights not clear and does that mean I don’t get as much natural light in my building?

Zenon rooflights are manufactured from translucent, naturally-diffusing GRP. The light levels passing through Zenon rooflights can be comparable to transparent materials, subject to weight and specification. Unless direct vision is required through a rooflight, then diffused light is a more appropriate option. The light is scattered over a wider area reducing the uncomfortable effects of hot spots, glare and gloom within the building.

Do you offer bespoke rooflight manufacture?

We have tooling to match the vast majority of fibre cement and metal roofing profiles. If we don’t have the profile you need, we can produce the necessary tooling  at a cost depending on the quantity required. Sheet lengths are generally manufactured from 1.2m to 7.5m but can be made them shorter or longer to meet specific requirements. There would usually be additional cost associated with this. Please contact us for more information.