Rooflight manufacturer partners with Henkel

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Sunsquare, the first BSI accredited manufacturer of rooflights and skylights, has never been a company to rest on its laurels. The desire to make the best possible product was the reason why Sunsquare was founded in 2004 and this remains its guiding principle today. As a result, it is continually scanning the market for new technology to enhance product performance and improve manufacturing processes. And testimony to that, is Sunsquare’s recent adoption of Henkel engineering adhesives and dispensing equipment for a variety of applications.

Based in Bury St. Edmunds, Sunsquare is the brainchild of Technical Director James Boughton, a talented design engineer who could see that roof and skylight design was stuck in a rut. He sold his house and car for the funds to set up Sunsquare in opposition to the then market leader of flat roof skylights; a bold move, but one which has certainly paid dividends.

Eight years ago, Justin Seldis bought-in to Sunsquare as Managing Director, to take the company to the next level from a sales and marketing perspective. Today, under the successful partnership of the two owners Sunsquare has a turnover of around £5m, a workforce of nearly 50 and two factories, selling products all over the world. Its products regularly feature on the TV programme ‘Grand Designs’ and also boast a notable number of ‘firsts’.

Sunsquare rooflights were the first to be kitemarked, a standard that Sunsquare actively pursued for an industry that, hitherto, was not scrutinised. It was also the first manufacturer in the industry to opt for heat soaked, toughened glass to exclude impurities for better performance, and the first to have its products CE Marked. And this fierce commitment to continuous improvement endures with traditional methods frequently making way for innovative processes.

James Boughton explains: “For example, just because the industry has always used neutral silicone to seal its glazed units, that’s no reason to presume it’s the only way or, more importantly, the best way to do it. The biggest problem with silicone is its life expectancy, and this is one of the benefits we have gained by working with Henkel.”

Indeed, when Sunsquare first opened discussions with Henkel at a trade exhibition this was one of several practices that proved ripe for change. Since that first meeting, four applications for Henkel engineering adhesives have been proposed, extensively tested and proven. The process has also created an effective working partnership between Henkel and Sunsquare, not just to address ongoing design and production issues but health and safety concerns too.

Shortening time to market

Although there are standard Sunsquare designs, most of the company’s products are manufactured to architects’ specification. The framework, which comprises designed-for-purpose elements, rather than off-the-shelf profiles, is constructed in the first of the company’s two dedicated factories in Bury St. Edmunds. To minimise airborne contamination, glazing and assembly are conducted in a separate factory. An important driving force behind changing bonding and sealing methods was the need to equalise the output of both production units.

Around 35 frames can currently be produced per day, but glazing and assembly can only be completed on 25, a problem that could be largely attributed to the handling and curing times of the previously used bonding and sealing adhesives. Sunsquare already has an enviable record of fast product turnaround despite this production imbalance but, true to form, it wants to do even better. It has 48-hour turnaround in its sights so speed and efficiency, both in terms of the adhesive’s characteristics and its method of application, are now more important than ever.

The first of the Henkel products now employed to address this need is most commonly used to bond windscreens in trains, buses and other vehicles facing harsh environments. It is a single-part, polyurethane TEROSON direct glazing adhesive with built-in UV stability which, when applied to a vehicle, gives a drive-away time of just 1 hour. The product’s credentials for use in the safety-critical automotive industry together with its cure speed and ability to bond without the need for a primer, proved very attractive qualities for Sunsquare.

The only preparation that’s needed is for the frame to be cleaned with Henkel’s TEROSON VR20. This product is suitable for cleaning the bond area as it had been specially developed to remove any silicone residues that remain on the glass surface and which can compromise the efficiency of the bonding process.

James Boughton confirms: “By comparison with our previous glass bonding adhesive, the TEROSON adhesive gives us longer open time but cures much quicker. The bondline is sufficiently hardened for us to clean off any excess within the hour and a good degree of cure in just four hours.”

More time savings and greater durability

Further and significant production time savings have also been made by replacing the neutral silicone, traditionally used in this rooflight industry to weatherproof bond lines, with another TEROSON product. Unlike silicone which is simply a sealant, the TEROSON alternative is both a sealant and an adhesive that boosts the durability and performance of the end product.

The chemical basis of this TEROSON product is a silane-modified polymer which reacts with moisture in the air and cures to form a high-performance polymer. Henkel adhesives incorporating this technology contain an adhesion promoter as part of the formulation and are proven to provide excellent weathering and ageing resistance. Indeed, the specific product recommended by Henkel for this particular Sunsquare application is more commonly used in the manufacture of showers and was extensively tested by Henkel to ensure it provided the performance that Sunsquare required.

This opaque, black adhesive and sealant is now applied as a bead to the parallel edges of each glazed joint. A polyurethane foam packer is then put in the channel and the adhesive flooded over the top to encase it. A thin film of LOCTITE spray solvent is then applied to surface to make the adhesive a little more spreadable so that any excess can be skimmed off to create a flat and clean seam. The solvent also enables the adhesive to be easily removed from the glass.

To optimise the application of the TEROSON adhesive sealant, Henkel has also installed a 25k piston drum pump with a dispense ratio of 24:1. The final system will have two guns; one for fine line applications such as the sealing of Sunsquare’s pyramid style rooflights and the other, high flow, for channel flooding.

James Boughton explains: “The silicone we used before took over 2.5 hours to skin over and even longer when the ambient temperature was lower. Not only does TEROSON outperform the silicone, it skins over in just 20 minutes and is sufficiently hardened for us to move the glazed unit in an hour. This means it can be moved to a crate to cure fully, so we can increase our throughput.

“With the addition of the drum pump we also have greater control over how much product we use and ultimately this will result in further cost savings.”

Protecting the workforce and environment

Another successful application for Henkel has been the use of one of its TEROSON black windscreen primers to apply an opaque mask around the edge of the glazed frame to protect upstands from UV light. It also makes the unit more aesthetically pleasing at it effectively hides the mechanism.

After application, the previously used primer dried to form a very uneven surface but, as the TEROSON primer can be roller-applied, it is both smooth and gives a clearly defined edge. Furthermore, it cures in just 20 minutes. The success of this application isn’t judged purely in terms of its efficiency, however. Another big benefit is VOC reduction as the TEROSON product is free from chlorinated hydrocarbons and aromatic solvents.

MD Justin Seldis confirms: “As well as striving to be the best at what we do, Sunsquare is also very proud of its green credentials. Indeed, the company has just been shortlisted for ‘Manufacturer of the Year’ in the Business Green Leaders Awards run by the Carbon Charter.”

James Boughton continues: “In its recommendations for appropriate adhesives, Henkel guides us with VOC reduction in mind. We have a very good working relationship with the Henkel team. Nothing has been rushed, we have worked together stage-by-stage to arrive at the best solutions.”

Sunsquare also takes advantage of Henkel’s POD system, a secure and easy-to-use web tool for ordering LOCTITE, TEROSON and BONDERITE brands. This facility, coupled with regular monthly visits by a Henkel sales engineer, to evaluate adhesive usage and projected needs, ensures there is no delay in supply to interrupt production.

Time and component savings

The final Henkel adhesive application is in the assembly of the framework. Cleats made from Zamac and aluminium have, for some time, been bonded into the frame to provide additional strength at points of stress. Although the adhesive Sunsquare had been using was sufficiently strong for the purpose, it was described as being ‘gloopy’. Consequently, it oozed from the joint after application, wasting product and involving additional clean-up time.

To address this issue, Henkel recommended a LOCTITE acrylic structural bonding adhesive whose thixotropic formulation would not run out of the joint. To ensure it would provide the necessary bond strength it was also subjected to extensive lab testing by Henkel and the outcome was very positive. Indeed, thanks to the strength of the bond, Sunsquare has subsequently been able to dispense with stainless steel straps that were previously needed to support the structure under stress.

James Boughton concludes: “We are saving the cost of the straps as well as minimising adhesive wastage and eliminating clean-up time. We can’t yet quantify how all our process changes are benefiting Sunsquare but our newly appointed process manager is working on it.”

For a company which has such sharp focus on innovation, optimising production processes is an essential element in funding further research and development of the next generation of rooflights. Sunsquare clearly values its partnership with Henkel in this regard and the two continue to work together at making the best, even better.

More information about Henkel engineering adhesives and dispensing equipment can be found at

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