Marmox’s XPS Multiboard cuts heat loss across the envelope.

Controlling construction costs, while attempting to further cut heat loss, is going to be increasingly challenging for specifiers as the Government’s Part L Building Regulation revisions are rolled out and the new Future Homes Standard comes into effect.  Happily, however, there are already some well-proven and highly versatile insulation products available to the industry that can contribute to improved energy performance in both internal and external roles for retrofit and new-build applications.

Echoing the way in which political leaders of the individual UK nations have often taken different approaches to protecting us from the deadly Covid virus, construction professionals across the British Isles continually deal with separate sets of building regulations, which contain varying targets and methods of calculating compliance on energy performance. The latest U-values and other key figures are set out in the 2021 Marmox Multiboard Technical Guide. This offers specifiers a concise reference for improving the energy performance of the entire building envelope, including extensions and conversions, as well as new developments and comprehensive refurbishment contracts.

Unlike SIPs (structural insulated panels), which form a complete building system, Multiboards are a highly versatile and easy to use board product that can uprate the energy performance of many different building elements, from solid brick walls to lightweight steel framing, as well as floors, ceilings and roofs. Furthermore, the unique construction of Multiboards makes them almost totally waterproof, enabling them to form impervious linings, including tanking wetrooms, or high- performance substrates for render and cladding finishes.

Across the range, each thickness of board is encapsulated in a thin but strong layer of glass-fibre reinforced polymer modified concrete. This provides significant load-carrying capacity for applications such as flooring and balcony style ‘promenade tiling’, while also offering moisture absorption capabilities that create an excellent bond with render, mortar, adhesives or plaster finishes.

A thermal conductivity value of 0.034 W/mK means that extruded polystyrene (XPS) is not as thermally efficient as some other rigid insulation materials, but it does deliver on a wider range of benefits.  Crucially, unlike PIR or phenolic insulation, Multiboard’s XPS core maintains its effectiveness when exposed to water, with phenolic foam actually behaving as a thermal conductor when saturated. Furthermore, Multiboard can be secured directly against substrates, such as blockwork or old solid brick masonry, instead of having to be ‘stood off’ using timber battens.  Not only does this reduce the amount by which it encroaches into occupied spaces, it also reduces the risk of interstitial condensation causing damage within the wall zone.

The space issue also highlights a principal difference to thermal laminates – aka insulated plasterboard – where the insulation is bonded onto the back of 10 or 12mm gypsum boards to give a level of strength and a surface for plastering.  Opting for Multiboard means virtually the entire depth is preventing heat loss, and therefore even a 10mm board employed as a tile backer will make a significant contribution to occupant comfort and overall energy performance.

Hythe house hits energy targets with Multiboard
Among the most visually striking recent applications of Multiboard is a unique residential development in Hythe, Kent, where resistance to the aggressive coastal climate was a key factor in the specification process. Self-builder ‘Gez’ Glover employed a high-performance SIP system to create a 334-squar-metre self-build on the Cinque Port’s stunning Cliff Road, which steps down the steeply sloping site as a series of rectangular elements. He purchased three dozen 12.5mm Multiboards to carry the cladding around the main entrance, line the inner face to an elevated balcony, and form a tile backer in the bathrooms.  He also purchased Marmox 360 adhesive, jointing tape and special plastic washers which combine with the fixing screws.

“We didn’t want the building to look too modern in the setting, so we went for a mix of exterior finishes, including multi-coloured stone slips from Marble Mosaics and the dark coloured Rockpanel Uni cladding panels which surround the main balcony,” says Glover. “With the guidance of our consultant, OSG Architecture, we started searching for a cement particle or other suitable substrate board, before coming across Marmox Multiboard on the internet. Given the elevated coastal position, the boards had to be fully waterproof, while we also needing to comply with fire regulations for exterior cladding use. The lightness of Multiboard, which enables you to install large sections without difficulty, combined with easy cutting and fixing, were all additional attractions.”

Light, strong, waterproof and simple to install, Marmox Multiboards are an ideal insulation for use in a ‘fabric first’ approach to cutting energy consumption.

Contact Details
For more information please call 01634 835290, email or visit the Marmox website.