The key to unlocking the full potential of rainscreen or rear ventilated facades in retrofit projects is to ensure all the components making up the system offer assured quality and performance, especially in the formation of the substructure. Here, Gary Robson, business development manager at EJOT UK, explains why
CORRECTLY designed, specified and installed, a rainscreen system can give a sustainable new life to existing buildings in a lower carbon built environment. This is particularly important in Scotland from a strategic perspective as these systems have become integral to projects, such as office conversions and school improvements, in line with the objective of National Planning Framework 4 (NPF4) to prioritise reuse of existing buildings.
The effectiveness and suitability of these types of facades in refurbishment projects, however, is heavily dependent on the performance and structural integrity of the substructure system required for its construction. These systems may be hidden from view once the façade is complete, and often a lower priority at the concept and design stage, but their contribution to success is significant.
Balancing thermal performance with fire safety
By their very nature, rear ventilated facades allow for deep layers of insulation to be applied to the original building, offering an immediate thermal upgrade. However, the performance of the insulation can be undermined by thermal bridging in the substructure.
While aluminium brackets and rails have traditionally been favoured because they are lightweight and low cost, this type of metal is known for its greater heat conductivity when compared to stainless steel. When the cumulative effect of hundreds of brackets across a façade is considered, the thermal bridging effect can therefore be substantial. Switching from aluminium to stainless steel can cut heat loss so significantly that it may be possible to reduce the thickness of the insulation used in the façade or achieve an even lower overall U-value without increasing the depth.
The insulation’s thermal performance must, of course, be balanced with the need to minimise fire risk. In addition, open or closed state cavity fire barriers may also need to be integrated to prevent fire spreading. To ensure cavity barriers are installed in line with manufacturer recommendations and the building’s life expectancy, it is vital to choose the right type of fasteners. EJOT can provide the solution here through a range of bi-metallic and A2 or A4 stainless steel fasteners.
Using a stainless steel substructure like EJOT CROSSFIX will also support enhanced fire safety objectives because the metal retains a higher degree of mechanical strength at high temperatures compared to aluminium. This is why the CROSSFIX system is classified with an A1 fire rating according to EN 13501-1.
Compatibility with multiple substrates
Given the huge variation of construction styles in many older buildings, particularly those that have been extended over time, façade substructures in refurbishment projects must often work across numerous substrates.
The EJOT range can facilitate this, spanning everything from the backing structure framing, profiles, brackets, fasteners and fixings, all supported by substantial test data with many also independently certified with European Technical Assessments (ETAs).
Providing structural integrity
Bringing an existing building up to today’s standards using a rear ventilated façade demands a substructure capable of withstanding the various loads the façade will be subject to throughout its design life. If a complete subframe system is specified such as CROSSFIX, which can be used with constructions as diverse as light gauge steel framing and traditional brickwork, it may be easier to confirm its ability to accommodate these loadings given the calculations and test evidence provided in the supporting ETA.
Overcoming wider industry challenges
Well-conceived substructure components and systems can also help to streamline the delivery of façade projects offering efficiency gains at multiple points in the supply chain. This can be beneficial from a labour optimisation perspective, reducing errors and avoiding administrative burdens which can often hinder refurbishment projects.
For example, the EJOT Konsole bracket is designed to be used with both horizontal and vertical rails, meaning there is no need for two different products where the façade requires both rail orientations. This reduces the risk of the wrong brackets being used on site and simplifies the ordering, stockholding and stock management processes.
