Paul Barrett from ROCKWOOL UK outlines the importance of robust installation methods when specifying insulation, and why a more holistic approach is needed
Until very recently, the UK’s net zero strategy has been dominated by discussions on how we can roll out energy-saving technologies effectively, and our transition to renewable energy – leaving the fabric of our buildings somewhat overlooked.
While ECO+ may signal greater recognition of the role of the building fabric and specifically insulation in the fight against climate change – full details of the scheme are yet to emerge – it’s largely been forgotten that the cheapest, cleanest, safest energy is the energy we don’t use.
To cut greenhouse gas emissions in line with the Paris Agreement, help households reduce their energy bills, and bring about a greener and more sustainable environment, we must address building performance – fabric first – and place more emphasis on how buildings perform not just when built but beyond.
Changes to Approved Document L in England, introduced in 2021, place greater scrutiny on closing the gap between design and as-built performance, which is undoubtedly a step in the right direction. Yet performance gaps often occur in areas that can’t be seen. As such, we need more stringent monitoring of the build quality; in particular, ensuring properly installed, durable insulation is used to achieve the required performance once built and occupied.
The importance of fit
The first step in achieving this designed performance is to be certain that insulation is fitted contiguously and without gaps. Stone wool insulation makes this process easier as it is highly pliable so can be closely friction fitted, without the need for impractical levels of precision cutting. This simplicity minimises the margin for error, supporting reliable and effective thermal performance that reduces thermal bridging.
This process also applies to abutments between insulation boards, another area that can be prone to thermal leakage. The composition of stone wool insulation allows individual slabs to knit together to create a seamless fit and the workable nature of stone wool insulation supports the delivery of designed U-values.
For continuing performance, dimensional stability is key. Building materials naturally expand and contract over time which can lead to the formation of gaps and voids. Stone wool maintains its shape and properties over time across a wide range of temperatures, and has the resilience to accommodate building movement when fitted under compression. It has a proven ability to provide consistent performance – even up to 55 years – without a drop in its thermal properties. And because of its high-density semi-rigid composition, it will not slump in the cavity.
The role of innovation
The UK’s drive to net zero must also be supported by building product manufacturers, leading a charge with innovation that delivers on thermal performance in reality as well as the commercial factors that can sometimes be barriers to specification.
With this in mind, last year we introduced products featuring thermally efficient stone wool insulation with solutions for cavities and ventilated cladding systems.
From a cavity perspective, this next generation of product provides a 13% improvement in thermal performance over the existing/standard stone wool cavity slab, plus delivers space-saving benefits. For example, to achieve 0.18 W/m²K, only a 150 mm thickness is now needed versus 175 mm of standard stone wool cavity insulation within the same build-up.
Likewise, with ventilated cladding systems and sealed structures, specifiers can typically save around 15 mm on the wall thickness compared to traditional stone wool products. Applying that saving over a 22 metre x 22 metre building of nine storeys, for example, can yield an extra 99 ft2 of usable or profitable floor space.
Beyond the thermal
Climate change and the need to reduce energy consumption have necessitated a focus on thermal efficiency as the primary driver for insulation choice; yet thermal performance should not be seen in isolation or focused on in detriment to other critical factors that affect the long-term safety and comfort of buildings.
As stone wool insulation is manufactured from naturally occurring volcanic rock, it has a natural, innate non-combustibility, meaning that many stone wool solutions achieve a European Reaction to Fire Classification of A1 – the highest possible rating. What’s more, the dense, non-directional fibre orientation of stone wool and its open porous structure, traps sound waves and reduces sound energy for acoustic performance.
Given that heating buildings equates to nearly a quarter of UK emissions, by reducing the gap between design, build and ongoing performance, we can make strong inroads towards net zero – as well as ultimately deliver better buildings for generations to come.
Paul Barrett is head of product management at ROCKWOOL UK