VIEWPOINT
HELPING YOUR CUSTOMERS FIX THE INSULATION
PERFORMANCE GAP Matt Neary, national sales manager at Knauf Insulation
MERCHANTS PROVIDE THEIR customers with the insulation needed to build energy-efficient, quiet and comfortable buildings. But there is often a performance gap between what’s been designed and the finished construction and, as regulations tighten, closing this gap is an increasingly important goal. By offering advice and expertise, merchants can empower their customers and position themselves as invaluable partners. In this month’s column, we will look at some of the common causes of the performance gap and how your customers can fix it.
Taking stock
It can be easy to overlook storage for insulation, but it’s crucial that it is protected from weathering and other damage while kept on site to preserve its performance. The polyethylene packs often used to deliver products are not designed for long term storage. Insulation needs to be stored indoors, or under cover and off the ground to avoid contact with ground moisture. Your customers must not use insulation that’s become saturated with water. Any kind of physical damage to the insulation also makes it unsuitable for installation. Common issues such as crushed corners of slabs can affect the performance of the insulation, causing thermal bridging or making airtightness impossible to achieve. Customers should stick closely to the manufacturer’s guidance on storage and if in doubt about the condition of the product, err on the side of caution.
The right product for the application Using the right product for the application and thinking
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about the impact of material choice is crucial to ensuring the insulation performs as expected. For example, rigid boards can be difficult to install without air gaps forming as they require precise cutting and taping. Due to construction tolerances, minor imperfections in the substrate and the natural movement of the construction over time, achieving and maintaining a flush fit with these boards can very difficult, even if they notionally offer the required performance. By contrast, mineral wool is flexible and can conform to minor irregularities such as mortar snots inside a cavity wall. Where slabs and rolls meet, they ‘knit’ together, requiring no taping to achieve a continuous, airtight layer of insulation. This minimises air gaps and maximises thermal performance.
The installation fundamentals The quality of the installation will make or break the thermal, fire and acoustic performance of the insulation. Closely following the manufacturer’s guidelines is
always the best starting point, but there are some fundamental rules for installation that apply regardless of the application or product.
Firstly, air gaps need to be minimised as much as possible. This means fitting the insulation flush with the substrate, making sure the edges of slabs, rolls or boards are fitted tightly together, and that airtight tape is used to seal the edges if necessary. Customers will need to fit insulation around any service penetrations, which may require precise cutting, depending on the product used.
Secondly, the insulation must be installed in a continuous, unbroken layer that minimises ‘thermal bridging’ – localised areas of heat loss that can cause condensation, rot and mould. When insulation is interrupted in a predictable, repeating pattern by wall ties, joists or studs, it’s called a ‘repeating thermal bridge’. When the cause of the interruption is irregular, for example at a wall-to-floor junction, around a window or a gap in the insulation, it is called
a ‘linear’ or ‘non-repeating thermal bridge’.
Both linear and repeating thermal bridges need to be considered at the design stage and during construction. This means, for example, ensuring that loft roll is pushed into the eaves of the roof to touch the top of the wall insulation.
Trusted insulation partners
Helping customers close the insulation performance gap is about more than just supplying materials—it’s about sharing the knowledge and practical advice that ensures those materials are used effectively. From proper storage and product selection to meticulous installation, every step matters in achieving the energy efficiency, comfort, and regulatory compliance that today’s construction demands. By supporting customers with this guidance, merchants can position themselves as trusted partners in delivering high-performance buildings. BMJ
www.buildersmerchantsjournal.net May 2025
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