Insulation manufacturer ROCKWOOL® has released a Technical Bulletin announcing the results of an independent study conducted by the University of Salford Thermal Measurement Laboratory into the impact of gaps in the insulation layer and their effect on thermal performance.
In a series of tests and studies, the impact of gaps in the insulation layer and its effect on thermal performance were replicated.
Ten samples of stone wool insulation of various densities were tested to ISO 8301:1991 ‘Heat flow meter apparatus’ and BS EN 12667:2001 ‘Thermal performance of building materials and products’, two standards related to heat flow meter methods.
The tests were conducted in accordance with product standard BS EN 13162:2012+A1:2015, ‘Thermal insulation products for buildings’.
High resolution Scanning Electron Microscopy (SEM) was used to demonstrate that when two separate slabs are tightly joined together, the gap between them closes, and the individual fibres knit together to form a continuous network of fibres containing trapped pockets of air.
Results from the thermal conductivity tests show that, when considering five product types over the density range of 27 to 152 kg/m³, there is no loss in thermal performance between a stone wool slab and two tightly jointed pieces.
The ROCKWOOL ‘Performance Gap’ Technical Bulletin found at https://rockwool.link/pg-tb outlines the findings further.
Commenting on the Bulletin and its conclusions, James Francis, Product Manager at ROCKWOOL added: “ With the introduction of the Future Homes Standard and low-carbon heating systems, it is more important than ever that buildings are designed to maintain high energy efficiency standards. However, an air gap as small as 6mm is enough to increase heat transfer by 158% of the design value.
“Based on independently measured data from the University of Salford, we conclude that when our stone wool slabs are tightly joined together, the edges knit together, providing a continuous insulating layer of trapped pockets of air with no gaps and no associated loss of thermal performance. This finding is a hugely positive step when it comes to addressing the challenges of the performance gap.”
All declared thermal conductivities can be found in their respective Declaration of Performance on the ROCKWOOL website.
