unaffected by air infiltration and offer excellent levels of thermal efficiency. Recent product innovations mean that the advanced phenolic cavity boards now have a lambda value of just 0.018 W/m.K. This latest development further reduces the insulation thickness needed to deliver a desired U-value for the entire cavity wall construction. Much like existing phenolic cavity boards,
these lower-lambda advanced phenolic cavity insulation boards are available with foil facings which are well-suited to partial fill applications. These facings are classed as low emissivity. Put simply, this means their shiny surface helps to reflect radiated heat back into a property. As a result, they can significantly increase the thermal resistance of the cavity and reduce the thickness of insulation required. However, these facings still require a 50 mm
[
Once you have your plot, the key question is how to get the most from it
] There is a huge variation, and the solution to
the issue of space is a simple one. Phenolic insu- lation cavity boards are already widely used throughout the UK construction industry; they are easy to handle, have a fibre-free core, are
million m2 successfully installed
8.5
clear cavity to be maintained, so a further development has been the addition of water- tight polypropylene fleece facing. This helps to protect against moisture ingress, allowing the air gap to be reduced to just 10 mm. The gap between the board and the outer facing can be simply maintained with the use of a retaining clip which fastens to the wall ties and holds the insulation in place. A self-adhesive breather tape should be used to create a continuous water-tight facing. The combination of lower-lambda phenolic insulation boards with this new facing can significantly reduce whole wall construction thicknesses. Take, for example, a traditional
cavity walled construction, with a 102.5 mm brick outer leaf and a 100 mm medium density block inner leaf. A 90 mm thickness of lower-lambda phenolic insulation, together with a 10 mm air gap,
is all that is needed to
achieve a whole wall U-value of 0.18 W/m2
.K. This construction could be applied to
help meet the Building Regulation/Standard requirements right across the UK, even in Scotland where they are most stringent.
A well insulated approach
Any self-build is a project of passion and most owners are looking to create a property which will last them a lifetime. It’s important to keep that in mind when it comes to decisions such as the insulation specification. While it can be tempting to scrimp on the thermal performance to reduce wall thicknesses, ultimately this decision could lead to much greater costs in the long run as a result of higher energy bills and may even lead to the property being deemed non-compliant. Lower-lambda rigid phenolic insulation
boards offer a straightforward solution. They allow homeowners to stick with the tried and tested masonry cavity wall construction approach while keeping the walls both slim and well insulated. This should help to keep you warm without burning a hole in your wallet.
Adrian Pargeter is head of technical and product development at Kingspan Insulation
Enq. 164
The UK’s No.1 Underscreed Acoustic Layer
That’s the same
area as 8,500 Olympic size swimming pools*
Outstanding sound proofing performance
Suitable for all types of concrete floors and screeds Low cost solution
Lightweight rolls, easy to cut and quick to install
Robust detail treatment for E-FC-5 and E-FC-17
01634 296677
www.cellecta.co.uk technical@cellecta.co.uk
Enq. 165
selfbuilder & homemaker
www.sbhonline.co.uk
41
*Calculations are based on the size of an Olympic size swimming pool.
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