As per the documentation for Eurowall® +, the clear cavity can be reduced to 10mm due to the innovative tongue & groove interlocking joint.
Eurowall® Cavity is certified for use in conjunction with a 25mm cavity. However, some warranty providers will not accept this and require a 50mm cavity, as do Scottish Building Standards. A wider cavity should be used in exposed locations.
If in doubt, seek advice from your Building Control Officer.
Where can I buy Recticel Insulation products?
Recticel Insulation's products are available via number of stores across the country.