Insulation By installing an External Wall Installation system on your property, you are increasing its thermal performance. This is both cost effective, saving upto 40% on your heating bills in addition to being more environmentally friendly. All of our EWI systems are over-coated with aesthetically pleasing custom finishes. All of our EWI systems are backed with a minimum 10 year guarantee and are issued with a BBA certificate and are compliant with current building regulations. We use market leaders ‘Wetherby building systems’ as our render and solid wall material supplier, specification and guarantee partners.