Delivering a successful retrofit project in the UK today requires more than installation expertise it demands full alignment with PAS 2035 , the national framework governing whole house energy efficiency upgrades . This standard ensures every project is assessed, designed, coordinated, and delivered with long-term performance in mind. For property owners, housing providers, and developers, choosing the right contractor is critical. Below is a carefully structured list of the top PAS 2035 compliant retrofit contractors in the UK , selected based on compliance capability , end to end delivery , and real world project execution . What Makes a Contractor PAS 2035 Compliant Before selecting a contractor, it is essential to understand what PAS 2035 requires: Whole-house assessment approach (not single upgrades) Defined roles : Retrofit Assessor, Designer, Coordinator, Installer TrustMark registration for compliance and quality assurance Integration with PAS 2030 for installation ...