Cost of Double Glazing Units
across the UK

# Double Glazing Units: Trade Body Accreditation

The main regulatory bodies governing double glazing installation in the UK include the Fenestration Self-Assessment Scheme (FENSA), which certifies installers who meet building standards without requiring Local Authority approval, and the British Standards Institution (BSI), which sets quality benchmarks for manufacturing and installation. The Glass and Glazing Federation (GGF) represents legitimate traders and sets codes of practice for member companies, while Trustmark is a government-endorsed scheme that identifies vetted, trustworthy traders across the home improvement sector. CERTASS also provides third-party certification for window and door installation work. Understanding these bodies matters because they indicate a company has undergone independent verification, holds appropriate insurance, and agrees to follow established standards for workmanship and customer service.

Verifying a provider's credentials is straightforward: ask to see their certificates and cross-reference them directly on the relevant trade body's website rather than relying on claims alone. FENSA-registered installers can be checked via the FENSA portal, Trustmark traders appear on the Trustmark directory, and GGF members are listed on the federation's site. Request evidence of public liability insurance, guarantees on materials and labour, and proof of any relevant qualifications. This verification matters significantly because accredited installers are legally accountable to their schemes, must follow strict codes of conduct, and offer you recourse if standards aren't met—protecting you from rogue traders, poor installation, and costly disputes.

Accredited double glazing providers typically charge 10 to 20 percent more than unaccredited competitors, reflecting the costs of maintaining certification, insurance, and compliance with quality standards. While this premium may seem unnecessary at first glance, it usually proves worthwhile because you gain formal guarantees, protection through the trade body's dispute resolution process, and ass