certass vs fensa

Fensa vs Certass: What’s the Difference and Which One Should You Choose?


When installing new windows and doors, it’s important to make sure you choose a competent and trustworthy installer. Two leading installer certification schemes in the UK are Fensa and Certass. Understanding the key differences between these two certification schemes can help guide your decision. But what’s the main difference between Fensa and Certass and how do you decide which certification to prioritize when choosing an installer? Getting familiar with the Certass vs Fensa comparison can help provide assurance that your new windows and doors meet important quality standards for installation.


Fensa, which stands for Fenestration Self-Assessment, is an independent organisation that vets window and door installers. Installers must pass various competence checks and adhere to Building Regulations in order to be Fensa registered. This registration lasts for five years before installers have to re-register and prove their continued competence.

Fensa Registration Process

The Fensa registration process is quite rigorous, including various checks such as site inspections, financial checks, and reviews of installers’ work and knowledge. Installers’ work is inspected onsite, and they must demonstrate up-to-date working practices and knowledge of Building Regulations.

Fensa Guarantees

If you choose a Fensa registered installer, they must provide you with an insurance-backed guarantee that promises to rectify any issues caused by the installer for at least 10 years after installation. This gives you considerable peace of mind.


Certass (Certificate of Assessment for the Installation of Replacement Windows and Doors) certifies installers to confirm they are competent to fit your windows and doors to a good standard. The focus is more on self-certification than independent checks.

Certass Registration Process

The Certass registration process relies more on installers assessing their own skills and work. They self-certify that they have undertaken training and work to industry standards. There is less rigorous and frequent assessment from Certass itself in terms of site checks and inspections.

Certass Guarantees

Certass registered installers can issue an Insurance Backed Guarantee, but only if they choose one of Certass’s registered guarantee providers. So this guarantee is not necessarily included or standardised across all Certass registered installers.

Key Differences

While Fensa and Certass have some similarities in certifying window and door installers, there are several notable differences that customers should be aware of.

Installer Checks

Fensa has much more rigorous and frequent checks of installers’ work and competence, including site visits and inspections. Certass relies more on self-certification from the installers themselves, with less independent verification.

Registration Process

Similarly, Fensa has a stricter registration process that installers have to go through, including various competence checks. Certass focuses largely on installers assessing their own skills and processes when going through certification.


The insurance-backed guarantee for faults and issues is mandatory across all Fensa registered installers. With Certass, the guarantee is optional for installers to provide customers.


Due to the more rigorous registration and checks, Fensa registration tends to be more expensive for installers. This cost may sometimes be passed on to customers. Certass offers a more budget-friendly option.

Which One to Choose?

So when considering whether to go with a Fensa or Certass registered window/door installation company, which one is right for your project?


Ultimately, it depends on your priorities as a customer and what you want from the certification scheme:

  • If you want stricter oversight and assurance of installers’ work, choose Fensa. Their robust checks offer greater confidence in installers’ skills and knowledge.
  • If getting an automatic insurance-backed guarantee is important to you for peace of mind, again Fensa is likely the better fit.
  • However, if you are satisfied with installers self-certifying their competence and want a more affordable option, then Certass registered installers may suit your needs.

For many customers, the rigorous installer checks and guaranteed insurance-backing provide greater confidence and value for money over the long run. But Certass meets a demand from budget-conscious consumers too. Evaluate your priorities and decide which certification scheme makes more sense for your windows/doors installation.


In summary, Fensa and Certass both offer installer certification schemes with some differing priorities:

  • Fensa focuses on extensive competence checks and guarantees to reassure customers.
  • Certass meets demand for more affordable installation options, though with less oversight.

When choosing between Fensa registered installers and Certass registered installers, consider your priorities in terms of budget, guarantees provided, and confidence in oversight of installers’ work. Fensa ultimately offers more stringent checks and assurances if that is worth the extra investment for you.


Is Fensa considered better than Certass?

Fensa is widely seen as more rigorous and thorough in vetting installers. But Certass can be an acceptable option too based on customer priorities around cost and guarantees.

Which certification offers better consumer protection?

Fensa offers higher levels of consumer protection given the required insurance-backed guarantees and thorough competence checks on installers.

Do all Certass installers provide guarantees?

No, guarantees are optional for Certass installers. Fensa guarantees are required.

Is one certification higher “ranked” than the other?

There is no formal ranking system. But Fensa does demand more of installers in terms of stringent oversight and assurances for customers.

What certification scheme do experts most recommend?

Industry experts often highlight Fensa as providing greater reliability and scrutiny around installers. But Certass has satisfied many customers too.