Having new windows installed is a big project, and one that you want to make sure is done right. So, it is important to choose a glazing installer that you can trust to carry out the work on time, on budget, and in line with your specific requirements. With this in mind, we have put together some of the certifications you can look for when choosing a glazing installer.

FENSA registered double glazing installer in MertonFENSA Glazing Competent Person Scheme

This government-authorised scheme is one of the best indicators of quality you can find in the glazing industry. It essentially means that a glazing installer has been carefully assessed for fitting replacement windows and doors in line with the latest Building Regulations.

The Consumer Protection Association (CPA)

Being a member of the CPA is a good sign that a glazing installer cares about providing their customers with peace of mind that their property is in safe hands. The CPA offers training and certification for tradespeople, and supports them in providing guarantees on products.


Merton Windows are on Checkatrade for double glazing installers in MertonWord of mouth is often the best way to ensure that the glazing installer you’re hiring is as good as they say they are. You can use checkatrade.com to see what previous customers thought of aspects of an installer’s services – including everything from tidiness and courtesy to workmanship, reliability and timekeeping. At Merton Windows, for example, we have an average score of 9.82, with average scores being above 9 for each of these aspects.

British Board of Agrément

Brands like Kommerling, which we use for our double-glazed window ranges, have received approval from the British Board of Agrément for their security standards. This is an excellent thing to look out for when choosing a glazing installer, as it highlights the quality of windows on offer. Approval is not given out lightly, so windows have to be really secure to earn it!


Although not technically a certification, Planitherm is a good thing to look out for in your search for a glazing installer. It essentially shows that a glazing installer uses highly energy-efficient glass in their windows, which can help you significantly lower your heating bills.

Here at Merton Windows, we care about your peace of mind and satisfaction, and are dedicated to delivering high-quality windows that are installed with professionalism. That’s why we are part of the FENSA Glazing Competent Person Scheme and the CPA, have excellent ratings on checkatrade.com, and use products from Kommerling and Planitherm. If you live in Balham, Dulwich, Barnes or a surrounding area, contact us today for a free, no-obligation quotation.