Questions to ask window installers

A quote tells you the price. The right questions tell you whether the company behind it will still be there when you need the guarantee. Before you sign anything, work through the questions below with each installer. Good firms answer them without hesitation; the ones that dodge or bluster are telling you something too. These questions to ask window fitters take ten minutes on the phone and can save you a great deal of grief.

Are you FENSA or Certass registered?

Replacement windows are notifiable under building regulations. A registered installer can self-certify the work and issue the certificate you will need when you sell your home. Ask for their registration number and check it. If a fitter cannot certify their own work, someone will have to pay building control to inspect it — and that someone is usually you.

Is the guarantee insurance-backed, and what does it cover?

“Ten-year guarantee” means little on its own. Ask whether it is insurance-backed, so it survives if the company ceases trading, and ask exactly what it covers — frames, sealed units, hardware and the fitting itself. Get the terms in writing. This is one of the biggest differences between two quotes that look identical on price.

Exactly which windows and glass am I getting?

Ask for the frame system, the colour, and the precise glazing specification — the energy rating and U-value, not just “A-rated”. If noise or west-facing rooms are a concern, ask about acoustic or solar-control glass. Understanding energy ratings explained before the conversation means you can tell a genuine upgrade from a marketing label. Our jargon explained guide is a handy companion for this question.

Who actually fits the windows?

Some companies sell nationally and subcontract the fitting to whoever is local that week. Ask whether the fitters are employed or subcontracted, how experienced they are, and whether the same team does the whole job. Poor fitting undoes good windows, so this matters as much as the product. For context, the reviews behind the UK’s No.1-rated installer on Trustpilot repeatedly praise tidy, punctual fitters — that consistency is exactly what you are trying to confirm.

What is the full price, and how is payment staged?

Ask for the total including VAT, the deposit, and when the balance is due — a fair installer does not want most of the money up front. If you want to sense-check the figure, it helps to know what windows actually cost so you can tell a keen price from an inflated “discount”. If spreading the cost matters to you, ask what options exist; any funding and contribution options are subject to eligibility and a home survey.

Turn the answers into a decision

Once you have asked the same questions of each company, you can compare the answers as well as the prices. Take them back to the hub on how to compare window quotes, and if any reply set off alarm bells, cross-check it against our quote red flags guide before you go any further.

Free Window Quote is a free quote-matching service, not an installer. All quotes are free and no-obligation.