By Jon Vanstone, chair, Certass TA.

Spend time around genuinely skilled installers and you notice something mildly unsettling. The best ones almost never talk about windows.

They talk about the kitchen that never gets warm. The back bedroom where condensation appears every winter morning like clockwork. The conservatory that becomes a greenhouse in June and an ice box by October.

They talk about the traffic on the road outside, the child who cannot sleep, the extension that cost a fortune and somehow still feels like a garage. What they are describing, you eventually realise, is not a building, but it is a life.

This is more than a sales technique, and is a fundamentally different theory of what the job actually is.
The glazing industry is, by tradition, highly technical, and rightly so. Thermal values, solar gain, ventilation, acoustic performance and structural specification are not decorative details. They are the difference between a building that performs and one that merely exists. Installers need to understand them fluently, and specifiers need to apply them intelligently. None of that changes with this approach.

But here is the thing: nobody in the history of domestic glazing has ever looked at their kitchen window on a Tuesday morning and thought, “that centre pane U-value is doing sterling work.”

What they think, if they think anything at all, is that the room feels different. Maybe quieter, sometimes brighter and often warmer without quite knowing why. The technical specification has done its job precisely by becoming invisible.

And the installer who obsesses over communicating that specification may be the one least likely to help the homeowner understand what they are actually buying.

People do not buy products, they buy the mental and physical experience that products create. The window is, in an important sense, beside the point. What is being purchased is a quieter bedroom, a conservatory that is lived in rather than avoided, a kitchen that finally feels connected to the garden. The frame is the mechanism, and the life is the product.

Summer makes this particularly legible. As temperatures rise and routines shift, homes reveal how they perform rather than how they looked in a brochure. Rooms that passed specification in February become uncomfortable in June. Bi-fold doors either deliver the feeling of inside-outside living or they do not. Extensions become genuine family rooms, or they remain the expensive place where the treadmill lives. The homeowner’s relationship with their glazing becomes vivid and specific in a way that winter rarely allows.

The installers who ask better questions are already exploiting this gap. Not “what specification are you looking for?” but “which room bothers you most?” Not “what’s your budget for the project?” but “where does the condensation appear?” Those questions are not merely rapport-building, they are diagnostic.

They surface the real problem, which is almost always described in lived experience rather than technical language, and they dramatically increase the likelihood that the right solution gets specified and sold.

There is a commercial logic here that deserves to be taken seriously. An installer who understands the family’s actual problem, rather than simply the window they think they want, is more likely to specify correctly, less likely to face a dissatisfied customer at the end of installation, and far more likely to generate the kind of referral that no marketing budget can buy. Understanding behaviour pays.

As the industry moves towards greater accountability for whole building performance and the lived experience of occupants, this understanding will matter well beyond the sales conversation. The question of how buildings feel to inhabit is becoming a design, regulatory and reputational concern, not merely an anecdotal one. Installers who have spent years developing genuine insight into how homes behave are sitting on something valuable. The industry should work out how to capture, reward and build upon it.

In the meantime, the simplest measure of a genuinely skilled installer may be exactly this: how long does it take before they mention the product?