Sir,

In response to Murray John's letter in last week's Observer regarding conservation. Replacing wooden windows with uPVC double-glazing may seriously dent a property's value, as well as spoil its character. The thicker frames, fake glazing bars and inappropriate proportions of vinyl windows can be a big turn-off for homebuyers.

Heritage groups and estate agents agree vinyl windows can affect the value of a period house. Brenda Hobday, of Winkworths, says: "uPVC windows could cost £5,000, but they would easily take that off the price. You could get £5,000 to £10,000 less because of the way the property looks."

Even the Crown Estate is proposing wooden replacements after tenants in Gore Road, Hackney in London, protested against uPVC. The Peabody Trust has also switched back to wood. However, the uPVC invasion continues unabated and threatens many Tenby properties.

You need (and are unlikely to get) listed building consent to install vinyl windows in a listed building, even if the building is not in a conservation area. But most house-owners face no such restrictions.

Why is uPVC so popular? Government regulations to conserve energy now apply to replacement windows. There are wooden windows that comply with part L of the building regulations, but "wooden window manufacturers don't knock on your front door at five o'clock in the evening or phone your house," as pointed out by Adam Frankling, of the British Woodworking Federation (BWF). Modern wood comes from sustainable forests, so timber is much more environmentally friendly.

The claim that uPVC is cheaper is also debatable. Every house is different. uPVC windows do not require painting, but it is a spurious argument to say they require less maintenance. Sunlight can make the vinyl brittle, while pollution leaves it pitted and grey. And uPVC windows cannot be repaired, only replaced. Their lifespan is generally reckoned to be 20 to 30 years, but it could be 10 years in the worst case.

BWF accredited factory painted timber windows do not require repainting for eight years and are guaranteed against decay for 30 years. As long as properly looked after, they should last a lifetime. There are wooden windows around Tenby that have been there for easily 150 years and are still in good condition.

If you want to cut heat loss, heritage organisations have booklets with advice on draught proofing. 'Repair rather than replace: that's always been good conservation philosophy,' says the Victorian Society's Richard Holder, speaking for all the conservation experts. Windows are the beginning of most refurbishments and everyone should consider wisely before filling yet another skip with material that should be preserved.

How far Tenby wishes to conserve the remainder of its own unique fabric is up to its businesses and residents. Compliance at least within the conservation area should be possible in Tenby, but many choose to turn a blind eye. The slide into quasi-conservation by way of a Disney-style theming of the town must be challenged before the councils' much-heralded heritage is botched and destroyed.

Richard Walker,

1 Lexden Terrace,

Tenby.