A properly-built conservatory with good ceiling height can be a useful additional room in any house

Estate agents used to advise people not to build conservatories if they intended moving within 10 years, on the basis that they would never get the value of it back. We've come a long way since then and these days conservatories are considered a plus, if they are well built, well proportioned and blend in well with the overall design of the house.

" If a conservatory is to be a permanent and comfortable aspect of a house, it needs to be carefully designed and constructed." says Ronan O'Hara of Hamilton Osborne King.

"You can add a €3,000 conservatory and waste your money. But spend €10,000 and you really add value to your home. If you are thinking of installing a cheap lean-to, don't bother and save your money. However, if you add a properly-constructed, well proportioned sunroom or conservatory with good ceiling height, it can only be a good thing," says O'Hara.

Geralyn Byrne of Sherry FitzGerald is more cautious. "The reality is that most conservatories are not all-year-round rooms," she says.

"If you add on a conservatory, make sure it is a room you can use not just in spring or summer. It has to be versatile." A disused conservatory can be turn off for buyers particularly if it seems cold and damp off season. Estate agent Felicity Fox agrees. The only way to go, she says, is to build a part-brick, part-glazed conservatory with a slate or tiled roof. "It's more like a sunroom and is way more functional," she says.

A fine example of this is the garden room in the Garden House in Enniskerry, Co Wicklow which was on the market through Hamilton Osborne King last year. Located off the kitchen with floor-to-ceiling arched windows, a glazed dome in the roof and French doors out to the garden, the room had an informal dining area.

Significantly adding to the character of the house, the garden room was a huge selling point for prospective buyers, says agent David Ashmore.

A good alternative to the traditional conservatory is something like Heritage Buildings' oak-frame garden room, which falls halfway between a conservatory and an extension.

Quicker to install than an extension, it's more solid and much warmer than a normal conservatory. People who want to extend kitchen, dining and living areas are looking for something different, says Peter Vallely of Heritage Buildings. Prices for an oak-frame conservatory from Heritage Buildings start at €38,000 and go up to €100,000.

If installing a conservatory, make sure the conservatory fits with the style and tone of the rest of your home, don't sacrifice too much of your garden and always get professional advice from an architect or specialist at the early planning stage.

A conservatory needs shade for sunny days and a good heating system if it is to be used all year round. Underfloor heating will ensure a snug atmosphere in colder seasons. Blinds are a must to control temperatures in the summer. Or you could simply leave one area of the conservatory with no floor at all, plant climbers into the earth and let them clamber all over the roof to create natural shade.

One last thing: don't invest in expensive cane furniture until you try it out first. Modern cane and rattan looks good, but the chairs and sofas can be uncomfortable to sit in with outsize cushions that slide all over the place. Try traditional Lloyd Loom chairs instead.