If you are thinking about buying a greenhouse, take the following features into account:

• Check that the ridge height is at least 1.7 m (5 ft 6 in), making sure that you take protruding roof ventilator openings into account.
• The amount of headroom will also depend on the height of the eaves. For a comfortable working space, these should be at least 1.35 m (4ft 6 in).
• Check that the cross bracing on aluminium alloy greenhouses is sturdy enough to make the structure rigid.
• It can be expensive to replace glass of a non-standard size such as those used in a Dutch light greenhouse, so bear this in mind when choosing a design. A standard size is 60 x 45 cm (24 x 18 in) or 60 cm (24 in) square.
• If you are going to need your greenhouse to be consistently warm over the winter, think about installing double-glazing. However, this will increase the cost significantly.
• Bear in mind that the total roof ventilation area should equal one sixth of the floor area - you may need to install additional ventilators.
• Gutters and downpipes are often optional; however, they are very useful for channelling rainwater so that it may be collected and used for watering. They will also prevent rain from flowing from the roof, damaging nearby plants.
• Side ventilators are excellent for providing a through-flow of air during the summer. Make sure that these close tightly to prevent heat loss in the winter.
• Sliding or hinged doors must be at least 60 cm (24 in) wide - more if wheelchair or wheelbarrow access is required, and without a 'lip'. Sliding doors have the advantage that they can be opened at any width to provide additional ventilation, and will not slam in wind. Make sure that any door shuts tightly and does not let in draughts.
• A kick panel at the base of the door reduces the risk of the glass panel breaking.
• When comparing prices between different greenhouse models or suppliers, bear in mind that a base may be an optional extra. The majority of timber- framed structures will need one. Some bases will come with a step, which may make wheelchair access and wheelbarrow use difficult.
• Any greenhouse that is not attached to a brick base should be secured using ground anchors.