GREENHOUSES

GREENHOUSE ADVICE

Greenhouses are invaluable in a garden for creating an effective growing environment for plants and vegetables. However, there are many different factor to consider before buying and installing one.

Greenhouse Location

Ideally, greenhouses should be located where they can be in direct sunlight throughout the day. Its location should also shield it from generally cold northerly or easterly winds, which can reduce temperatures and impede the growth of its contents.

An east-to-west orientation will marginally increase light levels during the darker months of winter, whereas a north-to-south orientation is best suited to summer crops such as tomatoes, with both sides of the greenhouse experiencing a few hours of sunlight from the east and the west direction.

Timber Or Aluminium Greenhouses

Aluminium has traditionally been the most common form of construction for greenhouses because it doesn't require any direct maintenance and the core structure is very thin which maximises light penetration. Timber frames greenhouses, however, are (in our opinion) more attractive as a structure, using a traditional building material which is generally better-suited aesthetically to many garden styles.

That said, the timber frame does need ocassonal maintenance unless it is formed from more expensive, better quality and lower maintenance cedar-wood timber. Wooden frames also tend to be a little thicker than aluminium.

Greenhouse Shape & Size

As a rule, the taller a greenhouse is at its eaves, the better the light penetration and growing performance and scope. The roof ridge should ideally be of sufficient height to allow the fitting of a suitably sized door to allow ease of access by a typical adult. It should also be sloped at a gradient to allow rain to run off and to encourage the escape of excessive levels of heat.

A fully glazed greenhouse, with glass elevations from ground to roof is the most flexible of constructions, but elevations which are walled half way up can help reduce heat loss.

Greenhouse Ventilation

It is critical that a greenhouse has adequate ventilation, ideally through the use of roof vents. Vents which open and close automatically are invaluable, but they often need supplemented with manual intervention of opening doors and windows.

Motorised vents which are activated by heat sensors are generally more efficien and reliable.

Greenhouse Glazing

Glass. The best glazing material is undoubtedly glass. It allows around 90% of light to pass through, it doesn't deteriorate and critically, reflects the heat radiated from inside the greenhouse back into its structure instead of being lost altogether.

Toughened glass should ideally be used, at least for the doors. Polycarbonate sheeting has its advantages as an alternative, including being shatter-proof, lighter, quite durable in bad weather and good at retaining heat. However, it transmits 7% less light than glass, limiting its effectiveness.