Glasshouse structures

Getting the best performance from your greenhouse is key to investment decisions, says Sally Drury.

Greenhouse: buyers can select from latest developments in materials and construction
Greenhouse: buyers can select from latest developments in materials and construction

DOWNLOAD our table of Glasshouse suppliers and products here

Used for propagation, plant and food production, displaying plant collections and for research, the greenhouse lies at the heart of horticulture. While growers, professional gardeners, botanists and researchers use different forms of greenhouse, their buildings will all have been designed to provide the best possible environment for the plants.

They have evolved over the centuries so today we can find structures varying from shed-sized greenhouses on allotments through lean-tos in the walled garden and ornate houses with botanical collections to geodesic domes such as the Eden Project and the vast acreage of industrial-scale commercial production houses.

Optimal performance

In all cases, building a greenhouse is an investment and as owner you will want to get the best performance from the structure and its associated equipment. Technical innovation has led some greenhouses to be clad in polyethylene film or twin-walled polycarbonate sheeting rather than traditional glass. Inside, the greenhouse can be filled with all manner of high-tech options depending on the purpose.

The owner of a new greenhouse has an enviable opportunity to select from the very latest developments in materials, construction and environmental control systems, such as at Red Roofs Nursery in East Yorkshire. Following handover and planting in January, the first crop of tomatoes in its new glasshouse is now in production.

Here owner Chris Durnford is not only fully committed to the future of UK tomatoes but also determined to play his part in increasing the share of premium home-grown varieties in the UK. Investment in a 700sq m packhouse and an extra 16,660sq m of fully fitted new glass with 6m posts indicates the level of Durnford's commitment to the future.

The construction project at Red Roofs Nursery is the result of close co-operation between Certhon, which took care of the glasshouse and heating, and CMW Horticulture, which supplied and installed all the equipment and managed the whole project. The themes throughout the new facilities are efficiency and cost savings, with emphasis on using the latest materials and technologies. For Durnford it means he has a glasshouse that enables him to grow in exactly the way he wants.

Energy saving in the new glasshouse results from installation of both overhead and side screens, controlled by an extended and updated Priva Integro computer.

"Research has shown that one of the most important factors contributing to high production is the creation of an even glasshouse environment, without cold or hot spots," says CMW Horticulture director Ian Metcalfe.

"Side screens around the perimeter prevent cold spots in the outer rows, apex seals above the trusses eliminate the movement of cold air above the energy screen and a Priva fan tube system under the crop gutters ensures even distribution of heat in the crop.

"The overhead screen is fitted with Svensson Luxous flame-retardant material that will deliver 47 per cent energy saving along with class-leading light transmission, so that Chris will be able to close the screen during part of the day as well as through the night, thereby improving energy efficiency even further."

Ideal climate conditions

The heating and irrigation of the new block at Red Roofs Nursery has been fully integrated with the existing 24,000sq m of glasshouses and heating system, including boiler and combined heat and power, to create a total of six zones. This enables Durnford to produce speciality tomatoes such as Garrincha, Solarino and Apetetio in the ideal climate and irrigation conditions for each.

Two new tanks have been connected to the existing buffer system to provide an additional 300cu m of heat storage and create two open-buffer systems working in tandem. This unusual configuration, controlled by the Priva computer, was designed by Certhon to make the best use of the existing system.

The control system was commissioned and monitored by CMW Horticulture technical manager Gorden Badham, who worked closely with Durnford throughout the project. Other than the new tanks, no extra heating capacity was installed, so it is imperative that the existing heat sources are used efficiently.

Flexibility and security

In the pump house, two new Priva dosing rigs are connected through underground mains to the irrigation in the houses via valve manifolds that allow any combination of the six zones to be supplied from either or both of the rigs, giving flexibility and security. Durnford explains: "The new pump house setup means that I now have the option to vary irrigation, timings, quantities and EC in every zone according to the tomato variety and stage of growth."

The drain collection, recirculation and slow sand filter disinfection system originally installed by CMW in 2007 has also been extended to accept the increased capacity.

Getting harvested produce to the new packhouse efficiently is a top priority, so an internal transport system now links the packhouse to all the glasshouses. Electric hydraulic platform trolleys for crop work and a Quattro scissor maintenance trolley ensure maximum efficiency in the crop rows. A spray robot adds further to efficiency and helps to reduce labour and chemical costs.

Buying tips

Before you sign the order for a new structure, make sure that you know the answers to the following questions:

- What is the purpose of the new structure and will the design meet those aims?

- What is the budget for the structure and all the associated equipment in terms of monitoring, control, ventilation, heating, irrigation, lighting and energy saving?

- What is the light transmission of the new structure?

- Will the new structure save on energy, and how?

- Does the supply/build company have a sound track record of producing structures for horticulture and is the firm financially solvent?

- What is the delivery schedule and who is project managing the build?

- If there is an old structure to be dismantled and removed, can any part of it be recycled and who will be responsible for the process?

- What are the warranty conditions?

Fitting the land

This 16.4m-long structure, installed by Griffin Glasshouses on the Sunley Estate in Godmersham Park near Canterbury in Kent, tapers from 5.4m to 4m and is stepped to accommodate a 0.5m fall in the ground level from one end to the other.

Each partition in the house is independently ventilated and the structure has internal water storage with appropriate benching to allow plants to be tended easily and effectively. The Griffin Glasshouses team worked closely with the estate manager and gardeners to achieve the required three-quarter span construction.

Griffin, based in Hampshire, specialises in bespoke glasshouses, greenhouses and orangeries in the UK and overseas. The company was founded in the 1960s by David Griffin, who produced a patented design providing insulation for the glazing bars so reducing heat loss and improving structural strength.

Fitting the design

Always pushing the boundaries of greenhouse design to create structures with a contemporary feel, Hartley Botanic launched its Westminster model as part of its award-winning garden at last year's RHS Chelsea Flower Show.

The Westminster is intended to sit as comfortably in a cottage garden as it would in a modern, formal garden setting. Its front-facing double doors invite visitors into a space that could be used for plant production, overwintering tender species or as a garden room.

Measuring 3.1m wide, 4.34m long and 2.92m high, it is supplied with 4mm toughened safety glass cushioned onto thermal plastic rubber so there is no glass-to-glass or glass-to-metal contact. The choice of colours includes olive and forest greens, stone, ivory and white.

Hartley Botanic has a history going back to 1938, when founder Vincent Hartley patented his original aluminium design and produced greenhouses that were uncluttered and practical.

Today the company has a reputation for supplying greenhouses varying from small units for individual gardeners to glass structures such as the RHS Rosemoor Plant House and the Bonsai House at Royal Botanic Gardens, Kew.

DOWNLOAD our table of Glasshouse suppliers and products here

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