CASTA/Greenhouse design programme

Thema:
Structural design

Dutch greenhouse construction is successful around the world. A major reason for this is the efficient design of our greenhouse structures. Most glass-based greenhouses have been designed using the ‘CASTA/Kassenbouw’ programme. We developed this programme together with companies from the sector. It’s also being used internationally.

Design programme for greenhouses

The design programme has been in use since 1989. Its introduction helped drive the rapid scaling up of the Dutch greenhouse sector. The programme enables greenhouse constructors to efficiently customise calculations for the substructure of ‘Venlo’ and other types of greenhouses.

TNO expert Hans 't Hart explains the programme as follows: "The programme provides insight into the consequences of the various alternatives. The structure will be economically attractive and as light as possible, without compromising structural safety. The verification calculations comply with the NEN 3859 greenhouse construction standard and the Dutch Buildings Decree. CASTA/Greenhouse design can also deal with foreign construction standards."

Handy for greenhouse constructors and growers

The CASTA/Greenhouse design calculation programme (see image) provides customised solutions to growers as well as greenhouse constructors. Growers are supplied with greenhouses specifically tailored to their businesses, at the right mix of price and quality. There’s optimum light transmission and safety is ensured in the best possible way. Growers can easily insure their greenhouses because they meet the Dutch greenhouse construction standard.

Screenshot of calculations in Casta/Greenhouse design calculation programme

Hortivation foundation

The Dutch greenhouse construction sector was involved in developing CASTA/Greenhouse designfrom the outset. The Hortivation foundation was set up for this purpose. Board member Dave Fennema of Dalsem Horticultural Projects calls the programme the jewel of greenhouse construction: ‘The programme saves us months of work and we can serve growers much better.

Collaboration with TNO went smoothly. We understand each other well and there’s mutual trust. We’re now working on improvements, for example by expanding the tool with new modules and adaptations to the latest developments and requirements. In this way, we make optimum use of fast calculation systems, which can handle increasingly complex calculation models.’

Hans 't Hart: ‘We already have a lot of contact with the sector, and other entrepreneurs who want to join Hortivation are very welcome. There are also opportunities for foreign greenhouse constructors to collaborate.’

Calculating light levels in greenhouses

Light transmission is a key element in designing a greenhouse. The less light a greenhouse structure intercepts, the less artificial light is required. The greenhouse is then more environmentally friendly and energy costs for growers are lower. We therefore develop models that calculate how much light a structure blocks.

High light transmission

Light transmission – the amount of light that a greenhouse structure lets through – is an important part of greenhouse design. High light transmission means that growers can obtain larger harvests with the same amount of energy. Designers and constructors, just like growers, therefore want to have exact calculations for this factor as early as in the design phase.

Subsidy through Green Label Greenhouse certificate

A greenhouse with sufficient light transmission can also qualify for a Green Label Greenhouse (GLK) certificate and thus for an attractive subsidy. Awarding the certificate fits in with the objectives of the Dutch greenhouse horticulture sector as a whole, which is striving to increase sustainability.

Simple calculation

Using software with our IDT method, you can calculate light transmission in a simple manner. Constructors can enter the profiles of the structure in the database and the programme will then calculate the light interception factor. These data can be used when applying for the GLK certificate.

More complex models

In addition to the IDT method, we’ve developed more complex models that can be used in combination with existing tracing software to run calculations for new situations. With ray tracing, a large number of individual light rays are followed, which may originate from refraction or reflection, for example. This makes it possible to calculate the influence of a deviating screen package, for example.

Calculation tool for light transmission

Another example is a calculation tool that simultaneously calculates both light transmission and the electrical yield of PV panels in a greenhouse roof. Greenhouse designers and constructors can use our models when they’re working on product development and want to know the influence on the light in a greenhouse. Feel free to contact us on this topic by e-mail or telephone.