Greenhouse concept with high insulating cover by combination of glass and film: design and first experimental results

Dutch greenhouse horticulture puts a lot of effort in reduction of energy demand. Using (multiple) thermal screens, mainly during night, is the most common way to reduce heat losses in practice. In winter, even during daytime, transparent screens are closed, which saves energy, but results in significant reduction of light at plant level. For additional saving a substantial increment of greenhouse insulation is needed. Double covering materials can reach very high insulation levels, resulting in energy savings of 50% compared to the use of single glass with screens. Drawback of insulating glass panels are high investment and problems with snow accumulation in Northern latitudes. A new greenhouse concept with a new type of covering material has recently been developed. The insulating cover consists of a combination of a high transparent glass panel in combination with a high transparent and durable plastic film (F-Clean). The insulation properties are flexible. By blowing warm air through the split, possible snow accumulation is expected to be avoided. The new greenhouse concept has a new roofing structure including a different type of ventilation for a Venlo greenhouse. In a feasibility study, different combinations of different types of glass with different types of F-Clean have been investigated at Wageningen UR LightLab. Different model calculations have been carried out to study the effects on greenhouse climate and energy consumption. The results of a feasibility study with the search for the best combination of glass and plastic film in terms of transmissivity and light diffusing properties as well as the calculated energy savings of the total greenhouse concept are presented. In summer 2014, this concept was built on a scale of 500 m² at the research station of Wageningen UR Greenhouse Horticulture in Bleiswijk. The first results of a tomato experiment, using new crop growing strategies are presented.