Greenhouse condensation
The crops require a favourable environment in which they can reach the maximum possible production, as long as it is not at the expense of their organoleptic properties. What is intended with climate control, of course, combined with the rest of the equipment is to manipulate the climate of the greenhouse until reaching the optimal conditions or at least as close as possible to the optimum, thus achieving that the plant has everything that you need.
One of the concerns of the producers is when condensation occurs, which means, that the greenhouse air is saturated and the temperature drops, creating a high thermal difference between the interior and exterior surfaces of the greenhouse. It is in these cases when water condensation appears on the internal surface of the roof generating, among others, unfavourable effects on the growth and morphology of the crop and accumulation of water on the crops, soil and structure of the greenhouse, causing the appearance of diseases. This phenomenon usually arises more frequently in the early hours of sunrise, it is also possible at night and in the early afternoon, when the temperature drops sharply and the greenhouse has more humidity with transpiration. The problematic months are from November to May; in certain areas, the worst periods are April and May, due to higher levels of solar radiation combined with cold mornings.
With the aim of proposing solutions, Rodríguez Díaz, A. (2009): Prediction methods and condensation control techniques in greenhouses, doctoral thesis, School of Agricultural Engineering (UPM), Madrid has been consulted, which established an analysis to evaluate the effect of ventilation and heating system on the appearance of condensation, developing predictive models of the probability of condensation. The greenhouse that was used had a roof and side window, a thermal screen and two heating systems: underfloor heating and hot air. Its structure was made of galvanized steel and Gerbera jamesonii and Helianthus annuus were grown inside.
The effectiveness to avoid or eliminate condensation in the heating system was evaluated. Both the radiant floor and the hot air heating were tested without ventilation during the main night period. They were tested in five strategies to be followed, comparing the climatic parameters to determine which combinations had the greatest effect on condensation. The greenhouse situations were observed without heating and with underfloor heating and the combination of this with the presence or not of the nocturnal thermal screen and the presence or not of nocturnal ventilation, with different degrees of opening of the roof window.
After comparing the values of the relative humidity inside the greenhouse, it was observed that the strategies that used hot air reduced the humidity from 27 to 34 per cent with respect to the strategies that used underfloor heating and the combinations of underfloor heating with nocturnal ventilation got a significant reduction of condensation, 73%. The combinations of underfloor heating, daytime roof ventilation and night roof ventilation obtained the lowest values of condensation. The heating strategies that used thermal screens showed lower values of average daily condensation, due to thermal screens retaining the heat and the greenhouse air reaching a higher temperature, decreasing the relative humidity and therefore the possibilities of condensation.
In J.Huete Greenhouses we offer an additional strategy to the combination of heating, ventilation and the thermal screen which will make minimal the probability of condensation appearance at your greenhouse. In resume, if you install a double-inflated plastic coating on the roof and recommended in cold countries also on the perimeter, with the ideal combination of two plastics with different characteristics depending on the weather, along with our anti-condensation gutter and the use of the systems mentioned above, designed by our company according to the climatology of the area and the needs of the crop, reduces the possibility of the appearance of condensation at practically zero values.
For more information, do not hesitate to contact us.
info@jhuete.com | (+34) 968 807 368 | www.jhuete.com
