Anti-condensation coating for glass
In the Netherlands the levels of light are low in winter. We can compensate for this by using additional lighting, but it is also important to let in as much of the available natural light as possible. One way of getting more light in is to reduce light loss caused by condensation.
An anti-condensation coating for film has already been on the market for some time but in some instances this does not meet requirements for application on glass. It is for this reason that an anti-condensation coating has been developed for use on glass. An anti-condensation coating causes the surface on which the moisture condenses to become hydrophilic so the moisture cannot collect on the glass as droplets or thick lines, instead it spreads out evenly to form a thin layer of water. The advantage of this is that it increases the light transmission through the greenhouse covering, such as glass or plastic film. The light transmission gain that is attainable when there is an even layer of condensation can be up to 9% more than with condensation droplets.
Since the summer of 2015, Mardenkro has been conducting field tests on their new AntiCondens Glas coating. 60 litres of AntiCondens per hectare is needed for optimum results. Therefore, if diluted to 1:15 around 1000 litres of fluid per hectare needs to be sprayed on the inside of the greenhouse covering. The coating is applied by hand in a number of locations. A test has also been conducted into the mechanised application of the coating which was performed using equipment that is usually used for spraying glass with detergents. The optimum spray pressure, nozzle, nozzle stroke, spray wand position and the travel speed were all looked at. It emerged that without many modifications the existing equipment that workers currently work with could be used for optimum application of the coating.
After application, measurements were taken to determine the difference in light transmission between treated and untreated glass. This was done by continuously measuring the PAR transmission over a number of days. By plotting the values onto a graph and comparing the light intensities for each day, a picture of the light transmission differences throughout the day was built up. The daytime light intensity was calculated and used to draw up a comparison. After application of the AntiCondens coating, the increases in light transmission range from 2 to 14%. The fact that these differences are so large could be attributed to factors such as varying levels of contamination on the glazing. Other situations were measured revealing very little or no reduction in light transmission. It is likely that there was no condensation on the glazing during these periods because of substantial ventilation.
It is important that the glass is clean and 100% dry before applying the coating and that the coating is allowed to dry completely before the glass is again exposed to moisture from condensation or other causes. During the coming season, Mardenkro will continue intensive monitoring of the trial sites as well as conducting trials on larger surfaces.
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Loss of light through condensation
Water droplets on the inside of greenhouses due to condensation can cause considerable loss of light.