Greenhouses allow us to cultivate in climates that are variable in temperature, protect from the wind and provide a cleaner space free of pathogens and predatory insects. While the insulation of the greenhouse covering will raise the temperature in even mild to chilly weather, some windy and cold over cast days negate the insulation and advantages of greenhouse growing.
Some utilize basic gas burners to heat air on cold days, which works but the drafts and gaps in a greenhouse structure can quickly lose that heated air and drive up costs. Heated air can chill very quickly, which is why we use wet walls in dry and hot conditions to use evaporating water droplets to chill air quickly. The heated air method can also be counterproductive by its tendency to rise escape via vents in the roof and leave the lowest areas of your greenhouse colder than desired.
A more efficient method is utilized wherein a network of small water pipes are embedded in the concrete, covering the entire floor in a looping zig zagging pattern. These pipes are connected to a water boiler and a pump to send the water coursing through the pipes in the floor. The advantages of the underground heated water pipes are due to the thermal inertia of the concrete and the water itself. This means it takes a lot more energy to heat both water and concrete, but smaller amounts of energy to keep it at the temperature you as a cultivator decide. The even constant heating will ensure a proper climate year-round.
Heating the floor also takes advantage of the nature of hot air rising aiding air mixing. The rising heat also raises your irrigation water to a slightly higher temperature a. Non-heated concrete floors can also add a cold layer close to the root zone and negatively affecting the plants metabolism and even root shock. Heated floors can help you achieve the best temperature for your plants, contributing to even growth and ideal metabolism and uptake of nutrients.
One of the disadvantages of a greenhouse at certain times of the year is when the dew point is high enough for water to condensate out of the air and falls onto your plants, creating conditions for molds, mildews and other ailments, a heated floor can help your greenhouse to not fall below that dew point and save you on crop losses, or energy lost with dehumidifiers or even drastic anti-fungal sprays. This same mechanism can prevent condensate that attaches to the poly coating, lowering the light passing through and thereby lowering the potential growth of your plants.
The even heating provided by the in floor radiant heating can also allow you to use a baffle system when drawing in colder outside air, allowing it to heat up and preventing cold spots when ventilating in the winter.
Other advantages of a floor heating system are larger areas for your plants to cover, lowering the number of walkways and allowing for more canopy. Greenhouses built without in floor piping sometimes will add heating pipes to their growing tables to provide ideal root zone temperature, these pipes will degrade over time and leak and may need replacing, while the piping under eh concrete with last as long as you operate the greenhouse.
Working with your greenhouse designer to undertake constructing a proper greenhouse that lasts and is energy efficient takes time and effort. While the in-floor system may raise the initial cost, the saving your green house will gain year over year will ensure your business stays as healthy as your plants!
by Damon Lippert