The central goals of all greenhouses remain the same, regardless of the particulars. At their most basic level, greenhouses create a safe, warm place for plants by utilizing solar radiation. Rays shine in through transparent windows and heat is trapped within the building. Warmed air near the soil begins to rise towards the top of the greenhouse, pushing cool air downwards. There, the cooler air is warmed, and the cycle continues. This circular pattern of warming and cooling raises ambient temperature within the greenhouse much faster than it would outside. Air circulation is utilized to ensure that no areas of stagnant air reduce the effectiveness of the turnover.
In moderate climates, warmth from the sun alone may be enough to heat a greenhouse. Thermal batteries or earthen walls can trap and contain the daylight heat to hold the plants over through the cold nights. However, in cooler environments, artificial heat may be required in order to keep temperatures above freezing. A greenhouse built close to a home can be connected to central heating and cooling to accomplish this. However, those located further away from the central home may require some form of onsite heating. Of course, electric and gas options are available, but these present some issues of expense, pollution, and risk. Passive sources of heat, like geothermal batteries, heat sinks, or heat pumps, are an excellent, low-cost option to supplement your greenhouse’s heat system.
Like in most practices, too much heat can be a concern. In order to keep plants from overheating, heat control can be installed in the form of an automated ventilation system, or by merely opening and closing windows during the day. Circulating air not only maintains a stable temperature, but it also cycles the carbon dioxide necessary for plant growth.
The Perfect Placement
Siting your Greenhouse
Where your greenhouse ultimately lives will have large impacts on the long-term health and effectiveness of your plants and design. A larger greenhouse will typically need to be freestanding, with its own independent foundation and structure. A smaller design can be nestled next to a porch or breezeway against your home. The closer your greenhouse is to a preexisting structure, the more likely it is that you’ll have access to water and electric hook-ups. However, a building on its own will allow sunlight to permeate from more angles, and customized, specific specifications are easier to add.
Things to consider while choosing the perfect place for your greenhouse:
- First and foremost: what are you intending to grow? How much are you expecting to house at any one time? Larger, taller plants will need more room to grow outwards and upwards. Certain plants might like warmer, more humid temperatures, or may be particularly sensitive to heat. Once you know what the ideal environment looks like for your intended crop, it’s much easier to make decisions about what’s best for your project.
- Secondly, what are your options? What challenges or opportunities does your land offer? A sloped hill will need additional construction in order to create a level foundation. However, an extended vertical wall on a south-eastern slope could provide a huge opportunity for additional light throughout the year. How easily can sunlight access your land? Are there trees or structures that block light during different times of day? Some shade may be beneficial if things tend to get too warm during the peak of summer.
- How do you intend to power your greenhouse and water your plants? A greenhouse close enough to a preexisting property can likely be connected to the original hook-ups. A considerable distance can be covered with the assistance of an electrician or the laying of additional pipes. However, it may be more economical in some cases to simply power the greenhouse on its own. Small, individual solar panels are becoming more and more affordable, and can provide enough energy to power a small ventilation or irrigation system. Water can be collected from rainwater and recycled.
- Thermal batteries are a great, low-cost way to add additional heat to a greenhouse. While the sun can warm the greenhouse during the day, dropping temperatures are most concerning during cold nights, especially in the winter. A thermal battery is any material that absorbs heat from the sun during the day, storing it as passive energy. As the temperatures in the greenhouse drop, heat is released from the batteries, preventing the greenhouse from becoming too cold. Thermal batteries can come as heat sinks, black water barrels, or even an exposed earthen or brick wall.
- Geothermal heating systems are growing in popularity, especially in private and DIY circles. Geothermal systems harness the natural heat of the earth, found under just a few feet of surface soil. This heat is collected in various different ways. Sunken greenhouses provide the foundation of the greenhouse with exposure to open soil. As things cool down at night, the heat from the soil is absorbed into the air, warming the entire greenhouse. Geothermal heat can also be accessed via a heat pump system. Air is pushed through underground passages. If the air is cooler than the soil, it absorbs its energy and heats up before being pushed back into the greenhouse.
