Greenhouses create a safe, warm place for your plants by utilizing solar radiation. Rays shine in through windows and heat is trapped within the building. Warmer air near the soil begins to rise towards the top of the greenhouse, which then pushes 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 remain.
In moderate climates, warmth from solar energy 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 some places or seasons, artificial heat may be required in order to keep temperatures above freezing. Energy can also be used to provide enough heat/humidity to maintain ideal, unseasonal temperatures throughout the winter. A greenhouse built close to a connected building can be connected to central heating and cooling to accomplish this. However, those located further away from connections may require some form of onsite heating.
Typically, on a homestead, you’ll primarily be growing food for you and your family to eat. This kind of farming is called subsistence agriculture and has existed for centuries. It’s recommended that each member you intend to feed be delegated between 5 and 20 full plants per year. This of course depends on how much you intend to feed the individual, and what kind of plant we’re talking about. For example, while one person may only need one pumpkin to satisfy them for a year, you may need closer to 20 or 30 potato plants since it’s such a high-use vegetable.
Where you place your greenhouse on your homestead is a big decision. 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, a barn, or another kind of building.
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. These are also easier to customize and make fit specific specifications.
When deciding where and how your greenhouse should look, it’s important to consider: 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.
What challenges or opportunities does your land offer? A sloped hill will need additional construction in order to create a level foundation. But: An extended vertical wall on a south-eastern slope could provide a huge opportunity for additional light throughout the year, especially in the wintertime.
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? Small, individual solar panels are becoming more and more affordable as technology advances. These 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. Dark, dense materials are particularly good at absorbing this 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 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.
