How to Heat a Greenhouse Without Electricity

Summary

In this video, Gardener Scott addresses the common myth that greenhouses stay warm with little effort, especially in cold regions. He explains the importance of thermal mass for retaining heat in unheated greenhouses and demonstrates how to calculate the amount of water needed for this purpose. Scott uses concrete pavers, gravel, and water-filled containers to increase thermal mass, aiming for a 260-gallon target. He also adds Styrofoam insulation to retain heat and reflects on the greenhouse's improved nighttime temperatures, promising a future analysis of its impact on both heating and cooling.

Takeaways

• 🌡️ Greenhouses in cold regions like Colorado can lose heat at night despite warming up during the day.
• 🏡 Insulation in a greenhouse helps retain heat but can also trap cold without proper measures.
• 🔥 Thermal mass is crucial for retaining heat in unheated greenhouses, with materials like concrete, rock, and water being effective.
• 💧 Water is the most efficient thermal mass for warming an unheated greenhouse due to its heat absorption and release capabilities.
• 📏 Determining the amount of water needed involves calculating the greenhouse's square footage and adjusting based on regional climate.
• 🏞️ The video suggests a formula for calculating water volume based on sun exposure or floor area, multiplied by a factor related to climate harshness.
• 📦 The use of 55-gallon drums, totes, and other containers is practical for storing water to serve as thermal mass.
• 🎨 Painting containers black enhances their heat absorption and retention, aiding in the greenhouse's thermal regulation.
• 🌡️ The addition of Styrofoam insulation and reflective surfaces helps to minimize heat loss and radiate warmth back into the growing area.
• 🌡️ The video documents a noticeable increase in nighttime temperatures, indicating the effectiveness of the thermal mass strategy.
• 🌤️ The potential dual benefit of thermal mass is highlighted, suggesting it can also help moderate temperatures during hot summer days.

Q & A

Why do greenhouses lose heat at night even if they get hot during the day?

Greenhouses can lose heat at night because the insulation that helps retain heat during the day can also hold in the cold when it gets cold outside. Without supplemental heating, the heat can be easily lost.

What is thermal mass and how does it relate to greenhouse heating?

Thermal mass is the ability of a material to absorb, retain, and then release heat. In the context of a greenhouse, materials with high thermal mass, like water, can help retain heat and keep the greenhouse warm.

Why is water considered the most efficient thermal mass for an unheated greenhouse?

Water is the most efficient thermal mass for an unheated greenhouse because it has a high specific heat capacity, meaning it can absorb and store a lot of heat before it starts to increase in temperature.

How can one determine the amount of water needed in a greenhouse for thermal mass?

The amount of water needed can be determined by calculating the square footage of the greenhouse's floor or the surface area exposed to sunlight, then multiplying it by a factor based on the region's climate and winter length.

What are the target ranges for water storage in the greenhouse mentioned in the script?

The target ranges for water storage in the greenhouse are between 260 gallons (using the lower factor) and 390 gallons (using the higher factor).

How does the use of concrete pavers and gravel contribute to thermal mass in a greenhouse?

Concrete pavers and gravel contribute to thermal mass because they can absorb, retain, and release heat, helping to maintain a warmer temperature inside the greenhouse.

What is the role of Styrofoam insulation on the north side of the greenhouse?

The Styrofoam insulation helps to reduce heat loss by providing an extra layer of protection against the cold. It also has a reflective surface that can help radiate heat back towards the plants.

How does the thermal mass affect the greenhouse's temperature during the day and night?

During the day, the thermal mass absorbs heat from the sun, preventing the greenhouse from overheating. At night, it releases the stored heat, keeping the greenhouse warmer than the outside air temperature.

What other considerations are there when determining the amount of water needed for thermal mass?

Other considerations include the presence of other thermal mass materials like concrete or gravel, how much the greenhouse is used during the coldest months, and the desired temperature range.

What are some practical ways to store water in a greenhouse for thermal mass?

Practical ways to store water include using 55-gallon drums, 27-gallon totes, gallon jugs, and even repurposed containers like four-gallon cake frosting containers, which can be painted black to absorb and hold heat.

What is the expected outcome of using thermal mass in the greenhouse as described in the script?

The expected outcome is that the greenhouse will maintain a warmer temperature at night compared to the outside air, and potentially help moderate temperatures during hot summer days by absorbing excess heat.