Getting your Greenhouse Groove on

By Kathleen Miller

Gaia’s Farm and Gardens

Getting your Greenhouse Groove on

Gaia (Mother Earth) Grows is a sustainable living, gardening, and farming column.

Sustainable living, gardening and farming are based on an understanding of ecosystems, the study of relationships between organisms and their environment.  It has been defined as an integrated system of plant and animal production practices that will last over time. Having a harmonious relationship with Gaia (Mother Earth) provides food for people, enhances the natural environment upon which the community depends, makes efficient use of resources and integrates natural cycles that sustain economic viability as well as enhances the quality of life for the community as a whole.

Sustainable Greenhouses for Northern Colorado

The feeling a greenhouse gives you is the “greenhouse groove” or “greenhouse Zen.”  It is an ideal place for growing a wide variety of fruit and vegetables throughout the year, reducing your household’s reliance on air-freighted, high carbon supermarket food and providing a quiet space for meditation, yoga or just relaxing.

A sustainable greenhouse is designed to hold large numbers of plants, including ones of considerable size. In colder parts of the United States, greenhouses are equipped with heating devices so that even tender crops such as tomatoes and peppers can be grown in the coldest months.  

Your greenhouse should face south to get maximum winter sunlight and may need shade to protect the plants on hot, sunny days in the summer. If you are not able to locate your greenhouse in an area with southern exposure, the next best choice is east because plants benefit from the morning sunlight. A western exposure also is acceptable, but plants do not do well in a north-facing location.

Greenhouses can be bought or built in a variety of sizes and designs, from a geodesic dome to a simple lean-to against your home. Greenhouse manufacturers sell complete kits that the homeowner can assemble, but for economic and personal reasons, many gardeners prefer to build their own from scratch.

I have a freestanding Quonset-shaped greenhouse that is simple, economical to operate, and much of the materials besides that greenhouse plastic were purchased locally or recycled. I use this greenhouse to start seedlings in the winter months to be ready to plant outside in spring. I am in the process of designing a lean-to greenhouse that will be attached to my home and that can use the heat from my house while providing heat to my home in the colder months. If your greenhouse is attached to your home, a concrete foundation should be put in that extends below the frost line because of the freezing temperatures in Northern Colorado. Otherwise, frost heaving can distort the greenhouse form and cause glass breakage, structural damage and even damage to your home.

If it is a freestanding greenhouse it can rest directly on the ground or on a base of 2-inch-thick patio blocks or 8-inch thick concrete blocks. The sills should be of rot-resistant redwood or else treated with wood preservative, especially if the greenhouse rests on patio blocks or on the ground. In windy areas, the greenhouse should be secured to a permanent foundation or else be anchored to the ground.

Greenhouses require electricity, so your design should accommodate electrical wiring and connections. Many greenhouse suppliers offer plug-and-play electrical systems to streamline the process. If you don’t feel confident that your design will adequately meet your requirements, consulting with a manufacturer may be a better option for first-time greenhouse builders.

Heating costs in greenhouses can account for 60-70% of all energy consumption.  For more eco-conscious people, consider more sustainable energy solutions. If space allows, consider implementing utility-grade solar arrays as a primary energy source. Modern solar energy solutions can capture up to 2,500 terawatts of accessible power at an affordable rate. Solar fans are also available at many greenhouse supply companies allowing you to cool your greenhouse more sustainably in the summer months.

A small wind turbine connected to your sustainable greenhouse can provide the electricity to power energy-efficient bulbs that can provide warmth or electricity to your crops over winter, increasing your yields and the number of fruits, vegetables or flowers that you are able to grow.

Gaia’s Tips on Creating a Sustainable Greenhouse

• Insulate Greenhouse Walls

If you have a freestanding greenhouse it is wise to insulate the north wall. If you live in a sunny area, you may also consider insulating the east and/or west walls. Start with the side receiving the winter prevailing winds. Some people retrofit an existing greenhouse for winter by using a foil backed “bubble wrap” type of material on the north, east and west walls and north portion of the roof. This material is commonly sold as “Reflectix” insulation. It is found in hardware stores and sold by greenhouse supply catalogs.

• Insulate the Foundation

The foundation of your greenhouse should not be a heat sink. If the ground is freezing cold outside, then it will conduct directly through your foundation, making it cold inside. The solution is to insulate your foundation’s outside perimeter with Styrofoam board, usually 1 to 2 inches thick. This insulation should be placed vertically and extend down to a minimum of 1 foot. If you live in gardening zone 4 or less, consider even deeper foundation insulation. Set the foam-board insulation against the outside of your greenhouse foundation or if no foundation place the vertical insulation in a trench around your greenhouse perimeter.

• Use Double or triple glazing

“Glazing” is the term for the greenhouse skin which the light shines through. This is a must for an energy-efficient greenhouse and essential for any sustainable greenhouse. Glazing should be tightly sealed and free of dust or dirt. Glass can be used but double or triple greenhouse glazing is the more sustainable way to go.

• Winterize Your Greenhouse

Vents and doors must be weather-stripped, and cracks must be caulked and checked for wear every year. I usually do an inspection for any potential air leaks in the fall before the cold weather comes. Plug all leaks with caulk, foam or some other form of insulation.

• Use Thermal Storage

This is the use of rock, water or other dense thermal mass material in which to store the incoming solar heat. Water is by far the most efficient and easiest material to use. In your sustainable greenhouse, a cheap and efficient way of storing water is in black 55-gallon oil drums. Fill with water and place along the north wall to store the sun’s heat. For smaller greenhouses look for the 30-gallon metal drums. Many owners of heated greenhouses also have installed containers of water to increase heating efficiency.

• Side Wall Curtain Ventilation and Solar Fans

Roll-up greenhouse sides — sometimes called sidewall curtains — help to maximize natural ventilation by allowing heat within the structure to escape while also allowing fresh outside air into the greenhouse. This passive form of ventilation is very helpful for controlling greenhouse humidity and preventing the formation of condensation which can lead to plant disease. Roll-up curtain setups can be highly customized to suit your unique greenhouse and growing needs. Hand and crank assemblies, roll-up door assemblies, aluminum poly latches, clips, conduit and hardware is all available at greenhouse supply companies and your local hardware store.

• Build a Rocket Stove Mass Heater

A rocket mass heater is a clean-burning, high-performance burner usually put together using a majority of recycled and/or natural materials, such as cob. Rocket mass heaters, use small amounts of wood burned efficiently at high temperatures to heat up a thermal mass, which then slowly radiates the heat outward for many hours.  This is a great way to extend the season, warming the greenhouse in the winter months and it is a great place to warm your seedlings because they germinate faster with bottom heat.