How to Design a Year-Round Solar Greenhouse

| 2/11/2015 10:14:00 AM

Tags: greenhouse, solar greenhouse, passive solar greenhouse, Lindsey Schiller,

Attached Solar Greenhouse Orientation

What is a solar greenhouse? Don’t all greenhouses use the sun? Well yes, but a solar greenhouse uses the sun’s energy not only for growing, but also to provide all of the greenhouse’s heating needs. In contrast to traditional all-glass or all-plastic greenhouses, which often rely on fossil fuels to grow year-round, solar greenhouses can create warm year-round growing environments using only the power of the sun, natural materials and energy-efficient design. As a result, they can grow much more --citrus, avocados, fruiting tomatoes - year-round using less energy, water and resources.

Bananas in a Solar Greenhouse 

 Here are the seven basic elements of solar greenhouse design. By following these, you can create a naturally abundant, self-sufficient growing oasis, allowing you to grow more with less energy and hassle. For more on designing your own solar greenhouse, see The Year-Round Solar Greenhouse: How to design and build a net-zero-energy greenhouse, which includes how-to info as well as many case studies for tailoring your structure to any climate.

1. Orient the Greenhouse Toward the Sun (the South)

This is where solar greenhouse design begins: the sun. The sun is not only your source of light for growth in the greenhouse, but your source of heat. Thus, if growing year-round in cold climates, you need to capture enough solar energy through your glazing to heat the greenhouse. Glazing is just a word for transparent materials, such as glass or clear rigid plastics. All these light-capturing materials should face where light is coming in: the South if you are in the Northern hemisphere (*For the rest of this article we’ll assume a location in the Northern hemisphere). The sun moves higher and lower throughout the year, but it is always South. A very small percentage of light comes directly from the North, and thus these sides are better off insulated.

2. Insulate the North and Everywhere Else

Solar greenhouse design depends not just on capturing enough solar energy, but trapping it in order to keep the greenhouse warm enough during cold periods.

11/2/2017 4:18:41 PM

About concerns over condensate on a house wall, that forms one wall of the added greenhouse: People have been adding a "greenhouse" or warming space, on the south sides of their houses, for ages. Never heard of anyone complain about condensate happening on or in the house wall. Maybe ventilation is a Thing? As for insulating the ground in a greenhouse?!? NOT! Not even for deep frost lines. Why? Because the mean-temp of earth is about 55F., about 4' down into the earth. When you park a greenhouse on top, there will be some cold encroachment where the walls meet the ground....that is where insulation is needed, vertically, below-grade....unless you earth-berm the walls 2' to 4' high above grade, and about 2' to 4' thick from the greenhouse walls. There are people in seriously cold climates, excavating 6' or more into the ground, laying the properly calculated length of 4" tubing to accommodate the cubic feet of greenhouse interior, run the tubing to manifold for intake and outlets, then back-fill half the depth of the excavation, so that the greenhouse is well-bermed, as well as recirculating the earth's mean temp, to keep the greenhouse from freezing....from the one's I've seen, those are working extremely well, with no, or little added the upper Midwestern States, where winters can drop to -50F. IF you instead isolate the greenhouse from the ground, you will have huge heating bills just for the greenhouse. Bottom line: USE the earth's mean temp to your advantage!

6/2/2016 10:21:14 AM

christopher, The frost depth where I live is 40" deep, do I want that frozen ground encroaching under the walls of my greenhouse? NO. That is why we insulate the foundation of the greenhouse to keep the frozen ground from touching the growing soil. Not insulating the bottom allows the ground heat to percolate up.

3/24/2016 3:14:53 AM

Actually, insulating the greenhouse will prohibit the thermal mass exchange in the greenhouse. It will cause your external temperature to be what it is above the earth instead of allowing the earth to regulate the greenhouse temperature during the winter. DO NOT use insulation. It work hundreds of years ago without it. And there's a reason for it!!

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