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.

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!!

12/15/2015 4:34:12 AM

wow, I have never seen a underground green house before that looks great! If I had one of those I dont think id need some many I would like a change from my generic green house, one of those is definitely something to look in to this summer!

3/12/2015 7:39:38 AM

A great article with lots of technical details! But it really can distract the reader's attention when authors misuse the word "loose" when it should be "lose" ; why is this so common recently?

3/6/2015 4:47:34 PM

Suzi, I agree with Scott -- if the shorter axis of the greenhouse does not face mostly South you will not have enough light in the winter and shoulder months. Furthermore, having a lot of glazing (glass or plastic) face west is dangerous in most climates: it can easily overheat the greenhouse in the afternoon.

2/14/2015 11:58:53 AM

From all the information I've gathered and my own observations having the long axis of the structure going east-west (long side facing due south) is critical and the results will be unsatisfactory if it's off by too much.

2/14/2015 10:28:49 AM

would it make sense to add this on to an existing building if the length of the greenhouse faces west? south is open but would be the short section of the greenhouse.

2/13/2015 8:19:20 AM

'how would you avoid mold in the shared walls? " That's a question that's been on my mind lately too since I'm building a passive solar house and will be adding a greenhouse. One factor to keep in mind is that if the attached structure is heated this will usually be one of warmest surfaces in the greenhouse. Most condensation will occur on the windows and other cooler surfaces. Just keep this moisture from running into the wall. I'm sure there's more to it than that so I hope others with more experience can add to this

2/12/2015 11:18:53 AM

With regards to attached greenhouses, how would you avoid mold in the shared walls? Thanks!

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