In Search of a Low-Cost Greenhouse


| 3/6/2009 5:11:27 PM


Tags: greenhouse, thermal mass greenhouse,

Lori DunnA greenhouse has always been on my list. You know the list I speak of, everyone has one. It is the mental list that we all keep of things we would like to have someday. That “someday” came for me when my husband suggested we go ahead and put up a greenhouse.

I was extremely excited with the thought of being able to get a jumpstart on our gardening, and experimenting with different plants and flowers, but I also knew we needed to be economical about it. We couldn’t afford to incur a large expense in the construction of the greenhouse, or in the heating of it later. This sent me on the path of the internet highway to do some research. As you can imagine, I found lots of information on all kinds of greenhouses. There is everything from prefabricated kits that come with everything you need to instructions on building your own greenhouse out of many different materials. What I found that caught my attention the most was information on a thermal mass greenhouse. This type of greenhouse uses energy from the sun to store heat, and then release that heat at night when it is needed. Energy from the sun = free, just the right price!

According to the information I found, many things can be used for the “mass” to collect the heat and energy from the sun. Anything that retains heat would probably work. Some of the items listed included soil in raised beds, wood, block or brick foundations, concrete, or even the floor of the greenhouse. But the most effective and least expensive thermal mass is water! Again, water = free! It didn’t take much for me to decide that a thermal mass greenhouse was the way to go for us. But how would we store the large amounts of water that would be needed? The recommended amount was about 2-3 gallons of water per square foot. Apparently, a common practice is to store the water in containers along the back wall of the greenhouse, or use 55 gallon drums filled with water to support the benches in the greenhouse. In one instance I read about, someone had used the method of water in barrels under their benches. They said it kept the temperatures in the greenhouse above freezing except on the very coldest nights. On those nights, they used a very small space heater as a supplement to keep the temperatures up.

My husband and I have a great setup to use this type of greenhouse. Our basement wall is underground on three sides. The fourth side is exposed and faces in a southeastern direction. We came up with a plan to use the face of the exposed basement wall as the back wall of our greenhouse. It would face the right way to capture the heat from the sun. The block wall in the back could store some of the sun’s energy, and we would also use barrels of water on both sides of the greenhouse with planking across the tops of the barrels as bench tops. The wall we wanted to put the greenhouse against has a window into the basement. I thought we could also use this to our advantage. We heat our home with a woodstove in our basement. This keeps our basement nice and warm too. If we built the greenhouse around that window, then on the coldest nights, we could open the window and use a small fan to pull some of the heat from the basement into the greenhouse as a supplemental heating source. I was excited to test all this and see if it would work!

Building a thermal mass greenhouse

We began construction in March. We decided to make the greenhouse 8 feet deep by 24 feet long. My husband was the brains behind all the measurements. He came up with all the figures and sizes for making the correct cuts, and attaching the greenhouse to our basement wall. With some help from our son, my greenhouse soon started to take shape. It wasn’t long till we had a frame in place.

Loisj
8/17/2015 10:54:37 AM

Actually, once you get the plastic issues with the chickens addressed - they are actually great to have in the greenhouse due to the high BTU output they give out. Your greenhouse sounds like a smaller version of the one that Anna Edey built on Martha's Vineyard in the 90's. She was a great visionary and practitioner of sustainable living and builing. Her book "Solviva" is well worth a read!! I wouldn't be without it. Although, it's been a lot of years since she began, and advancements have been made - her core principles remain solid. You can check it out on solviva.com as well.


Sergiy Polovenko
4/16/2012 11:02:54 AM

It is better if you put your greenhouse to the south facing wall. Itwont give you much from the north side


Lori
4/6/2009 12:52:39 PM

Hello Nebraska Dave! Ahhh yes, seasonal work. My dad has a wood shop in which he now makes his living.( We used to operate a small sawmill till we had to shut down due to the economy.) During this time of year, my dad makes all kinds of wooden flower planters that get sold to greenhouses all over this state, and a few others. These early spring months when the growing season is just getting under way, and Easter and Mother's Day are just around the corner are very busy for him. Very much the same for orchard growers too, when the fruits start to ripen and need picked. Lots of people are needed for long hours to get the fruit picked, but when it's all picked, everything sort of comes to a halt. And oh what fun to try and put plastic on a greenhouse in windy conditions! I didn't know it was the responsibility of the plant supplier to erect shelter for the plants at these stores! I always assumed the store itself did that. My own greenhouse plants are coming along nicely. I have Asters, Snapdragons, Petunias, Delphinium, Zinnias, Sunflowers, Nasturium, pansies, Parsley, Tomatoes, zucchini,and cucumbers all through the ground and I am still waiting on Peppers, Watermelon, Heliotrope, Rudbeckia, and Jacob's Ladder to germinate. It is so much fun to check the progress every day to see how things are coming along and what may have poked it's head through the ground during the overnight!





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