Monday, April 27, 2009

Greenhouse construction update

Building this greenhouse was actually the motivation for me to start this blog. Today, I am finally getting around to an update of the progress of its construction- mainly with some pictures.
I have written a few posts about the greenhouse; a general description of the green house is here, plans for the greenhouse can be seen here, and my plan for heating the greenhouse is here.

In general, I am constructing this greenhouse out of recycled materials, and I have designed it to be energy efficient with the site and our latitude in mind. Our plan is to grow hardy vegetables in the greenhouse all year long, and use to it start plants and extend the growing season by a couple of months for warm weather vegetables (read: hot peppers).

It has been a really fun project, learning about greenhouses, designing the greenhouse and accumulating all the pieces. Since it is almost all made from recycled or reused materials, accumulating the parts has taken a while

Site preparation was slow- I had to remove and pot up all the plants that were in the greenhouse footprint, including 50+ bitterroots. This was compounded by my eagerness to begin the project this spring and the reality of having to wait for many species to come up.All these potted plants filled up our nursery and even filled up space in all our raised beds. We will grow these plants for another week, and transplant them to our front yard- where we started a little makeover project- more on this in another post.
Also, we will probably donate some of these plants to the Clark Fork Chapter of the Montana Native Plant Society's annual native plant sale- at the Missoula Farmer's Market on May 16th. Depending on the quantity and diversity of plants he have left over, we might even have a plant sale of our own at the Missoula Farmers Market in late May or early June. Below, all the plants are removed from the greenhouse area.

Initial grading and 8" compacted gravel base, onto which the treated 4x6 foundation was installed, and secured to the ground with lengths of 36" re-bar.

After a lot of deliberation, and a lot of advice, I finally decided to use just a compacted gravel base and pressure treated wood foundation for the greenhouse. I considered almost every iteration of building a foundation. My friend Barry finally convinced to me to build it this way (if it goes wrong, it is his fault). Actually Barry is a fantastic carpenter and builder, so I totally trust him.
Below is the compost furnace before going into the ground. It is a 30" x30" x 36" deep box, insulated from with ground with 2" rigid insulation. I installed it on top of 4" of cobble/ gravel for drainage. You can read about the compost furnace here- if it works it will heat the greenhouse in the winter. If it does not work, we will have great storage in the greenhouse- either as a root cellar or as my wife puts it, a place to store sweaters in the summer.

Below is the compost furnace installed, notice the 2" rigid insulation over the part of the greenhouse that will be covered with brick flooring.
On top of the insulation I laid down landscape fabric and 4" of compacted gravel (see below). The insulation should keep the floor warm and restrict heat loss to the ground. Below, you can see the greenhouse floor and the separated part to my left is for a raised bed (on the south facing side of the greenhouse).

The next step is to lay down 1" of sand and install the brick flooring. The brick is 100-year old salvaged Missoula brick. It should make a really nice floor.


  1. That looks like it is coming along great! I have tons of materials to build one as well but would like to find salvaged lumber. I have old windows and doors, lots of em. Love the bricks too. I would love to find more for the edging of my beds.

  2. Hi Dave- you two have been very busy. I can't wait to see how more of this project comes along. It is obvious a lot of planning has gone into it already. The compost furnace intrigues me greatly. Please keep posting about the progress.

  3. Wow! I'm so impressed! Can't wait to see if your passive heating works.

  4. What a great project. I like the plans. You've already put so much work into this. It's going to be a wonderful addition to your garden. Well done!

  5. I'll be interested to see what the compost furnace does. My compost heap is really quite hot in summer when it gets some sun, but got quite cool this winter when it did not. I noticed because I'd moved it to a shadier spot. But I gather you'll have some sun, so I'm really hoping all will be well. Great project!

  6. I hope to see the green house when is finished. Great energy and a very good effort!Live the green!!!!!!!

  7. Thanks for the link from GW!

    Most of the questions were answered.

    One last question: Is there any insulation under the in-ground section of the greenhouse? There will probably be a fairly large amount of heat transfer along that joint.

    Other than that: WOW! Way to go! This is almost everything that I have been thinking about doing myself. (I'm still in full research mode!)

  8. Wow…wonderful. I love green home. I like your all tips. Thanks for sharing it.