Monday, 15 October 2012

Greenhouse Design

There is something that we started this spring that I am extremely proud of, and that is our self built greenhouse. From start to finish this greenhouse was designed and built by ourselves (well actually the building would not have gone so smoothly without our very own professional Calum who is a neighbour of ours and very handy to have around. Community building....).

We have spent a lot of time during the last winter to find a good design for a year-round greenhouse and in the end came up with our own design modelled after a greenhouse built by the University of Vermont (I just can't find the link right now. I will put it up when I find it). This design featured a long slanted side and a normal roofed side. We adapted the angle of the sun side (long slant) so that the winter sun more or less penetrates the plastic at a 90º angle. Our winter sun angle is roughly 22º on December 21st. In the end there were some technical difficulties on how to cut angles and nail the whole thing together so the actual angle of the greenhouse is slightly off, but should do the trick anyway.

Greenhouse design and shape are very individual. I like our design as it looks a bit different from your box standard greenhouse or poly-tunnel. It has the architectural flair of modern least I think so. 
The dimensions of our greenhouse are 16x10 feet in total area. The maximum height is 11 feet at the peak. Due to my neighbours experience we decided to build the platform first, then nail together the trusses (we used gang-plates for this) and then slot everything together in place. I initially wanted to build it from the frame up. Due to the final height of the construction I am glad we did it this way. 

The floor is insulated with 2 inch styrofoam plates. This is one of the most important places to insulate. A lot of cold gets in through the floor. The floor itself is 1/2 inch plywood. OSB is not that good since it can't cope with water at all, and there will be some over the floor during everyday use. The whole construction sits on 4x4 treated beams. 

Putting up the trusses after we constructed them on the ground was quite simple and a relatively fast process. I think this way was a lot easier than trying to nail the top together balancing on a step ladder. After everything was put together, we squared the whole building using 2x4 planks to get it ready for the plywood walls.  

After the walls went on the building was really solid. Not even a hurricane would move this now. Well, maybe now, but not when it is filled up with all the thermal mass that will be in it. 

The day we finished the walls was extremely windy. We couldn't put the plastic on the greenhouse without asking for a lot of trouble. So by the time we finally found the weather and the time to finish the job it was an evening during the week, and light was getting dim....


....ran out actually, but nevertheless we got it done. And the next day we saw this...

The grand total at this stage was roughly $800. 

Next post I will describe the steps we have undertaken so far and are still planning for winterising the whole thing and making it warm. In the meantime, please leave a comment on what you think of the design and maybe post some ideas of your own.


  1. Wonderful, welldone! I love it. Just curious though, about the plywood floor. Is not this a high maintenance, soon to be renewed material with moisture etc? I'm in southern Australia where although we get winters commonly down to freezing, overall greenhouses stay quite warm, hence the watering, and used often for propagation, hence humidity. We would make a concrete floor (to capture and recycle water, also thermal mass,) or gravel (drainage, thermal mass, cheaper). How does your situation and climate affect your choice of materials? : ), A.

    1. Hello, sorry to have left replying to your comment so late. Time just flew by!
      When we planned this greenhouse, it was supposed to be a short-term (3-5 years) test of principles. We wanted to make sure that we got the placing and the sun angles right before we made it a permanent structure. Then there's the fact that, in the winter, maintaining high enough temperatures for high humidity would be quite energy-intensive (-20C plus severe wind chill) and in those months we would have been concentrating on things like kale and other winter crops that do not want high humidity anyway. With these considerations, we were prepared to go with a more short-term and cheaper material for the few months that excessive moisture would be a problem. In the end it was a good thing, because we should have set it about 10 feet further to the West. That would have been really frustrating if we had poured a concrete base....
      With your climate requirements, plywood would definitely not be a good option as you clearly know. Besides the concrete and gravel option, there is also the rammed earth option. There have been people who have used these floors in their greenhouses (dammit, cant find the links now. Will post when I do, promise.) in various climates with mixed results. If you have the earth available, or can dig down as part of your greenhouse installation, then the majority of the cost is the machinery rental (Pneumatic Earth Sand Rammer, loads of different kinds of brands, check your local tool rental facilities.) Or, there is the manual tool that amazon sells for about 20 quid here. It depends on your physical and time constraints and how often you would actually need it.
      Using a concrete or a tamped earth floor also gives you the option of placing heating pipes under your floor that are attached to a stove or a rocket mass heater so you can moderate your winter temperatures. But since you say 'overall greenhouses stay quite warm', then this may not need to be a serious consideration for you.
      By the way, if water conservation is as much an issue for you as it is in other parts of Australiia, you could put a French drain-type set-up into a gravel floor. The outlet can be designed to run into a bucket that you can retrieve periodically and re-use the water. A small hole under the outlet (to sit the bucket into) and a twistable pipe elbow (to get it out of the way when you want the bucket) should work. I don't know if you have the room, or the necessity, but it's an idea I just had so if it works for you, let me know how it goes. If not, meh! ;-)
      I would check out if there are examples of tamped/rammed earth greenhouses in your region and if anyone has run into difficulties with the material/humidity combination. It may suit your needs (and your pocket!) just as well as the others, and (I think) makes it much more aesthatically pleasing.
      I hope this (belated!) ramble helped you out. Thanks for reading!
      Have a great day,

  2. This is great, I love this design. So I was wondering if you could explain in some more detail on how you made this and what you used. So I just started working on a ranch about an hour south of LA and was also wondering how well this design would work in the climate here. We are looking into greenhouse designs and just trying to find the most sustainable and cheapest way to build one.