You must design for that load.
I also have concerns with the roof, I don't know if it will hold up...
Are they insulated glass of just plate glass?
Yes, the windows and their dimension are the same as the real ones I have.
Excellent, as long as you have a plan for the space you won't be caught off guard by no having enough space.
I don't but it's more than enough to what I planed. I will still have some space if I want to add something.
I'm not sure what you mean with wall truss.
No more than 600 mm on center.
I'm not familiar with the expression and googling it didn't help much. I still don't know the price of the wood but I'm thinking I can reduce the cost by reducing the number of vertical boards. If anyone know how wide can I space the boards in order to fill them with slip straw I would appreciate.
You will then just have the same work in a different way, nothing really changes. You still will have to deal with roof loads, you still will have to deal with frame work for the window. This is why many folks opt for the "timber frame" or "post and beam" approach, then create the thermal mass afterward. Your design is o.k. but by trying to avoid the timber framing, you just made work someplace else, you really didn't make much easier, just different.
My motivation is going down, I'm felling this isn't doable... I started considering using straw bales instead, what do you think about it?
The window have to sit in a structural frame of some type, wood, steel, stone, and it should be a minimum of 450 mm off of grade. very well flashed to drain water, or you will loose the frame work to moisture damage in just a few seasons. You could build something that sits closer to grade, but I'm afraid that design would be in stone, and that is beyond the tools you have and your skill sets at this time.
1º- Because it didn't need to be so tall, I decided to take out the wood that was supporting the windows. The question it raises is if there's any problem if the frames are directly touching the foundations, or embedded in them. Illustration can be found on the greenhouse located in the origin.
I know you have chosen to not timber frame, but you must frame the structure in something, especially the windows. The window must be framed, they also must be protected from the weight of the roof, and they must be flashed to drain water or any wooded frame work will quickly rot from moisture damage.
2º- If you look at the bottom of the window frames you'll see that there isn't anything supporting the glass. The glass is very heavy so I'm not sure what is the best option to solve this.
If it is not treated with Borates it will become a mess of "wool moths" very quick. It also will be heavy enough to still require a frame work more substantial than what you have.
I'm also considering using wool instead of light straw on the roof. This would make it lighter and would solve the problems with the excessive load.
What do you mean with "off grade" and "well flashed"?
About the frame, I'm just trying to use the less wood possible.
with an appropriately sized wooden frame, as steel and stone are outside the scope of the project. That is why I suggested a timber frame in the very beginning. You have a lot of wood in the structure now, it just is in a different configuration.
The back wall doesn't have poles or beams but it has 11 pieces of wood that will help support the roof weight. How do you suggest I should do to support the roof weight on the front wall (glass wall)?
Yes, that's part of the challenge, and then the framework is the other. I have facilitated frames that sat only maybe 50 mm off of finished grade. The frame was a mix of stone and timbers made of cedar wood. With the correct design and material you could even have the glass on grade, but that is much more advanced design.
Jay, about the grade, I'm confused because I see a lot of industrial greenhouses with the glass at grade level. This glass is at 90 degrees with the floor and mine isn't so I'm guessing that's the problem, right?
With out seeing the actual insulated glass in it's frame work it would be difficult for me to completely asses this. I could say this. If the windows you have are design as skylights, then they many have adequate flashing and protection from the elements. If they have been design for a vertical walls, they are doomed to have water damage unless properly flashed and protected. In many cases, such as you are building, the water must run off and out of the window assembly. If you seal the bottom in the wrong way, you will trap water there because it will not be able to drain away. Try and find some links on the internet that show window details and tell me what you learn.
About the flashing, if you see the sketch you'll see that the glass is protected by the wood frame except on the bottom. The guys that made the frames told that if they framed the glass completely there would be water infiltration on the bottom. I asked them if it was OK to put silicon on the side of the glass, where it rests on the frame, but they said that I shouldn't do it. I don't understand why. In my mind it would only create an extra protection against the water...
Good concept, and I do remember that, but your design is becoming more problematic, as it grows in complexity with the different systems it will rely on to function. Why build one building on top of another if you can build them as an integrated system.
I didn't include eaves in the sketch but, like we talked before, I was thinking about doing a "second roof" on top of the first one. It would be spaced to let air flow and bigger in order to prevent rain coming from the sides. This could use independent supports to avoid over-loading the weight of the structure.
That can work for the walls to a point but then it must function as a support for a very heavy roof. When you are thinking and designing anything, remember that the system as a whole must work in concert with the other components, change one and others change or fail because of it.
I don't know how to use light straw in another way. Everything I've seen/read about it shows the light straw compressed between two wood boards. Being so, I might as well use this wood to double function and serve as skeleton for the structure.
I know what I am about to write may seem discouraging, but I don't want to give you poor guidance either. If you had a good design finished, all the materials reading to go, and the tools/manpower to do the work, you will just get this project done in three months if you start tomorrow. I am saying this, not to discourage, but to be honest. If you think you will come back to this location. I would advice to make your goal, finish a good working design, finish the foundation, and material collection, so someone can move forward, or wait til your return to do the rest of the work. Rushing, especially on your first build, does not often give good results.
About the budget, I already explained my situation. I don't have a fixed budget because I'm doing this as a volunteer on a farm and the farm owner is the one deciding what is reasonable to spend.
I still don't know when I'm leaving but I still have, at least, 3 more months here. Of course I want to finish it before because my main interest is not the building but what is going inside.
Ah yes, a very common misconception. "If it is small it must be easier," as you are learning, this is far from the truth. You still have all the elements of large architecture, then throw in the burden of it being a Green House, and you have a entirely new set of additional challenges with moisture, plus you have added "supper insulated" into it. If you have been building for 10 to 20 years, these things would not seem so challenging, but for a beginner...that's a lot of work.
Personally, I believe that I the problems can be solved but I would like to ear your opinion. I'm having a hard time understanding why does a small construction like this one needs so careful planing. I tough that the size would allow me to build it without going into to the details of construction.
Good, put in the foundation to the specs of you CAD drawing. Can you post photos of the site that is ready for concrete?
Foundation I was thinking concrete. I already made a ditch on the ground with the area of the greenhouse. I still don't have the timber or the concrete but I can take care of that this week.
Yes, that about correct.
1 Space the windows from grade level
2 Find a way to secure the glass in the frame
3 Seal the glass on the window frame
4 Include eaves
5 Include door
6 Add more structural strength
It is called the "splash effect, and the way you have your frame designed you need to be this high because of it.
But why does it have to be 450 mm from the grade? I understand that sitting directly on the foundation could create problems but, the way I see it, there's no need to make it go 450 mm apart. Wouldn't it be enough to use some wood beams and create a place for the windows to rest?
Lets deal with this a little latter. I don't know if you need metal or not, but you will have to get the window at exactly the correct angle for the design.
2 This is going to be tricky because between the bottom of the glass and the bottom of the frame I'll have maybe 10 or 20 mm. Anyway, like the guys that made the frame suggested, I think that I'll attach metal supports to the frame and let the glass sit on those. I know that when I do this I can't leave any metal sticking out on the bottom that would prevent rain from drain off.
As long as water is not dripping on the wood, or through "capillary effect," running in under the window. Flashing may fix this, foam can suck it in like a sponge.
3 Despite what they told me, I've found on the Internet a lot of products like silicon or foams that are used to seal the glass in the frames. Thinking about foam, wouldn't it be possible to put foam on the place where the glass is going to sit and then, before it dries, secure the glass in place? This would close all open space between the glass and it's frame making it air-tight. The excess foam can be cut off when it dries.
I fixed that in my design, you should be able to get 150 mm x 150 mm with no trouble.
I don't know if I'll be able to get poles of wood as big as those ones but it's just to give an idea of how I'm thinking to do.
Not needed now.
I added a pole in the middle of the greenhouse for extra support. I would prefer not to have it there but I think it won't be a big problem.