Design Questions foundations, kneewalls
This greenhouse will be located on our homestead at 9800' in the rocky mountains. We are zone 4. I'm attaching this greenhouse to an existing lean-to structure that is 16'x24' (the greenhouse will be attached to the long wall). I plan on using 1/3 of the greenhouse area as a chicken/duck coop. I'd like to try to use some of their night heat for the greenhouse in the winter, and also use solar gain to keep their coop warmer in the winter. Sheep and goats will also contribute to night time heat in the adjoining building and will also provide CO2.
I'm planning to make this a solar greenhouse and have read several books on the topic. Along the back wall I will be using containers full of water for heat sinks. My vermicompost bin will be in there as will a 300 gallon aquaponics tote system.
I believe I'm going with a tilted sidewall to catch winter sun and optimize angles. The front of the greenhouse will be partially subgrade as this is going on a hill but unfortunately the southern facing wall is the HIGH wall so front will be submerged about 12"-18". South wall (tilted wall) and part of roof will be clear, E&W walls will be mostly solid.
Questions I have so far:
1) Foundation-I'm planning on preserved wood foundation as I know how to work with wood better than anything else. I'm going to use 4x6 timbers. I see some sites recommend 2 timbers all the way around, others only one. I definitely will have more than one in front as I have to make at least grade height-but what about round the back where I'm attaching this to the existing structure-would you still use two timbers or is that overkill? Then I was wondering should I use all timbers along the front deeper wall or would I be better off setting posts, setting timbers on these and filling the space under the timbers with concrete block and then insulate the outside wall?
2)Kneewall-I wouldn't mind additional height in the front as due to the slope of the glass, there is not a lot of height for the first couple of feet. I'll already have 12-18" in front due to grade, but was wondering are there pros and cons to kneewalls? Is there an optimum height? I just read on one site that not a lot of useful light comes in down there anyhow? This would greatly improve the coop end of the structure as I could do nest boxes or something along there.
3) Glass/Polycarbonate- I will be using both glass/polycarbonate. I'm taking down a Santa barbara greenhouse that is falling down and recycling the 6mm polycarbonate panels (I have 8 4'x6') panels and then some assorted sizes from the roof and ends. I also have some double glazed patio door glass and some windows too. Would you use the polycarbonate on the roof, glass for the sides. I was even considering doubling up on the polycarbonate on the roof or would I be better off using it all around and not using the glass at all?
Any other suggestions before I get going would be greatly appreciated. I'm attaching an outline of what my plan is for now. I already have one change I'm considering and that is to make the north greenhouse wall a little higher than the structure it is attaching to, and then putting openable panels along it to let heat out. Good/bad idea? I could always make part of the roof openable.