Passive greenhouse idea

Hi y'all.

Got some reclaimed double-glazed windows the other day and have been playing around with this idea for a small passive bermed walipini greenhouse. This is just a rough design concept, not a construction plan. I think I've got the windows angled at 30deg. I made them circle around to capture morning and evening sun. Will fill the gaps between the windows with soft plastic probably, and do the same for the door to let in more light. Thinking of burying IBC water storage in the berm.

Some context: We're on a mountainside just shy of the arctic circle. Year-around temps average 4c, don't swing very far beyond -10c and 15c. Growing season is very short. Frosts 9+ months of the year. In the summer the sun sets very briefly in the north and then rises again in the north. In the winter... forget about it -- sun doesn't rise for a good three weeks. Spring and fall the sun is low-ish in the sky and circles from the east to the west. Embarrassingly not sure of my elevation, but our trees bud a month later than the ones that are a 25 minute walk down the hill towards the sea. Can snow pretty heavily. 4 meters deep in some areas this year.. and it's still thawing. Though, the location I have in mind is not that bad.

Goal is not to grow year round. Just three seasons.

Would love to hear some insights from people with greenhouse experience in similar conditions.

Living in Australia, I cannot imagine what its like where you are.
The basic concept of your plan is good and I have a few questions;
- Are the IBC's to store water or to act as thermal mass?
- Is the berms purpose to provide shelter from cold winds or draughts?
- Could you include large rocks for thermal mass?

From; Artic greenhouses
BENEATH THE CLEAR, POLYCARBONATE DOME encasing a former hockey arena, Ray Solotki, executive director of the Inuvik Community Greenhouse, tends to flourishing beds of vegetables and flowers. Temperatures in Inuvik, a 3,200-person Canadian town located 120 miles north of the Arctic Circle, can plummet below -40 F°.
But inside the greenhouse, it’s often too warm, with temperatures easily reaching 100 F° in the summer.

“We don’t really have a cold problem like a lot of people think we do,” says Solotki. “We have a heat problem, because of the sunlight.”
24 hours of summer daylight keeps the greenhouse balmy, while accelerating vegetable growth.
Crops grow so speedily here that in early July, three weeks into harvesting, Solotki merrily reported collecting over 220 pounds of food.
The North’s midnight sun makes greenhouse gardening surprisingly productive, with everything from leafy greens, squash, tomatoes, and beds of flowers soaking up the extra light.

From; Arctic Gardening
Arctic Gardening 101
In addition to a short growing season, the arctic presents several other challenges to a gardener.
The first is day length. In the winter, the sun sometimes doesn’t even peek out above the horizon, but places like Alaska are famed for their midnight sun.
Long days can cause regular crops to bolt, sending the plants into seed prematurely.
In a northern garden, you can beat bolting by selecting varieties known to perform well under long days, sometimes called arctic circle plants.
These are usually sold in garden stores in a cold area, but if you are buying online, look for brands especially made for long summer days.
For example, Denali Seed products have been tested and perform well under extremely long summer days.
It’s still important to get cool-weather crops like spinach into the ground as early as possible in spring for harvesting before mid-summer.
From; Igloo greenhouse
There are other greenhouses in the North, but this one combines passive solar design and hydroponics to overcome the harsh conditions on the north shore of Hudson Bay, and is scaled to serve the hamlet of about 1,000 people.
Inside, a reflector captures warmth from the sun, which is stored in a large black tub of water that heats the greenhouse.
Just three to four hours of sunlight a day are needed to maintain the correct temperature.

- Are the IBC's to store water or to act as thermal mass?

Both. Planning on collecting rainwater.

- Is the berms purpose to provide shelter from cold winds or draughts?

I was thinking it would help redirect the cold northerly wind up and over, keep the interior temps more stable by insulating and adding mass. Also help blend the structure into the surrounding nature.

- Could you include large rocks for thermal mass?

Yeah I should make that interior back wall out of stone, except leave a gap to expose the IBC (painted black) to the interior sunlight as well.

Impressive goal. I think you are on the right track, but I have no experience in that climate.

One thing I can comment on is ibc placement. If you sink them about a foot down they make a good base for a work or planter table.  Multipurpose space savings.

Eliot Coleman talks a LOT about winter harvesting. He does not do winter growing, he plants it to grow in the fall and coast through the low light of winter to be harvested fresh even though it doesn’t really grow in the lack of light

R Scott wrote:One thing I can comment on is ibc placement. If you sink them about a foot down they make a good base for a work or planter table.  Multipurpose space savings.

Eliot Coleman talks a LOT about winter harvesting. He does not do winter growing, he plants it to grow in the fall and coast through the low light of winter to be harvested fresh even though it doesn’t really grow in the lack of light

Thanks, I'll check out Eliot Coleman. I've done tomatoes in my window and picked them in December. They were perfect.

How do you get the water out of an IBC that is sunk down a foot?

Wow! Great project, and I like your mock up pictures.
I'm not so far north as you (only 57.4ish) so we do still get a bit of daylight through winter, sometimes even sun! I'm also toying with the idea of an earth sheltered greenhouse. Getting the windows is the bit that would push me into doing it too. Also I've got a SE facing slope where I'm thinking of locating the dug out.

Nancy's Greenhouse Scheming

Have you calculated the angle of windows that will give you the most light through? I'm thinking of leaving mine pointing due South, to get the most winter sunlight, but I guess if you're aiming at autumn/spring maximisation the calculations are slightly different.
I think you're right about the height of the IBCs. If you want gravity to help distribute the water then they need to be elevated. I've got an old water butt that I can use with a gutter to catch the run off above the roof and bring it inside.

Nancy Reading wrote:Have you calculated the angle of windows that will give you the most light through? I'm thinking of leaving mine pointing due South, to get the most winter sunlight, but I guess if you're aiming at autumn/spring maximisation the calculations are slightly different.

I've just been checking the shadows in SketchUp for the different times of year, and this seems a good compromise. Really good direct sunlight on the growing area during spring and fall throughout the day. A bit worse coverage at noon during the summer.