Walipini Roof Angle

Hello there! I want to construct a walipini design greenhouse. I've read as many information as I could but one thing that embarrassed me is the roof angle. I live in a town in Northeastern Bulgaria, 43 degrees latitude. Can you help me calculate my roof angle so that I can maintain an aquaponic system in it through winter and summer. Mind that the average temperature is roughly 11 degrees - 20-35 degrees during warm seasons and 10- -1-,-2 degrees during autumn and winter. I would really appreciate any help & suggestions because this is my first time ever trying such construction. Thank you in advance.

Sez Ko,

I found a ton of great information on a greenhouse for an area a little further north than you are, Calgary I believe.
The builder has a ton of great information and talks about the angle of glazing, size, roof angle, window angle for
your latitude formula.

Designed Greenhouse

Greenhouse Update 2 Years Later

Lots of good information in the comments too.

I also found this post with a ton of information on Walipini Greenhouses from permies. Walipini Information

Also more information, like Walipini's are also called "pit greenhouses", helpful to know the various names when searching for
new or old information, Walipini Googled

Thank you for the helpful suggestions guys! But I figured out that 43 + 23 degrees latitude won't do well for a roof angle. I now have newer information which is 43 +15 = 58 but "However, as long as the glazing angle is within 45 and 75 degrees you will be within 5% of optimum – therefore it often makes more sense to design the building to height restriction and material constraints vs optimal glazing angle. " So my angle can be safely made 50 or 60 degrees. So now I'm thinking about a 50 degree roof angle. What do you think? I plan to make the pit greenhouse at least 3 metres deep on the north side with a 50 degree angle.

Not knowing Bulgaria's weather I have little suggestion of what is best. I guess I always
assumed hoop houses were round because of there construction material. Other houses
roofs were there shape because of "snow load". I can imagine there are better reasons
than these but if your area had a large snow amount you may want to take that into
account.

I thought of another permies thread talking of Winter Greenhouses and you may
want to go there and garner suggestions. I made reference there of a Minnesota
couple that had built a green house on the back of their dairy barn, they buried rocks
in the ground and piped hot air from the ceiling to the rocks to hold in heat. They
also had planned on putting in a wood heater to replace another conventional one
to help with their cold winters. It is a really good article, they use rain gutters stacked
or suspended from each other to maximize growing area.

Here is the thread Winter Greenhouse Information

I was looking around this morning and found this link to a previous Permie's Bermed Greenhouse.
They talk of using patio door frames and doubling up of the windows so they get 4 panes of glass
and three dead air spaces, very nice information. They use separate solar collectors to help heat
the surrounding walls which seems like overkill but you can't argue with the results.
This is a quote of information on his site, the link is below the quote.

The overall dimensions of the greenhouse are 42' X 16'.

The green house is bermed up on the north side with a 6 foot wall. I used recycled patio doors for the glazing.

I heat the concrete walls with the solar panels (that is the tubing in the walls).

When it was -6 F degrees out side it was 46 F inside this past winter.

Bermed Greenhouse

Could you help

I'm in the UK and building my Wallipini and aiming to put a curved/dome polycarbonate roof on top of 5 foot straight walls.

I'm south by the sea so snow is not an issue. The roughly east and south wall have angled sloping roof  beds with opening velux windows and all the wall apart from the north are glass.

Do you think ventilation or the roof angle will be ok? No ventilation on the roof just  large opening glass door to the east and south, and solid  insulation to the north

Welcome to permies!

Sounds like an exciting project!...Can you tell us how big the structure is (floorplan)? The larger it is, the more important and difficult ventilation will be. I suspect there are guidelines for greenhouse ventilation somewhere.

The roughly east and south wall have angled sloping roof  beds with opening velux windows

So are these like cold frames? I'm trying to visualise what you mean.

the main walls are 14 feet long  by 11 feet wide. Yes the sloping roof go out four feet both sides and angle up to the top of the five foot wall

Hope that makes sense, not sure how to share a photo, which would help

Quick searching gives:

https://blog.bcgreenhouses.com/greenhouse-ventilation-guide

As a general rule, you'll want roof vent openings to equal roughly 15 to 20 percent of your greenhouse's floor area

https://www.rhs.org.uk/garden-features/ventilation-and-shading-greenhouses

Smaller greenhouses have a higher glass to floor area ratio, and should ideally have an even higher percentage of ridge ventilation

the door of small greenhouses offers an alternative means of ventilation which partially compensates for lack of roof ventilation. Side ventilation, commonly by louvres, is less effective than roof vents.

Have you just the one door? It would probably be better if you could get some sort of through draft. I used to have one door at either end of my tunnel (which was on a slope) and that seemed to cope well, but I'm a bit further north that you.

So only the North wall is solid? The others are in effect double glazed by a coldframe type bed area rather than earth sheltered?

Yes the walls are double glazed with one large front door and a
4 by 2 feet fully opening window to the west


The floor area is dug down 2 feet , apart from at back where there are some water barrels at the north insulated wall.

I could cut a roof vent like you have in a regular greenhouse but not sure how that goes with the roof curve

My aim is extend the spring and autumn growing season.

I've got a photo pending

My gut feeling is that with the door and the window you ought to get a reasonable through draft. You could consider some shading in summer to reduce the temperature, but that would obviously cut down on the light levels too.

I know you said you have a dome polycarb roof planned, but I wonder if a roof vent, like are available for polytunnels, might be retrofitable, if you do feel that temperatures get too high in summer: see https://northernpolytunnels.co.uk/product/polytunnel-roof-vent/ for example. Maybe there is something else available - I'm thinking a swing bin lid might be a frugal option if you could work out how to fit it!

Thanks Nancy

That's really helpful and a good plan to fit a vent if the house becomes too hot.

Instead of a regular solid roof to the north for shading, I'm growing a grapevine, chocolate vine and goji berry climbers to provide shade in the hot summer months.

Thanks

Midge

Midge Lury wrote:Instead of a regular solid roof to the north for shading, I'm growing a grapevine, chocolate vine and goji berry climbers to provide shade in the hot summer months.

Lovely! I didn't know goji would climb. I would suggest you might get more cooling effect from climbers grown on the outside of the roof. Many grapes would be happy outside in your area, and theoretically chocolate vine (Akebia) too. Isn't Akebia evergreen? I'd check that too, as you won't want the shading in the winter when the light levels are reduced.