New to forum - walipini help needed

Alrighty, hello all!

Just in initial phases of designing a walipini here in NC. I need all the help I can get! Please double check my calculations and correct my wrong thinking if you see any.

Ok, my thought process is this - our latitude is 35 degrees in Canton, Nc (near asheville), so that plus 23 degrees is 58. The angle of the front greenhouse wall will be 58 degrees, so pretty tall. If I just run the angle to the top, the back wall will be 6 or 7 feet above the ground level losing much heat. I'm thinking about making a flat roof on top of the structure 1. to shade against hot summer sun and 2. to make the structure not as tall. Of course facing south, the structure will be (I'm thinkin) 18 by 40 feet or so. I've got a slight hillside I can dig into, but nothing spectacular - only with a 1 or 2 foot drop from the back to the front. I was thinking of a radius front window, but that would increase reflectivity and reduce the light intake in the winter and the summer both - not to mention making the construction harder. So I'm concluding that a straight angle up at 58 degrees from the south wall to a terminus probably 5 or 6 foot up, then straight back at a level angle to the back or north wall, making somewhat of a solid "roof". I'm planning on using 2X8's or something similar for the structure on this part. It seems like my back wall might very well be 10 or 12 feet tall, which is fine - I'm thinking that a higher ceiling might help air flow and summer heat.

I want to put temp controlled vent fans on both ends so its somewhat automated. I'm thinking 1500 to 2000 cfm air movement will be sufficient given its very insulated. Attic fans might be utilized on a temp control unit for this. (I'm cheap)

I want to include black water barrels on the north wall for mass, and I'd love to put a rocket mass heater in there with the exhaust running UNDER the water barrels the length of the building. In this, there are 2 questions - has anyone else done this to heat water barrels, and how long can the exhaust be before causing problems (I'm looking at nearly 40 feet)? I'm honestly thinking that I would only have to run the heater on nights that get below 30, but time will tell.

I want to include a cold sink area with an elevated walking area over it, with also a drain pipe downhill for emergency water drainage (suppose a water hose burst, I dont want a pool). I was thinking perhaps the cold air could also flow out the 6" or so drain pipe under planting level.

So what do you think? Is my thinkin' right? crazy?

Thank you for your time

What did I miss? do you have to have a certain number of posts on permies to get a response or newbies need not apply?

perhaps I'm just impatient.

Hi Matt and welcome to Permies!

You certainly don't have to have a certain number of posts or anything like that to ask questions! If I could offer you any kind of sound advice, I would. But greenhouses are not my specialty. So we'll wait for one of the many greenhouse folks to respond.

I've added a few flags (!!!) to your post so maybe it will catch their eye. Sometimes things go by FAST on these forums.

Also, if you go to your profile and edit the "location" box to state your location, then it will show up under your name each time you post and that will help people answer you too as so many answers depend on your climate/location! (yes - I know you have it in the body of your post - but sometimes people just scan these things).

Thank you for your kind words, I was getting disheartened. I will add my location.

After thinking about this for a few days, the straight up North wall may have turned out in my mind to be not as efficient as a A-frame type roof, like a normal house, with only the south side in glazing. I saw another post that had that design and I really liked it. A new question in my mind is how to surface that north roof face - shingles on plyboard with insulation on the inside, or perhaps tin on plyboard..... insulation on inside with glazing under it to keep moisture out of the insulation or something else.... I'm trying to keep my costs down, but I keep seeing that flying away with the exhaust from the greenhouse.

Lets see if this attachment works on here....

This is a very simple drawing of the newest version of what I'm trying to do. The glazing side will be 9.5 feet long, and the roof side will be 15 feet long. Is that enough glazing to support good plant life, and do I need to include some kind of skylights in the 15 foot long roof?

I'll be following answers to your post, as I'm planning on doing a walipini as well this spring (weather permitting - lately Jersey has not been consistent for weather). Have patience, Matt - this forum is HUGE, so it might take a bit of time before someone with some info sees it.

I missed the post until today. Sometimes things just get lost because it is such a big place.

Your math sounds right, but I only got as far as putting it on paper myself.

The idea to put the barrels on the "bench" to warm them is a good one. That long for a straight run on an 8" system will probably work. If you do a 6", I wouldn't go all the way. maybe mount it in the middle and only heat half the barrels (the ones that don't get as much solar gain in the winter).

Attic fans may be good cheap answers for ventilation, but having at power-free greenhouse vent would be good.

Your cold sink/drain is a good idea, I was going to do the same.

Dealing with that north side roof is what discouraged me from the walapini and put me back to a basic hoophouse.

Hi Matt, I think I can take a stab at this.

First a couple of questions I would suggest you ask yourself. What do you want to grow in your greenhouse? When would you like the greenhouse to perform best? What kind of temperatures would you like to keep? What is the mean annual temperature for your location?

I know that most of what you can find on the internet about solar greenhouses suggests a crazy steep glazing angle. In my experience, and in the experiences of my teachers this is not the way to go. I've even known people who rebuilt their entire greenhouse because the glazing angle they used was too steep. I could see the super steep glazing angle working for people who only want to grow hearty stuff in the winter (the temperature will fluctuate dramatically) and not use the greenhouse for the majority of the year.

Even if this is your goal I think that 58 degrees is way too steep for your latitude. With this angle your greenhouse would be optimized to catch the maximum sun on the winter solstice. The single shortest, coldest, day of the year is when the greenhouse would perform best. Every other day of the year this glazing angle is sub-optimal. In my designs I can't rationalize anything steeper than perpendicular to the equinox azimuth. For 90% of the designs I do the glazing angle is even significantly lower than perpendicular to the equinox.

The new alchemy institute experimented with radial glazing, they found that it increased the surface area while decreasing light transmission, so it reduced the performance of the greenhouse in both ways. This is one of the reasons why the corrugated roofing that people use is such a poor choice.

A higher ceiling will most certainly help air flow. Air stratifies by temperature, 1 degree per foot. I would recommend passive ventilation with solar venting arms and earthtubes, for a natural way to cool the greenhouse. Much cheaper in the long run as fans that can handle enough CFMs use significant amounts of electricity.

I'd LOVE to have the greenhouse warm enough to grow anything I wanted in there. I'd like salad greens along with any other little thing I could toss at it, be it tomatoes or peppers, citrus or bananas. You know, understory shade loving things like greens under a citrus tree or something like that. I'd really like for it to perform all year long - that being said I dont want a solar oven in the summer.

http://en.wikipedia.org/wiki/Climate_of_North_Carolina

Above link is to average temperatures around here, near Asheville. Average of 80's june through august, and 40's december and january. Sadly enough, its -1 right now and its looking to be 15 to 20 for several days. The glazing angle I concluded was based on latitude plus 23*. You mentioned equinox azimuth, I'm having trouble getting that angle figured out to say the least. Have you built many greenhouses? Everyone around here just uses hoop houses and grows greens in the winter, but I want a true year round greenhouse. I'm not trying to be a punk, I just want to make sure I'm getting this right, and everywhere you look there's conflicting information.

Isnt the glazing angle supposed to collect all the sun it can in the winter and reflect a good bit in the summer? This makes sense in my head, but it looks also like half of it will be shaded fully in the summer, and that doesnt sit quite right with me. You reckon I ought to just do both sides in glazing and even out the roof sides? I SURE dont want to do it wrong, because I dont have the money to rebuild it in a year.

I'd love to not pay for fans running, but I'm scared the thing will get way too hot in the summer. I'm familiar with solar venting arms, but not so much with earthtubes. Could they really cool the place that much?

Oh, and I'm at 2700 feet in elevation if that means anything here.

Am I making the azimuth calculation too difficult? is it just my latitude? My brain just officially turned to mush.

You do have this document, right? http://www.bensoninstitute.org/Publication/Manuals/Walipini.pdf

Keep in mind the design is built for high elevation, low latitudes. Areas that have near vertical sun in winter and summer sun actually north of vertical (for northern hemisphere). When you get out of the tropics, the roof angle doesn't work the same as a pit.

I did read that document - that is where I got the 58 degrees glazing. our latitude of 35 plus the 23.5

I just reviewed the Benson Institute's article once again. A lot of the information in this article is really great, but I find the section on solar orientation to be very misleading.

Using the latitude plus 23 they conclude that 39 degrees is the best glazing angle for their location. In their diagram they show the 39 degree angle measured from the north wall to the glazing. This is the inverse of how glazing angle is usually measured for a solar greenhouse. Typically the angle is measured from the horizontal to the glazing, so a 90 degree glazing angle would be vertical, rather than horizontal. More importantly the angle that is drawn is not even remotely close to 39 degrees, it looks more like a 75 degree angle from north wall to glazing, or a 15 degree angle off of the horizon. Furthermore all of the pictures and diagrams of walipini's in this article are about the same angle, which is not at all close to 39 degrees, no matter which way you measure it. Needless to say I find this section VERY misleading and confusing.

If you desire to grow anything that produces fruit (which it sounds like you do) I would go with a much shallower glazing angle (like what is drawn in the article) so that you get good summer sun in order to ripen the fruit. The equinox azimuth is the middle of the winter and summer solstices. I am a greenhouse designer, consultant, and builder by trade, specializing in earth powered greenhouses, so it's safe to say I've built one or two

One of the big problems with a steep glazing angle is that it will heat up very quickly on a sunny winter day but will still be cold on a cloudy day. With this type of design you get some pretty extreme temperature fluctuations, which are hard for plants to cope with. I wouldn't build any north facing glazing into the greenhouse, in northern climates this attributes to a lot of heat loss without any solar gain.

In Montana even when it gets over 100 degrees we are still able to keep the greenhouses from overheating with a passive ventilation system. New Pioneer magazine recently ran an article on my greenhouses that goes into more detail about the earthtubes with a nice graphic.

So how do you find the azimuth angle? Is it 39 for here? ( I saw that somewhere, but couldnt find it again just now!)

I want to get this thing started, but I have to have an accurate drawing of the finished angle before I begin so I can figure out materials cost.

I'd love to learn more on the earthtubes, but its still a foreign topic to me. What size would I need for my (future) greenhouse of 18 by 40ish? And could I find that article online?



Thanks for your help by the way.

Gaisma | Asheville, North Carlonia, USA

You can use the Sun Path Diagram to determine the angle of the sun at different times of year. I usually use the noon solstice angles to determine the range of appropriate glazing angles.

New Pioneer | Underground Greenhouses

It's not the whole article but it shows the graphic on passive ventilation with earthtubes.

I do appreciate that Zach, but I dont see sun angle on there at all! I may have missed it, but I dont see it

You can use the Sun Path Diagram to determine the angle of the sun at different times of year. I usually use the noon solstice angles to determine the range of appropriate glazing angles.

Each circle is 10 degrees, this is the sun's path over a year.

so, 35 degrees is ours (for the azimuth) if I'm reading it correctly? thats our lattitude


I dunno!! counting from one way its 65 degrees, but that doesnt make sense, so subtract that from 90, the range of the thing, and get 35, which is our lattitude. that doesnt quite make sense. if you follow the circle around from the other side, that puts the middle at 55 degrees, which I thought you said was far too steep. I'm truly confused now, I'd really appreciate it if you could help me understand this.

bump

This graph is looking at the elevation of the sun in the sky for different times of day and year. There is no set angle but rather an angle for a given time of day and year.

At noon on the summer solstice (the green line) the sun will be about 78 degrees in the sky. Noon of winter solstice (blue line) is about 30 degrees. Noon on the equinox (grey line) is 55 degrees. So the perpendicular angle of these solar elevations would give you the best solar gain at noon on that day of the year.

I use this to determine the time of year that I would like to catch optimal sun with a given design, and then check how optimal or sub-optimal the solar gain is during the other times of year. If you were to use a 58 degree glazing angle like you first suggested you would catch 98% of the winter solstice sun but just under half of the summer solstice sun. If you want to grow what you can with big temperature swings in the dead of winter this is a good strategy, but if you want to grow out of climate perennials they will need more summer sun for the fruit to ripen.

Permaculture News (Geoff Lawton's site) featured a blog post on walipinis today: http://permaculturenews.org/2014/02/05/robs-modified-walipini/

Here's the video:

Hi everyone. New here. OK, so after reading this forum and reading the Benson document from 2002 on walipinis, I am somewhat confused still. In the section "Angle of the Roof to the Sun" on p. 6 of the Benson document, they say this: "2) Add approximately 23 degrees which will make a tilt angle of 39-40 degrees for the La Paz area." I'm not in the La Paz area, and I have no idea where the 23 degrees came from. I assume the 23 degrees number is some sort of constant, but I have no idea what that constant is or where it came from. Earlier in the book, it was clear that the writer wanted you to gain the best heating during the 3 winter months and reflect heat during the summer months.

Now I hear Zach Weiss saying that's probably not the best idea, especially if you wish to grow tropicals. Having done some research on Zach's work, it's obvious he's someone who knows what he's talking about. I want to grow some tropicals and citrus in mine here at -34.5205°N 94.3105°W. I got a chart from the University of Oregon SRML for my lat and long, but I don't know what I'm looking at. I'm attaching a PDF of that chart to this post. 57 degrees is a very steep angle, one I am not too keen on building.

So I guess I just want to know how best to go about angling the thing. If I want avocado, banana and citrus year round, I mean.

It seems to me that the writer of this document is really sold on the add 23 degrees to latitude concept, but the people who are actually building them are not, as none of the pictures have anything close to this angle. I think the add 23 degrees is pretty bogus, as what and when you want to grow is an important factor in determining the glazing angle of a greenhouse, and is different for different people.

Kevin, if you look at the y axis of this graph you will see solar elevation in degrees. This is the angle of the sun off of the horizon. The plot shows the solar elevation from sunrise to sunset for different times of year. The summer solstice is the top line, and winter solstice is the bottom. You can use this to find the range of angles that the sun is at throughout the year.

A perpendicular angle to the elevation of the sun will give you the maximum gain at a given solar angle.

Thanks, Zach Weiss! I think the 23 degrees is from this: Earth's axial tilt is 23.4°. There is still not much sense in it and I like your explanation better.

Zach, I am at 41° North and I want to grow tomatoes, cucumbers, and bell peppers all year round. I want to increase more summer solstice sun to encourage more growth period so that throughout of the year it will continue producing fruits. So I would have to reduce winter solstice sun approx to 75% and increase close to 75% of summer solstice sun? Will that works? If not, what's the best approach with Walipini to support grow out of climate perennials?

bump

Zach is not around here anymore?

R Scott wrote:You do have this document, right? http://www.bensoninstitute.org/Publication/Manuals/Walipini.pdf

Keep in mind the design is built for high elevation, low latitudes. Areas that have near vertical sun in winter and summer sun actually north of vertical (for northern hemisphere). When you get out of the tropics, the roof angle doesn't work the same as a pit.

The link for the pdf was taking me to a different site. I believe the benson institute merged with an LDS site... or something like that.
I couldn't find the pdf on the new site anywhere so google to the rescue.
Here is the link for anyone else interested.
Walipini PDF

Daniel Pinnell wrote:So I would have to reduce winter solstice sun approx to 75% and increase close to 75% of summer solstice sun?

I don't really understand this question well enough to answer it. Are you saying that you plan to set the angles so that you catch 75% of the winter solstice sun and 75% of the summer solstice sun? Depending on your winter climate you may not get enough sun to really grow tomatoes and peppers that taste any good in the winter. It sounds like you'll have a multi-pitch roof, is that correct?

Hi Matt,

I'm quite late to the party, but if you are still designing / working on this, happy to help.

The traditional rule of thumb for glazing angle is your latitude + 15 degrees. Our research has corroborated this.

To also see whether you have an appropriate angle for your depth of the greenhouse (based on your sketch seems like the back will be shaded) you can create a very simple model in SketchUp (pretty easy program to learn); they have a shadow feature there you can turn on and see how much of your greenhouse will be illuminated. You have to geo-locate your model first.

Also, I've written a couple posts on underground greenhouses generally, after seeing / researching them a lot. You can find that here: http://www.ceresgs.com/#!blog/c1whn

We do this for a living, but happy to answer questions for free -- feel free to shoot an email. info at ceresgs dot com.

Best of luck.

Matt,

I think we've spoken before about this project. Just wanted to throw in the fact on the roof calculations you actually have a bit of tolerance when choosing a roof angle. Many angles -- close to a perfect angle of incidence -- will yield good amounts of light.

See article here:
http://www.ceresgs.com/#!Whats-the-best-roof-angle-for-your-greenhouse/cf3k/551dccd70cf21d84af73bc1e

Best,
Lindsey

Thanks for the link, Lindsey. It is very helpful.

A lot of what Zach said makes sense, and it sounds like the angles commonly suggested aren't the best. I agree with that, seeing the recent popularity of people using earthtubes after dealing with those high roof angles at higher latitudes, but the balances between angles for summer light, angles for winter heat, then avoiding summer overheating just made this go from lat+23 to something way more complicated. So your research is very much appreciated.

Hey, fun to read about other people's experimentation with walipinis.
Ours is getting into pretty good shape now, but I'm having issues with water and with mold risk.
I'm trying to find a hand pump to pump out the water as it collects in the cold sink. For now I'm just bailing it out with buckets.
I found a hand-crank EZ pump on youtube that looks like it works, but people who bought it from Lehman's old-fashioned parts store have had issues with it and say it won't prime.
http://www.ebay.com/itm/Crank-EZ-Pump-Hy-Capacity-PN-8301252-/251699842901?hash=item3a9a7acf55:g:pE0AAOSwGWNUU-LI

I'm also concerned that with all the moisture the walipini will develop mold problems.
Just put in an ammo box stove to add heat during the cold Minneapolis winter - worked pretty well and should help with the moisture.
I'm trying to route the heat through the dirt walls to harvest some more of the heat into the wall - the ground is frozen but thawed when i put the smoke duct on top of it, so I'll try to bury it deeper and keep more of the heat.