Introduction: A Greenhouse for the North

Picture of A Greenhouse for the North

I always wanted to build a greenhouse so when I found an article explaining how to build one for $50, I immediately started to build mine.

The first problem I encountered was that the design was not appropriate for heavy snow falls. It would collapse under a few inches of wet snow. So I decided to alter the design a little to make it more sturdy and prevent any snow accumulation at the top. The ogive shape adds strength to the top part of the greenhouse while making the roof angle steeper.

I should also mention that it cost me more than $50. Part of if is that I didn't have any wood lying around. Another price increase came from the fact that I had to use thicker wood. The last bump in my total cost comes from the fact that Whitehorse is a pretty isolated town and you get to pay more for every piece of lumber/hardware.

Step 1: Materials and Tools

Picture of Materials and Tools
  • 12 foot long 2x4s. You'll need at least 12 of those. Take the pressure treated wood if you want your greenhouse to last more than a few years. You can usually find ACQ of PWF lumber at the hardware store.
  • 6 mil plastic sheet. You will need at least 22 feet wide by 16 feet long. If you can't find anything larger than 10 feet, you can tape 2 sheets with construction tape.
  • Some plywood to hold the 2x4 together.
  • A bunch of screws. Drywall screws work well and you can get a lot for cheap.
  • A bag of tie-wraps. They need to be long enough to wrap around a 2x2.
  • 3/4" Schedule 40 PVC tubing. Take the gray one because it's resistant to UV light. You'll need 10 of them.
  • 2 feet rebar. You will need 8 oth them to hold the pvc pipes.
  • 45 degree PVC connectors 3/4" inside diameter. You will need 5 of them.
  • Optional: 6 round quick pins if you want to be able to dismantle the greenhouse easily.
  • 4 metal fence posts
  • 4 2 by 4 end brackets

Step 2: Build the Sides

Picture of Build the Sides

The original plans are using 1x4 lumber. However, in Canada, you really want to upgrade to 2x4 trusses. Snow can be pretty heavy.

Start by connecting 2 PVC pipes together using a 45 degree connector. If you don't want to glue the pipes so that you can dismantle it later, use round quick pins to attach them.

Temporarily attach both ends of the assembly to each side of a 11 feet 2 by 4. This gives you a rough idea of the dimension of the side of your greenhouse.

You can now decide what size your door should be. Mine is 3 feet but you can make it larger if you want to drive a large wheelbarrow throught it. The height is also up to you.

Now that you have decided the width and height of your door, you can measure and cut all the other pieces of wood (cf drawing).

Cut some plywood, apply some glue and drill it onto the 2 by 4 boards. It will keep everything strong and square.

Drill holes in the PVC pipe in the 4 locations mentioned on the drawing and use tie-wraps to keep it even stronger.

You can now staple plastic on each sides. Cut a hole in one of them for the door.

Step 3: Attach the Sides Together

Picture of Attach the Sides Together

Your first task is to find a 12' by 12' space that is flat enough to put your greenhouse.

Once you found it, hammer 2 fence posts at one end. Make sure to align the posts with the vertical sides of your door. If you chose a 3 feet wide door, put your fence posts 3 feet 4 inches apart.

When you can't push the posts deeper into the ground, place one side of your greenhouse against the posts and drill holes through the 2 by 4 and use zip-ties to fasten it to the posts.

Repeat the whole thing 12 feet further to set the other side of the greenhouse. Make sure they are aligned.

Use two 12 feet 2 by 4 and screw them onto the plywood on each side using end brackets. You should end up with 2 strong beams joining both sides of your greenhouse.

Step 4: Assemble the PVC Pipes

Picture of Assemble the PVC Pipes

The greenhouse is now solidly anchored to the ground but we still need to put the ribs to it.

Hammer some rebar every 3 feet from one side. Put them at an angle as we will slide the PVC tubes onto it.

Create more PVC assemblies (2 10-feet PVC tubes + connector + pins). You'll need 3 of them. Slide them on the rebar and align them the best that you can. Screw the pipes on the horizontal trusses. Fasten them with tie-wraps to prevent any movement.

A second horizontal beam is added lower on the ribs. This ensures that the plastic does not collapse through the PVC tubes during high winds and snow storms.

Another important element is the crossed wires you can see on the last picture. They create diagonals, making sure that the greenhouse stays square over time. The wires cross over the middle PVC pipe on each side.

Step 5: Cover the Pipes With Plastic

Picture of Cover the Pipes With Plastic

Time to cover the greenhouse.

Use your 22' by 16' plastic film and wrap both ends around a 12 feet long 2 by 2 (along the 16' edge). This will add some weight at the bottom. It will also make it easier for you to roll the bottom to ensure a better air flow.

I made my 2 by 2 from a 2 by 4 cut in half using a circular saw.

Put the whole plastic film over the greenhouse, center it and staple it to the vertical sides. Fasten the film with 1 by 2 boards on the frame and trim off the excess

You can see that in my case I used construction tape to create a plastic sheet long enough.

Step 6: Make a Door

Picture of Make a Door

Make a door to the dimension of the opening of the greenhouse. If the opening is 3 feet, make the door slightly larger (3' 3" for example).

You can use 1 by 2 spruce or pine to keep it lightweight. Some plywood in the corners will keep everything straight. You can also add the crossed wires we saw previously to prevent any movement over time.

I added a barrel latch on the outside and a simple hook on the inside. The door is screwed on the greenhouse using 2 hinges.

Step 7: Grow Vegetables

Picture of Grow Vegetables

The configuration inside the greenhouse is up to you. I created a raise bed in the middle to keep the ground warm (the ground can be pretty cold in the Yukon). The 2 beams at the top are strong enough to hang growing baskets such as tomato plants.

The center of the greenhouse is quite high and can accommodate fast growing plants. The sides are better suited for herbs and lower vegetables.

Here is a list of plants I successfully grew in the greenhouse:

  • Mint
  • Basil
  • Oregano
  • French Tarragon
  • Rosemary
  • Cilantro
  • Various Peppers
  • Zucchini
  • English Cucumber
  • Various Strawberries
  • Parsley
  • Arugula
  • Tomatoes (Coeur de Boeuf, Coeur de Pigeon, Stupice, Sun Sugar)

Step 8: Ventilation

Picture of Ventilation

After a few months of use, I realized ventilation is crucial. Too much humidity creates mouldy conditions whereas too much heat prevents plant growth and makes some flower sterile.

I installed a 12V computer fan on top of the door and hooked it to an arduino using a temperature/humidity sensor and a 5V relay. A wifi shield sends data so that I can monitor the conditions inside the greenhouse while at work.

The system works fine but the fan is probably a bit small since the temperature decrease is minimal.

I used the DHT22 Sensor for its range of temperature and humidity.

The wifi shied is the CC3000 from Adafruit.

I followed the tutorial available on this page. However the Xively service is no longer free so you will have to find a similar service.

The electronics can be housed in a food container screwed on the inside of the greenhouse. I put mine beside the door, not far from the fan. The sensor should be placed in the shade at plants temperature to get a realistic reading.

Comments

MaximeP21 (author)2016-07-22

Hey Thomas,

How's the greenhouse going so far? Thinking of building this design for my backyard, just want to know is there's any changes you make to it since you've built it?

(forgive my english)

Max

ThomasJ1 (author)MaximeP212016-07-24

Hi Maxime,

I think I would reinforce the roof if I lived in a place where I get a lot of heavy snow. Sometimes, there can be a foot of snow accumulated on top because the plastic sags a bit between the ribs and creates flat areas. It doesn't matter too much for me because snow is pretty light in the Yukon. Hower on the east coast of Canada, snow is a lot heavier and it may damage the plastic or the PVC ribs. Adding a 2" PVC tube under the plastic sould solve the issue.

There is also the problem of ventillation. The first year, I kept the base of the greenhouse open (about 1 foot) and got a good harvest. The second year, I stapled the plastic all the way to the bottom and got mold which killed most of the plants.
If you don't live in a windy place, I would leave the bottom of the greenhouse or the door open.

ethanmohan (author)2016-03-13

Hello, can you please tell me where you purchased the plastic from, I cant seem to find anything that will work.

Great structure!!!

ThomasJ1 (author)ethanmohan 2016-03-13

Hi Ethan,

I live in Canada so I got it from Home Hardware but I'm sure you can find the same kind of plastic anywhere. Look for "Vapour Barrier" 6 mil.

Here's a link: Vapour Barrier 6 mil

-chase- (author)2015-08-23

Where are the dimensions? You only give general over all dimensions.
And you show 20' pvc on the sketch but state 10' in the instructions.

I'm the boss, I need the info... the specifics... the specifications... how am i suppose to take over and feed the world if you don't include how long to cut the boards. Geez...

Nice build btw ;-)

ThomasJ1 (author)-chase-2015-08-23

Hey Chase, I used 10' PVC pipes because that's the only thing they had at the hardware store. The original plans claimed for a 20' hoop but I figured that 2 10' pipes with a 45 degree connector would be stronger under the snow.

The greenhouse is as long as the boards you choose. I found 12' ACQ 2x4s so I made the greenhouse 12' long. You can go longer but you might need more "Ribs" in your design.

For the sides, once you attach the hoop to each side of the base board, you only have to chose a height and width for your door and measure the distance to the PVC tubes all around. There is no general measurement.

-chase- (author)ThomasJ12015-08-24

Actually it's the dimensions for the front and back I was referring to. The measurements and angles help allot prior to the build.

Also, as an added note here, the lack off a ridge line, (top center), is a major structural weak point. And more than likely will collapse with little weight. Looking over the link you built yours from. It was his ridge line that failed. Not the front or back.

Making your front and back stronger, definitely improved the design. Makes something that will last. But the ridge line needs to bide addressed quickly if it's to stand through winter.

I have currently an A- Frame design I made. Heavy ridge pole. Twenty plus foot tree limb fell the other day during a rain storm. The ridge pole saved the structure. Though it did come through the tarp.... just saying.

- chase -

ThomasJ1 (author)-chase-2015-08-24

Hey Chase, I can measure the front & back tonight and give you the dimensions.

Regarding the ridge line, I was planning on using a 2 inches PVC pipe or a 2x4 originally. However, the ogive shape of the ribs helps distributing the weight of snow sideways instead of downwards. This is the principle they used when building cathedrals.

It is true that the plastic sags a little between the ribs when there is 10 inches of snow on top but the structure itself does not bend. But feel free to re-enforce the ridge with some support, it can only make it stronger.

-chase- (author)ThomasJ12015-08-27

That would be great. Adding dimensions and the angles to your drawing would be a huge plus.


I noticed you didn't raise it. (Use stone or cinder blocks under the bottom most 2x4's (forgot the tech name for them) aren't you concerned about rot? I realize they're pressure treated, but they rot fairly quickly when laying on the ground.

Here there's a huge issue e with carpenter ants and termites killing the trees off among other things. When it's quiet I can hear them chewing at my A-Frame and other timber I gathered for building and even the firewood. Lol.

In seeing a couple other post regarding heat. For heat, if you go that route, you might want to consider a rocket mass heater of sorts. I'm thinking of trying a style I saw using an army surplus ammo box and running the stove pipe under ground "S"ing it back and forth a couple times before the exit pipe. Doesn't take up as much room as the 55 gal type. Should heat the rock I'll surround the pipe with underground, be an efficient burner and hopefully do the job using less firewood. It's a thought... That and since yours has full Sun, you might consider as well as a passive solar type heater. I hear they work even if only during sunny days.

Anyway, looking forward to seeing the pics and especially the dimensions... and thanks for taking the time to get them post build.


- chase -
ThomasJ1 made it! (author)-chase-2015-08-27

Chase, I updated the drawing and included the dimensions of my own greenhouse.

The plastic film actually goes around the bottom 2x4 so it's not resting directly on the ground. However, by doing so, you will need to cut small openings in the film to avoid water accumulation: water evaporates, condensates on the plastic and falls at the bottom and you can end up with a few cups along the bottom 2x4 and the door.

For heating, the rocket stove with underground pipe sounds like a good idea.

Unfortunately, I haven't found a picture with all the snow on the greenhouse but I have one from last winter where the snow is all accumulated on the sides.

-chase- (author)ThomasJ12015-09-13

Thanks for the dimensions Thomas.

Happen to know the angle of that cut on the outer top edge?

Couldn't find a pic that wouldn't make me jealous... that's gorgeous. That is a true Aurora in the night sky, no PS layover? Yeah, looking at the green house... lol.

I'm going to try a rocket mass heater this year. Small one using a 20 gallon as opposed to the 55 gal. Use 6 inch pipe surrounded by natural rock topped with an inch or so of soil. Two crossings width wise of the pipe should do it. I'm going to shoot for about a foot of rock surrounding the pipe. My hope is a single burn every 12hrs should hold the temp above 72 degrees Fahrenheit.

Look for a video on tent rocket mass heater by Sergent Pepper I think his screen name is...? He has a couple vids with experimental builds. I'm basing mine off one of his builds.

I'm definitely going to add a ridge line though. And give it a straight side wall up to about 5' 6".

I looked for a calculator for the type roof you have, found a couple for gothic style. But nothing for the curves except graph style plotters.

Sweet pic... dang sweet pic...

Thanks again for taking the time to get the measurements.

- chase -

ThomasJ1 (author)-chase-2015-09-13

I just checked on the greenhouse and the 2x4 which makes the top of the door opening, is cut at 45 degree angle on each side. However, it will vary if you create a higher or shorter door.

Thanks for the videos, that looks really interesting.

-chase- (author)-chase-2015-09-13

here are those rocket stove mass heater for tents vids.

Start with the first and watch his progression

And his screen name is Sukkot Prepper not Sergeant Pepper... what can I say, I was drinking a Doctor Pepper while typing. ;-)

I combined some of the ideas he had and added some of my own. I'm also adding a flue cutoff right before it exits the "tent" so once the burn is done it can be closed, preventing hot air from just flowing out the exhaust. That should help is my thought. Won't know till I try it.

-chase- (author)ThomasJ12015-08-24

Has this build seen snow yet? If so, impressive that it held without the ridge pole.

Likewise, I'd consider at least a 2x3 for the ridge line for support. Drilling holes and inserting the 45 would be an option, then run a screw through and through to bind them..

I used 30' saplings to make my A-Frame. Crossing the legs and lashing the ridge pole to them is how I did that build.

But I really like your build. More room than a traditional A-Frame. Thought I'd give it a go next.

ThomasJ1 (author)-chase-2015-08-24

Yes I was covered in snow quite a bit. Our winter usually lasts about 7 months in the Yukon. I'll try to dig a picture and post it along with the dimensions.

deepsquid (author)2015-08-28

Looks awesome. Question: Are you concerned about using pressure treated lumber around things you might eventually eat? Doesn't pressure treated lumber contain arsenic and other poisonous chemicals?

ThomasJ1 (author)deepsquid2015-08-28

Thanks deepsquid, I used ACQ lumber which has a treatment based on copper as an alternative to arsenic. Here's some more info about it: https://en.wikipedia.org/wiki/Alkaline_copper_quaternary

tthomas10 (author)2015-08-27

this is nice. a built a greenhouse out of old windows, i like this though!! currently trying to get RaspiViv working but my DHT22 have decided not to work, nice instructable!!!

juicer62 (author)2015-08-25

You have a problem here, but you may not know it yet. I built my own greenhouse back in 2008, very similar to yours. The problem? That plastic sheeting you use disintegrates very quickly when the sun hits it. My 6 mil plastic lasted from November to March. Then, it started tearing and shredding. I patched it, then the disintegration accelerated faster than I could patch. That plastic MUST BE UV STABILIZED!! Or, you will have nothing but a nice frame after 4 months.

ThomasJ1 (author)juicer622015-08-25

Hi juicer, The greenhouse was built last year and has been in place for about 18 months. It survived 2 summers and a 7 months winter with its fair amount of snow so far. I know it won't last as long as greenhouse plastic but it hasn't started to disintegrate yet. I'll replace it once it shows signs of wear.

jnorv (author)2015-08-23

You could add another set of horizontal ribs and a second layer of
plastic to insulate it. that would cut the night time heat loss down a
bunch.

ThomasJ1 (author)jnorv2015-08-23

I was thinking about something like that. Having some kind of plastic curtain or bubble wrap that I could draw at night. A set of lighter ribs inside would be a solution indeed. Thanks

maggasaki (author)2015-08-20

I live in Iowa and am new to gardening - this is my first year. Given how cold it gets here, what could I grow in this greenhouse? I'd like to grow food year-round if possible up here!

ThomasJ1 (author)maggasaki2015-08-20

This greenhouse is not a heated one. It only captures heat from sunlight. At night, it cools down to a few degrees above ambient temperature. I made it because in the Yukon, the average summer temperature is 19C and you need more than that if you want to get tomatoes and peppers for example. I really made a difference on most plants I grew.

If you want to grow food year round, you would probably have to place a heat source inside and switch the 6 mil plastic for something with more insulation.

However, I would suggest that you grow winter greens which tolerate frost during the winter season and switch to heat-demanding veggies later in the season.

jnorv (author)ThomasJ12015-08-23

You could add another set of horizontal ribs and a second layer of plastic to insulate it. that would cut the night time heat loss down a bunch.

maggasaki (author)ThomasJ12015-08-20

Ah! Gotcha. Thanks for the reply and suggestions!

sweetpea1145 (author)maggasaki2015-08-20

See if your library has a copy of Elliot Coleman's "Winter Harvest". He grows in northern Maine year-round and his latitude is farther north than you, meaning you get more direct sunlight than he does. Very good information.

maggasaki (author)sweetpea11452015-08-20

Thanks for the resource!

Johenix (author)2015-08-20

Well, Now, For cheap heating, I would put about 50-100 laying hens in a restricted pen under the central table. Well fed and watered the little ladies will supply you with eggs, heat, and organic fertilizer for next year's plants.

ooohlaa (author)Johenix2015-08-23

You may not realize it but that is definitely animal cruelty. Its like locking up a bunch of humans in the bathroom on top of each other. They start pecking each other's feathers out of frustration, and the factory farming industry solves it by cutting off their beaks. Its a real sadness.

BlackSheep0ne (author)Johenix2015-08-23

No. the birds need more room than that not to be cruelly confined, plus that will create an excess of ammonia in your greenhouse air. It's not a good idea at all.

khardinger (author)Johenix2015-08-23

Good idea

ThomasJ1 (author)Johenix2015-08-20

This is actually a great way of generating heat and keep things friendly for the environment. I have seen a few designs where people keep compost and manure between upright pallets to heat the entire greenhouse.

Johenix (author)ThomasJ12015-08-22

I did some more thinking and remembered a couple of books on "Straw Bale Gardening". In the early stages the bales are dosed with nitrogen fertilizer (ammonium nitrate, ammonium sulfate, or urea) and water to encourage fungal growth to break down the straw into nutrients for the plants with considerable heating. I think I might use 100*F/ 40*C water for the daily wet down to help it start.

If you put the bales in so their lengths were cross wise to the length of the greenhouse and put a 5Ft x 16Ft cattle fence panel down the center of the bales you would have a tomato and cucumber trellis. Run a soaker hose on a timer along the bottom of the trellis.

Plant the bales "Square Foot" style with one tomato plant surrounded by 24 carrots per square foot.

You ought to be able to reach in two feet or so to pick fruits growing on the trellis.

ThomasJ1 (author)Johenix2015-08-22

Wow, thanks Johenix, I never thought about that! You just gave me a bunch of ideas for next year's crop. I'll do some research on that "Straw Bale Gardening" technique. By combining this and a bubble wrap plastic liner, I might be able to start the growing season earlier than usual.

Gordyh (author)2015-08-23

You might be interested in checking out Builditsolar.com Gary has a large variety of green house designs (free), with option's for moderating temp's and holding the heat in for release at night. During the early and late season vented heat is wasted heat ;-)

The simplest is raised bed's that use black barrel's (even 5 gallon buckets) filled with water as the base, you would probably need some kind of glycol to keep them from freezing and bursting when the temp's really drop. This will absorb excess heat during the day and release it at night as needed. When you don't need the heat the barrel's can be covered with mylar film to keep the barrel's from heating up. Emergency blankets from a sporting goods section is a cheap source for mylar film.

One guy used J tubes in the barrel tops to connect them in series, water is pumped from one end up to a car radiator in the peak with a fan to blow hot air threw it and the heated water returns to the other end of the string or barrels.

Another more involved option is to dig an insulated rock pit under the green house. A perferated 4" pipe is run along the bottom of the pit and solid pipe up to the peak. A fan at the top pushes hot air down into the rock's and can be blown out at night as needed.

There are too many other option's to go into here. Like the insulated pit Greenhouse that uses the earth heat to grow food year round in most cases.

Gordy

ThomasJ1 (author)Gordyh2015-08-23

Thank you Gordy, I just had a look at the website and I am impressed to see so many different designs and ways to build a greenhouse. The energy loss is something I will focus on for the next growing season. I thought about the water barrels but never actually implemented the idea.

AldoG1 (author)2015-08-23

I need a freestanding paint booth for spraying some plastic chairs I found. Nice paint booth, oh, I mean, greenhouse. I live in Los Angeles, a greenhouse is not as useful as it is in Whitehorse.

khardinger (author)2015-08-23

Great Job & Nice to share with us, have a wonderful day

Beekeeper (author)2015-08-23

This is a very nice and sensible design. I have something similar in southern Manitoba and used greenhouse poly that has lasted 10 years so far. Two of my most successful crops in the greenhouse, apart from tomatoes, are peas and spinach. You can seed the spinach in fall and as soon as the sun warms the ground in spring, water and the spinach jumps out of the ground.

julian.thrussell (author)2015-08-21

This is a slight change to Thomas's great design. A roll of plastic water pipe is used, it's very strong, flexes and low cost (often free as left overs). The pipe is just bent in a hoop and secured at each bottom end by sliding it over a short pole set into the ground. If a snow point is needed a top 'backbone' made from a single square section of wood allows you to cut the pipe and screw the ends to the wood into a point, or use pegs if you can be bothered.

For the covering, you can get all sorts of UV resistant plastic sheet. Scaffold sheeting is really fantastic and will last a decade or more, but it is more expensive. Big building sites often just throw it away after one use. Harder ribbed plastic sheets can also be used. I find fairly thin plastic is easily damaged by birds, sticks and footballs. Bubble wrap is an excellent inner layer for more insulation.

Thank You Julian for the tips, I will definitely keep the bubble wrap in mind!

As we are renting, I did not want to build anything that would be hard to dismantle and collapse but for my next build, I will consider the hard corrugated plastic like yours.

JmsDwh (author)2015-08-20

Very nice! I especially like the Arduino integration. How does this hold up in the wind? How long does this greenhouse extend your growing season? I imagine the Yukon season is already pretty short.

ThomasJ1 (author)JmsDwh2015-08-20

The growing season is usually 90 days. You can get frost in June and people usually put their plants and flowers outside during the second half of June.

This year, I planted tomatoes early May. It wasn't warm at night but it was enough to keep them from freezing.

I usually get to harvest tomatoes in late September. Hardiest plants such as tarragon and parsley can be harvested a bit later.

I'll take some pictures of the Arduino set up

JmsDwh (author)ThomasJ12015-08-21

Do you plan to keep the plastic on it all year? Did you get snow after the roof was put up?

ThomasJ1 (author)JmsDwh2015-08-21

Yes The plastic stays on year round. We got quite a lot of snow last year, however Yukon snow is usually dryer and lighter than east coast snow.

At some point, there was probably 8 inches all over the greenhouse. A good kick from inside with the back of the shovel makes it slide to the bottom. Then you need to shovel the pile of snow that sits upon each wall otherwise it creates tension on the plastic.

It holds up well to the wind. At first, I did not attach the bottom half but high winds were lifting the sides. Now it holds up fine even at 60 kph gusting wind.

siteground-hosting (author)2015-08-21

thanks

shockingcanon (author)2015-08-20

You are right about the plastic, one season, probably not more. It will cost more, but greenhouse plastic would last 5+ years.

mpp1 (author)2015-08-20

May I ask how many seasons this lasts? I am no expert, but I don't believe that polyethylene last for very long.

Am I wrong about that?

sweetpea1145 (author)mpp12015-08-20

I'm talking about the plastic (6-mil) that comes rolled up that you can get at Wal-Mart or most hardware stores. The building wrap is different, and it looks like it does last longer.

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