Heated Greenhouse

I'm planning to build a greenhouse. Now, I have considered 2 options for the structure and several options for heating it. I will be using it for starting seeds and protecting cucurbitae from rain during the summer.

Structure Option 1:
PVC hoops and 100% DIY for approx $300

Structure Option 2:
Steel hoops, partial DIY, for approx $450

Heating Option 1:
Rocket Mass Heater, expensive in my area due to lack of parts

Heating Option 2:
a cheap wood burning stove such as are used for heating tents for winter camping, approx $165

Heating Option 3:
An electric heater with coolbot thermostat, about $300

I'm leaning towards the combo of Steel hoophouse and tent stove. But I'm posting my options here for advice.

As far as the structure goes, let me just throw out a third option.  I have built several greenhouses from cattle panels, and for cheap and DIY, I don't think it can be beaten unless you have access to some other free material.  It would be very easy to make one that used two layers of plastic rather than one.

With regards to heating, if you just want it to be used for starting seeds and protection from rain in the summer, I don't think I would bother with heating at all.  

Trace Oswald wrote:As far as the structure goes, let me just throw out a third option.  I have built several greenhouses from cattle panels, and for cheap and DIY, I don't think it can be beaten unless you have access to some other free material.  It would be very easy to make one that used two layers of plastic rather than one.

With regards to heating, if you just want it to be used for starting seeds and protection from rain in the summer, I don't think I would bother with heating at all.  

Do you suppose you could post some pictures of your cattle panel greenhouse? I'm having trouble picturing it.

Hi Ryan;
Your options for building, depend on location / budget / climate...  And how long you want your greenhouse to last.
For starting seeds in the spring in Ohio, you would want some form of heating.  

I use a RMH in our greenhouse/studio.   Seedlings are set on top of the mass.  Keeps their little roots nice and warm... they grow like crazy.

Building a rmh can seem very difficult to a new builder.  Supply's can be hard to find, especially in rural areas.
The benefit of using a rmh over a steel camp stove, is not needing to rush out and build a fire early every frosty morning.

An electric heater would do the job ... if easy and quick is what you are looking for.

My personal choice would be a RMH using the half barrel method.
A steel hoop house , hopefully with a double plastic layer.

thomas rubino wrote:Hi Ryan;
For starting seeds in the spring in Ohio, you would want some form of heating.  

I use a RMH in our greenhouse/studio.   Seedlings are set on top of the mass.  Keeps their little roots nice and warm... they grow like crazy.

Building a rmh can seem very difficult to a new builder.  Supply's can be hard to find, especially in rural areas.
The benefit of using a rmh over a steel camp stove, is not needing to rush out and build a fire early every frosty morning.

(Shortened for brevity)

What if I added significant thermal mass to the stove? Like covering it in cob?

Ryan Hobbs wrote:Do you suppose you could post some pictures of your cattle panel greenhouse? I'm having trouble picturing it.

Here's some videos of cattle panel greenhouses Edible Acres cattle panel greenhouse videos

I'm basically going to copy this guy, but make it longer. And where he used wood for the foundation, I'm going to use t-posts. And where he used the polycarb panels, I'll just use the greenhouse poly.

Ryan, mine has the plastic taken off for winter but here are plans to make a simple one.    This one is by a guy called Texas Prepper.

Ryan Hobbs wrote:I'm basically going to copy this guy, but make it longer. And where he used wood for the foundation, I'm going to use t-posts. And where he used the polycarb panels, I'll just use the greenhouse poly.

If you make it longer than two panels, I would recommend adding more braces at the areas the panels come together.  I made mine 4 panels long and just wired the cattle panels together.  We got a really wet heavy snow and it nearly caved the panels in.  The roof was pushed down a foot or more shorter than it was supposed to be.

Trace Oswald wrote:If you make it longer than two panels, I would recommend adding more braces at the areas the panels come together.  I made mine 4 panels long and just wired the cattle panels together.  We got a really wet heavy snow and it nearly caved the panels in.  The roof was pushed down a foot or more shorter than it was supposed to be.

Hmm, I was thinking 8 panels. So every other joint needs some wood bracing? I was thinking of adding a ridge pole and/or giving the roof a 90 deg bend so the snow is shed off a 45 deg angle.

Ryan Hobbs wrote:

Trace Oswald wrote:If you make it longer than two panels, I would recommend adding more braces at the areas the panels come together.  I made mine 4 panels long and just wired the cattle panels together.  We got a really wet heavy snow and it nearly caved the panels in.  The roof was pushed down a foot or more shorter than it was supposed to be.

Hmm, I was thinking 8 panels. So every other joint needs some wood bracing? I was thinking of adding a ridge pole and/or giving the roof a 90 deg bend so the snow is shed off a 45 deg angle.

I personally wouldn't bother with putting in a bend, the panels are fairly strong, and they are heavy gauge fencing.  With a 2x4 ridgepole and a couple extra braces you should be fine.  If we get a lot of really heavy snow that builds up, I just take a broom and knock it off.  8 panels will make a nice sized greenhouse.  That's more than 32 feet long.  The only other issue you may have is getting enough ventilation to keep it from getting very hot.  Mine goes over 100 degrees quickly even with the door open on sunny days that aren't too cold.  If it's closed up and 50 degrees outside, you'll have a sauna.  With the additional length, you made need to add a solar fan to keep enough airflow.

I made a cattle panel greenhouse for my chickens in the winter (Chicken winter greenhouse).  I put a dodgy ridge pole down the middle for snow and I still have to sweep it off a couple times a year.  I raised up one side (north) with pallets on the ground.  That way the plastic can go all the way down to the ground on the South side and the pallets can act as insulation on the North side.

For ventilation in a long greenhouse, what about having the poly join at the middle (16' mark) in such a way that you can roll it back towards the ends?  Then the air can come in from the two ends and rise up out of the middle of the long greenhouse.

Mike Jay Haasl wrote:For ventilation in a long greenhouse, what about having the poly join at the middle (16' mark) in such a way that you can roll it back towards the ends?  Then the air can come in from the two ends and rise up out of the middle of the long greenhouse.

Trace Oswald wrote:I personally wouldn't bother with putting in a bend, the panels are fairly strong, and they are heavy gauge fencing.  With a 2x4 ridgepole and a couple extra braces you should be fine.  If we get a lot of really heavy snow that builds up, I just take a broom and knock it off.  8 panels will make a nice sized greenhouse.  That's more than 32 feet long.  The only other issue you may have is getting enough ventilation to keep it from getting very hot.  Mine goes over 100 degrees quickly even with the door open on sunny days that aren't too cold.  If it's closed up and 50 degrees outside, you'll have a sauna.  With the additional length, you made need to add a solar fan to keep enough airflow.

I planned to make it so the sides could roll up and the gable ends would have vents for summer use that I could close in the winter.

Mike Jay Haasl wrote:That way the plastic can go all the way down to the ground on the South side and the pallets can act as insulation on the North side.

For ventilation in a long greenhouse, what about having the poly join at the middle (16' mark) in such a way that you can roll it back towards the ends?  Then the air can come in from the two ends and rise up out of the middle of the long greenhouse.

Those are both really good ideas, thanks for posting them.

I just had a crazy idea. What if we made ultra-light boats out of cattle panels and extra greenhouse poly? Or if the poly isn't strong enough, we could use canvas and tar?

Ryan Hobbs wrote:I planned to make it so the sides could roll up and the gable ends would have vents for summer use that I could close in the winter.

It's amazing how much these things heat up.  The reason I suggested having the plastic able to be parted at the midpoint of the greenhouse is so that the heat can rise up out of it.  Maybe with a relatively short height hoop, having the sides rolled up will be enough.  

Another option would be to remove the plastic entirely for the summer.

Mike Jay Haasl wrote:

Ryan Hobbs wrote:I planned to make it so the sides could roll up and the gable ends would have vents for summer use that I could close in the winter.

It's amazing how much these things heat up.  The reason I suggested having the plastic able to be parted at the midpoint of the greenhouse is so that the heat can rise up out of it.  Maybe with a relatively short height hoop, having the sides rolled up will be enough.  

Another option would be to remove the plastic entirely for the summer.

My concern is that it would leak during the seed starting. That's why I think I should make hatches that can close tightly.

I worked out the dimensions:
Using 50 in x 16 ft cattle panels, eight of them, the greenhouse will  be 5 ft 1 in tall, 33 ft 4 in long, and 10 ft 2 in wide. the height can be changed to a more comfortable 7 ft by raising the  foundation of the arch to 2 ft above ground level. This will add 4 ft  of width to the cover. additional 1 ft of cover width allows attachment to roll up device

Ryan Hobbs wrote:10 ft 2 in wide. the height can be changed to a more comfortable 7 ft by raising the  foundation of the arch to 2 ft above ground level. This will add 4 ft  of width to the cover. additional 1 ft of cover width allows attachment to roll up device[/tt]

Ryan, I made mine narrower than that so the frame could be standard 8 ft lumber.  That gives me more height.  I'm not certain how tall mine is, but I'm guessing 6 ft 6 in or so, enough for me to walk in easily.  I like the idea of raising it and adding insulation to the north side like Mike mentioned.  I'm getting ready to make another one, I'll be doing it that way.

One solution to tempature control would be an air to earth heat battery.
This consists of lengths of drain pipe, the black corrugated stuff,  buried in earth,  and a fan to push hot air through them.
The water vapor in the hot air condenses on the sides of the pipe and drains into the surrounding soil, taking heat with it.
So on your hottest days,  draw air from the peak of the greenhouse roof and replace it with cooler,  dryer air from the soil.

Some use these systems to store heat on an annual basis,  some use them to store heat on a daily  basis.

These systems work best when the volume of soil to be heated is insulated from the rest of the earth.
To me,  this invites the use of raised beds,  to avoid extensive digging.

One use that I haven't seen tried is wood heat plus air to soil heat exchange.
A little camping woodstove surrounded by thermal mass could be fired hot and fast for a relatively clean efficient fire.
Nowhere as good as a rocket stove, but much better than a low smoldering fire.
An air to earth system could capture wood stove heat from the air.
To enhance heat transfer, part of the mass of on the woodstove could be water,  and evaporation from  that water could be captured in the air to earth system.

Something interesting happened today. I was at the doctor office waiting to be picked up and I was chatting with some folks, and when we started talking about gardens and green houses, a lady piped up that her son had 2 commercial greenhouses he wanted to get rid of. So I gave her my contact info and now I'm just waiting for the call to talk business. I'm excited about the opportunity, and could really save us some time and money.

Lets hope that works out Ryan!   What a score it could be!

thomas rubino wrote:Lets hope that works out Ryan!   What a score it could be!

The lady said it might be a week before her son returned from his business trip. The suspense is killing me.

Editd to add: I just got the e-mail!!! I'm horse trading now.

Ryan Hobbs wrote:

thomas rubino wrote:Lets hope that works out Ryan!   What a score it could be!

The lady said it might be a week before her son returned from his business trip. The suspense is killing me.

Editd to add: I just got the e-mail!!! I'm horse trading now.

Congrats.  I hope you can work out a deal.

Trace Oswald wrote:

Ryan Hobbs wrote:

thomas rubino wrote:Lets hope that works out Ryan!   What a score it could be!

The lady said it might be a week before her son returned from his business trip. The suspense is killing me.

Editd to add: I just got the e-mail!!! I'm horse trading now.

Congrats.  I hope you can work out a deal.

Deal is done, I've got them on layaway now: two 24ftx48ft greenhouses. Gonna take a few months to pay for them, but there it is. I have to open a special savings acct to do the layaway, but yup. One is gonna be modified into a chicken run and coop. The other will be a regular greenhouse.

SWEET RYAN!!!    Congrats on your score!

thomas rubino wrote:SWEET RYAN!!!    Congrats on your score!

Thanks Thomas. I'm very happy about it--->   ^__^

Hey great to hear about the Greenhouses Ryan! (You know I am always rooting for you I hope). I love to see a great person get ahead.

As for heating, I noticed around here the Amish put in a woodstove in their greenhouses about 1/3 of the way from the front of it. Then they run the stovepipe out the back at a very shallow angle all the way to the backwall at the top, then turn it of course and go up a bit for draft, but I assume they do this so that the chimney helps heat the greenhouse with a minimal of wood.

Travis Johnson wrote:Hey great to hear about the Greenhouses Ryan! (You know I am always rooting for you I hope). I love to see a great person get ahead.

As for heating, I noticed around here the Amish put in a woodstove in their greenhouses about 1/3 of the way from the front of it. Then they run the stovepipe out the back at a very shallow angle all the way to the backwall at the top, then turn it of course and go up a bit for draft, but I assume they do this so that the chimney helps heat the greenhouse with a minimal of wood.

That I can do! If you remember my old post from before we got the farm, I had an ondol for heat as an idea. This seems a lot simpler but basically the same concept. Do you suppose the stove would need an air pipe coming from outside?

Good deal mr Hobbs!
Would it help heatwise in summer if the greenhouse was on a hill. So the greenhouse is sitting at an angle. There is a high bit and a low entrance and then you make it so that you have a big window at the highest point and at the lowest point you open the door... Naturally you'll get a draft. Would it be enough for tropical plants not to die of heatstroke? I'm thinking of ginger, sweet potatoes , bell peppers and melons..
I worry that the metal will damage the poly plastic, what if it is changed by ropes, i read that in the comments. You'll need "beams" across. A bit more framing. And then tie it together with rope. Knot it around every beam. It will make it more square then round, but so what. Any thoughts/ experience?

some thoughts for you...some subtle forms of heat you could use are thermal mass, and possibly a compost heater, yes this a thing.

the warmth of even a simple compost pile, enclosed within the greenhouse, can put out a lot of heat. but maybe a bit more particular, compost used as heating usually has pipes going through it to heat up water. connecting this with thermal mass heating in the form of black plastic barrels and drums of water...

Hugo Morvan wrote:
I worry that the metal will damage the poly plastic, what if it is changed by ropes, i read that in the comments. You'll need "beams" across. A bit more framing. And then tie it together with rope. Knot it around every beam. It will make it more square then round, but so what. Any thoughts/ experience?

and totally yeah this is what i do with cheapo poly twine and rope...make a lot of diagonals and lines of rope around so the plastic sits on top of that and is further held together around the outside.... through winter....in the original cheapo greenhouse style...

well even though the OP figured out his query, on the original topic...i have definitely used both methods mentioned, cattle panels, and also PVC.  we had one cheap greenhouse ish structure that had been a mini carport type thing, but we got for free and used to keep plants a bit longer each season...and also to store sensitive trees and perennials...

i happen to have some pics...attached...been sorting pics lately...these are older...

Outstanding thread!  You all have hit me right where I've been heading!

I live in central South Carolina, so for the most part I don't have to worry about snow.  But, we do have to deal with temps down in the 20's overnight at times.  Right now I'm working with a friend in his family's former tobacco greenhouse... 200'x36'...  That's a lot of space to work with!  So, I'm partitioning off about 60' to be our main area and leaving the rest for (hopefully) in ground crops like carrots, kale, collards, broccoli, cabbages and the like.  We've already started some tomatoes and peppers, and will be starting more next week.  We plan on putting these in ground in the 60' section.  We plan on providing needed heat to this part, whereas we're hoping that the rest will be able to maintain a healthy growing attitude in their protected mini-clime.

I love the idea of the cattle panel greenhouses!  I'm thinking of building a couple at about a 6x12 or 6x18 length and selling them at a local feed mill.  I'll see how that pans out and let you know.

I also have picked up the frame from one of those canvas covered equipment/car ports, 24x13 and about 7 feet in height.  I've already bought greenhouse plastic to cover it along with tapes, etc.  I'm planning on trying to heat it with a buried black PVC pipe buried about 6' deep under the greenhouse and using a solar powered fan to move the air through the PVC system into the greenhouse proper.  If it doesn't heat the entire place, it will at least raise the temperature so I won't need as much propane to maintain an adequate temperature level.

A note on some of the cattle panel greenhouses, above.  Make sure you have adequate ventilation for the top of the structure, moreso than at ground level.  Your heat will rise and need to be vented.  You also don't want to have too much of a cold draft going across your plants, either.  Side vents/curtains will allow you to open up the greenhouse during Spring and Summer when temps begin to rise and allow you to use it for a longer period.

Two things I want to grow... oranges and bananas... There is a Satsuma variety orange that is fairly cold tolerant down to the upper 20's so I'm hoping it will work well within a greenhouse.  Banana plants grow around here but I've yet to see any fruit from any of them.  Maybe... just maybe...

Dave

David A. Smith wrote:
Two things I want to grow... oranges and bananas... There is a Satsuma variety orange that is fairly cold tolerant down to the upper 20's so I'm hoping it will work well within a greenhouse.

I'm not sure if this would work, but what about poncirius trifoliata as a rootstock for the satsuma orange?

Ryan Hobbs wrote:

David A. Smith wrote:
Two things I want to grow... oranges and bananas... There is a Satsuma variety orange that is fairly cold tolerant down to the upper 20's so I'm hoping it will work well within a greenhouse.

I'm not sure if this would work, but what about poncirius trifoliata as a rootstock for the satsuma orange?

thats the common practice and type of rootstock. almost ALL commercial citrus trees you purchased grafted are on "flying dragon" or one of the other cultivars of trifoliata.

in zone 8 you might as well plant a type on own roots, being that it may at some point die back to the roots. like most plants, they are hardier at the root than any of the above growth.

good luck with your citrus. s. carolina is probably solidly zone 8 so i say it's a go =)

bananas, unless you get the few hardiest types, is quite tricky and would definitely require more fussing with and a good greenhouse.

Travis J. wrote:As for heating, I noticed around here the Amish put in a woodstove in their greenhouses about 1/3 of the way from the front of it. Then they run the stovepipe out the back at a very shallow angle all the way to the backwall at the top, then turn it of course and go up a bit for draft, but I assume they do this so that the chimney helps heat the greenhouse with a minimal of wood.

Great tip from Travis. And then you could even place mass around the length of the horizontal stovepipe. Put a masonry shelf above the pipe and then rest your seedlings on top. maybe with reflective panels to direct the heat up to above the pipe. Or wrap the whole horizontal pipe with some form of box surrounded by mass like gravel. Many fun options...

Peter George wrote:

Travis J. wrote:As for heating, I noticed around here the Amish put in a woodstove in their greenhouses about 1/3 of the way from the front of it. Then they run the stovepipe out the back at a very shallow angle all the way to the backwall at the top, then turn it of course and go up a bit for draft, but I assume they do this so that the chimney helps heat the greenhouse with a minimal of wood.

Great tip from Travis. And then you could even place mass around the length of the horizontal stovepipe. Put a masonry shelf above the pipe and then rest your seedlings on top. maybe with reflective panels to direct the heat up to above the pipe. Or wrap the whole horizontal pipe with some form of box surrounded by mass like gravel. Many fun options...

Alright, so I'm thinking a RMH without a barrel, all cob (because it's cheap) Just a j-tube and a cob bell... I know it's not great for instant heat, but could it work for slow steady heat? And then wrap the cob in some kind of mass like a gravel box with plastic over the top for that warm bench? Then metal stovepipe out the end and above the hight of the roof?

Edited to add: I have a book I could use to get demensions for an all cob furnace. It's a book on kilns, but it has all I need for drafts and how long I can make things.

I think I heard that cob and greenhouses don't do well together.  Something about condensation, humidity and irrigation affecting the cob.  But I could be wrong.  Here's a thread that could be worth a review:
Rocket stoves in Greenhouses, our own forum topic

Mike Haasl wrote:I think I heard that cob and greenhouses don't do well together.  Something about condensation, humidity and irrigation affecting the cob.  But I could be wrong.  Here's a thread that could be worth a review:
Rocket stoves in Greenhouses, our own forum topic

I followed that post.

What do you think about a masonry "Kiln" which is on its side like an anagama, but instead of being one large tube, is several smaller tubes?I can crank it way up and it will stay hot for a week. It can be made of house bricks and compacted earth. Humidity will not really matter.

I don't officially know much about it but it sure seems like masonry would be a great material for a heater in a greenhouse if the brick is available or cost effective for your goals.  The anagama was new to me but the pictures online are neat.  Is that a way to fire an entire village's pottery in one go?

It seems like an ideal wood based heat system for a greenhouse would be one that you could fire up once a day on cold evenings or every other day at less cold times.  Lots of mass so the exhaust is at a low temp.  And not necessarily a metal bell/drum since you hopefully don't need or want fast/hot heat.

Mike Haasl wrote:I don't officially know much about it but it sure seems like masonry would be a great material for a heater in a greenhouse if the brick is available or cost effective for your goals.  The anagama was new to me but the pictures online are neat.  Is that a way to fire an entire village's pottery in one go?

It seems like an ideal wood based heat system for a greenhouse would be one that you could fire up once a day on cold evenings or every other day at less cold times.  Lots of mass so the exhaust is at a low temp.  And not necessarily a metal bell/drum since you hopefully don't need or want fast/hot heat.

One potter can usually fill a multi chamber naborigama in 3 months. An anagama of the size of Kanzaki Shiho's kiln can be filled by a production potter in about a month. His kiln is fired for 8 days and the ashes that settle on his pots make a crusty natural glaze. I'm not a production potter, nor a Japanese National Living Treasure, so my little gas kiln is plenty for my individual pieces. I'm shifting away from my carved bowls and teaware and getting into sculpture, so I might build a wood burning kiln for sculptures specifically. It depends on what you're doing. A Bizen Climbing Kiln Is an example of a village size kiln. Look that up, it's bloody huge.

A relatively small kiln can heat a greenhouse effectively. I'm thinking the size of my own cob anagama that I had at my last house. I am only worried that it would come to some misfortune in the greenhouse environment.