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help me heat my greenhouse for zero cost after initial investments

Here's the deal. I have a small 6x8 or so greenhouse that I've had four 3 or 4 years. I've never grown any plants inside but I would like to start growing nepenthes in it, and not just khasiana ;)

I live in zone eight, and recently have been thinking about various methods of harnessing energy from the environment and using it as heat.

So far here are ideas I've come up with to keep my greenhouse at a comfortable 55-60 during december nights.


Caulk Caulk Caulk
Add insulation to the north wall, cover in plywood and paint black
Glaze all panels and add bubblewrap insulation
Insulate the floor.
Add gravel to the floor to act as a heatsink.
Make a solar water heater and use the hot water to somehow heat the greenhouse???
Move my rain barrel inside, paint in black, fill with water and seal tightly.


Any more ideas, the more the better. My goal is to have zero heating costs after initial investment.
 
I've head of people keeping a compost heap inside, which releases a lot of heat... but that's probably only good for larger greenhouses. All your ideas are really good though and in zone eight might be enough. You might want to keep a heater backup though in case something fails, so your plants don't die. If you don't mind a small cost after initial investment, you could use heating pads and heat the individual trays, which would be much cheaper than heating the whole greenhouse.

You could also live in there... I'm sure the plants would appreciate the warmth and CO2. :)

Good luck!
 
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Since it is a fairly small GH, you could probably use a small space heater to warm the GH. I'm sure it won't take too much energy to run one if you could insulate the GH.
 
Since it is a fairly small GH, you could probably use a small space heater to warm the GH. I'm sure it won't take too much energy to run one if you could insulate the GH.

I have though about using a space heater, but decided against it.

Let me say this first, I'm not a fatalist.
That being said, let me say this...

I want my greenhouse to be heated in a way that isn't dependent upon the activity of the sun, the electrical grid, and the condition of the nations economy.
In the Victorian Era many greenhouses went cold across Europe and America.
I'm not a fatalist, I'm simply thinking long term.

For example.... It's a fact that solar flares have occurred in human history and knocked out power grids. While it's not a common occurrence, if my greenhouse relied on a space heater a solar flare could spell disaster for it's inhabitants. I wouldn't have room for all the plants on my already full windows.

If my greenhouse is truly self sustaining (other than repairs, etc) I could move the easier HL plants off of my window and into the GH (in shade at first) and grow the more tender intermediates and HL species indoors
Also, the more passive the heating system is the less chance for mechanical failure.
A space heater may fail to work, but a barrel of water will always absorb heat and release it at night.

---------- Post added at 10:56 PM ---------- Previous post was at 10:50 PM ----------

Here's a video of a solar water heater that heats water to 120F. It's on the roof of someones car port.

I just installed a carport like the one in this video. The roof is basically flat, there is only a slight slope of an inch or so. The carport is also near the hose faucet and less than ten feet from my greenhouse.

The question is, how would I use the hot water to heat the greenhouse? What about running the tubing from the carport into the greenhouse and snaking it through the floor?


Here's the video
I would skip to 3:43 the intro is a lot of fluff
<iframe width="420" height="345" src="http://www.youtube.com/embed/sBAi_TVNaiM" frameborder="0" allowfullscreen></iframe>
 
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Hi muscipula

I would bury the pipes in the greenhouse soill, (can you insulate the greenhouse soil from the outside soil by use of polystyrene slabs or similar?) the idea being to heat a relatively large mass, so the heat gets released slowly over a period of time, similar to your water barell idea. This would have the added benifit of adding 'bottom heat' to any plants sunk into the soil.

Probably plastic pipe would be the easiest as you wont need to make a load of joints, although its coeficient of heat transfer isnt as great as metal tubes so you will need to use more.

Putting in a radiator or just letting the pipes conduct heat in air, will rapidly heat (when you dont really need it i.e. the sun is out so presumably warming the greenhouse) or cool the space, which is undesirable.

Sounds like a usefull project, I'm also zone 8 so am interested in the results, good luck and let us know how you get on.

Cheers
Steve
 
Hi muscipula

(can you insulate the greenhouse soil from the outside soil by use of polystyrene slabs or similar?)

Cheers
Steve

I am not sure Steve. The easiest way to insulate the ground would be to add a foam insert to the bottom of the greenhouse. But stryofoam would compress under the weight of me walking on it and definitely under the weight of a rain barrel filled w/water to act as thermal mass.

This is something my mother mentioned earlier, if the ground is not insulated I'll lose heat to conduction.

Okay new challenge? How do I insulate the soil if I need to? :-))
 
Hi muscipula

I was thinking of the vertical aspects only, i.e. from the green house base vertically down say 700mm (28-30") to be lined with polystyrene, on the premise that heat rises, the downward disipation of heat would a) be small in value and b) if the heat is contained at the sides, the bit that goes downwards could be deemed as benificial as it then forms part of the heat sink.

So the the polystyrene would not actually be walked on so wouldnt compress.

Cheers
Steve
 
While it's not a common occurrence, if my greenhouse relied on a space heater a solar flare could spell disaster for it's inhabitants.

In a climate such as ours in the PNW it is possible to rely on "passive" techniques to capture what heat you need to maintain a greenhouse for highland species, under most circumstances. However, it is worth keeping in mind that once or twice every winter, we experience a few nights that dip down to as low as 8F, and there isn't a passive heat system on earth that will prevent serious freeze damage to the contents of any greenhouse that does not make use of artificial heating. You may be able to engineer a system that works when night temps do not drop below 40F, but beyond that, you will need to have a backup system at the ready.
 
In a climate such as ours in the PNW it is possible to rely on "passive" techniques to capture what heat you need to maintain a greenhouse for highland species, under most circumstances. However, it is worth keeping in mind that once or twice every winter, we experience a few nights that dip down to as low as 8F, and there isn't a passive heat system on earth that will prevent serious freeze damage to the contents of any greenhouse that does not make use of artificial heating. You may be able to engineer a system that works when night temps do not drop below 40F, but beyond that, you will need to have a backup system at the ready.

hmmm..... I wonder if there is a more efficient backup system that a regular old space heater.
I wonder if I could make use of some victorian technology.

---------- Post added at 08:59 AM ---------- Previous post was at 08:45 AM ----------

Here's a link on victorian greenhouse technology
http://winsfordwalledgarden.com/gre...enhouses&Page=Victorian_Greenhouses_Home_Page
 
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However, it is worth keeping in mind that once or twice every winter, we experience a few nights that dip down to as low as 8F, and there isn't a passive heat system on earth that will prevent serious freeze damage to the contents of any greenhouse that does not make use of artificial heating.

I beg to differ. There are many passive solar homes in subarctic regions that can maintain inside temperatures above 40F throughout entire winters at sub-freezing outside. A small fully glazed greenhouse has substantial heat loss and dismal thermal mass, but I think it's possible to at least prevent a hard freeze for a single night with a little ingenuity. A greenhouse can withstand arbitrarily large temperature drops if it's big enough - the difficulty with small ones is that they don't have the thermal mass to store enough heat to last through a cold night.
D, check out this guy's compost heater: http://onestrawrob.com/
On the off chance that your greenhouse is near your house, it might be possible to warm it with exhaust from your heater. Also, what are you growing? If most of the plants in your greenhouse can withstand a light frost, you might also consider setting up a smaller enclosure within the greenhouse to shelter the most sensitive individuals, and heat that instead of the whole space.
~Joe
 
  • #11
My greenhouse is right next to my house, and there are windows right next to both ends of the greenhouse. Only problem is these windows are full of plants. My room only gets to about 60F in the winter
I might be able to circulate the air in my room into my greenhouse, having one duct pumping warmer inside air into the GH, and the other duct bringing it back into my room. I have a solar powered exhaust fan with a thermostat, that could be useful for doing this. I think I would need some way to warm the air though.

I want to grow HL nepenthes in the greenhouse like lowii, khasiana, rajah, mikei, etc. The idea of me setting up a greenhouse is so I don't have to confine nepenthes to a tiny space. But I have thought of a coldframe within my gh.

I'm browsing that link you gave me Joe, but there's a lot of info.
Do you have a direct link to his compost heater?
 
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  • #12
There is a lot of energy wasted in a domestic household, e.g. hot gases from gas boiler flue (can be in excess of 60'C), hot water from bath, washing machine, shower, sinks etc, hot air from tumble dryers, all of which are simple disposed of either to atmosphere or drains. I've also read about heat being extracted from sewage pipes. Problem is capturing and storing the energy can be difficult and expensive.

BTW, if you are a little frugal you could leave the water in a bath after bathing until it gets cold. That way the heat is transferred to the room :)
 
  • #13
There is a lot of energy wasted in a domestic household, e.g. hot gases from gas boiler flue (can be in excess of 60'C), hot water from bath, washing machine, shower, sinks etc, hot air from tumble dryers, all of which are simple disposed of either to atmosphere or drains. I've also read about heat being extracted from sewage pipes. Problem is capturing and storing the energy can be difficult and expensive.

BTW, if you are a little frugal you could leave the water in a bath after bathing until it gets cold. That way the heat is transferred to the room :)

Actually, this could be a very good idea... pumping "waste" hot water into the greenhouse in general. If you arrange the water from a shower to go into the drum in the greenhouse, you could get a lot of radiant heat. You'd just have to rig it so the water goes outside afterward.
 
  • #14
what about woodgas?
Gasifiers have been used to power tractors, taxis. They can also be used to generate electricity and they can run on scrap wood soft or dry and possibly junk mail.
 
  • #15
I'm browsing that link you gave me Joe, but there's a lot of info.
Do you have a direct link to his compost heater?

Whoops, sorry, didn't realize how hard it is to find from the main page. Here we are:
http://onestrawrob.com/?cat=32
I don't suggest recirculating air from your house to your greenhouse and back - just slowly pump it one way. The greenhouse will be damp and stuffy at times and you don't want to blow that back into your house on a muggy day. But the house air will almost always be warmer at night, and just a trickle of that warm, (relatively) humid air will make a difference to the climate in the GH.
As for growing your Nepenthes in the greenhouse, you're going to have to make some hard choices. You'll need exhaust fans to keep temps from getting too high, and even if you use passive heat you'll need an emergency heater every once in a while - there's the matter of getting thermostats to control it all, too. (I suppose you can get some of those snazzy emergency exhaust vents that open automatically when the temperature reaches a high enough point, but especially with a smaller greenhouse, you'll want a fan as well due to the small thermal mass.) You can get away with a no-power setup for a while, but eventually there will be an accident or a weird weather event you didn't plan for, and powered devices are just better suited for emergencies like that. I suggest gradually moving your biggest, hardiest plants first to optimize the use of your indoor space. Also start collecting greenhouse parts - vents, fans, swamp coolers, controllers, etc. If you buy just a few things at a time, and scavenge for used stuff, it'll be much more manageable than doing it all at once.
~Joe
 
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