How do you heat your greenhouse?

I just built my greenhouse a few months ago. I ended up getting a small 6x8ft as a gift from the inlaws that had been collecting dust for a long time(still in the box).

Here are the methods I both plan to use... and am currently using...

1) I plan to seal up all edges with caulk.
2) I plan to litteraly use some insulation... preferably reflective and water resistant on my shaded North wall... and wall against the garage.
3) I already purchased a 55gal food grade drum. ($15)It is black... and filled with water to absorb heat and then release. It's on the North wall and could benefit from some Sun hitting it from all sides. (see #2)
4) I made the entire floor out of cheap concrete tiles in the middle for path... and the cheapest dark grey gravel I could find everywhere else.
5) On the nights where it gets down into the low thirties(and colder)... I currently just use some old fashioned light bulbs on top of the plants. Even my Tomatoes have been thriving in the cold!(mid 20s) I just did that as an experiment and will let them expire soon.

I was considering a space heater... but @1500W... I could just put in up to 25 Bulbs rated @ 60W! The lights would be gentler... more direct... more even... and since I only have 4 bulbs... much cheaper on power. In the future I plant to somehow attach a single bulb to a thermometer and have it come on when the temps drop only. I will only keep a bulb on my meyer lemon tree... and anything I am growing from seed.

The Water barrel was super cheap... and doubles as an emergency source of drinking water. That barrel would last my family of 4 good while. It would be sweet to set up a fish growing system inside it some day... solar powered of course.

Any more ideas and/or suggestions as to what I could do more?

I want to give the house an exo-skeleton of cheap/heavy duty cattle fencing next summer... and let scarlet runner beans or malabar spinach run up it every year for shade. Cheaper than shade cloth.

Thanks!

since its so small i would just throw an insulated blanket over it at night. cover that with a waterproof layer. you could run a heat bulb if you were in real cold areas. take it off in the morning.

That is a good idea. Thank you Jordan.

However, I know myself... and I will never take the time to do something like that unless it gets below 0deg F or something. Juggling my work life, new home, and new family of four has other things higher on my priority list.

I am thinking that other than the lemon tree... I will just grow lettuce and brassicas in there during the cool months. Mainly using the greenhouse to clone cuttings and germinate the next crop rotation for my four small gardens.

I live in zone 7b - 8a depending on which map you are looking at. So if the temps drop down low they don't stay there for long... and they don't go very low either.

Barrel in the GH
small fountain pump in the barrel
pump is on a timer, pumps water through tubing coiled on the ground in the sun
water returns to the barrel

greenhouse cover: 6mil plastic, construction grade, single layer, drafty
barrel: 55 gallon plastic, mostly full
pump: about 12 watts
tubing: 3/4" PEX, black, 400 feet
timer: comes on when the sun hits the hose, turns off when it goes behind the trees
Barrel Temperature: I've had the barrel up to 140 degrees
GH Temp: I've seen it as low as 41 in the morning, 28 outside

Never lost anything to frost or cold.
Zone 8b/9a

Ken Peavey wrote:Barrel in the GH
small fountain pump in the barrel
pump is on a timer, pumps water through tubing coiled on the ground in the sun
water returns to the barrel

greenhouse cover: 6mil plastic, construction grade, single layer, drafty
barrel: 55 gallon plastic, mostly full
pump: about 12 watts
tubing: 3/4" PEX, black, 400 feet
timer: comes on when the sun hits the hose, turns off when it goes behind the trees
Barrel Temperature: I've had the barrel up to 140 degrees
GH Temp: I've seen it as low as 41 in the morning, 28 outside

Never lost anything to frost or cold.
Zone 8b/9a

Great Idea for an addition to the rain barrel!

Please keep those ideas flowing.

Thanks,

A barrel that is burried in the center of the floor and filled with water, will thermosiphon heat from beneath. A pit greenhouse with a sunken barrel could draw heat from 8 ft below the surrounding surface. In my area, soil at that depth always stays about 15F above freezing. A loop of pipe run from the barrel and through the grow beds, would thermosiphon whenever the water temperature is higher than that of the beds, and would stop flowing when the greenhouse is warmer. I can't think of a cheaper means of using geothermal energy.

Dale Hodgins wrote:A barrel that is burried in the center of the floor and filled with water, will thermosiphon heat from beneath. A pit greenhouse with a sunken barrel could draw heat from 8 ft below the surrounding surface. In my area, soil at that depth always stays about 15F above freezing. A loop of pipe run from the barrel and through the grow beds, would thermosiphon whenever the water temperature is higher than that of the beds, and would stop flowing when the greenhouse is warmer. I can't think of a cheaper means of using geothermal energy.

OMG that sounds like a great idea. I am picturing the water at the top of the barrel getting cooled by winter temps... then sinking down to the bottom... while the warmer water from the bottom pushes towards the top. Then... like you said... when the air in the greenhouse gets warmer than the soil below... the warmer temps will stop the water in the barrel. No need for complicated moving parts that consume energy or ever wear out.

I need to make a list out of all of these ideas when this thread is completed! Maybe a sticky?

Sadly I cannot do the barrel in the ground. The main power wire for my house runs about 3 feet below my greenhouse. Dead center.

Another way to harness deep down heat, would be to drive scrap aluminium rods or angle iron deep into the soil. Aluminium transfers heat along it's length very quickly. Fins that are attached to the airborne portion of the rod, would allow it to shed heat more readily. For best results, the central portion of the rod should be wrapped or painted with an insulating material.

An earth tube loop could be set up. It would work by convection, just as the barrel does.

I have a good greenhouse site above a steep slope. An earth tube that starts down the slope below the greenhouse floor level, would give an updraft of warmed air to the greenhouse, whenever air temperature drops below that of the soil. A baffle may be required to prevent cold air from flowing down the tube once the ground cools off late in the season.

Dale Hodgins wrote:Another way to harness deep down heat, would be to drive scrap aluminium rods or angle iron deep into the soil. Aluminium transfers heat along it's length very quickly. Fins that are attached to the airborne portion of the rod, would allow it to shed heat more readily. For best results, the central portion of the rod should be wrapped or painted with an insulating material.

An earth tube loop could be set up. It would work by convection, just as the barrel does.

I have a good greenhouse site above a steep slope. An earth tube that starts down the slope below the greenhouse floor level, would give an updraft of warmed air to the greenhouse, whenever air temperature drops below that of the soil. A baffle may be required to prevent cold air from flowing down the tube once the ground cools off late in the season.

Your post just made me realize something...

The frame of my greenhouse is made of aluminum. Therefore, the whole structure may be working against me!

I just bought some insulation for the North... and garage walls. I will be either wrapping or covering the frame as well. Maybe expanding foam?

I also got a DC Hot Water pump(3GPM) with matching 15W solar panel from Amazon. I cant wait to get everything installed.