I am in 6b (southwest PA) trying to lower the costs of heating my greenhouse, and I am unsure of the best way to do it for my situation.
I overwinter tropical pond plants in the greenhouse as well as citrus trees and seed starting.
I was told that it’s more efficient to heat water (thereby warming the air) than to heat the air.
Last year I just had one 110 gallon tub that I heated, and I also heated the air.
This year I have more tubs (4) that I can use if it makes more sense.
I am sure that no amount of water heating will eliminate the need to run my heater, but will heating 3-4 tubs cut down on the need to run it?
I get full sun, so even in the dead of winter, it’s often toasty as heck in the greenhouse during the day.
Any Insight?
by _rockalita_
4 Comments
During the day you could setup a solar hot water heater.
If I remember correctly The water has a larger thermal mass, and it doesn’t cool as slowly as air might. You can always get clear plastic sheeting to put on top of the greenhouse to help keep air transfer down.
The water tubs are temperature stabilizers. They will heat up and cool down more slowly than the air. The stategy to that is during the day when heat is excessive, it can be absorbed somewhat (though slowly) by the water bodies, then after dark when the sun is gone, that heat can be slowly sloughed off the bodies of water (called a “heat mass”). In theory at some volume, this will lower your overall heating costs at night. This is why people sometimes paint the water reservoirs black, so they absorb that much more light/heat during the day.
However.
Not everyone is going to like this.
I argue that you need *so much water*, that is you need such seriously substantial heat masses — to make a measurable difference on your energy bill — that you end up with very little square footage in your greenhouse that isn’t occupied by water tanks. A few hundred gallons of water is going to do very little (because your greenhouse is rather large), it’s almost not worth bothering with it. I would be intersted to see if you put a 2,000 gallon black tank in there, if even *that* would show up as DOLLARS saved on your energy bill, it might be only cents.
Some greenhouses put the heat mass on the north side of the greenhouse, and back it with earth, and yadda yadda. Basically, this heat mass strategy *can be* effective when really done well, but just putting some jugs and tubs of water probably isn’t going to cut your energy bill appreciably.
It’s definitely worth an experiment though, it hurts no one.
https://preview.redd.it/cmx7cos54sqd1.png?width=1080&format=pjpg&auto=webp&s=27ee6ea11a8eb69b86b08e4031671aaba6087486
I use water totes and black gallon water jugs, infrared heater, circulation fan, but I also cover with a solar pool cover which is basically a very heavy bubble wrap. GA 7b/8a
Look up hydronic heaters, might find what you’re looking for. They blow air over hot water, and if you’re already gonna have warm/hot water around would save tons on electric.