First time owning a GH and have been trying to keep temps from dropping too low without the use of electricity.
Read that you can use water as thermal mass to capture heat during the day and release that energy at night. Went out and got some trash cans to store the water. Since then, I’ve noticed the temp in the greenhouse has consistently been 5F degrees colder than outside when the sun isn’t out.
Any ideas why?
by Cu0ngpitt
11 Comments
Is the water in the trash cans ever getting higher than the ambient temperature? If not, they would act like a heat sink and have a cooling effect on the surrounding area.
Or I could also be way off. 😂
Without a heater, you can expect the greenhouse to be 5-7* F warmer than outside.
I’m guessing the trash cans with water in them don’t ever have the chance to warm up to the point where they’d be able to absorb/retain heat all night.
Sometimes my exhaust fan works so well that it will be colder than the outside temp for a short while.
With that being said, without insulation, you’ll struggle to keep it much warmer than ambient, as the other user mentioned. The heat will leave just as quickly.
For the water in the trash cans to heat up, the cans need to be exposed to as much direct sunlight as possible. The idea is for the black trash cans to absorb sunlight and heat the water inside. In your picture, the cans are hidden under the plant shelves; I can’t image they get much sunlight there.
Are you exhausting the air at night ? Are all windows closed after nightfall ? Sounds like your heat sinks are turning into cold sinks.
I have never considered using the trash can method….it seems to me, for them to be any use at all, they need to be exposed to direct sum light all day in order to warm up enough to be useful…. that is space that is needed for plants…..If those are them under the shelves and that is all the light they get, it might be possible that they never warm up enough to do any good….are they coolor than out side? I’d check water temp, but that seems odd
Maybe you need to heat them during the day, so extract the thermal energy at night
It looks like that spot doesn’t get near enough direct light if you leave the buckets there.
Someday I’ll have a greenhouse
.. someday
Put a 100 watt fish tank heater in a few of them. Could even go higher for those. Relatively low cost just need an extension cord
I have a larger GH and use propane.
However, around my Mitragyna trees, I have 35 gallon black plastic tubs.
I place 2 heat lamps pointed directly at the water about 3 feet away.
These are turned on before well before the propane, and it keeps the area warm enough. Heat lamps aren’t my favorite, but I only built mine in Oct, so I’m still adapting.