- Thread starter
- #31
LaurenRitz
Almost Self-Reliant
This moring 17 and 28. Pretty good, far better than I expected.
Cattle panel greenhouse
- Thread starter LaurenRitz
- Start date
- Thread starter
- #32
LaurenRitz
Almost Self-Reliant
This morning, 10 and 23. Spinach is still alive. We'll see how it fares after this next cold snap.
Ingrid_Grace
Power Conserver
this looks awesome 
- Thread starter
- #34
LaurenRitz
Almost Self-Reliant
It's supposed to get down to the single digits tonight, so I brought the one pot in. The others are all too big and heavy for me to move. Arugula and cilantro were starting to recover. Tonight, tomorrow night and Monday night will give this thing a good test.
- Thread starter
- #35
LaurenRitz
Almost Self-Reliant
According to my thermometers, -4 and 9. It's following the same pattern as my first greenhouse.
I am now curious to see some real temperatures from a traditional passive greenhouse. Everything I have been told is being contradicted by my experience.
Not really unexpected, but I'd still like to figure out why. My experience often goes against the common knowledge.
I am now curious to see some real temperatures from a traditional passive greenhouse. Everything I have been told is being contradicted by my experience.
Not really unexpected, but I'd still like to figure out why. My experience often goes against the common knowledge.
Last edited:
Hinotori
Sustainability Master
- Joined
- Nov 2, 2011
- Messages
- 5,884
- Reaction score
- 13,097
- Points
- 373
- Location
- On the foot of Mt Rainier
I have a couple old books from the 70s that say that black painted water barrels should be put in the sunniest place to act as heat sinks to help with temps
- Thread starter
- #37
LaurenRitz
Almost Self-Reliant
I have some gallon jugs flled with water, but that's all at the moment.
My first greenhouse was designed for the location. No need to go into a lot of detail, but it backed on a hill and I assumed the difference between my own measurements and the traditional greenhouses was because of that. This is 3 now, and all following the same pattern.
With a single layer of glazing, no insulation, and no thermal mass, common knowledge says it should get 2 or 3 degrees at best. Most people say a greenhouse will maintain the same as outside ambient. That is not the pattern I am seeing, and this is my third greenhouse.
The first had an inside/outside spread of about 13 degrees during the winter, going up as high as 18 when it got really cold. 2nd I never kept regular records, but it seemed to be around 12. That one backs on the house. This one seems to be 9-10 degrees, with again the gap getting wider as it gets colder outside.
All were entirely passive. Only the first had significant thermal mass. So why do many people say that a greenhouse won't hold heat, and will have the same temperature inside as outside during the winter? Have they just accepted what they were told, or is there something different that changes the situation?
I don't know.
My first greenhouse was designed for the location. No need to go into a lot of detail, but it backed on a hill and I assumed the difference between my own measurements and the traditional greenhouses was because of that. This is 3 now, and all following the same pattern.
With a single layer of glazing, no insulation, and no thermal mass, common knowledge says it should get 2 or 3 degrees at best. Most people say a greenhouse will maintain the same as outside ambient. That is not the pattern I am seeing, and this is my third greenhouse.
The first had an inside/outside spread of about 13 degrees during the winter, going up as high as 18 when it got really cold. 2nd I never kept regular records, but it seemed to be around 12. That one backs on the house. This one seems to be 9-10 degrees, with again the gap getting wider as it gets colder outside.
All were entirely passive. Only the first had significant thermal mass. So why do many people say that a greenhouse won't hold heat, and will have the same temperature inside as outside during the winter? Have they just accepted what they were told, or is there something different that changes the situation?
I don't know.
Hinotori
Sustainability Master
- Joined
- Nov 2, 2011
- Messages
- 5,884
- Reaction score
- 13,097
- Points
- 373
- Location
- On the foot of Mt Rainier
Everything inside plus the floor will warm in the day and slowly cool at night. I would never expect an actual greenhouse to be outside ambient air temp. Would kind of suck for their purpose if they did that. Even a cold frame can make a significant difference in inside temp.
I can tell you that just a plain plastic trash bag can make a couple degree temp difference overnight. Same with a tarp thrown over.
I can tell you that just a plain plastic trash bag can make a couple degree temp difference overnight. Same with a tarp thrown over.
flowerbug
Sustainability Master
the ground retains some heat and that is what is radiated upwards from further down which doesn't freeze (well, ok, most places i know of that talk about greenhouses and gardening will not too likely be places that freeze down far enough to matter for purposes of this conversation 
)...
during the day even a few degrees difference will get absorbed by the ground and then be radiated at night. the more thermal mass you can get in there that will be surface area exposed to sunlight and the warmer air will then be more energy that is available each night to keep things warmer. a few gallons of water is not enough, but it is better than nothing at all. a larger barrel painted black or several barrels in a line where the sunshines in.
i would never expect an enclosed place to be as cool or cooler than the outside temperature at night because the radiated heat is trapped by the enclosure and that will always be some amount of difference as long as the enclosure is sealed well enough to prevent it from leaking out. the more insulation factor you have the slower heat is lost which increases the difference, but also the larger the difference the more heat is lost... so there is always trade-offs and curves going on.
)...during the day even a few degrees difference will get absorbed by the ground and then be radiated at night. the more thermal mass you can get in there that will be surface area exposed to sunlight and the warmer air will then be more energy that is available each night to keep things warmer. a few gallons of water is not enough, but it is better than nothing at all. a larger barrel painted black or several barrels in a line where the sunshines in.
i would never expect an enclosed place to be as cool or cooler than the outside temperature at night because the radiated heat is trapped by the enclosure and that will always be some amount of difference as long as the enclosure is sealed well enough to prevent it from leaking out. the more insulation factor you have the slower heat is lost which increases the difference, but also the larger the difference the more heat is lost... so there is always trade-offs and curves going on.
