Just curious - how many year-round greenhouse/indoor gardeners?

[Tropicaltoba]

In Winnipeg, just north of you for a 225 sqft (very well insulated attached greenhouse) costs up to 4 dollars a day to keep ultra tropicals alive during the coldest winter months. At the university of Manitoba they built a Chinese style greenhouse that was passively heated almost stayed above freezing all winter (had hot compost piles in it). Here is the link to the paper.

https://library.csbe-scgab.ca/docs/journal/48/c0611.pdf

[brian]

Has anyone created a passive solar style greenhouse, requiring little to no extra energy input?
Something using a similar concept to this:
https://www.mainepublic.org/environment-and-outdoors/2023-01-25/this-maine-home-can-stay-70-degrees-without-a-furnace-even-when-its-freezing-outside

These passive solar designs always seem to ignore the common winter condition of "freezing, windy, cloudy, wet for days in a row" where there is no meaningful solar heating and any accumulated thermal mass is gone by the second night. 

I have spent a ton of time thinking about insulation and greenhouse energy efficiency over the years.  The biggest problem is that the insulative value of  even the best glazing is awful when compared to something like a proper insulated wall.  The only solution that makes sense to me is to have some kind of insulating blanket that can cover the greenhouse at night.   Finding something that can do this while surviving the elements, wind, moisture, etc is though.  It seems chinese growers would use thatch and simply roll it up manually twice a day and replace it as needed.  Having something automated and long lasting will be expensive and heavy, something like polyurethane rolls on a spool.

The floor of a greenhouse is a massive heat sink, too, so you have to insulate the foundation perimeter and possibly the floor

If you accept that the insulation will be poor and focus on cheap energy things like geothermal are options.  Or solar-heating a large mass of water and extracting the heat at night. 

At some point if you have zero air exchange it will harm the plants and you'll get mold.  Once you start air exchanging your heating efficiency drops drastically.  Things like heat recovery ventilators exist but more expense and complication there.

I am fortunate enough to have piped natural gas which is dirt cheap.  It costs me around $100 per month to heat my greenhouse in winter.  If I used electric it would probably be triple that, and propane some where in between. 

[brian]

In Winnipeg, just north of you for a 225 sqft (very well insulated attached greenhouse) costs up to 4 dollars a day to keep ultra tropicals alive during the coldest winter months. At the university of Manitoba they built a Chinese style greenhouse that was passively heated almost stayed above freezing all winter (had hot compost piles in it). Here is the link to the paper.

https://library.csbe-scgab.ca/docs/journal/48/c0611.pdf

Yup, I was not aware of this greenhouse design until after I spent years thinking about it and came up with basically the exact same design on my own that it turns out the Chinese have been using for a long time!   That is re-assuring to me that it is the right choice

[brian]

here's the diagram from that article of the chinese greenhouse design


I had built a model of a design I want to try that is frameless... I am thinking the arch effect of a 8-12mm thick bent plastic glazing panel might be strong enough on its own

[Tropicaltoba]

Brian u are spot on about multiple cold cloudy days. When that study was done winnipeg was know for cold clear skies in winter (-40). The past couple of years the winters are milder, which is nice, but the sun is gone too. This week is really the first time we’ve had sun for 2 months.

I used to put aluminum backed styrofoam panels on 40% of my glazing to try and capture heat and help contain reflected light. It did help with the heating but it still decreased the available light and I had bunch of citrus dieback as dark hot rooms are bad for plants.

Also cool idea, it’s nice to see I’m not the only one who makes models and tries to invent things.

[Tropicaltoba]

Btw when doing research for my zone 3 greenhouse I did find company that offers glazing with quintuple panes (yep 5). I wonder how much light get through?

[brian]

Btw when doing research for my zone 3 greenhouse I did find company that offers glazing with quintuple panes (yep 5). I wonder how much light get through?

I bet it is pretty poor.  I think last time I looked even 3-ply seemed not worthwhile.  That far north you might be best off with flat dual-pane insulated glass perpendicular to the winter sun angle (nearly vertical!)

[Daintree]

Yeah, heat is the big thing with greenhouses! I tried the water barrels, but the second the sun quits hitting them they would release their heat, and by 11:00 pm I was heating the air AND the water, since water always equalizes to the air temp.

We too have cheap natural gas here. My 700 sf greenhouse costs $42 per month to heat. However, we are on a year-round payment system, so even in the summer with the furnace off it is $42. Not complaining though!

I have fiddled with so many things for heat - thermal blankets that you have to put on every night and then get shredded by the wind and used as nesting material by squirrels; hot composting, which took up half the greenhouse and required a lot of "food" and babysitting; the above-mentioned barrels; bubble wrap which filled with water, turned green then fell down; those emergency mylar blankets on the north wall; heating my greenhouse pond to hot-tub temp with a homemade heater that shocked the sh1t out of me, and probably some  other things I have blocked from my mind.

 Insulating the foundation, a thick layer of bark on the floor (gravel froze my bare feet at night and baked them in the  daytime so I knew it was having the same effect on potted plant roots), and pay the gas bill has been the best thing for me.  Funny thing, we actually inherited a natural gas well in Texas, and payments from that offset about half of the heat bill!

Cooling in the summer is way easier. Though we are at 2800 ft and have no clouds in the summer, I have found that a good coating of shade paint, a mister system and massive airflow works better than shade cloth. The cloth helped shade it, but the plants hated it. Just sat there and stared at me all summer, refusing to bloom.

Cheers, Carolyn

[Tropicaltoba]

Brian,
Im sure you’re right. I’ve double double pane low e glass, and with cleaning the inside glass 2x year, i usually loose 30% of sunlight according to my light meter (umol/m not lumens). It’s maxes out just over 1000umol even during the winter (but I try to have high co2 levels (2-3x atmospheric) so I want as much light as possible).

[brian]

One nice thing about covering the greenhouse at night is you can run grow light without the light escaping (and bothering nearby animals & neighbors).  I live in a fairly dense suburban area so I don't run grow lights, but if I could get a solution to cover the greenhouse glazing at night I would

[Tropicaltoba]

Carolyn, you have birds and a pond! What’s in your pond?

Cherimoya dude, There is a nursery called “sage gardens” here just outside the city. They keep at it a 15c in winter and he uses geothermal (the ground freezes to 8ft here) He is all into organically as well, take a look at their website. He’s a pretty nice guy and I’m sure if u have his shop a call he’d let u know how week it works.

[Daintree]

I wish I could afford some fancy automated covering system!
I have seen some in greenhouse catalogues.

And yeah, my previous back fence neighbors did complain about light from my greenhouse. However, she also said that my greenhouse plants were causing her allergies, so...

We have geothermal in parts of Boise, but not where we live. That would be so cool!

So, my greenhouse pond is about a hundred gallons, and I mostly use it for watering plants in the winter. Even with heat tape, the hose water is too cold. So I heat the pond with a 500 watt aquarium heater so my ultra-tropicals don't get cold feet when I water them.  I have tried goldfish and tilapia in the pond, but since I use it for watering, the fish don't like getting fresh cold water all the time.  Plus, being a lazy fertilizer, I tend to just put MiracleGro in the pond and water/fertilize at the same time using a sump pump.  So I kept having to catch the fish, put them in a bucket, hose out the pond when I was done watering, etc. Got old real fast! I would love to put in a second pond just for fish, if I can figure out where to put it.

Carolyn

[Tropicaltoba]

Brian, I’m In the middle of the city and I run my 1800watt leds them from 7:15 am to 8:15 pm (when it is cloudy/dark). it good for the plants, but more for the predatory insects that go dormant when the sun is <12h. We only get 6 hours of sun in the winter so the gh glows from About 4:30 pm onwards. I’ve asked around and no one seems to mind, I even catch people hanging outside and just looking at the plants in the winter. Also no one has thrown rocks at it yet.

[W.]

Has anyone created a passive solar style greenhouse, requiring little to no extra energy input?
Something using a similar concept to this:
https://www.mainepublic.org/environment-and-outdoors/2023-01-25/this-maine-home-can-stay-70-degrees-without-a-furnace-even-when-its-freezing-outside

These passive solar designs always seem to ignore the common winter condition of "freezing, windy, cloudy, wet for days in a row" where there is no meaningful solar heating and any accumulated thermal mass is gone by the second night. 

These passive solar house designs also always seem to ignore aesthetics with most being ugly as hell, the best only being bland, but all being incongruous to neighborhoods and landscapes (like a black, badly-proportioned house being plopped in the Maine countryside). I am also not enamored with their potential for irreparable or hard-to-repair age-related failures; frankly, I do not believe these houses will age well. Like most things constructed today, they are made seemingly to fail and be replaced. Such a throwaway mindset negates the positive environmental impact of their low energy consumption by building in a requirement to replace items that have high embodied energy.

Here is an example I cited when I worked in historic preservation. Vinyl replacement windows are very popular, touted as a way to save both the environment and money. The Obama administration attached all sorts of tax credits to their installation for that reason. Yet, they are a scourge, particularly to historic buildings, damaging to a building's historic fabric, the environment, and the building owner's pocketbook. I will not bore everyone with all the details, but one Kentucky study showed that it took between 30 and 45 years to recoup the initial expenditure of industry standard replacement window installation, while the windows themselves maintained their optimal energy savings for only 10 years, after which time their energy usage, air leakage, and insulating quality were no different in performance than historic wood windows in average condition. The difference between those replacement windows and the historic ones they replace, is that historic windows in suboptimal condition can be reglazed and repaired, often onsite and with only a modicum of skill and energy expenditure. Their replacements themselves have to be either completely replaced or sent back to the factory for repair once they are no longer functioning properly.

So, as you may be able to tell, I am not going to be demolishing my house and replacing it with the latest and greatest and greenest and trendiest. I will be sticking with things more tried and true because, as Neil Young sang, "Old ways comin' through again."

[hammer524]

Does anyone have a comprehensive set up similar to this seller?

https://www.youtube.com/watch?v=hGxy-abbKWk

My plan is to pay the design fee and buy a 24' x 48' hoop house from Grower's solution

[tru]

W. makes a lot of great points! Devil's advocate: it's clean energy that is accessible, and solar panel prices keep plummeting. If it's your only source of energy it's risky but if you are treating it like a discount on your energy bill I think solar panels are becoming more much worthwhile.

The transparent solar panel technology is super exciting to me, someone made solar panels that only filter green light leaving plants directly over the solar panels to grow as if they were in full sun. Truly amazing stuff will get distilled down and made public accessible, all we have to do wait. Imagine a field that pays for its own upkeep

[Tropicaltoba]

Problem with the green filter is u won’t want any plants if they are just grey instead of green.

[tru]

Problem with the green filter is u won’t want any plants if they are just grey instead of green.

I'm confused; why would that kill the plant?

[drymifolia]

I had built a model of a design I want to try that is frameless... I am thinking the arch effect of a 8-12mm thick bent plastic glazing panel might be strong enough on its own

The kind I used (Palram Sunlite 8mm twin wall) has really thorough instructions on the bending radius and weight capacity (snow load) for arched installations:


Source:

https://palram.canto.global/direct/document/nibdh82n615vv53iumsrcgfc33/_tGOM1Av8_kZfcqyy8lRLcEwFBM/original?content-type=application%2Fpdf&name=SUNLITE+Technical+%26+Installation+Guide.pdf

[Tropicaltoba]

Sorry Tru, was trying to be funny, but have tough time conveying that in text. The plants would be fine (they’d absorb all the non green spectra of light like they always do), but because the green light had been filtered the green light would not longer be reflected on to your retina after it hits the plants…so the plants wouldn’t appear green anymore.

[tru]

Sorry Tru, was trying to be funny, but have tough time conveying that in text. The plants would be fine (they’d absorb all the non green spectra of light like they always do), but because the green light had been filtered the green light would not longer be reflected on to your retina after it hits the plants…so the plants wouldn’t appear green anymore.

No you're good it just went over my head lol  but wow never even thought about that! too bad I'm ridiculously colorblind already 😅

[brian]

drymifolia, yes I have seen the bending and loading guidelines but I can't find anything relevant to a frameless structure.  My plan is to simply order some long panels in varying thicknesses, bend them to their limit, and pile weight up on them and see how they deform.  If they can handle a reasonable snow load then I'll just try whichever thickness has a bend radius that results in the desired greenhouse depth!   A minimal frame might still be needed, but I am fairly sure purlins can be avoided this way which makes it much easier to clean and mount curtains for insulation on interior.

[Tropicaltoba]

Brian, seems brilliant. Like a more durable hoop house. Are u thinking about using the osteo only in winter?

[brian]

I'm looking for some land near my house for sale that I can build greenhouses on.  Right now I can't really add more because I am under suburban zoning rules.  Once I have land I'll try a bunch of designs and see how they work out.

[Plantinyum]

 I have been an indoor grower for like 5- 10 years since i started to maniacally collect whatever tropical fruit species i could get my hands on. Here in zone 6- 7 at 830 m above sea level, growing tropical stuff is hard, althought i have a greenhouse now i still have the house chock-full with plants, placed near the brightest windows. They really hate it in winter for alot of reasons, lack of light being the major one.
I will say that the ones that are in the greenhouse / inground are doing fantastic. I see most people here that have greenhauses are having their plants stay in there potted. I hardly have anything potted in the gh, only a few plants that will go out in summer. I hate having potted stuff in there since i made it with the solo reason and idea of everithing thats inside to be planted inground.
The walls are 20cm thick,60-80 cm deep into the ground on south and west side, and around 40cm  on the north and east sides where i have it incorporated into the pathway. The walls
have 5cm thick styrofoam on both sides. All this was with the idea of keeping the internal soil isolated from the cold soil outside.
Construction is a standart greenhouse one with square metal
pipes 2 cm width, 1mm thick, galvanized. The policarbonate is 4 mm thick . Its ment to sustain a 80 kg snow load per square meter(its 3 on 4 m), thats what i remember from the instruction list. Snow hardly ever persists on the structure, the form combined with the warmth that comes from below quicly melts and slides it off. On the outside of the policarbonate i have 1 sheet of big balloon bubble wrap, on top of which i have 1 layer of clear nylon. Those 2 additional layers ive attached to the structure via the same screws that are supporting the policarbonate.ive NEVER had a problem with it blowing off , the way ive fixed it is keeping the layers nice and tight on top of each other. Yes, water gets between the layers at places, also inside the bubble wrap, but ive never had it green up or get dirty becouse of this. Green algae i have a lot of on the inside of the greenhouse, mainly on the walls.
Heating- last year i was heating with a wood stove, what a horrible experience that was, dont reccomend, although i pilled my plants trought winter fine i needed to stay till late evening to set the fire so it would last the night. I also almost lit the greenhouse on fire on several occasions, on which the chimney got fire, as i said, dont reccomend!  This year i made a radiator heating system, i dug a 20 meter long, 60 cm wide, 80 cm deep canal for the pipes that cary the water from our fire place. Did the digging myself and at one point was questioning my existance, now im real happy i did it though as i knew the alternative was nasty aff. The inground pipes also were insolated with a very thick 20+ cm stirofoam on every side, filled the crevices with fixing foam.
I have 3 radiators, 1 140cm by 60cm and 2 60 by 80 cm. They are sufficient at this point , succesfully keep the inside 15 to 20 c at -7c outside temp.
The 2 barrels i use for wattering, i fill them with water from my ponds, in a matter of a day the water is warm and ready for use, they also add a little of a buffer heat as they are heated up by the radiator.