Suggestions and opinions requested.

I've been trying to research greenhouses. It's not always easy to compare, but I think this is a good greenhouse for my needs.

My needs are:
Zone 7b
Overwintering of citrus trees and palms (from October to March/April)
Ability to heat/maintain temperature above 55 or so
About 100 square feet

If I understand correctly, this Palmram greenhouse has 10mm double wall polycarbonate, which seems pretty decent. I think it should be easy to heat to the temperature above.

https://canopia.com/product/gl...

Thoughts?

I used to sell Palram Greenhouses. They are not the best, along the line of most cheap greenhouses. They are NOT 4 season greenhouses no matter how they advertise them. 10mm double wall poly is decent, but still not that insulative. Expect to have a high energy bill if you plan to heat to 55 even in 7b. I had a similar greenhouse in zone 6B before I bought my new one, and I was paying over $100 a month for heating during the spring seed starting period, almost $200 the year I tried to grow all winter, and I was shooting for temps in the 40's, not 55.

There are no shortcuts when it comes to retaining/or adding heat. The better the greenhouse and its passive heating elements/abilities, the more you will pay for the greenhouse, but the less you will pay in heat in the long run.

My 2nd greenhouse I went with 16mm triple-wall polycarbonate glazing, a brick floor, a 425 gallon pond, and 25,000+ BTUs of Phase Change Material to boost the passive heating.

The greenhouse runs 15-20 degrees higher inside than the outside temps at night, but I still have to provide heat on nights when it falls below 20 degrees.

Could you elaborate on what 25k BTU's of phase change material is? I have a single pane glass GH with tropicals in Zone 7b that i'm heating with a 24k mini split heater/AC unit and i'm afraid to open my electric bill.

I would be terrified of your electric bill too (I know I'm afraid of mine). I think Jim is talking about this:

https://ceresgs.com/water-barr....

jpm995 said: Could you elaborate on what 25k BTU's of phase change material is? I have a single pane glass GH with tropicals in Zone 7b that i'm heating with a 24k mini split heater/AC unit and i'm afraid to open my electric bill.

Phase Change Materials (PCM) take advantage of a fundamental property of nature:

The natural tendency of materials to absorb heat when they melt (phase change from solid to liquid/gel) and to release heat when they solidify (phase change from liquid/gel to solid).

My PCM panels begin to "melt" at 65 degrees. So, if my greenhouse goes above that temperature, the PCM panels begin to store heat. Once the temperature drops back below 65, they begin to solidify and give off heat.

They are supposedly much more efficient than barrels of water painted black and take up only a small percentage of space compared to the amount of water you would need for the same outcome.

Lucy68 said: I would be terrified of your electric bill too (I know I'm afraid of mine). I think Jim is talking about this:

https://ceresgs.com/water-barr....

[quote="Lucy68"] I would be terrified of your electric bill too (I know I'm afraid of mine). I think Jim is talking about this:

https://ceresgs.com/water-barr.... [/quo
I went to the Ceresgs site and they say they no longer carry phase change material. Probably wouldn't be a good option for me as i really don't have a north wall on the GH. I opened the south wall of the shed to attach to the greenhouse.

This older thread offers some ideas for insulating greenhouses:
The thread "Solar Covering Over Our Greenhouses" in Greenhouses forum

jpm995 said:
I went to the Ceresgs site and they say they no longer carry phase change material.

I noticed that and doing more research, my understanding is they stopped carrying them because the PCM has a limited life expectancy. Apparently more, better stuff is in the works.

I think my greenhouse has triple wall poly, and it holds very little heat. I recently did a test, and it cost me $10 a day in propane to keep it above 40F. If the price of propane hadn't increased 2.5x in the last three years, maybe I could have justified it, but not at the current price. If the sun would ever come out, I wouldn't need heat during the day, but the sun has only been out 3 days in the last month. Blah!

I guess I'm getting very confused. So let me first change this—I'd like 80-100 square feet, temperature of say 50 minimum with heat.

From this thread below, I thought everyone was saying I'd be able to heat a greenhouse for less than $100 per month.

The thread "Have/considered a heated greenhouse, LMK what you think" in Greenhouses forum

I thought everyone there was saying that was reasonable. Now I'm this current thread it seems like everyone is saying it's impossible. What am I missing?

I've seen so many greenhouses with 8 mm panels, 4 mm panels, single pane glass. 10mm panels seemed like it would be an improvement.

Where can I get a good insulated greenhouse? Solexx 5 mm? Something else? Help!?

MoonShadows said: I used to sell Palram Greenhouses. They are not the best, along the line of most cheap greenhouses. They are NOT 4 season greenhouses no matter how they advertise them. 10mm double wall poly is decent, but still not that insulative. Expect to have a high energy bill if you plan to heat to 55 even in 7b. I had a similar greenhouse in zone 6B before I bought my new one, and I was paying over $100 a month for heating during the spring seed starting period, almost $200 the year I tried to grow all winter, and I was shooting for temps in the 40's, not 55.

There are no shortcuts when it comes to retaining/or adding heat. The better the greenhouse and its passive heating elements/abilities, the more you will pay for the greenhouse, but the less you will pay in heat in the long run.

My 2nd greenhouse I went with 16mm triple-wall polycarbonate glazing, a brick floor, a 425 gallon pond, and 25,000+ BTUs of Phase Change Material to boost the passive heating.

The greenhouse runs 15-20 degrees higher inside than the outside temps at night, but I still have to provide heat on nights when it falls below 20 degrees.

Can you tell me what greenhouse you have? Is it custom?

Lucy68 said: I would be terrified of your electric bill too (I know I'm afraid of mine). I think Jim is talking about this:

https://ceresgs.com/water-barr....

Same— Can you tell me what greenhouse you have? Is it custom?

Rubi said: I think my greenhouse has triple wall poly, and it holds very little heat. I recently did a test, and it cost me $10 a day in propane to keep it above 40F. If the price of propane hadn't increased 2.5x in the last three years, maybe I could have justified it, but not at the current price. If the sun would ever come out, I wouldn't need heat during the day, but the sun has only been out 3 days in the last month. Blah!

Can you tell me what greenhouse you have? Is it custom?

jpm995 said: Could you elaborate on what 25k BTU's of phase change material is? I have a single pane glass GH with tropicals in Zone 7b that i'm heating with a 24k mini split heater/AC unit and i'm afraid to open my electric bill.

Hi, I'm my other thread I thought you said you weren't paying much to heat your greenhouse. What did I misunderstand? Can you tell me what greenhouse you have? Is it custom?

TheMadPlanter said: Same— Can you tell me what greenhouse you have? Is it custom?

Its a Charley's Greenhouse twin wall polycarbonate construction. When first built back in 2001, I was overwintering stuff that wouldn't survive outside and bringing my orchids in to my sunroom for the winter (they spent the summer in the greenhouse). Now, I just can't manage the move of so many orchids so i'm leaving them in the greenhouse overwinter.

Originally, half a dozen heat lamps kept it warm enough for citrus, cymbidiums and hardy tropicals. Now, I am using a small greenhouse heater (with a small Buddy Burner as backup). So far, so good. But,... BIG but, I also have solar panels. They haven't helped much this winter because they need sunshine to work. And our house is all electric so the banked summer solar is used up just trying to keep the house warm.

If I had to do it all over again, I would spring for heftier polycarbonate. Not all polycarbonate is created equally so what seems like a good deal isn't necessarily so. You are talking about mm of thickness but the important part is how many walls of polycarbonate, how much air space between layers and the quality of the polycarbonate itself. Research the companies carefully - a good greenhouse is pricey but worth the expense in the long run.

One more point, don't limit the size by what you think you need now. Go as big as you can both space and cost wise. I told Hubby 6 x 9 would be more than enough. He built 12 x 16. I wish it was 16 x 20.

So what I would do different? Buy a bigger greenhouse with thicker polycarbonate layered walls. That expense is once. Heating and cooling are always. My plants are too expensive to try to replace.

TheMadPlanter said: Can you tell me what greenhouse you have? Is it custom?

I have a Riga XL5. Here are the specs: https://www.exaco.com/rigaXL-g...

They also make a "Regular" Riga series starting with a 7'x8'. The glazing on those is double wall.

No matter what greenhouse you buy, unless you want to go very custom, very insulated - like the CERES greenhouses - you are most likely going to pay a lot for heating if you want to keep the temps at 55 or so even in your zone. 99.9% of greenhouses are NOT made for 4 season growing EVEN though they are marketed as such.

What we are trying to do is squeeze another season out of a building that is not made to grow in during the winter. Would I ever try to grow citrus or summer veggies during the winter? No way, the heating bill would kill me. All I am trying to do is keep my greenhouse at 35+ (which is still task on the coldest nights - last night was 9 degrees) for plants that can tolerate these kinds of temps like spinach, lettuce, cabbage, broccoli, etc.

If you have room in your house and you can move the citrus and palms, it would be cheaper to put them in a room in your house with some quality grow lights.

Florian Greenhouse built my greenhouse! They call it the Geneva model, it has double glass panels! I am still really happy with it 23 years later! Lucy, yours is the same age as mine!🙂

The advice we were given was to built it as well and as large as you can afford. Many people try to get by with a poorly thought out design and lose a lot of plants. On the 2. attempt things get usually better.

My advice would be to attach the greenhouse to the house if that is possible! On sunny Winter days mine is a nice heat sink and helps warming the house during the day. We have the oil heat circulating by connected ducts between house and greenhouse.

Ursula said: Florian Greenhouse built my greenhouse! They call it the Geneva model, it has double glass panels! I am still really happy with it 23 years later! Lucy, yours is the same age as mine!🙂

The advice we were given was to built it as well and as large as you can afford. Many people try to get by with a poorly thought out design and lose a lot of plants. On the 2. attempt things get usually better.

My advice would be to attach the greenhouse to the house if that is possible! On sunny Winter days mine is a nice heat sink and helps warming the house during the day. We have the oil heat circulating by connected ducts between house and greenhouse.

I think that is another great route to go, Ursula, but unfortunately many folks don't have the resources to go that route. Even my Riga XL5 that I bought for $12,000+ cost me over $24,000 when I was all finished. A good, well insulated, strong, and enduring greenhouse is really expensive. Cutting corners or going "economical" just won't cut it.

I am always amazed at folks (no one here being referred to) who want a 4 season greenhouse to grow Tropicals for under $500 in Cold zones (including heating). The is no animal available. Yet, there are so many greenhouse companies that won't tell you that just to make a sale.

Their best bet is to grow in their house, that is warmed all winter anyway, with some quality grow lights.

I really don't remember what my greenhouse cost but looking at Charley's Greenhouse website, it would have be a lot now. We have a pack of really crazy friends who got together and poured the foundation, put in the floor and built the greenhouse (of course, we were 20-something years younger). Everyone got to put their name and handprint in the cement - unfortunately, we didn't plan ahead well and the greenhouse walls sit on the handprints and signatures.

Just did the calculation of what my greenhouse would cost now - $20,000! Yikes!