Hello everyone! I'm new here so I apologize if this isn't posted in the right spot.

I'm also new to hobby greenhouse growing. Could I get some tips, please?

I live in a zone 7 area and I have a greenhouse kit (palram mythos 6x8X7 ft kit) on a brick perimeter foundation. I got the thing put together and I wrapped the entire inside with large bubble bubble wrap in an attempt to insulate it. I plan on laying down wood shavings on the floor, using black water drums as thermal masses, and using a 1500 or 2000w electric heater to heat the thing. I plan on growing Vanilla planifolia for fruit.

My question basically boils down to this. Can I do this in a cost effective manner or am I going to be paying big bucks just to heat the thing up in the winter? If that does sound like a bad plan, does anyone have any tips on how to make it better?

Thanks for reading this and I hope to hear from you all soon. Have a nice day!

I'm not sure about cost but I do see some problems with your plans, specifically with the wood shavings and the electric heater.

Greenhouses with orchids are wet drippy humid places. The wood chips will rot and harbor bugs and diseases and the heater will get wet and short out.

Use brick or gravel on the floor. Whatever heat source you decide upon, make sure its rated for outdoor/greenhouse use.

Thanks for your reply Daisyl. Thank goodness I didn't put the wood shavings down yet!
The electric heaters I've been looking at are rated for greenhouse use but I'll look for shorting issues in the reviews.

If its rated for greenhouse use, raising it up on something or mounting it to the wall should be enough. Make sure you have lots of fans pointed in every direction to stir the air. Otherwise you will develop mold problems in airless corners.

I'm curious about the black drums for thermal mass. That will take a lot of space in a small greenhouse and in zone 7, I'm not sure they are necessary. Where is your Zone 7? Do you get snow or wind?

I grow orchids and have seen Vanilla orchids for sale but have never thought about growing one. I have seen them in orchid houses - they are huge plants hanging all over the ceiling. I didn't think I could manage an orchid that big but then I got a Nepenthes which has essentially taken over one side of the greenhouse. I can deal with it by cutting it down every couple years but that would be counter productive for a vanilla orchid.

Covering the floor with dark pavers/blocks set in sand would be a good idea. No worries about rot or harboring pests, and it would increase the thermal mass heated by sunlight. Rather than blowing hot air from a single source, I bought a patio heater with three quartz radiants and rewired them to a thermostat, to heat the foliage directly.


Going on 12 years with no problems (except bugs).

Daisyl, we get some snow in the winter (although less and less every year it seems... 😬) And we get some wind storms every now and again. It's never too brutal though and my greenhouse is protected by my shed and fence. It gets down into the low teens as far as temperatures (F) go frequently. I haven't grown vanilla orchids either so I'm just throwing myself into it. 😅 Fortunately, my greenhouse is going to be nearly dedicated to these things.

Subarctic: Thanks for your reply! And that's incredible! Are the quartz radiants more efficient than electric heat typically?

For a 12' x 12' (144 sq ft) I mounted four 500W elements. A typical small electric space heater uses 1500W plus the power to run the fan. In physics terms, the difference is that the radiants warm the foliage (green absorbs lots of heat) without having to heat up all the air on the way. On ski mountaineering trips, I would place a dial thermometer on a dark green conifer bough. In bright sun it might read 50-70°F while the surrounding air was at 10°F. So radiant heating is rather effective for plants. I also have black containers for the tomatoes which conduct heat to the soil, and dark pavers which absorb the rest.

Water-filled black heatsinks can help on cold nights if they are exposed to direct sun during the day. They don't absorb much heat from the air. On a south-facing wall, I mounted four 75 gallon tanks, which are also the water source for the greenhouse.


An alternative is to get a large galvanized livestock tank and paint the sun-facing side black. You can place a benchtop over it, as long as it's waterproofed on the underside.

Growing Vanilla planifolia requires a lot of warmth and sun. Otherwise they will be reluctant bloomers! No flowers, no vanilla beans.
Is this a free standing greenhouse? An unheated shed blocking the wind in my opinion will not shelter the greenhouse much at all. You need to wrap the greenhouse from the outside to cut down on heat loss. I used 6 mil plastic sheeting over wooden lathe creating an air pocket to slow heat loss.

Electric heaters are the least efficient way to heat. I had a 9 x 12 freestanding greenhouse in my yard back from 1975-1980. It was very expensive to heat back then! Very expensive!!! Mucho dinero.
In 1980, I went with a larger lean to greenhouse, 21 x 16x 10' high. I used a brick floor with wood chips underneath the benches. The bricks were set in 6" of rolled sand.
I my experience, zone 7 on Long Island, growing in a greenhouse, yours is too small to think about solar heating from water tanks. You need a lot more space for that. The smaller the growing area, the more rapid it will heat up during the summer and the quicker it will cool during the winter.
With my big lean to, there was oil fired hot water baseboard. I had 40' of it. But on chilly, windy nights, it was subjected to a much more rapid amount of heat loss. The breeze, even over ten miles per hour blowing across the outer surface replaces the slightly warmer air escaping through the glass with colder air carried by the breeze. With all of my cubic feet of space on cold, below 25 degrees, breezy nights, I used a supplemental kerosene heater of 50,000 Btu's. It's the BTU output of your heater that matters, not the wattage. There is a formula that you can probably find on line where you multiply cubic feet x temperature to figure out just how many Btu's you need. If the formula tells you that you need 35,000 Btu's and your heater produces 25,000 Btu's, you are going to have a severe heating problem. It will run constantly!! $$$$$$$$$$$$$$$
Vanilla planifolia will sulk and be unhappy below 50 degrees. It likes to be warm and sunny like a typical Vanda orchid.

The plus for me was with the big lean to on the south side of my house, there was a substantial savings in home heating oil, about 300 gallons each winter. It was a solar blanket on my home. It increased the humidity indoors where colds became very rare for me and my family.

Anyway, I wish you good luck in you venture and I hope I have armed you with some information!!!
Btw, I grew all kinds of orchids in my greenhouse for 34 years total.

Subarctic. That certainly does seem like I could heat my plants with less energy using quartz radiant heaters. I've read that these radiant heaters use infrared to directly heat objects. Have you had any issue with the infrared light effecting plant growth? I know plants focus on the visible spectrum but I have heard that far-red light can cause etiolation.

BigBill. Thanks for the info! I found an online calculator for determining BTUs needed to heat based on outdoor temperatures, insulation U-factor, surface area of the greenhouse walls and desired minimum temperature. I was unsure what the heat loss factor would be. I found a value for my greenhouse walls (4mm twinwall polycarbonate U-factor = 0.70) but since I wrapped the inside with plastic large bubble bubble wrap, I'm unsure of the new value. I used the value for 16mm triplewall polycarbonate (0.40) on a guess and ended up needing 4500 BTUs assuming the outside temperatures dropped to 10°F. Do you think that's a reasonable value for a 6X8 or is my math way off?

Have you every used propane heaters? Is there an advantage to using kerosene over propane?

I used kerosene because back then it was readily available. It purchased it 5 gallons at a time and I got about 3 nights worth of heat from the 5 gallons.
It kept my greenhouse at about 60 degrees even on a breezy night in single digits. I think I used about 15-20 gallons over the course of a typical winter.
As gas as bubble wrap goes, I have no idea as to it's effectiveness. The lathe wood frame covered with 6 mil plastic seemed to meet my needs. I bought it in 100 foot rolls and got 3 winters per roll. Back then the rolls of plastic was about $45. I hate to think what it is now. Home Depot carried it.

ValleyHerb9619 said:Have you had any issue with the infrared light affecting plant growth? I know plants focus on the visible spectrum but I have heard that far-red light can cause etiolation.

If your plants get plenty of sunlight, the limited time they are exposed to the radiants shouldn't be a problem. Here's one of my tomato plants:

ValleyHerb9619 said:Have you ever used propane heaters? Is there an advantage to using kerosene over propane?

For extreme cold (-20°F) I use a small propane heater with a portable tank outside.


Having used kero for years in lamps and occasionally in an Aladdin space heater, I prefer propane: it doesn't smell or spill or have a wick that needs trimming and cleaning, nor flare up unpredictably.

I'd like to point out a couple things:

This greenhouse is 6 x 8 ft, where are you putting all this stuff?

The air temperature for orchids is important, not just leaf temperature. You will have to keep the air temperature in the entire greenhouse at between 75F (nighttime) and 85F (daytime) winter and summer. Radiant heat won't work unless it has a fan - only things close to the heat source will be warm and they will be really hot, not just warm. Radiant heat is very zonal - how will it heat the part of the plant behind the rest of the leaves?

Propane gas byproducts kill orchids so your heat will be electric or kerosene. It would be nice to warm your greenhouse with sunshine but how much cloud cover does your area get in the winter? Your greenhouse is not that well insulated.

I looked up the specs on your greenhouse and I'm a little concerned. The snow load is 15lbs/ft and wind rating is gusting to 56mph. Snow is heavy, it weighs over a pound per inch. I'm concerned you will have a crushed greenhouse in the first big storm unless it has blown away first.

A math error there.

I found this reference for snow weight:
"Depending on moisture content, snow can weigh from 1 pound per cubic foot to over 21 pounds per cubic foot.""

So 1 inch deep of the wet snow at 21 lbs/cubic foot could weight 1.75 lbs/SF at one inch depth. A 15 lb/SF snow load rating would allow for 8.5 inches of wet snow.

I have zero experience with vanilla orchids and their temperature needs for fruiting in winter.
Seems like a tough one to start with for a winter greenhouse.

DaisyI said:Propane gas byproducts kill orchids so your heat will be electric or kerosene.

??? Kerosene heaters give off lots more hydrocabons, toxic byroducts, particulates, etc. than propane.

You're right. No kerosene either. I guess that's why we chose solar.

If you keep the wick on the kerosene heater clean, frequency depends upon the hours that it is used and how clean the kerosene is, your fumes will be cut drastically. I cleaned my wick at the end of each winter. Replaced it every other year and with my orchid flowers being very sensitive to ethylene pollution, I never had a single blossom damaged. Not one.
I think ethylene comes from usage of kerosene and other hydrocarbons, from the uneven burning. Kind of like a by-product.

When kerosene heaters first came out in the early 80's, maybe a little earlier, so many problems occurred because people ran out of, or would not use, kerosene. They substituted gasoline!!! Big no-no. That lead to many explosions, fires and deaths. Kerosene was more expensive.
"Oh, kerosene heaters were bad, they were dangerous"!!! The heater didn't put gasoline in it instead of kerosene, a stupid human did! I used one for 28 winters. 28!!! I would not hesitate going that route again.

Plus the room/greenhouse must be properly ventilated! It can't be sealed tight. I use to crack a window in the greenhouse and cracked open the sliding glass door to my dining room.

When I used kero for my Aladdin lamps, the local bulk retailer would be out pretty often, so I used to go to the airstrip (closer than the town) and fill a 5-gallon can with Jet A, helicopter fuel. It was cheaper and worked fine. There might be additives, but I didn't burn enough to have any ill effects (and the old log cabin I lived in was well-ventilated: I could feel the wind between the gaps in the chinking).

Electric is actually cheaper here, in the heart of hydroelectric, than any fuel I've compared it to. But I know it's more expensive for most people.

One consideration with ground heating systems is that you can lose half your heat right into the ground. Proper, deep insulation and radiant reflectors are vital for a ground contact system.

I heat the water in the big koi tanks in my large greenhouse, and with the all the falling water they put a fair bit of heat (and moisture) into the air. Electric air (not radiant) heaters kick on when needed. And when it get particularly cold I have propane as my emergency backup.

But I think every situation calls for a different mix, and it can pay to do your homework in calculating BTU loss in your structure (easily done by measuring steady state temperature before and after adding a known BTU value heat source on a night when temperatures are fairly constant), and calculating BTU/lb of fuel costs so that you're comparing fuel costs properly.

I do have venting when I run gas, and I keep CO alarms in there, just in case.

Smaller structures require simpler systems, but can go wrong faster, too. I always having monitoring on any greenhouse containing material I care about.

Here in NW Oregon, Zn 8b, I've been using 8 - 48"x20", 100 watt heat mats on the shelves, with 4 thermostats that can adjust from 68 to 80, to heat the potted plants in my 8'x8'x16' Aadco GH, with a corrugated fiberglass cover and a plastic interior lining . I also use an electric heater with the thermostat set at between 40 and 50 depending on the plants in the house, to supplement on really cold nights. It does a very good job.

It's great that you've already insulated your greenhouse with bubble wrap and have plans to use thermal masses. These steps can help a lot. To make it even more cost-effective, you could think about these things:
Use a thermostat: Consider getting a thermostat for your heater. This can help keep a steady temperature and prevent the heater from running too much.
Check for drafts: Make sure there are no gaps or drafts that could let the heat escape.