Newb asking for help. New palram canopia orangery greenhouse (100sq ft, polycarbonate with 0.7mm wall and 4mm corrugated ceiling, guessing R ~1). Has a new biogreen electric heater 1500W (5100BTU equivalent) with 163m^3/h air flow.
This setup is only making the green house 2-3F warmer than outside. Was expecting +15F at least. Heater turns on and blows warm, but I didn't measure the air temp (I will be able to with an IR gun).
Questions:
- Am I wrong about expecting +15F vs outside? Or did I simply get a dud heater? What is a good delta T for the air coming out of the heater vs air in green house?
- What would be a good heater/setup to use?
- Any other tips? What am I missing?
Thank you to those who may share knowledge 🙏

@ZeroKelvin, I think it depends upon where you live. The heater will be less efficient with (I assume) twin wall if you live in Alaska or Minnesota. I live in central California. My twin wall greenhouse stays pleasant enough for citrus and a few other not quite winter hardy plants with a milkhouse heater (5100BTU) but my low temps are in the mid to upper 20's.

If I expect a really cold night, I have a small propane Buddy-Burner.

I'm wondering the same thing. My GH warms up nicely when the sun comes out but it's the nights I worry about. Right now I have a radiant heater (for a chicken coop) I hope works for keeping my lemon tree alive. I live in Z7b.

Does your heater have a fan? Or do you have fans to circulate the air? Radiant heaters heat the air immediately around them. Chickens can move closer to the heat source but plants can't.

I only try to keep my greenhouse above freezing as citrus and the few other plants that I winter in the GH can handle those temperatures. The orchids move to the sunroom.

You can use a heat lamp over top of especially sensitive plants - I use a couple over the cymbidiums.

ZeroKelvin said:
Questions:
- Am I wrong about expecting +15F vs outside? Or did I simply get a dud heater?

Yes, you are wrong. Unfortunately, these companies will sell you the "dream" that you can grow year-round, but their greenhouses just don't have the insulation needed for 4 season growing. With the greenhouse you have now, it's like trying to heat your front porch that is wide open. I used to be an online independent dealer for Palram. Their greenhouses look really nice, but only perform well in moderate environments. FORGET WINTER unless you want to spend a lot of money.

What is a good delta T for the air coming out of the heater vs air in green house?
- What would be a good heater/setup to use?
- Any other tips? What am I missing?

Insulation, insulation, insulation!
Heat sinks, heat sinks, heat sinks!

@ZeroKelvin Have you considered bubble wrapping your greenhouse over the winter? It might give you 10 degrees warmer. It seems to be helping quite a bit in my smaller Palram Oasis.

I think you may want to look at adding some type of thermal mass to capture heat during the day, barrels of water that type of stuff. Another option might be to evaluate the heater you have and if you dont have a radiant heater maybe look into that, the oil based ones are good from my experience of producing heat. You can get heat powered fans to help distribute the heat around or a fan and direct the air through a heated radiator. Also with heat you are mostly looking at retaining it inside in the cold temps so filling up any gaps and cracks can help reduce the heat loss through convection. Last thing might be to also add in some thermal bridging between the frame of the greenhouse and the panels to reduce heat loss from conduction. What zone are you in and what style of greenhouse do you have wood/metal?

Good advice @BlueCollarChris -- welcome to NGA!