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greenhouse Using a propagator outside with the lid on

I'm trying to grow pepper plants and I have an idea that I can barely find any information about. Sources seem to agree that the best way to grow peppers, using a propagator, is this:

1. keep the lid on and make it warm (say, 28°C);
2. as soon as the first seeds germinate, open the vents;
3. within a few days, remove the lid entirely.

I'm worried that leaving the lid off is not good for the plants because my house is cold and dry. Right now it's 16,5°C and the humidity is 39%. This website for example mentions that the ideal humidity is 70%: https://thehotsauceguy.ca/grow-hot-peppers-indoors/ . I can easily achieve that by leaving the lid on the propagator, which would also make the temperature higher (it's a heated propagator). Why does everybody recommend taking the lid off?

Another idea I have is to place the propagator outside (the temperature is between 0° and 18°C). My reasoning is that the plants will receive more direct sunlight, and the wind will refresh the air inside more quickly with the vents opened. That's something that also nobody seems to do and I wonder why.
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Taking the lid off is to prevent the young seedlings from damping off wich occurs when there is too high humidity and bad airflow. You could still cover them with a bigger cover though. I keep mine in an old aquarium, after germination i take of the lids of the germination trays but i keep the aquarium closed. Temperatures inside still stay around 23C due to the heating mat inside. After a week or two i transplant them and from that moment on they shouldn't have much problems with 16,5C and some lower humidity. Putting the propagator outside with our current temperatures is not a very good idea... the windchill will most certainly kill them!
We have to work with the same climate. I germinate and let the seedlings grow in an unheated and unisolated garage. Leaving them outside would give them some sunlight, but not much, these times of the year. Not enough for what they would like. So I use growlights.

I let my seedlings grow inside a plastic grow tunnel (with heat mats) on the garage window sill. It's not ideal, the temp outside the tent can get quite cold and it creates a very high humidity. I try and resolve that with a fan and some luck (😀), to prevent the seedlings damping off. It' s giving me plants I can work with, even though it's not perfect.

When they're bigger or when I need more space in the germination chamber, I move the repotted seedlings up to the unheated attic, where I have a grow tent I recently bought on Marktplaats. The tent isolation gives it some warmth, but the attic gets quite cold as well, so it's not steaming hot inside. Not sure what would be best to up the temp here with a few °C. Maybe I'll figure that out next year.

I've been saving up for a green house, but those would be to cold too these time of the year.

Growing peppers is hard man. 😅
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I placed the propagator outside today because it was sunny. The plants still look fine, though it was probably too hot because the heat became trapped inside the propagator (which would also happen if it was indoors). When there is sunlight maybe it's better to leave the lid of because of the heat, which means it's more important to give enough water in the morning, because the soil dries quickly with direct sunlight.

I will keep using the lid for now. It does help with humidity as long as there is no sunlight. Maybe it helps that my propagator is pretty large, (60×40×25 cm) which makes it somewhat like the aquarium that you talk about, Sulsa.

Grow lights is probably a good idea as well for the plants but I didn't want to go that far with buying expensive equipment,
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