Temperature in Winter

you have a water heater ? you can put it near something that makes heat ....

Use a ventless propane heater. It will give extra CO2 as a bonus.

If you only do autos you only need worry about 4 hours even with an led (1 with a good reactive fan set up) otherwise line it with kingspan probably minimum 50mm but 25mm might be enough. I have 2 layers of aluminium double bubble it's reasonably effective but I'd recommend more

Let your lights be your heatsource. Instead of LEDs, run HPS, and set your lights to be turned on during the coldest part of your day.

add lights

i grow inside an insulated box for temps and sound reasons and it works alright so far id try to insulate the tent within the gardenhouse as only the tent needs to keep the heat, change airflow to intake air at the top and exhaust on the bottom to optimise the use of the lamps heat, maybe if possible let it turn on and off every so often to be able to heat up the tent a bit better aslong as the circulation volume stays acceptable overall why not i dont see a way around a timed heater at least under 12/12 light the idea here is that the thick walls of the house and extra tent insulation keep enough heat so that you have to heat the least amount possible to keep a comfy 20C°+ in the tent id get 2-3 drywalls or Thin wodden plates , 2-4 cm thick insulation (i like those firm or soft woodfiber plates) and some stable wooden struts (2x4 cm maybe) first of attach insulation towards the gardenhouse wall and floor, then measure and fit in a frame for the dry wall on the left side combine the frame and drywall, put in and attach the insulation for the door/frontside repeat and id probably just let it "loose" and move it in whole every time i need to get inside so its easy to disassemble for a warmer season

Greenhouse heater. The gas is the best as it produces co2 which can increase final harvest up to 50%,yeh 50%.Google greenhouse heaters and you'll see the gas ones and the electric bars. Keep them in the house as long as poss especially when they're small. Keep them off the floor and use a heat mat. You could grow autos and keepo the light on as much as you want. I do mine for 22 hrs a day and give the lights a break for a couple of hours for warmth. You need it inside when using LEDs never mind a shed. Insulate the shed as much as poss. Anything from blankets to kingspan.Block those gaps around the doors and windows.

Can you run natural gas line to it? There's no "cheap" heat. that's cheaper than electricty around here, but depends a lot on local regulations and whether you already have a gas hook up. Plus, usually not work average people are comfortable with. Pay someone to do it so you don't blow up your house and have someone to take to court if they do, lol. Infrared heaters might be cheaper? They are more directional heat and you want something that can circulate better. the moment they turn off it cools down almost immediately - the difference between how it works and a heating element in a typical space heater makes it less optimal, i believe. send an insulated duct from your house? if well insulated, i bet the space heater won't have to turn on when the lights are on, or barely run. Gotta do what you gotta do or compromise on your plans.

For cheap you can insulate the outside of the tent with Styrofoam insulation. Grow autoflowers in the tent in the winter and run the lights for 20-24 hrs.

Hola! hay ciertas cosas que puedes hacer para que las plantas no sufran mucho del frío. En la etapa de siembra y crecimiento temprano, coloca las macetas sobre alguna silla o mueble, algo que la eleve en altura y no esté sobre el suelo. El suelo se enfría mucho y al estar en contacto con la maceta puede disminuir mucho la temperatura en la tierra y dañar las raíces. Coloca la luz a 20cm a una intensidad baja-moderada, así también le da un poco de calor. Intenta que las luces estén encendidas por la madrugada y por las mañanas. El calor de las luces puede ayudar a tus plantas. En caso de que utilices ventiladores o coolers, intenta no usarlos cuando las temperaturas estén muy bajas. No suele haber problemas de humedad con el frío. Si trabajas con defoliaciones, intenta mantenerlas con muchas hojas y solo quita las necesarias. Mantener un indoor denso en hojas pero funcional, ayuda a que no sufran totalmente del frío. Este invierno en Argentina fue duro, entre 0°c y 5°c por la madrugada - mañana. Pude mantener un ciclo de autoflorecientes y crecieron bestial. Tengo la misma carpa casualmente jaja el mismo color y todo. Espero que puedan servirte estos consejos! saludos, pasate por mi perfil!

Yeah that’s a tough one. It depends what kind of winters you get in your geographical location. I live in a climate where we get down to -40 Celsius in the winter. It would cost a fortune keeping a shed warm. Wood stove but that would probably not be a viable option and require modifications to your shed. I think you don’t really have a much of a choice to spend on the electricity to make it work. Unless you bring your set up indoors to where the climate is better controlled, but there’s probably also a reason the tent is in the shed so probably also not a viable option. There are natural gas heaters as well but again that would come with costs and modifications to the shed. That’s a tough one. I hope you find a solution that works for you.