I would like to get more insights on how greenhouse cultivation cost of production is effected by cold temperatures during the winter, lets say in states like Michigan? What is the impact on the gas / heat cost to sustain stable temperature inside the greenhouse and whether it is offset by lower electricity cost as you use sunlight ?
What is the overall comments regarding cost of production in cold states when selecting between indoor or greenhouse grow?
My generic comment is that it is gonna be cold and expensive.
The calculator has a list of heat loss coeifficients by insulation type. I think double layer inflated poly is the cheapest option with a decent heat loss coeifficient. Still, some quick math in the dead of winter is showing something like 900 gallons of propane for 3000sqft of grow space. This doesn’t include heat from lights, but still, that is a lot of BTUs to keep things in the 70s F°. There would be some variability to that depending on location and month. You’ll want to find the lowest low average temperature for each month for a specific location to determine max cost. You can also explore the cost savings of more expensive insulation types, such as 16mm polycarbonate, which has half of the heat loss as inflated double poly film, but vastly more expensive. Something like $3-4/sqft vs $0.20/sqft (plus some blowing equipment).
I lack additional information to give a less generic statement on the matter.
Edit to add: Thick polycarbonate sheets will last 10-20 years, and poly film lasts about 4 years. Thick polycarbonate should more than pay for itself in heat saving over 10 years, but it will cost a pretty penny up front.
Sunlight is one of the key factors in an advanced greenhouse design. The issue is the storage of that sunlight energy for gradual release during the colder months. A battery that is charged with heat and recalled 6 months later, so to speak.
Evacuated solar tubes can collect vast amount of energy, with most of the systems installed to supply domestic hot water, leaving the majority of the collected ‘summer’ to be dumped as waste heat.
Can be a scaled version of this, with plenty of local considerations in the design.