There is no cheap way toheat a GH even in Florida.

Macedonia:

With all due respect to any and all, anyone buying a 74 acre greenhouse should be consulting experts not beginners on a public forum. The cost will be hundreds of thousands of dollars a year, maybe millions.

My heating bill using the cheapest method here, natural gas, is $500 per year for 1700 sqft. That equates to $1,000,000 per year for 74 acres. I'm only heating to 1C where our average low is -1C. If you wanted to grow tomatoes and heat to 20C, the cost would be many million per year.

Heating would be bad, but have you given any thought to your water needs? Or electric?

Keeping something that cool would take quite a bit of power and watering that much acreage ..... ouch!

I think we're missing something here. Can't imagine even putting row covers on acreage. The structure alone would cost about the same as the queen's palace.

Doesn't add up. Sorry. Maybe he has 74 acres and wants to put up a small greenhouse on it.

From High Tunnels.org,

"Although there are many high tunnel operations in the state of Sinaloa, Mexico, this one operation has 375 hectares (925 acres) of high tunnels. They grow primarily beefsteak tomatoes, but also produce seedless cucumbers and bell peppers. It is the largest single complex of high tunnels in North America."

Here is a link that might be useful: High Tunnels .org

We are heating our greenhouse with manure layered with straw and wood chips on the outside. Rather then go into a long explanation of everything on here, you can go to FB and check out our page called "HomePlace" We are about done with the last stage and hope to have it operational with the next 10 days.