My main heater (propane) does not require electricity to start or run. It has a standard pilot light. My roof & front wall vents are heat operated and open and close automatically. Yes my supplemental electri heater and vent/circulation fans would go out but it would not be a disasterous problem for us in either summer or winter. This setup is by design by the way. We often go out of town and out watering, fertilization, misting, cooling and heating are all on auto-pilot.

How hot do your summers get, Fuzzy?

Just curious...how much wattage does a 6100 CFM ventilation fan (like sold by ACF) draw?

When you own any type of greenhouse that you plan on using to grow in the cold months, you need backup. Backup generator to run Furnace,Fans,Water heater,etc or some other type of backup heat source, like propane heater.
I use a standby generator and a sensaphone to call me if i am not home, i need power on in 30 minute during the day and 15 minutes at night before the greenhouse gets to cold.
During the summer using shade cloths over the greenhouse helps to keep temps under control if power fails
and to answer your question 6100 cfm fan will take 5 amps at 120v

Carl

You will need vents in the ends of your greenhouse. I have a small section of double polycarb at the top back panel that I remove in summer and I leave the front door open. Hot air vents out the removed panel and feeds in through the door. I can't imagine what you would keep inside the greenhouse in summer. In winter I heat with K-1 kerosene heaters. The next time I need to replace them I an installing a gas line and a blue flame gas heater. You can get thermostat controlled heaters which have a metal strip which is heated by the pilot light. The strip creates enough electricity to turn your thermostat on and off. My in-laws had a floor furnace that worked even when the power went out.

I wonder if a generator can be set to auto-start in case of power failure?

hair

There are many standby generators on the market.

Google: Standby Generator

Eric

It's a good idea to have manual drop windows in a greenhouse, in addition to fans. There are many days when just opening the house to air will be sufficient. I do that often when I have a sunny day in winter and don't want a fan to kick on and the louvers to open and suck icy air over the plants. In summer or any other time when you know you won't get a sudden temp drop..........the manual vents take over a lot of the cooling until it just gets so hot the fans kick on. Saves you $$$ and also buys you some time in a summer electrical outage to get more shade on, drop the sides, whatever until the fans get operational.

Sensaphones are great if you are in a position to leave and get to your g'house or have someone else get to it in an emergency. I have airhorns hooked up to my temp alarms because I either have a baby-sitter for my g'houses if I am away when crops are in, or I don't leave them for anymore than a few hours at a time.

Back-up heat is a good idea even with a generator. I have a maintenance man who will come day or night, but it doesn't help if it needs a part they don't have. I use propane fired torpedo heaters.

My g'houses will usually hold four hours without a furnace in the bitter cold before it becomes critical. Ask me how I know. LOL. My biggest worry is irrigation. I don't have my g'house well electricals modified to hook to generators. I never thought of it to be honest until I had to carry water by the bucket to thousands of poinsettias from my spring in a three day snow storm. LOL.

I've never thoroughly tested one of my methods (thankfully), but I'll share it. I have a line from the well through a "normally-open" valve to my overhead misting system. With power on, the valve is closed and systems function normally. If power is lost, the valve opens and mist turns on continuously. The idea is just to buy me enough time to get home and hook up the generator.

good idea, Stressbaby.

I go out of town (as in more than 9 hrs away) several times a year (family). Therefore, something automatic is best...but even if I can buy a little time until someone can go over and fix it, that might be sufficient.

I'd like one of those Standby generators - I think one for our house itself is a good idea anyway, but they're INSANELY expensive!

mairmetalforever...we see 90's F regularly in summer and we're all-glass too. It's not optimal, but with our interior shade cloth, our 4 auto vents and auto-misters we're find without power even on our hotest days. We typically also have a constant breeze to help.

FWIW, I'll probably use a French patio door with full-length glass as my GH door, and open both of the double doors wide open, pretty much through the entire summer.