velacreations

The surface freezes sometimes, but we do not live in a cold climate. For colder climates, insulate, bury, or possibly add a heater.

This is a great book to get your started with this: http://amzn.to/2eizexVAlso, just do a google search for "rocket mass heater" and you will find tons of information.The most important sizes are the cross section area of the exhaust tubing, it should match the burn chamber and be consistent throughout.

Id you add about 2/3 of the suggested amount, a few yeast will survive and carbonate a bit. Be careful with that, though, and if you want carbonation, you should use bottles designed for it.

that depends on how you bottle it, but several years. You can't freeze cider, you will only freeze the water part of cider, and the alcohol will stay liquid, but will be much higher concentration. This is called Apple Jack when you freeze the water out of cider.

Secondary cider fermentation typically lasts less than 6 weeks, so thicker plastic works fine for that, too. When there's fermentation activity, O2 penetration is less of a concern, because of the positive internal pressure from the CO2. It's the aging and post-fermentation where you have to be the most careful.There are plastic containers made specifically for fermentation, and they are a bit thicker and have special coatings/materials to prevent permeability.We've used plastic for a few years and have never had a problem, but we are usually bottling within 2 months.

Yes, we do use plastic. We actually use whatever we can get our hands on for fermentation containers!Plastic works fine for fermenting cider, because the cider is not in there very long, and there is a positive pressure from the fermentation. So, no oxygen is coming in during fermentation. I wouldn't use it for aging or any step where you will store your cider for long periods (more than a few months). The permeability of the plastic happens over time, so as long as you keep your cider there for short periods (under a month), you shouldn't have a problem.

yeah, it's really a matter of specific gravity instead of time. Secondary is over when you go below under .999 SG