>>1069168Greenhouses. You'll need lots of thermal mass in it (black-painted water barrels are best and you can top them to use as tables). You'll need to use those big rolls of bubble wrap to cover the greenhouse because a single glazing won't work. You may need 3 layers of protection. You can use a few different heating systems together. Passive solar that brings in hot air from a solar box, hot compost/manure bins that heat up as they decompose, and traditional heating for your area. You need to let in fresh air regardless of what you do and have a fan to move air around inside the greenhouse. You can do all this in a polytunnel, but working with a polytunnel in snow isn't all that fun.
Where I live, it gets to -15F at night a lot of times in the winter. The worst winter in my memory was -42F.
>>1069184 - >>1069200You should grow tomatillos so you can make fresh salsa. They grow like weeds and volunteer like mad.