The options for growing in cold climates are much better than most people assume. With Holzer permaculture's micro climate creation a great variety of foods can be grown outside with very little work. By selecting the heartiest of varieties and experimenting with cold climate foods many people have not tried before a great deal can be accomplished.
On Jean Pain mounds;
I am part of an organization called
Compost Power based in Vermont that is helping spread awareness and education about Jean Pain mounds. We teach a class on compost heat capture at Yesermorrow in Warren, VT. High field's composting has also been doing work with these and right now has a kick starter site raising funds to really dial in their system. Karl Hammer of Vermont Compost has a specific Jean Pain mix which he sells just for these mounds. There is a DIY guide on our website CompostPower.org.
I also design and build Earth Powered Greenhouses through my business Perpetual Green Gardens. By digging the greenhouse into the ground we make use of the ground temperature to buffer the greenhouse climate. In the winter the earth provides a constant source of heat. In the summer the ground temperature helps cool the greenhouse to prevent overheating.
This operation is based out of Montana but we travel all over. The original greenhouse has effectively yielded a zone 8 growing space in a zone 3-4 location. More importantly the greenhouse gives us 300 frost fee days as opposed to the 100 we get outside. This triples our growing season and gives us year round food without heating, fossil fuels, or even electricity. A growing space like Portland Oregon in our cold, dry, and high mountain local.
This enables us to grow (and produce) peaches, apricots, nectarines, figs, persimmons, pears, pineapple guava, and much more, none of which is possible outside.
If the temperature stays below -20° f for a full week the greenhouse will eventually cool to 15° f and that's where it seems to stay. But you could go even deeper and add a solar powered insulative blind if you wanted to be even warmer.
We use entirely passive systems so that our greenhouses function independently of electricity. Passive ventilation, geothermal heat, subterranean heating and cooling, rain water collection, pest control, and fertility. Healthy ecosystems are established so that 'pests' serve as food for other insects in the system and are controlled by nature. All of the plant matter that is not consumed is returned to the soil surface to feed the soil ecosystem. This process accompanied by the use of rainwater to promote demineralization of soil minerals makes upon the body of perpetual soils. By using these concepts the original greenhouse has become Moore fertile each year. 30 years of productivity with no fertilizer, soil amendments, or even outside composting. A self fertile system that doesn't need external inputs.