Another good book to check out is
The Solar Greenhouse Bock. It's a very in-depth look into how to build a greenhouse to maximize solar gain and insulation, which lowers heating costs.
I've been researching for three years and haven't got my greenhouse yet
Are you able to build a greenhouse attached to your house? That helps a lot in heating/cooling the greenhouse, and can also help heat your home in winter. Plus the convenience of being able to walk right in from the house. One big thing that gets overlooked when designing a greenhouse for the North is cooling! I work in a commercial greenhouse with roll-up curtain walls and if the air is still it can be over 20 degrees warmer inside than outside. We have sections that regularly get over 110F in the summer! When I build my greenhouse it will have ridge vents and ground level wall vents. Cool air will enter at ground level and get heated up. Hot air rises and exits through the roof vents.