If you have the property, and resources, make sure your house is tight. Then, dig a four foot trench that zigzags across a suitable part of your yard, taking care to call Mis Dig for location of underwater electrical, water, and gas lines. Lay PVC pipe into the trench, making sure it's water tight. Bring one end up from the ground, above the maximum snow depth, with a u fitting that points the pipe toward the ground. The other end of the pipe is brought inside your home, with an airtight fitting around the entry point. Place no-see-em proof screen on the outside pipe end. Install a wind-tubine driven, whole house fan to expell old air. The lower inside pressure will cause to outside air to travel through the buried pipe, and pre-warm it before it enters the house.
I most of the nation, even up where I live in U.P. Michigan, the temperature 4 foot underground remains at about 45 degrees F. It may not be toasty warm, but the fresh air will be much warmer than the direct, above ground air. As a bonus, hot supper air is replaced by cooler fresh air that again flows through the underground pipe in summer. You get free air conditioning, and air heating.
Another very good product is the Evacuated Tube Solar Collector. It works at any outside temperature. It's used to heat water, which can surround a heat exchanger through which your outside air gains access to your home, or run the hot water through room radiators to directly heat your home.