Four degrees is not much energy to add or subtract. Ordinary split system air conditioning / heating would be a comparatively inexpensive and quick installation. If you have your own ditching machinery it is possible to dig a ditch about 5 feet deep for about 40 feet, install a spiral duct underground and elbow it up inside a screened tower to use air through the ground temperature for cooling in the summer. It is also possible to dig a thin ditch the same depth and extend a coil of black poly pipe to be used as a geothermal cooling/heating coil for a water-based heat pump. A convenient well may be used instead. A high wall with solar panels above the snow line or a roof-top installation attached to a large insulated water tank will heat the home and hot water with electric backup. Post if you can't find geothermal heating or cooling by doing a web search.