Rebecca Norman wrote:I agree with Mike Jay above. You're probably getting the uncomfortable overheating in summer from the western windows or walls, and to lesser extent from the eastern or northern exposure. Our sun in Massachusetts is low and weak enough in winter that you probably shouldn't plant anything that will shed its leaves and cast dappled shade in the winter. This winter, check out how long snow lasts under the shade of deciduous trees -- I think you'll find it lasts a lot longer than it does in direct sun. So if your overheating is coming from the south, the suggestion above to install some kind of awning that you can retract seasonally is probably best.
In any case, increasing your insulation might improve your thermal extremes both summer and winter, and reduce overheating in summer as well as heating load in winter.