Greek Construction

I recently came across this announcement of the first Greek commercial premises to be BREEAM certified. This is a little piece of good news coming out of a dire situation but it got me to thinking about how one constructs buildings for the extremes of conditions experienced in many countries. In a way, in the UK we should have it easy - we have a relatively narrow range of ambient temperatures to deal with. What changes does one have to make to cope with both lower and higher temperatures? (I don't know - I'm no civil engineer). And what can one do to retrofit successfully? The little town house that we have stayed in during recent trips to Greece is a case in point. It has good thick walls which keeps the downstairs room nicely cool in the summer, but the upstairs room with a wood-lined ceiling immediately under the tiled roof can get very hot under the afternoon sun. Then again, on the few occasions that we have experienced a drop in temperature the house can be uncomfortably cold and the only heating is by portable electric fire or an traditional open hearth grate. There will be a lot of properties like this in the country. What would one have to do to make them more efficient? And what would be the cost?