*Disclaimer - many of these simply were derived from casual conversation and I have not done all the background research, so the range of specific accuracy may vary here.
One big one, which I was reminded of by a news article referring to Denmark - but Trondheim burns its trash for electricity and heat. The District Heating System is pretty interesting and quite large - covering (at minimum) the heat of all municipal buildings in the city. This is greatly minimizing the ventilation requirements of included buildings. Many buildings I've encountered (including my student apartment building) operate via passive/natural ventilation.
Some side notes with this... By trash, I mean 'avfall', or items not recycled in paper/plastic/glass/metal. I have further heard that all packaging plastic allowed in Norway is required to be of a certain compound which can be burned without releasing toxins into the air.
Also, building demolition and construction waste is highly regulated in Norway - 60% of materials removed from buildings are required to be reused or diverted from landfill, and localities commonly have centers for building material reuse/resale. These centers often employ people for sorting and cleaning materials on an hourly basis, creating laborious, but paying jobs for those with drug addictions and other problems hindering regular work.
Norway produces more electricity through hydropower than they use on an yearly basis. While commendable, there is a small catch to this.. Through the summers, a great surplus of energy is produced and exported through Northern Europe, but hydropower cannot be produced in the winter months, when rivers have frozen over. It is also during the winter that Norway consumes the most electricity for heating - this is purchased back from, sometimes unclean, sources in continental Europe. I have heard that in the 1980s or early 1990s, an ad campaign ran on the national television station actually encouraging Norwegians to use more electricity, because it is clean. The other concerning downside to this is that many appliances here, heaters and stoves in particular, run off of electricity, which is less than efficient.
To be fair, the (very progressive) building code in Norway is forcing incredible amounts of insulation and high R-values, and has planned for zero-emission buildings level requirements for the near future.
I am sure there is plenty more which will come to mind to be shared later.. But today, in the shadow of clouds of volcanic ash, one must recognize the shear power of nature - with or without humans and their destructive habits. I'm finding the flight groundings a bit refreshing in an ironic way.. The last time this Icelandic volcano erupted in the 1800s, it kept going for a full year - I cannot personally remember the last time in my life I went an entire year without taking a fuel guzzling flight, just imagine the environmental implications of grounding entire countries for any period of time.