St Mary's Beaminster have recently implemented wide-reaching changes to their Grade I-listed church building with a view to cutting its fossil fuel reliance. The team involved managed to bring in renewably-powered and effective heating, well suited to the needs of the parish, all whilst maintaining respect for the medieval fabric of the church. Given the extensive practical limitations that faced the project, and the extent of carbon emissions prior to it, the result of this work can be considered a success, even if it is too early to fully quantify the scale of change.
The Churchcare team at the Church of England conducted a case study on St Mary's, looking at practical steps they took to cut their energy use and work towards "net zero carbon". You can read the case study here.