Serious thought here about how to improve our Victorian semi.
#1 - Replace boiler. Current boiler is ~22 years old, but was class leading at 78% efficiency when we installed. Change to Condensing at 93% efficiency should lead to 20% improvement.
#2 - change our front sashes to slimline double glazed (12mm deep, argon/other gas filled). Units can be bought for about £1,300, not sure about the fitting cost. Uncertain benefit, but 6m2 of single pane glass does a lot to cool a room.
#3 - improve draftproofing on front door, consider if some sort of secondary glazing might be an idea for the stained glass, without making it look too naff.
Well, the results are in for #1, with two full months on a new boiler.
Clearly there is difficulty comparing one year with the next, but average temperatures haven't been that different year on year (if anything, cooler this year). Our comfort level has, if anything, increased yoy as this year we have been far more sedentary with Mrs Ham - she with the Ice Maiden extremities - still recovering from her ankle op in August. Hot water has been tuned down a little, flow temperature is lower than the old. Heat input into room implicated in #2 up there ^^ has been increased by the addition of another radiator, which enables curtains to be closed, makes the room cosy so stops Mrs Ham from whacking up the stat to the rest of the house to get the front room warm. We have shut off heating to rooms that aren't used and improved drafts on one or two doors.
So the overall result calculated based on average daily consumption - saving 19% in Dec and 21% in Jan is amusingly close to the expectation. I'll take that as a win.