The other detailing decision required less time staring at a computer screen. My husband removed the row of floorboards closest to the outside wall in bedroom 1, and installed insulation adjacent to the external wall between the ground and first floors. We had some hemp batt insulation left over from insulating underneath the ground floor years ago, and used this, cutting it to size. It means there shouldn't be a cold section of wall between the ground floor (internally insulated to ceiling level) and the first floor (internally insulated to floor level). With a detail like this, we'll never see the effect in terms of energy bills, but it definitely seems worth doing.