There is a popular misconception that traditional buildings are inefficient. That they are hard to heat, suffer from damp and that they are not pleasant to live in.

None of the above is correct - and if it is, something is wrong!
It is true that older structures tend to have more gaps and draughts, and that they tend to be less well insulated. But these are easy things to fix, and when you have done so you have the benefit of the thermal mass or potential - usually the masonry. This keeps the building hot or cool depending on the season - once at a temperature it’s harder to change it.
A common problem traditional buildings face is that when inappropriate works are carried out, their external envelope can easily become saturated. This means that they lose the insulating value that the mortar has and become very hard to heat. Therefore it’s important to consider the whole structure before jumping to insulate or fit secondary glazing.

Modern houses by contrast are often built with very little mass internally - timber stud walls, plasterboard and that’s about it. The external envelope is better insulated than a traditional construction which means it can heat up - or cool down- much faster. This means that in the summer, they can easily overheat through the windows, and the winter has huge fluctuations in temperature. This can cause condensation and other problems.

In terms of energy efficiency, it is important to consider the energy used to construct a building: or the Embodied Energy. Current UK regulations do not consider this - and this skews the perception of how efficient a building is. So the Eco houses you see on Grand Designs may cost little - or nothing - to run, but their massive environmental cost to build means that they take many, many years to ‘pay back’ what they cost.
Most modern houses don’t have anything like the level of efficiency you see on high-end, high-cost bespoke builds - but they do still rely on a lot of overseas materials, cement, concrete and glass. So they start with a lower cost, but also have less means to ‘pay back’ what they cost.

Traditional houses, however, tend to be built from the materials which surrounded their location - so they have a much smaller footprint from transport. Their ‘carbon footprint’ is tiny by comparison - as there was no means of using excess energy in 1840!
People naturally used materials which ‘cost’ less: lime uses less fuel to create than cement (and re-absorbs carbon dioxide as it cures), bricks were fired at a lower temperature -and of course no plastic was used.

With a carefully designed scheme of insulation - and any defects repaired - your traditional or Listed Building will be a joy to live in - and already be outperforming any new-built Passivhaus.