From the HES website:
Maintenance and saving energy
Building maintenance and repair is an important part of ensuring energy efficiency in traditional buildings.
Thermal performance of traditional buildings is reduced by:
- loose or defective pointing
- poorly maintained windows
- damp masonry
Reduced thermal performance leads to heat loss and higher energy bills.
Gaps around doors or windows let heat escape and cause draughts.
Building defects can cause masonry to become wet or stop water vapour escaping from the walls. A building with damp masonry will feel colder and its walls will also perform less well – heat moves more rapidly through wet material.
Maintenance must be carried out before insulating a building. Defects and water ingress can both stop insulation from performing at its best, and further problems may occur.