Underfloor insulation retrofit full demo

The full retrofit of rigid foam board insulation into the sub-floor of a victorian style ewardian house.
Thermal insulation of floors is an important part of insulation design, and in a house with ventilated sub floors there is the added issue of heat loss through unwanted ventilation from the sub floor into the rooms.
The insulation creats a thermal physical barrier, preventing airflow between the subfloor and room, whilst reducing heat loss from the room into the sub floor.
Note that the installation is not compliant with building regulations for new build homes in the UK, as the thickness of insulation is insufficient.
This is a great improvement to a location where there was previously no insulation at all, other than the boards, underlay and carpet.