U-values

U values are an indication of the thermal conductivity of building materials.  You will need these if try to calculate the amount of energy required to heat a building to a certain level.  While these values are well understood for standard building materials, renovations can be more of a challenge.  In our case, the U values for the new build extension are relatively straightforward, however calculating the U values in the existing buildings is more of a challenge.  The walls are solid stone around 500mm thick and will be insulated using a new Gyproc system.  The roof is also going to be revamped in terms of insulation (at the moment, there isn’t even roofing felt under the stone slates).  Even so the figures below show a significant performance difference between the new and the old parts of the building.

U values for the new build: