So this week we have finished the demolitions – the next step has been to begin the lining of the exterior front and rear walls with Poly-isocyanurate (PIR) insulation – now although this is not the most natural of materials (it is made from oil after all), it does have an extremely good thermal resistance (otherwise known as lamda – λ ) 2.25 m2K/W.
As our client does not want to lose too much of the rooms to insulation – we decided on this material as it reduces the thickness required.
In order to avoid cold bridging (definition – sections through the fabric of the wall of significantly lower thermal resistance than the rest of the construction) we are over battening and running another layer of Celotex over the top (see the photo to the left).
Overall this means that the overall construction of the wall achieves a U value of 0.19W/m2K – which in context is a great improvement over the 2010 building regulations standard of 0.28W/m2K for new elements under Part L1B – and a massive improvement over the 0.55W/m2K for a renovated thermal element.
We have also narrowed down the options available for the solar thermal/gas heating system (using a high efficiency gas condensing boiler for topping up when the solar is insufficient – but more on that next week.