The Refit West report identified that the biggest energy and carbon savings could be made from insulating all external walls on the inside. (The character of the property meant that the insulation would have to be on the inside – whereas a house with render walls would be more amenable to external insulation.) The calculations were based on reaching a U-value of 0.35, aiming to meet the standards required of a new build. The emissions savings estimation comes in at around a whopping 4 tonnes of CO2, and cost savings of £790 off our fuel bills each year. Having said this, I suspect (though am not certain) that this assumes we don’t replace the inefficient old central heating boiler.
When we got a quote from Footprint for this part of the work, it wasnt cheap – in particular, the costs were raised significantly by the need to remove and re-instate period features such as cornicing and picture rails. Given this, I asked Footprint how much more it would cost to increase the thickness of the insulation. As the main cost is labour and fitting, this made very little difference to the price, so we decided to go for it. We selected 70mm Quinntherm insulation, giving a U-value of 0.23 – significantly better than the 0.35 proposed in the Refit West report. Despite the significant cost, I would expect it to pay back in 10-20 years.
The work involves substantial disruption since the plaster on the external-facing walls must be hacked back, the insulation fixed in place within wooden frames, and plasterboard and re-skimming to finish. Of all the works, this is by far the most intrusive, so I am glad that it can take place before we move in.
Chris
Not quite as Rolls Royce as yours but I’ve discovered 12.5mm plasterboard with 50mm insulation pre-bonded (becoming readily available), allowing it to be fitted quickly (glue dabs) and avoiding putting wood into direct contact with a solid wall with inherent tendency to be damp (or maybe that’s just my old dry rot wound coming back to haunt me). I want to check it out a bit more in terms of (a) how it works (b) what it means for damp / breathability before using it more extensively but installation is a winner on the little bit I’ve had done so far.
Colin