Internal wall insulation
Please advise suitable material/products for covering internal wall surfaces to minimise heat loss for a retrofit cob, stone and
brick period cottage.
A potentially tricky question! The danger when internally insulating existing masonry buildings, and I would suggest particularly cob, is interstitial condensation. Internal insulation usually means not being able to have continuity around junctions such as floors with walls leading to moist warm air getting behind the insulation and forming moisture with mould growth.
Having said that, our construction division Green Building Company, has been insulating internally with 50 or 75mm polyurethane board for many years but have tried to cut down air movement ‘behind’. The thicker the insulation the greater the danger. Natural materials such as wood fibre board systems offer greater security due to their ability to ‘take up’ moisture and release again in more favourable weather conditions giving better protection to the buildings fabric.
Green Building Store supplies the EdenBloc natural insulation board or other options include http://www.ecologicalbuildingsystems.com/workspace/downloads/Gutex_energy_refurbishment.pdf or http://www.natural-building.co.uk/pavadentro_renovation.htm.
I have particular interest in your question because I was brought up in East Budleigh and spend a lot of my time in Branscombe. I always remember the collapse of a cob cottage in the village which was said to have happened because cement renders had been applied trapping moisture, probably from faulty roofing. Although this is a dramatic story, it has always made me aware of the potential frailty of ancient building methods such as cob.
Please send your green building and DIY queries to Bill Butcher c/o chayley@greenbuildingstore.co.uk
