We are installing pavatherm woodfibre insulation on the internal walls at the front of the One Planet House. This is a breathable system that will be finished with a lime plaster. The lime plaster has a 7 day drying time and therefore to minimise disruption to the tenants we are internally insulating one room at a time.
A representative from Natural Building Technologies came to the property last week to show the contractor how to put up the woodfibre board and plaster it.
We have decided not to insulate all the way up to the joists of the intermediate floor. When carrying out internal wall insulation, common sense suggests that we need to insulate all surfaces of external walls to ensure that we are minimising thermal bridges.
However, at this point there is also high susceptibility for uncontrolled air changes through the narrowed mortar joints. Research that Parity Projects have done with the EST and a variety of other contributors has shown that if these parts of the house are insulated, the risk of moisture build up is increased. This risk is increased when using a breathable insulation system because moisture is able to travel freely through the wall. As can be seen in the photo opposite, we are also putting interstitial sensors in the walls where there is insulation to measure the moisture of the wall over time.