INSULATION QUESTION? The house consists, from the outside, of 1, Roof tiles in Engaberat clay. 2, On 45mm bearing battens 3, laid on double counter battens with a vapor-permeable membrane Moniere diverol stretched over the entire roof between the two counter battens 28x70 + 22x70 which are placed on an existing plank roof (stick roof). This roof has historically been filled with wood shavings from the eaves up to 20 cm above the cold attic floor without an air gap. The rafters indoors on the upper floor are clad with 28 x140 rough-sawn planking from the eaves up to 20 cm above the attic floor surface, and then the rooms on the upper floor are clad with Tretex which has been wallpapered and painted, etc. So without a vapor barrier. Now to the question. What is the best replacement for the wood shavings? Which products and brands? Best insulation value versus the old method with wood shavings. Since this project will require insulation of loose-fill type without an air gap. Someone suggested Rockwool's loose-fill insulation since this insulation should also be flame retardant and vapor-permeable and can quickly transport moisture that enters the insulation and also be capillary breaking and draining?? Which sounds good. Others have recommended cellulose insulation like Ekofiber etc.? Can you also answer why there is such a divide between experts in the building conservation sector and contractors on this question of air gap or not?
The problem with loose-fill stone wool is that it transports moisture too well while also insulating. This means that the moisture quickly reaches the roof where it condenses and becomes water, which in the case of a sloped roof, runs back through the insulation and creates mold in the sloped roof wall.
It is considered that eco-insulation buffers/holds the moisture so that it doesn't get the opportunity to condense until it is warm or dry enough outside to release the moisture.
The most important thing, as I see it, is to ensure no moisture enters the construction; you achieve this with plastic or a vapor barrier on the inside and a vented cavity on the outside.
In your case, it sounds like you have a vented cavity between the membrane and the pitched roof! Then I think you can choose whichever insulation feels best but don't forget the vapor protection!
It is considered that eco-insulation buffers/holds the moisture so that it doesn't get the opportunity to condense until it is warm or dry enough outside to release the moisture.
The most important thing, as I see it, is to ensure no moisture enters the construction; you achieve this with plastic or a vapor barrier on the inside and a vented cavity on the outside.
In your case, it sounds like you have a vented cavity between the membrane and the pitched roof! Then I think you can choose whichever insulation feels best but don't forget the vapor protection!
The Divorol membrane is a diffusion-open fabric stretched over 22 mm battens, creating a space between the membrane and the shingle roof, but the membrane is sealed and adhered at the eaves flashing, and it runs over to the other side at the ridge. However, the air gap between the membrane and the roof tile is extended to 73 mm for better volume and ventilation towards the ridge, and at the eaves wedge, there is a bird strip with ventilated battens all in one. The house is old, from the 1930s, and has been insulated with wood shavings, so there is no vapor barrier or air gap, and I would prefer to avoid these as well. Heating is provided by a wood-fired boiler and wood stove, resulting in occasionally much higher room temperatures than in a typical house.
I believe that the main reason old houses rarely have moisture problems is that they are poorly insulated. The thicker the insulation, the greater the risk of condensation, and the longer it takes for the condensation to dry when conditions are favorable. Additionally, it is often said that organic insulation handles small amounts of moisture better than glass wool. No insulation can handle large amounts of moisture. If you do not want plastic, make sure it is at least airtight. No open joints between boards in the corners that are only covered with a strip; make sure the joints are filled. Moisture can migrate through plasterboards, but the large amount of moisture enters behind the boards if the air has a free path into the construction.