When planning the thermal insulation of the attic floor, reliable and proven materials should be used, i.e. providing protection against fire (non-flammable), improving the acoustic insulation of rooms (well absorbing sounds), ensuring a good indoor microclimate (vapor-permeable), hard to wet and safe for health. This is what Rockwool stone wool products are like. In addition to the use of an appropriate insulation layer, it is also important to properly shape the partition in this way, that the water vapor can escape from the attic rooms, produced by the inhabitants.
The layout of the roof slope materials divides its solutions due to the way of draining water vapor generated by residents and penetrating from the attic rooms to the outside. So we have two correct solutions: attic type leaky and water vapor tight.
Roof covering of the type of leakage to water vapor – when used on rafters, windproofing as a membrane with high vapor permeability (>600-800 g / m² / day). Water vapor flowing from the dry rooms of the attic will be led through the vapor-permeable layers of the slope to the ventilation gap. 2 – 3 cm between the windproofing (membrane) and the roofing material laid on the years and counter battens, and from there through the exhaust vents in the ridge to the atmosphere. Then we can use the entire height of the rafter cross-section to arrange the first insulation layer, and the insulation may come into contact with windproofing. Due to possible inaccuracies of the wooden roof truss, however, we recommend, so that the insulation has a thickness of 1 – 2 cm less than the height of the rafters – this way we will prevent the windproofing from being stuffed out (membranes) towards the ventilation gap.
Roof covering of water vapor tight type – when using full boarding with roofing felt on rafters or windproofing as an initial covering foil (FWK) with low vapor permeability (<600 g / m2 / day). Always remember about the thickness of the ventilation gap 3-6 cm, left under full boarding or FWK and above the insulation. An open gap will ensure ventilation of the roof and drainage of excess moisture from the attic rooms, therefore, you should also make air intakes into the slot (roof eaves, soffit) and outlets (kalenica, ventilation grilles in the gable walls). The insulation should have a stable thickness and adequate protection from the side of the gap, e.g. wire grate, so that the ventilation gap will not be clogged during its installation. The height of the rafters minus the thickness of the ventilation gap can be used to arrange the first layer of insulation.