Construction services

Insulation on rafters

The exposed rafters are often an architectural element of the residential area. They introduce a specific atmosphere and make, that the room is gaining height. There are basically two options for implementation. Decorative formwork is particularly common, visible from the side of the room, which is nailed to the rafters (boards are joined with a tongue and groove), and then an insulating layer is put on them. The second popular method is to assemble the finished ones, self-supporting insulating elements, which do not require a plank underlay and can be laid directly on the rafters. The substrate of the boards can be painted, paper or plaster. Some elements have a ready substrate that does not require further processing. Plates consisting of several layers are usually used, which meet stringent thermal insulation requirements and enable quick progress of works. Besides, there are also insulation systems, which are not laid on the rafters, but roof battens, covering the entire roof structure, including patches and counters. They also act as a second drainage surface. As in the case of thermal insulation boards, also in these systems a vapor barrier is recommended, located under the insulating material. It is placed directly on the rafters and fixed with battens, relatively – in the case of formwork – between boards and counter battens. The air between the laths is rather still and not full, unlike irf systems, ventilation function. Airing is most often done through air ducts, located in the insulation boards. When opting for thermal insulation on the rafters, you can choose from several types of insulation materials. Only self-supporting boards may be laid directly on the rafters. The most common insulating materials are: styropor, mineral wool (glass or rock), fibreboards and hardened polyurethane foam. Cork is a less common material. Individual thermal insulation materials differ in heat conduction coefficients. The lower the digit, the better the insulating properties and the smaller the amount of material needed to achieve the appropriate thermal protection index. This, in turn, affects the thickness of the building layer. The materials used for insulation on the rafters have a thermal conductivity coefficient of 0,25 do 0,45.
The choice of a specific material is determined not only by the thermal conductivity coefficient. The overall development system and the specific properties of a given material play an important role. For example, polystyrene is particularly light and drains water from its surface, mineral wool, on the other hand, is non-flammable and adapts well to the substrate. Wood fiber boards have the ability to store heat, and self-supporting elements made of hardened polyurethane foam ensure good thermal insulation despite its small thickness.