Sulęczyno village and its environs are an oasis of peace. Forests, a lake, and blissful silence, make it an ideal place to relax. Right here, in the midst of greenery, there is a climatic house covered with aspen-chip laths, which has just undergone roof renovation.
One of the reasons for starting this undertaking were frequent visits by feathery guests. These were house martins – harmless creatures, but capable of causing substantial damage.
Strange noises and high bills
The martins most likely got under the roof through the eaves and infested the empty attic space. A thick layer of mineral wool was spread on its ceiling, which insulated the building and the roof. It was to prevent warmth from the heated loft from permeating into the cold attic. The martins did not care about the cold, as they had found the perfect place for a cosy nest in the warm wool. That was where its offspring were born. The result of the animal's existence was faeces and leftovers, mainly the skeletons of rodents. The channels made by the martins in the wool also damaged the insulation layer. Thermal bridges, i.e. gaps through which heat could easily escape, were thus created. An additional indication that the attic had new tenants, as well as the unpleasant smell and suspicious noises, was also high heating bills.
The decision to renovate
In order to effectively get rid of the martins, homeowners had to carry out a renovation. We wrote about the fact that replacement of thermal insulation with modified polyurethane - PIR Thermano foam - was the best way to deter unwanted tenants. An additional spur for the decision to renovate was the terrible condition of the existing roofing. As the roof slopes were finished with non-impregnated woodchip laths, they had not only lost their original appearance, but had also begun to leak. On inspection it turned out that the wood was so rotten that it almost fell to pieces when you took it between your thumb and finger. It was decided to dismantle and install new timbers. At the same time, it was possible to get to the attic and fully assess the level of damage caused by the wild inhabitants of the house. The wool was ragged, and the only thing you could do with it was to throw it away, quickly replacing it with new thermal-insulation material - Thermano polyurethane. It was also agreed that the entire surface of the roof would be insulated - from top to bottom. Therefore, it was not necessary to replace the thermal insulation on the ceiling structure separating the loft from the attic.
Insulation over the rafters
After dismantling the previous roofing, as well as counter-battens and battens, it was possible to lay a tight layer of thermal insulation of Thermano PIR panels on the rafters. By using them, you can safely cut out the need to lay a vapour-barrier foil on the loft side, which is necessary when insulating the roof with mineral wool. The use of rigid PIR foam is a solution which will ensure that the martins will not want to come back. The structure of modified polyurethane includes micropores filled with pentane, which martins do not like. Thus, by choosing Thermano thermal-insulation panels for roof insulation, the investor was assured that they would get rid of the problem related to house martins.
An entire roof in woodchip laths
However, the investor did not intend to change the roofing. He only decided that this time the woodchip laths would be carefully impregnated, by using the immersion method. Again, 40-cm-long, 8-cm-wide and 4-5-mm-thick aspen-chip laths were used, suitable for roofs with an inclination angle of more than 20 degrees. They are lightweight, so they do not overload the roof truss. Their weight is only 18 kg/m2. In addition, densely laid woodchip laths do not allow rainwater to pass through. The surface is smooth, so rainwater runs off quickly. Unfortunately, the laying of wood-chip laths is difficult and very labour-intensive. A 200 m2 roof finished with them takes about 2 weeks. We should also remember that wood must be adequately protected against fire, fungi and bark beetles. In order for it to be serviceable for many years, you need to use the right chemicals, which entails additional work and a higher cost. But - for this result - it is really worth it.
How do you install thermal insulation?
1. The thermal-insulation panels made of 10-cm-thick rigid PIR foam are screwed to rafters through 4-cm-thick counter-battens. We recommend that the screws in the Thermano product are fixed alternately at 90° and 67° angle.
The former will prevent shearing forces and the latter will prevent pulling forces. The maximum screw spacing should be 40 cm.
2. The polyurethane panels are fixed with 20-cm-long screws. The depth of the screws in the rafters should be five times their diameters.
3. Before the counter-battens are installed, a vapour-permeable membrane is installed on the panels. In the case of thermal insulation with Thermano PIR panels, it is not necessary to use premium, highly vapour-permeable, membranes. Affordable pre-coverage films are sufficient.