fencersupply

Hi Luke, Great to hear you're planning to insulate your attic! I'll try to address your questions one by one: 12 cm of 035 Toprock Premium wool should be a good starting point. This type of insulation generally offers great thermal efficiency, and 12 cm is a decent depth, especially for average temperatures. However, it really depends on your local climate and the specific temperature you want to maintain. If you’re in an area with colder winters, you might want to consider adding another layer to ensure you meet the manufacturer’s recommendations, but the 12 cm should help significantly. With 2 layers of roofing felt and Katepal bituminous shingles, you’re already in a pretty good position. As for the gap under the boards, it can often be enough for ventilation, but I would recommend adding a vapor barrier foil if you’re concerned about moisture buildup. It’s always better to err on the side of caution to avoid condensation issues in the long run, especially if you’re heating the attic. For the ridge ventilation, make sure to leave a clear path for airflow. You can lay the wool up to the ridge, but ensure that it doesn't block the venting channels. If the insulation is too close to the ridge, it could obstruct the airflow and affect the ventilation system’s performance. You could also consider using insulation baffles around the ridge to keep the airflow unobstructed. Good luck with your attic insulation project, and let me know if you have any more questions! Best,