ᐅ Insulation boards used as cavity insulation between rafters in a cold flat roof system
Created on: 8 Jan 2019 14:53
R
Ronny.S
Hello everyone,
I would appreciate an expert answer. I am in the process of converting a garden shed. The roof consists of 23mm (about 0.9 inches) OSB boards, with roofing felt and bitumen membrane on top. Now, my question: I would like to fit standard insulation boards between the rafters as cavity insulation (see photos). Does this make sense, and more importantly, could condensation form there? The roof is ventilated through holes in the eaves (about 5cm (2 inches) diameter and spaced roughly every 60cm (24 inches)). I plan to suspend the ceiling using a wooden framework—that is, leveling battens at the right height and adding 100mm (4 inches) mineral wool insulation on top. Below the battens, I want to install a vapor barrier and then a second set of battens arranged perpendicular, to which I will screw the drywall panels. Does my construction approach make sense, or am I completely off track? Thank you for your answers.
I would appreciate an expert answer. I am in the process of converting a garden shed. The roof consists of 23mm (about 0.9 inches) OSB boards, with roofing felt and bitumen membrane on top. Now, my question: I would like to fit standard insulation boards between the rafters as cavity insulation (see photos). Does this make sense, and more importantly, could condensation form there? The roof is ventilated through holes in the eaves (about 5cm (2 inches) diameter and spaced roughly every 60cm (24 inches)). I plan to suspend the ceiling using a wooden framework—that is, leveling battens at the right height and adding 100mm (4 inches) mineral wool insulation on top. Below the battens, I want to install a vapor barrier and then a second set of battens arranged perpendicular, to which I will screw the drywall panels. Does my construction approach make sense, or am I completely off track? Thank you for your answers.
Hello garfunkel,
Thank you for your response. I took your advice and hired a professional. You are absolutely right. The insulation boards between the rafters are pointless and will be removed. My roof isn’t metal but covered with a waterproof membrane, yet ventilation at the ridge is necessary. I believe the specialist will install trapezoidal vents and seal them properly. The master roofer says everything will then be fine. A vapor barrier will also be installed and, of course, sealed correctly. Thanks for the answers.
Thank you for your response. I took your advice and hired a professional. You are absolutely right. The insulation boards between the rafters are pointless and will be removed. My roof isn’t metal but covered with a waterproof membrane, yet ventilation at the ridge is necessary. I believe the specialist will install trapezoidal vents and seal them properly. The master roofer says everything will then be fine. A vapor barrier will also be installed and, of course, sealed correctly. Thanks for the answers.