Insulation at rafter line
With existing buildings, the depth of the rafters tend to be 100mm deep (in some cases150mm deep), which limits the thickness of insulation which can be fitted between them. Furthermore the installed insulation, between rafters, must not impede cross flow ventilation, and be retained at least 50mm below the roofing felt.
Due to these restrictions, fitting insulation between rafters alone will result in a shortfall to the required target thermal performance. Therefore, in order to achieve as near as practical the target U-value an additional layer of insulation will need to fitted beneath the rafters.
The target U-value for attics insulated at rafter level is 0.20 W/m2K or in as much as is physically and economically possible.
Rockwool Flexi insulation
Find out out using Rockwool Flexi insulation at the rafter level of your loft can help you achieve a better thermal performance.
