Achieving a u value of 0 20w m meaning your roof will be better insulated than your walls will need 120mm thickness of rigid foam or 200mm of mineral wool or natural insulation.
Roof insulation level.
The amount of insulation installed in the lofts of new buildings has steadily increased over the past half century from about 25mm in the 1960s to 270mm today.
R value is a measure of insulation s ability to resist heat traveling through it.
Use rigid foam insulation panels on your flat roof before applying the final roof covering or inside the house before adding sheetrock or paneling.
Upgrading existing roof insulation.
Achieving greater r values in attics the higher the r value the better the thermal performance of the insulation.
Your attic should have a certain amount of insulation in it and the recommended level of insulation for your attic is dependent on where you live.
First things first you need to go up into your attic inspect the condition of the insulation and calculate the current level of insulation.
Hitting amazing levels of 0 13w m will need 300mm of mineral wool or 180mm of rigid foam.
The higher the r value the better the thermal performance of the insulation.
R value insulation chart find your zone on the map and then use the chart to determine the level of insulation you need to properly insulate your attic walls floors and crawlspaces.
Insulation level are specified by r value.