In new edition of H1/AS1, the schedule method requires wall construction R-values to be R2.0 in all six new climate zones. The increased R-values apply under both the schedule and the calculation methods of determining H1 compliance.
If using the schedule method of compliance, the number in the H1/AS1 document is the minimum R2.0-value and this must be met or exceeded. However, if using the calculation method or the modelling / verification method it is possible to use a construction R-value which is lower than this number - provided this is offset elsewhere and that the designed home performs at least as well as a reference building. By using construction R-value which is higher than in the table, it provides the ability to use a lower R-value on other elements or to adapt the home elsewhere such as using lower cost windows, slab construction or using a higher glazing percentage to increase natural light to the home.
It is worth noting that actual framing ratios should be taken into account, The H1 documents provides details on what needs to be included, but high timber ratios can make wall compliance in a 90mm frame a challenge.
It is possible to use a 45mm internal secondary layer to increase performance. For example, a simple 90mm frame with a R2.6 batt could achieve R2.0 construction value. By adding the additional layer R1.3 this could lift to R3.4 construction value.
Our wall insulation segments are designed for framed cavity applications, providing various thermal performance options to meet evolving construction needs. Knauf Insulation offers R-values from R2.4 in a 90mm cavity to R4.4 in a 140mm cavity.
There is little significant change to walls construction R-values in the H1 update. In new edition of H1/AS1, the schedule method requires wall construction R-values to be R2.0 in all six new climate zones.