...and you'll see why there are so many questions. Even your interior surface finish is a factor.
You blocks have a K value of 0.25 (see page 9) so according to the table on page 6, your wall is over specified - you could get away with an 85mm cavity.
Your builder should be building to the approved plans, not deviating to how he sees fit.
And more importantly, not quoting you for the specification on the plans and then using whatever materials he can find cheaper to increase his profit margin
Conforming to the appropriate u-value for the wall is irrelevant to you, if the builder has used some cheap lightweight blocks totally inappropriate in other respects
The wall's insulation value is just part of the criteria, not all of it
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