There is no point specifying the best system on paper if it is not put together right on site. Here are the main touchpoints to be aware of so that the insulation and airtightness system works as intended.
Insulation only works if it is continuous, i.e. there are no gaps in the insulation layer. Insulation that is not correctly installed, with gaps in-between, will never perform to its best. Boards for instance should be held in place by stainless steel wall ties, usually covered by a plastic disc, against the outer face inside of the inner leaf, when batts or boards are being used in a partial cavity wall.
The ties should be kept clean of mortar during construction as this could cause moisture to travel from the outside in. If the insulation is blown in post construction, it should be evenly dispersed throughout the wall cavity with no gaps.
