I recently came accross with SuperQuilt Multifoil Insulation in one of my air tightness projects. I´m not in the position to judge about the general advantages and disadvantages of that kind of insulation layer, but I have to raise some concerns regarding the air tightness and vapour control behaviour of Multifoil Insulation.
As coming from the specs of the manufacturer, SuperQuilt has a sd value of 348m (English specs) or above 3,000m (as printed in the German version of their specs). I didn´t get a response of the manufacturer so far, which explains the massive difference in between the two sd values and clarifies the real value at all.
Even for the case that the sd value is 348m "only", it means that the insulation layer is too tight to act as a vapour control layer, as it´s usually designed for standard roof structures in dwellings nowadays. Preferably vapour control layers with a certain permeability should be installed instead of vapour barriers. Membranes for air tightness and vapour control with sd values of 2m up to 50m are best practise for standard building structures.
What is the problem with SuperQuilt as vapour control layer?
When using SuperQuilt as insulation layer on timber structures, the complete layer must be taped and sealed to perfection. Every small gap and pocket will lead to a leakage, where warm air from the room will crawl through the SuperQuilt and meets cold structural parts behind, with the potential risk that condensation can be created. This dampness is trapped in the worst case in the building structure and can lead to building damages.
It is important to have the SuperQuilt Insulation taped and sealed to the highest standard, to prevent the risk of dampness and mould for the adjoining timber structure.
I have serious concerns regarding the current sealing practise, by using aluminium tape with a very low stretch and bonding performance to a wavy surface, as created by SuperQuilt and similar Multifoil insulation products.
I tried to get in contact with the manufacturer several times over the last few weeks but didn´t get any response regarding my concern so far.