You may remember I installed external wall insulation (EWI) back in 2014 and unfortunately small gaps opened up between the insulation and the fenestration soon after completion. These gaps were sealed with silicone and it’s now been 3 winters and there’s been no further movement so it would seem everything has stabilised. So what happened and what can we learn. Firstly, the training provided by the system supplier was woefully inadequate (something I suspect the whole industry could do better on) and compounded by a refusal to make a pre commencement site visit which considering that neither myself nor the installer had ever installed this or a similar system was indeed unwise. Secondly (as seems to be common practice in the industry) the installer used the same contractors who undertake the rendering for the installation of the insulation and as this requires quite a high degree of craftsmanship, especially with the T&G woodfibre boards this became a painful process to get right. On a recent job for a client we had to throw the specialist EWI contractors off the site and decided to use carpenters for the insulation but this causes problems for the guarantee and raises another issue the industry needs to get straight. Thirdly, I pushed hard for a pull out test but neither the supplier or the contractor was prepared to do one which was unwise as the test performed after the works suggested that it was quite possible that some of the fixings may well have been inadequate and while in general this may not be outside the margin of safety for the system as a whole, it could be an issue locally and may well have been the cause of the excessive movement of the narrow strip between the door and window. Surely it’s worth spending a few extra pennies to have longer fixings to avoid this risk? Fourthly, the APU beads which form the first seal between the fenestration and insulation were specified by the system supplier but were unable to accommodate even small differential movement and so were not fit for purpose and indeed it may be wise to not fit them at all but I have not yet got to the bottom of this one, but the industry needs to – there’s no point fitting APU beads if they fail and the gaps need siliconing! The possible issue of highly damp walls causing the woodfibre to swell / move still hasn’t been resolved as the system supplier would not provide any data on the moisture performance of the insulation or assist in testing the installation – surely, if we are to retrofit our old building stock then EWI is a critical part of the solution and we need to ensure robust installations. However, the installation is a success and is working very well – it was just a bugger to make happen!