Hi,
Can you elaborate on the good ways of doing this job. Spoke to 2 architects some time back and neither recommended it. One of them questioned that there is only a 15 year guarantee on the job and wondered what happens after that if anything goes wrong. I didn't get the time to question them for long on the merits etc.
The creation of thermal bridges is one of the main considerations with adding insulation to a building and especially true for ewi. There are 3 places generally where these tb's occur; top of wall, bottom of wall and around windows & doors reveals. Thermal bridging not only allow excessive heat loss but also significantly increase the risk of mould internally. Therefore, thermal bridging should be designed out where possible. Depending on the building, you achieve this by extending the insulation down to the wall footing, up past the soffit to the top of the wall (and ensuring the roof insulation seamlessly meets the ewi) and move the window / door frames outwards to be overlapped by the ewi.
What I often see quoted for is going only to the path level on the bottom, soffit level on the top and the windows & doors not moved outwards.
I also find that the knowledge base on the above is poor enough with quite a bit of misunderstandings on the subject leading to less than desired outcomes.
Also, in the majority of cases, the actual insulating material is the cheapest element of the ewi install and for example doubling the insulation thickness from say 100 to 200mm might only add maybe 10|% to the overall cost but make quite a bit of difference to conductive heat loss.
There are many buildings with well installed ewi in place for many decades without issue and if an issue arises I don't see why it couldn't be repaired / addressed like any other building defect. However, if you have a budding county hurler in the household who likes bating a sliotar against the gable wall then perhaps ewi wouldn't be the best choice!
Finally, there is little point in getting ewi done if your airtightness weaknesses are not addressed.