Thanks for your reply @Frank_Reif,
I should have probably mentioned that I’m planning other retrofitting along side this, roof etc, but wanted to keep the topic just about wall trusses for simplicity.
Looks like a very labour-intensive way to do it imo. They had a lot of money.
No doubt their budget was higher than mine, and also a much larger house too, but I think they did a lot of the works themselves so a simpler but labor-intensive approach made sense. It’s not too far from my house, and I recall seeing their black outer membrane for several months before they got their cladding on 
I’m undecided about doing the EWI myself, which is partly why I’m considering this option as it is one which I’m fairly confident that I at least could do myself, mechanically, with perhaps guidance from a retrofit consultant on detailing.
I also feel that a timber cladding is probably something which could be replaced more easily as it wears with age, than a rendering system… but that’s just a feeling…
However, it is better practice to have the air control layer on the masonry side, as well as the sheathings water and vapour control layer.
I haven’t seen any EWI systems specify an external air control layer, unless that is because in most hard-fit systems the parge/adhesive performs that function?
The usual suspects; punched opening, vertices, edges, and services; are where all the detail and the skill is needed. I’m confident with the theory, but don’t ask me about doing this in practice, let alone doing it productively.
Yep, absolutely thinking about all of those and planning to involve a consultant on the details once a general whole house plan is formed. But knowing whether an approach is even a possibility at this stage lets me know whether it’s something I could consider taking on myself with support, or something to just find an experienced retrofit contractor in Sheffield to do “off the shelf”.
Cellulose will likely be your most environmentally friendly option. Consider doing it alongside blowing in insulation elsewhere, such as your loft, because it’s the call-out fee and equipment that cost a lot, not necessarily the material.
There isn’t really any other application for a blown insulation:
- Roof & room-in-the-roof
- Is going to need rebuilding this-decade anyway by my reckoning, at which point I hope to just do roof and the EWI together
- Blown cellulose could possibly work with my plans for a warm roof, but flexible wood fibre can be fitted DIY from inside after the exterior works are done… so…
- Suspended timber ground floors
- Eh, possibly, but IDK if it would be “easier” than my plans for flexible fibre, as I assume both would need similar detailing for air and vapour control…
- Front stone wall IWI
- I’m planning wood or cork board for this at 100mm, and will be plastered anyway unlike the EWI which I’d prefer to clad with timber
Interior vapour barriers are highly suspect in these situations.
Could you explain that please? Do you meant that an internal vapour barrier would/could trap moisture in the fabric? I’m not planning to use internal vapour barriers against any of the exterior walls (but will be using vapour-closed boards in the bathroom to keep vapour in and vent it out)
My personal view is that 150mm rigid insulation systems, that are proven, are fine for retrofits. Save the money for the windows and doors, or the mechanical systems such as underfloor heating and rigid low static duct systems.
Could timber cladding be used at 150mm ish depths? Wouldn’t battens need fixing to the brick wall, leaving some thermal bridging? (I realise it’d be small screw heads and they could be covered but still seems counter-intuitive…
It may be a little like the tail wagging the dog, but I’m fairly taken with the style of timber cladding Bilton Design used, having seen it in person and also having looked at the cost of rendering…