Steico, lime and airtightness

[Pebble]

First post. I can't believe I've not found this place before!

We're renovating an Edwardian house. Mainly solid stone with a rubble filled gap. We're planning on internal wall insulation using a lime parge coat, 80mm steico and lime/mesh finish. We're having an ASHP and hoping to achieve an air change of 5. We have all new windows.

I have 2 questions.

1. Our architect is saying the sparkie should channel out on the internal face of the steico for cables and boxes. The sparky disagrees (I think he wants kingspan and an air gap!). What have others done about electrics when using steico?

2. A number of people have said we will never achieve 5 for air change as we will need to drill through the steico etc back to masonry to fix things like electric back boxes and curtain poles to the wall. Does anyone have any experience of trying to make a house airtight using these products and what did you do about fixing things to the walls?

Thanks

 

[Kearn]

Trying to make an old house airtight is an endless game…! Sorry!

To answer your question on the electrics, sparky should do first fix into the wall, hide cables in conduit in the initial coat. He’ll obviously need to calc for resistance based on the thermal load due to the insulation.

Neither of them I would agree with.

You ‘could’ recess back boxes into the boards and lose some localised insulation, no great shakes.

Alternative is you do it all surface mounted.

in an old building, I’m not sure a few screws here and there into the walls will change much in the grand scheme. There will be greater heat loss elsewhere no doubt….

 

[Lacan07]

First post. I can't believe I've not found this place before!

We're renovating an Edwardian house. Mainly solid stone with a rubble filled gap. We're planning on internal wall insulation using a lime parge coat, 80mm steico and lime/mesh finish. We're having an ASHP and hoping to achieve an air change of 5. We have all new windows.

I have 2 questions.

1. Our architect is saying the sparkie should channel out on the internal face of the steico for cables and boxes. The sparky disagrees (I think he wants kingspan and an air gap!). What have others done about electrics when using steico?

2. A number of people have said we will never achieve 5 for air change as we will need to drill through the steico etc back to masonry to fix things like electric back boxes and curtain poles to the wall. Does anyone have any experience of trying to make a house airtight using these products and what did you do about fixing things to the walls?

Thanks

You can buy special 'plugs' for fixing into wood fibre boards that mitigate some of the loss in airtightness, and insulation for electrical back boxes.

One of the problems I found when actually installing the wood fibre board is occasionally I'd drill into the mortar beds and not the brick which wouldn't then take the fixing nail. This obviously leaves a very slim but deep hole which you then have to try and fill.