EWI in Conservation Area

[Neil]

Hello,

I am looking to install EWI on a late victorian semi and have had initial talks with the councils conversation officer who didn't seem keen on the idea for a variety of reasons. The property is in a very dilapidated state with the render failing in many places. I suggested carrying out external to the rear sides and part of the front (bit set back from road) and internal to the largest front elevation (which contains numerous details).

His initial cencerns lay around breathability of phenolic boards and loss of features - namely stone sills, brick plinth which projects out at 45degress a metre above ground level and brick gable. Also the differences in window reveal depth from the 2 different elevations. The property is currently flat rendered down to the the 45 dgree brick plinth.

He has suggested internal wood batts insualtion which I am reluctant to carry out because of the state of the render to the outside, whereas internally the majority of the property has been restored. I have found a study/report of a property in west hampstead conservation area which succesfully overuled the condesation issue and allowed the phenolic boards to be used externally to sides and rear. The report sited that far greater risk was posed shoudl internal insulation be put inplace due to condesation caused by thermal bridging which doesn't occur with EWI. I intend to reference this appeal in the application or subsequent appeal.

I believe I can reset the windows to side/front (where EWI is proposed) further forward to match up with main front elevation reveal depth. In terms of the plinth one Idea maybe to remove the plint brick ad set futher forward so insualtion meets the the new line from below and above allowing enough space to place a brick slip to the vertical.

What I haven't thought of overcoming and need some advice is how do I re-creating stone sills? Moving them would be to distructive and I've thought about have a sandstone sill recreated and bolted to existing but this seems extreme if at all possible and would also create a thermalbridge. Another option would be to create the sill effect using a layer of EWI then render to match although I'm not sure if the drip line underneath the sill could be acheived.

Any help would be greatly appreciated as I hope to start the project this summer so time is tight. I've attached pics of the front and font side elevations you will see the state of the building and how EWI would be a massive help.

I've had my green deal assessment so any help on gettting me through the planning stage or indeed completing the job would be most appreciated. I'm not sure what ECO funding I will qualify for just yet but the carbon savings are fairly large.

[preeve]

Hi Neil
My colleague, Shane Conway at Northampton Borough Council, advises that you could try using a rockwool-based EWI system which would allow the building to breathe. This will require a greater thickness of insulation, but this might not be an issue if the property is not directly on the pavement. You would also need to use a breathable coating. He's had experience with a similar property and managed to get his planning dept to agree to this solution. He's happy for you to contact him if you want to discuss further.

Pippa Reeve
Northants Warm Homes

[Neil]

Hi Pippa, Thansk for the response. I think the thickness required using Rockwool may cause a problem as it will completely swally up the soffit roof line hence the reason for trying to use Phenolic to achieve the Building Reg requires with the least impact of visaul changes to buildings.

Do you have a direct dial for him?

[preeve]

You can contact Shane on 01604 837818.

Regards
Pippa

[aawuk]

I thought that some rigid insulations (at least one of PIR, PUR, EPS, XPS, phenolic, etc.), as might be used in external wall insulation (EWI), come in breathable form? I became aware of such rigid insulation for flat roof insulation which was, I think, 5 or 10% breathable or moisture permeable. However, I am puzzled about the requirement to have breathability of EWI, that's not a requirement I have heard of before. There is of course a whole class of EWI called rainscreen cladding, but I think that's used on tall blocks of flats where rain can be driven in by strong winds (basically there is a cavity which the rain gets to and this draws away the moisture downwards).

Another alarm bell rings when I read that the officer suggests IWI (internal wall insulation) using wooden battens (and presumably mineral wool and a vapour membrane, or plasterboard incorporating a vapour membrane). Surely most IWI nowadays is of the rigid insulation type, non breathable! Therefore no vapour membrane is required - just some spray foam insulation from an aerosol can, where services go through the insulation (er.g. cables for power sockets). You can even bank nails into some of those insulations. Suggesting the use of battens and mineral wool indicates the officer's lack of up-to-date knowledge of the solid wall insulation subject area.

[Neil]

Thanks for the response. I have the feeling the officer in question is taking the conservation concerns to letter of the law and it will be interesting to see repsonse from consultation, particulalry with case studies I plan to present or if it goes to appeal as there are many examples of Phenolic being accepted by the planning inspectorate.

The wood batts are actual solid boards very similar to phenolic not actual wooden battens then filled. They fit together like building blocks.