The front of our house is right on the street and we were refused planning permission for 'extending' 100mm into the street with external wall insulation.

I think we might get away with a thinner insulation treatment without planning permission, but aerogel seems to be the only material with adequate performance. Does anyone have any experience of EWI with aerogel, or know the pros and cons (other than the cost)?

No real pros and cons. You can use it in a built up render system as you would do a rigid board or Rockwool or else you can have it ready bonded to a render board and fix it in a dry lining type manner but externally. Aerogel Spaceloft fleece comes in 5mm and 10mm thicknesses. 40mm will give you a U value of 0.030 on a 9" solid brick wall

Have you checked the cost before you get too set on the aerogel route?

I started off thinking I was happy to spend more to get the best product until I found out just how expensive it is! 40mm might triple the cost of the EWI!

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How did I manage to quote myself??

Used in conjuction with a render board damage at street level would not be an issue, also the time for installation and finishing is vastly reduced
true (for accidental damage at least), but then your getting back up to a 60mm (The Spacetherm brochure quotes a u-value of 0.23 using 36mm on a 220mm solid brick wall plus a render board and render) thickness which may not be acceptable unless the entire street is doing the same (possible good solution in local authority grant funded scenarios?). Malicious damage is another matter however which is where my concerns for any EWI system on houses directly onto the street stem from.

Posted By: Peter_SIs it possible to insulate internally with 100mm to the front wall?

As above, this is where an aerogel internal dry lining laminate comes into its own

I agree but it will be down to how much is that extra floor space worth internally. Hopefully the cost of aerogel will reduce significantly with increased use making these questions obsolete?

Posted By: Peter_S(The Spacetherm brochure quotes a u-value of 0.23 using 36mm on a 220mm solid brick wall

Peter, I see you're having similar problems to me when quoting!

That Spacetherm reference is either a misquote or its wrong in the brochure. The U value of a solid brick wall is taken as 2.1 W/m2K i.e. an R value of 0.476. The thermal conductivity of Aerogel is 0.013-0.014 say 0.0135 so the R of 36mm of aerogel is 2.666.
Add that to the 0.476 and you have an R of 3.142 and therefore a U value of 0.32 W/m2K.

Aerogel's Spaceloft (Proctors call it Spacetherm) is no longer available in 9mm layers. It is now 5mm or 10mm.
So using 4 layers of 10mm the R is 2.962. Add that to the 0.476 and you get an R of 3.439 or in other words a U value of 0.29 W/mK. Allowing for thermal bridging through fixings and you're safe at 0.30 W/m2K

I agree that it depends on how the adjacent properties compare in this exercise. In theory at least or perhaps only you could use a 9mm render board, scrim the joints and finish with a textured paint, the whole build up just over 50mm.
Alternatively the solution would be to line internally. The same thickness i.e. 40mm + 9mm mag board could be used

Posted By: Peter_SThis throws up all sorts of questions regarding streetscape and EWI generally.
Is the property already rendered and therefore would not look much different with EWI and render to how it looks already? Will the 'charactor' of the property be altered substantially by rendering it?
Terraced type properties right on the street may not be a very practical use for EWI due to potential damage to the system at low level.
Is it possible to insulate internally with 100mm to the front wall?

I think the planning issue is appearance, not land ownership. Most houses here have rainwater pipes, porches, bay windows and other bits that stick out into the street. I just don't think the planners liked the idea of bringing the whole frontage forward.

IMHO our proposal would improive the appearance of the street. The property is currently 'stone'-clad and painted dark blue. Ye-es! The historical look for Brighton terraces is rendered and painted. So the proposed silicone render system would be in keeping with 'local vernacular', in a way that stone cladding is not.

Interestingly, our property already protrudes 40mm into the street, thanks to fake-stone slabs and adhesive. Suppose I were to remove the slabs + adhesive and replace them with aerogel and silicone render system totalling 40mm. The wall surface would not protrude any further than it does now.

We could insulate internally upstairs, but on the ground floor we have already fitted a kitchen which we don't want to disturb. Plus I'm totally sold on the thermal and weatherproofing advantages of external insulation.

Thanks for all the comments so far. At least I have some options...

I bet that they wouldnt take any enforcement action were you get on and do it.

Proof of the pudding is the stick on stone cladding, clearly that protruded and nothing said.

Posted By: john_connettIt might be worth investigating the Lockplate vacuum insulation system which claims to reduce the required insulation thickness by a factor of three

But note that vacuum panels are very vulnerable to damage. Any hole releases the vacuum and the performance disappears. So there'd need to be an impact-resistant render board or something and some way to make sure nobody ever put a screw into it etc.

Vacuum insulation seems to me like phase-change materials. Great idea but too many practical problems in most applications. Perhaps some future version will be more usable.

Reviving this one.... Any new experiences of using aerogel as EWI?