Opting for both IWI and EWI looks like a nice way of paying over the odds and getting the disadvantages of both ;-)

It depends a bit on where you are, for most regions EWI is permitted development provided you make an effort to make it look the same as the existing finish, so planning permission is not required.
Primary elevations are sacred from a regulations point of view, government guidance from 2013 explicitly states however that EWI is exempt to encourage people to insulate their homes. I will refrain from giving my opinion on your neighbours attitute (I am facing a similar "problem")

Posted By: bhommelsOpting for both IWI and EWI looks like a nice way of paying over the odds and getting the disadvantages of both ;-)

Yes, the cost is another factor. If the insulation job is too much of a compromise is it worth it? Maybe I improve the house in other ways and wait to see how it performs. Underfloor insulation in particular should make a noticeable difference and I will improve the bathroom and kitchen ventilation. I've lived in cold houses before and don't mind putting on a(nother) jumper, but here it's the condensation and mould in winter that I need to get rid of.

Posted By: WeeBeastie

Posted By: bhommelsOpting for both IWI and EWI looks like a nice way of paying over the odds and getting the disadvantages of both ;-)

Yes, the cost is another factor. If the insulation job is too much of a compromise is it worth it? Maybe I improve the house in other ways and wait to see how it performs. Underfloor insulation in particular should make a noticeable difference and I will improve the bathroom and kitchen ventilation. I've lived in cold houses before and don't mind putting on a(nother) jumper, but here it's the condensation and mould in winter that I need to get rid of.

EWI is fantastic, not least due to the thermal mass of the walls becoming part of the warm volume, and the lack of fussy detailing compared to IWI. It will be very hard to get the same effect through other ways of improvement (unless.....)

Maybe you could sell the benefits of EWI to your neighbours and have both front elevations insulated at the same time?

how about using the gutter downpipes to make it look less obvious
I post an example

.

I dont like the shallow eaves either . they look miserly :-)
theres also the benefit of a bit of weather protection and shading from deeper eaves
but to get the 200mm on we had to put up with it , fortunately when the places were built they had decent eaves

I assume you have done the calculations on the cost benefits of insulating externally and have shown this to your neighbour. If not then I would suggest doing so and trying to get them to do the same at the same time as this would reduce the overall M2 price and solve the look issue.

I have another neighbour who is very supportive and is pleased to see someone taking action to install energy saving measures. There are a couple of houses around here with EWI. However I'd think that many people are completely unaware of the existence of EWI, heat pumps etc. Most people I've spoken to don't know what heat pumps are. They know about loft insulation, UPVC double glazing and maybe cavity insulation....

Makes me wonder how attitudes were to the introduction of gas when it started to replace solid fuel.

well the marketing campaign worked well
I use the phrase "Cooking with gas" and my mother wasn't even alive then

@Jonti
I agree with all your points as probably most on here would.
It is just that for "normal" people, convincing them to spend several thousand £ on EWI to reduce the gas bill by a few tens £ per month is a big ask. From a purely financial perspective, even for my DIY EWI installation the payback time is well over ten years.

I doubt there will be legislation that would require people to install EWI or IWI, or swap the gas boiler for an ASHP to stay legal anytime soon.

Posted by WeeBeastie: 'lathe and plaster”

Incase it helps: lath and plaster linings seem to work differently from the solid walls that you may have read horror stories about IWI. Air circulates between the lath and the masonry and drys the masonry and allows for a drainage plane, a bit like an early version of a cavity wall, or Tony's modern 'plaster tents'. We found that removing a socket allowed a gale through, ditto under skirting.

If you EWI, you need to block the cold air circulation behind the L&P or it will negate the EWI, this will mean breaking into the room linings (disruptive) but think through the moisture consequences before you block it.

We took down the L&P and replaced with PIR boards between studs. We were careful to maintain the air circulation between lining and masonry, open to ventilated loft and underfloor, but sealed so it didn't get into the room. This is a common method round here when old buildings are converted.

Over a decade we did each room bit-by-bit when redecorating, and sometimes had cause to reopen the earliest walls, no sign of damp or decay. The house was much warmer, and less draughty.

The IWI was easy to join to the loft and underfloor insulation, but attention was needed to fix some cold bridges and insulation gaps at corners. The windows took over from the walls as the coldest condensation magnets in the rooms, so ventilation needed attention.

IWI has something of a bad reputation which is a pity because IWI and EWI each have their place and their limitations, neither is right for everyone, but we could get more houses done more quickly if we considered both.


Posted by WeeBeastie:"- u value no smaller than 0.5”

Be very careful, this number comes from the influential 'Breaking the Mould' study which applied specifically to west-facing porous walls in Dublin that had been IWI'd in a particular way and absorbed 70% of driven rain. The author was very clear that any walls with different climates, different constructions, would have different outcomes and 0.5 might be safe or unsafe there, but unfortunately the 0.5 number has been picked up and applied as a magic number all over the place.

Posted By: bhommels@Jonti
I agree with all your points as probably most on here would.
It is just that for "normal" people, convincing them to spend several thousand £ on EWI to reduce the gas bill by a few tens £ per month is a big ask. From a purely financial perspective, even for my DIY EWI installation the payback time is well over ten years.

I doubt there will be legislation that would require people to install EWI or IWI, or swap the gas boiler for an ASHP to stay legal anytime soon.

Whilst I agree that most do not see the reason to do upgrading now there is no doubt that gas will become the next big target for the environment. No new gas boilers from 2025 in new builds so I would be surprised if gas survives much beyond 2030.

For most there will be no cheap alternative fuel so the only way will be reducing the need to heat IMO.

Our existing studs were about 2"x1.5" iirc, we replaced some of them with treated 4x2s to give greater depth of insulation. As they bridged across the insulation, they were kept a bit warm from the inside.

(Another benefit they were stiff enough not to need mid height support pegs into the wall. And the existing studs were on weird spacings that didn't match metric plasterboards. )

But the studs are surrounded by insulation 2 sides and in contact with moving air, same as the rafters and floor joists are, so I wasn't too worried about them being damp.

Over different rooms we tried different setups, such as fixing sheet insulation over the existing studs to reduce bridging and avoid fiddly cutting insulation to shape. There were pros and cons such as trying to fix the plasterboard through thick insulation. We didn't do it scientifically enough to say one method was 'best’.