External wall insulation

[octonuddle]

Has anyone had this done and if so, has it made a noticeable difference to the warmth of your home? Also interested in cost…how much would you consider reasonable for a 4 bed detached house?

My friend had this done 10yrs ago under a government scheme and it's been an unmitigated disaster. You don't say what age your house is? Friends house was a Victorian end of terrace which had celotex added to the outside which was then rendered. But nothing was done to extend the roofline/guttering to the new front face, so water seeped in between the insulation and the wall, resulting in damp internal walls. It's been a total bloody disaster & said friend can't afford the costs to get it removed. I'm interested in this myself but I live in a conservation area and I don't think I'd be allowed to add anything externally.

Oh no!! Nightmare @EpicSneeze

House is 1950s …our roof overhang is pretty big so I’d hope not to have to do too much to roofing. Your poor friend

I'm interested in this too.

Have you considered internal wall insulation OP?

If done properly, it should work really well. But you should really think to insulate roof/loft in a way that there is no gap between the insulation of the wall and roof so there is no cold bridge. Also, I'd recommend insulating ground floor too in a similar manner.
Research Enerphit (retrofit passive house), there is loads of information online. You don't have to insulate your house to Enerphit standards as it has to be very thorough and is expensive but if done correctly, you would benefit a lot.
Enerphit is roughly £1k/m² of the house area.

Have a look at this: www.greenbuildingstore.co.uk/oxford-enerphit-plus/

Octonuddle, what type of wall insulation where you thinking about?

1.Cavity wall insulation is definitely worth it if you have a large area of external wall. It is simply, quick and fills the gap to keep house extra warm.
2.spray thermal wall insulation is not good. It gathers dirt, difficult to paint over and does not allow the building material to 'breathe'. A bit like pebble dash but looks like textured paint.
btw, do not use spray foam in the roof of attic! Mortgage companies refuse to lend money for properties with spray foam in the roof of a building, thinkplutus.com/learn/spray-foam-insulation/

I had cavity wall insulation put in about 10 years ago and we did notice house was Warmer. Can't remember cost.

I had the rubber seals (gaskets) renewed on the opening parts of my ancient double glazing recently. It's made the flat cosier. £250 for a large 1960s (1500 sqft) flat.

@Wiseflower we have solid walls and so can’t really get cavity wall insulation so it was suggested we consider EWI…it basically sounds like the house is wrapped in foam and then rendered on top. I like the idea of it as it doesn’t reduce internal flow space and can be done without much disruption to the house…but I don’t know anyone who has had it done and I get the impression it os pricey..

@cowsaysmoo £1k per sqm <faints> thanks for the link - that is the kind of thing we had in mind

We had it done to the upper half of our 4 bed detached house. Upper floor was solid breeze blocks pebbled dashed, ground floor is stone faced cavity wall. Conservation area so not permitted to do ground floor.
Has made a significant difference - considerably warmer. However, because it is such a big job, you tend to roll all the improvements in at the same time. eg we replaced all the upstairs window, from either single glazed wood windows or old double glazed (pre 2000 when standards improved) to new double glazed, so had an improvement from that too.
It is a job for skilled workmen - ie rooflines, wrapping insulation around windows revels (?). repositioning downpipes and other utilities.
The house warms up faster and retains the heat longer. We are also more likely to throw open the windows for 10 minutes on a morning in winter to ventilate as we know it will easily warm up again - so improving general air quality.

@SallyLockheart thats encouraging! We are also planning to do the windows at the same time. Have you Had any issues with condensation or damp walls? Also… do you mind me asking how much it cost?

No problems at all and as it is warmer, we tend to ventilate the bedrooms more than before. Had it done in 2018 but I suspect costs have gone up quite a bit since then - materials, labour and scaffolding. We paid approx £16k plus windows.
from a payback period point of view it’s a very slow return but comfort heating levels in the house are much better and we upgraded the very tired pebbledash with a more modern textured render

Thanks @SallyLockheart that sounds exactly what we need…I don’t really mind the slow payback if it means I will be warm. We rarely open our windows as it is so cold! The thought of being able to swing them open whenever is lovely. Our external render is looking tired and needs redone too so all in all seems like a sensible way to kill a few birds with one stone.

Just be very careful on what material you buy. I do not trust the Buildings Regulations at all after Grenfell (that was solid wall insulation).
Rockwool is most definitely not flammable and as far as I am aware, it is the only one that isn't

That is some what misleading. There is no evidence of standard insulation used in normal domestic homes having any fire risk. If EPS is used as insulation, that is the same as some insulation used in cavity wall insulation and there are no reports as far as I know of cavity wall insulation casing fires.

I had cavity wall insulation done last week - it was originally done 20 years ago but there were gaps. It cost around £1500 but that was the top up volume. Noticeable difference in temps, I really notice it as I'm doing night feeds for a newborn and it's definitely warmer. Heat stays longer in the rooms too.

I looked at having it done under the recent green homes grant. My house is a large detached 4 bed with lots of angles. Like yours, it had no cavity, so the options were to either insulate internally or externally. The external option was to glue large Kingspan insulation boards to the front and then render over the top. The two quotes that came in were for around 14,000. I am not sure whether prices were inflated because of the 5,000 grant, but in the end I didn’t go ahead as neither company were prepared to come to Norfolk and I kept going around in circles with the grant paperwork. The government dept dealing with this eventually closed the case as they couldn’t open the documents I sent and the scheme came to an end.

My house is concrete construction so no cavity wall. When we bought the house the front had already been externally insulated but the back wasn't. We built a full width ground floor extension to the back so the downstairs at the back is insulated now however the upstairs is not. You can really notice the difference being in the front bedrooms as opposed to the back bedroom which always seems colder even though it is a much smaller room. As we didn't pay for the external insulation at the front I don't know the costs of it but I would say from our experience it does make a difference

We had this done (EPS) on our stone house, like PP rolled in with re-roofing (double use of scaffolding!) and replacing our very nasty old windows. A while ago, so prices probably not useful now. Rendered in a tasteful goldy-cream :)

The house is now warm everywhere - it just never was before, and like others say, we feel much more able to ventilate it as well. Our gas bills went down about 50% iirc while the temperature definitely went up!

We had it done on a mid terrace (front and back) in 2015. It did make it very cosy, but we also replaced the windows and front door.

Rough costs then were about £6/7000 but we didn't pay as we won it in a competition from our council!

We have since moved but If my house were rendered now I would do it again. I don't want to cover the lovely bricks we have now.

How does external wall insulation work during a heatwave?

On one hand, the insulation slows down the solar heat from reaching the inside of the house.
On the other hand, once a house gets hots (and if the heatwave lasts long enough it will get hot), doesn't the insulation mean that the heat stays trapped inside?

In other words, could it be that external insulation could be better at preventing overheating if we get, say, 2 days at 30C (not enough time for the heat to reach the inside of the house), but not if we get a week or more at >30C and hot nights (like in 2020)?

I mentioned it because I remember that, during a heatwave, many newbuild flats, built with better insulation, took forever to cool down at night while poorly insulated house cooled down more at night.

@ParentOfOne funny we were having this discussion this week with the heatwave! I still think it is worth our while because for 95% of the year our house is freezing (Scotland) but we did wonder the same thing….on the 2 days a year when it is positively boiling outside, would that make the house uncomfortably warm….
Would be interested to hear from those with it.

@Clarabellawilliamson You won it! I’m envious!

We have extended our stone detached house. The extended wing is totally different from heat retention to keeping extreme heat out.

We have opted not to have cavity fill for the rest of the house. The reason is tens of thousands of people had retro fit cavity fill and then had problems with damp. Basically the pointing has to absolutely top notch as the cavity is there for a reasons...which is to prevent damp crossing. Filling it breaches that gap so it's a case of do it at your peril. A lot of companies now refuse to do retro fit for stone

Last time I investigated the possibility it was £120/m2, +the cost of moving things like down pipes and soil stacks. My overhang is big and so didn’t need changing but if you had a narrow overhang that would have to be sorted as well. I don’t know how that could be sorted except by putting a new roof on (~20k-~30k). That said maybe there are accepted ways of sorting that issue.

Thanks @Hiddenmnetter our overhang is huge fortunately… it was the first thing our architect noticed…that’s what got us started on exploring EWI. We are shifting pipes and putting in new windows too so it makes sense to do it all at once. Are you still tempted to do it? I need to figure out our square meterage to figure out the cost there…did that include re-rendering too?