Rebuilding outer leaf

[SteamyTea]

Insulation can be thought of as reducing air movement.

The material that the insulation is made from does not make a huge difference, it is picked for its mechanical properties, not it's insulating characteristics. 

 

In reality, well Physics, thermal conductivity is much more complicated and depends on the material's phases and structures.

 

Using

7 hours ago, saveasteading said:

Woozle

as a model, you can think of these little Gnomes (how I see them) passing buckets of heat to one another.  They initially pass them in any direction they like (radiative scattering), but eventually realise to be of any use, they have to take the most efficient path, which is the thermal gradient. Downhill for cooling, uphill for heating.

The shorter the path, the steeper the gradient is, so the Gnomes can pass buckets faster to each other.

[saveasteading]

19 minutes ago, SteamyTea said:

passing buckets of heat to one another. 

I like the buckets analogy. 

Struggling with the hill though. Isn't heating or cooling the same process of bucket passing? Downhill for poor insulation, uphill for good?

 

21 minutes ago, SteamyTea said:

it is picked for its mechanical properties, not it's insulating characteristics.

You mean that it can be woven from rock or glass or paper or oil, but the gas or air bubbles and maze of conductive routes are what matters?

[SteamyTea]

6 minutes ago, saveasteading said:

I like the buckets analogy

Thank you.  I could refine it a bit more and say they transfer the contents between buckets. That is closer to what is happening in the quantum realm (photons and electrons swapping over).

 

10 minutes ago, saveasteading said:

Isn't heating or cooling the same process of bucket passing

It is, except that as things get hotter, they radiate more energy, so heating up, past a certain point, gets rapidly harder and harder. For the same building, the heating and the cooling curves will be different.

 

13 minutes ago, saveasteading said:

You mean that it can be woven from rock or glass or paper or oil, but the gas or air bubbles and maze of conductive routes are what matters

Yes.

If you look up the densities of all the materials that make up the 'insulation', you will find that the solid part is quite a small fraction of the overall mass.

 

I used to have a spreadsheet of material properties (Kaye and Laby, NPL) that was useful for picking desired mechanical properties out.

[allthatpebbledash]

DELETED.

Edited Friday at 15:52 by allthatpebbledash
Added to other post

[allthatpebbledash]

On 20/12/2024 at 11:55, Mike said:

It's possible, but what's the advantage over your option 3 (Leave pebbledash in situ, inspect to make sure no cracks etc, fix EWI straight on top and render over)? Just seems to be adding unnecessary additional cost.

 

 

Then that's another big tick in favour of rebuilding - underpinning isn't cheap and it's presence (especially if because of subsidence) may add to the cost of house insurance and put off potential future buyers.

I agree, seemingly option 3 is most likely candidate.

 

On 20/12/2024 at 12:33, saveasteading said:

Somebody will be more up to date than me. But it is going to be something like £500/m of perimeter and a huge amount of mess.

Why does it need underpinning?

Existing original foundations in areas are under bearing. Engineer thinks it’s okay as settlement and all that, and I’m very close to sandstone too. But potentially can be corrected with localised underpinning if needs be. Don’t need to do the whole footprint.

 

On 20/12/2024 at 14:03, Conor said:

Realistically, you've two options if you want a warm house. 100mm EWI directly on to the existing walls. Don't worry about the 'dash. Second, is the knock and rebuild. Any talk about widening cavities etc is crazy.

 

We were in a very similar position, but with even less work than you are describing. Rebuilding on the same footprint worked out more cost effective once you calculate long term running costs and resale.

 

I’d be very interested in hearing the figures and sums that led you to determine this route. 
 

On 20/12/2024 at 16:00, Russell griffiths said:

£1000 per lin metre at the moment I’m led to believe talking to local lads. 

Wow.

 

On 21/12/2024 at 07:43, Russell griffiths said:

What’s the thoughts on Ewi on a cavity wall then. 
 

I was under the impression that a cold uninsulated cavity would still be cold no matter what thickness of Ewi is added. 
so with a cold cavity then isn’t the inner skin still cold. 
 

I thought IWI was the go to with a cavity. 

The cavity is filled so I understand EWI would be okay to use.

 

On 21/12/2024 at 08:49, lookseehear said:

I thought you could only ewi a cavity wall if the cavity was either filled (eg with EPS beads) or sealed, otherwise you end up with a well insulated outer leaf and a cold cavity.

Cavity is filled. But could top it up. And close up.

 

On 21/12/2024 at 09:58, Iceverge said:

 

 

Where the cost and time of past efforts make it mentally impossible to change course. 

 

 

 

 

I seem to be changing course more frequently than a ship without a rudder. As per my partner anyway. Thanks lad.

 

So. 
 

Don’t think I will rebuild the outer leaf.

Don’t think I will erect a third skin of brick creating 2 cavity’s.

I really don’t want to knock down and rebuild.

Thinking the most likely course of action is to either;

 

Strip off pebbledash, affix EWI, render over.

 

OR

 

Affix EWI straight to pebbledash, render over.

 

Whilst render is something I don’t particularly want as a finish, suppose I’ll have to get a craftsman on it to give it a half decent chance in looking good.

Edited Friday at 15:52 by allthatpebbledash
Deleted other post

[Iceverge]

18 minutes ago, allthatpebbledash said:

seem to be changing course more frequently than a ship without a rudder. As per my partner anyway

 

Changing your mind is part of this game.

 

It's got more to do with learning than indecisiveness. My plans went from renovations of an ancient cottage, to a shipping container build, to ICF, to masonry with EWI, to timberframe, to stick build, to wide cavity wall. 

 

At one point, each one seemed like the best course of action. ........until I learned more. 

 

Similarly with heating and ventilation systems and a Plethora of other choices. 

 

When you stop changing your mind one of two things have happened.

 

1.you've arrived at an absolute truth or 2.you've given up thinking. 

 

Try not to do the later and mistake it for the former. 

 

 

 

[Mr Punter]

I don't think it is worth stripping the pebbledash if it is sound.  You could remove any bellcast bead and strip of pebbledash that will throw the EWI out and make it up locally with some thin insulation.

 

EWI is quite effective, especially if you improve airtightness and ventilation.

[saveasteading]

1 hour ago, allthatpebbledash said:

Wow.

It is hard work, and very few people will do it. Dig a holeto the bottom of the footing. Get into the hole and dig under the foundations and down to the new depth, handing up earth all the while.

earth to garden or skip.

Pour concrete in the hole and pack it up super tight under the footings. Pay for the concrete and the small load premium.

move on an repeat.

 

Because it is difficult to pack up tight, the house may settle a mm or so.

 

If there wasn't really a problem then this may cause differential expansion when the ground recovers.

 

Your Engineer says it isn't necessary He knows the ground in your area. 

 

 

[lookseehear]

2 hours ago, Iceverge said:

At one point, each one seemed like the best course of action. ........until I learned more. 

 

This is the hard bit though - when do you actually commit to something? Or do you just reconcile yourself that you'll learn more after you've committed and just have to make the best of what you've already committed to?