What's more important for comfort U value or 'thermal mass'

[saveasteading]

3 hours ago, Gone West said:

650mm thick and is of sandstone/rubble construction

So sandstone, rubble and mortar core, then sandstone. ?

 Somewhere i have saved the information on this. In principle though:

That construction has a better  U value than the standard programs allow. This is because the central core is usually about 40% mortar with air gaps. 0.6 has been assessed, so it is nothing like regulation but not hopeless.

Plastering won't make much difference.

Plasterboard on battens will provide an air gap which will be beneficial but again, not a lot.

 

The point about the moisture slowly dispersing is interesting. I hadn't thought of that.

Studies show that moisture migrates to the bottom of the wall and 'rising damp' ( if there is such a thing), is negligible.

 

Is the stone not attractive?

We covered and insulated most of ours using vapour barrier, stud, and 100mm mineral wool,  but retained a feature area.

[SteamyTea]

28 minutes ago, saveasteading said:

Plastering won't make much difference.

Plasterboard on battens will provide an air gap which will be beneficial but again, not a lot.

You do get a film of air that moves upwards along the wall.  There is a general figure for this, outside is R = 0.04, inside is 0.13 m²K.W^-1 (here).

I am not sure how much a fixed air gap behind plasterboard will change thing.  I suspect it changes it for the better.

28 minutes ago, saveasteading said:

The point about the moisture slowly dispersing is interesting. I hadn't thought of that.

I seem to remember that the energy to dry out a building is very large.  It is to do with the phase change of water.  Water usually has a SHC of 4.18 kJ.kg^-1.K^-1 while changing to vapour it is 2477.2 kJ.kg^-1 at a starting temperature of 10°C (283K) (note that there is no K as the temperature does not change.  That is 0.688 kWh per kilogram of water.

I can't remember what value we used for the fraction of the mass of the structure was water, was not very high, 8% springs to mind (some stuff here), but realistically that will be very variable for rubble walls and really needs to be tested (cut a section out, weigh it, then bake in an oven overnight, weigh it again).

Most stone and brick has a SHC of 0.8 kJ.kg^-1.K^-1. That is a factor of 5 different for liquid water and nearly 600 as it turns to vapour.

So a significant amount of energy to dry out a wet house.

 

I have just turned on my living room storage heater as we are in for a few cold days.  I notice that all the windows get condensation on them as the liquid water is turned to vapour and re-condenses on the coldest surfaces.  I now have windows open a little bit, which really hurts me, but it is better than mould forming.

Edited January 8 by SteamyTea

[joe90]

9 minutes ago, SteamyTea said:

have just turned on my living room storage heater as we are in for a few cold days. 

It’s just started snowing here so lighting my wood stove.

[SteamyTea]

18 minutes ago, joe90 said:

It’s just started snowing here so lighting my wood stove.

Umm

You just winding me up now.

 

Actually, pumping cloud condensation nuclei into the local atmosphere may make it snow more.  More snow reflects more radiation back into the atmosphere, reducing the ability for the ground to reflect IR radiation to interact with the historically high levels of atmospheric CO₂ molecules.

But is also insulates the ground, trapping in extra energy that can be released later.

So probably no net benefit at the local level.

 

A quick look at my outside thermometer and it is showing -0.3°C air temperature.  The paving slabs (all 'thermal mass) are at -0.4°, the outside of the wall is at 0.2°C (little 'thermal mass') and the corresponding inside wall is at 16.5°C.  Inside air temperature is 21°C, RH is at 43% (lovely).

No snow though, but I don't care as I don't have to drive at the moment.

Edited January 8 by SteamyTea

[ProDave]

14 minutes ago, joe90 said:

It’s just started snowing here so lighting my wood stove.

Daytime high of -2 today, forecast -8 tonight.  Stove burning nicely.

 

I collected a load of firewood in the Landrover last weekend and going back for more this weekend.  This will be for next year or more likely the year after.  Chainsaw was busy Saturday afternoon.

[joe90]

3 minutes ago, SteamyTea said:

but I don't care as I don't have to drive at the moment.

Did you get your car fixed?

[TonyT]

1.9Deg C where I am, can’t be bothered with the stove tonight, burning gas instead!

[SteamyTea]

Just now, joe90 said:

Did you get your car fixed?

I have a feeling it is beyond repair.  Asked the garage to see if it is anything simple, but they are two men down, so no idea when they can look at it.

I am not pushing them as they have been so good to me this last couple of years and they are the nearest place to my house.

I may go looking for a small, economical runabout, as I am still clocking up silly annual mileage.  Two months mileage is over what my sister does in a year.

Just a shame I spent so much on it the last few months, but in all fairness, I should have spent that money 2 years ago.

[SteamyTea]

4 minutes ago, TonyT said:

where I am

Where is that then?

[SteamyTea]

Here is what has happened today down here.

 

[Roger440]

4 hours ago, Gone West said:

Thanks, that's really interesting. Food for thought.

 

What Ian R said would be my primary concern. 

 

Insulating will reduce the temp of the wall. And increase the condensation risk in the wall.

 

Problem is, so many variables and unknowns in an old wall like that. Including how damp, or otherwise it is. 

[TonyT]

1 hour ago, SteamyTea said:

Where is that then?

At home

[saveasteading]

2 hours ago, Roger440 said:

increase the condensation risk in the wall.

These walls breathe. sometimes more than we would want.

so any condensation should be slight, then evaporate. If it doesn't, it won't be absorbed by the hard stone but by the mortar in the central core.

Also, and I'm no expert here, skillful application of external lime pointing both encourages run off and evaporation.

[SteamyTea]

5 hours ago, saveasteading said:

external lime pointing both encourages run off and evaporation

This is often said, but I have not seen any evidence that it is more breathable than OPC based pointing.

 

[ToughButterCup]

13 hours ago, SteamyTea said:

...

And people wonder why I am a pedant about the correct usage.

...

 

... and the reason why you bring us all a warm smile every time you blow a fuse.

Edited January 9 by ToughButterCup

[SteamyTea]

4 minutes ago, ToughButterCup said:

blow a fuse.

Hardly, more tears of disappointment, for our education system.

Our old mate @DamonHD once told a story about his Father being told, by a youngster, that one of his science programs was a 'bit sciency'.

And

Stephen Hawking: 'Someone told me that each equation I included in the book would halve the sales.'

 

[Gone West]

13 hours ago, saveasteading said:

The point about the moisture slowly dispersing is interesting. I hadn't thought of that.

Studies show that moisture migrates to the bottom of the wall and 'rising damp' ( if there is such a thing), is negligible.

The house had been empty for a year before we bought it, and the climate is quite humid down here. My theory was that the fabric of the building, which is a mixture of sandstone and dense concrete block, hard plastered, had absorbed moisture. After we moved in it took a long time for the house to feel comfortable and at the time @SteamyTea explained about the large amount of energy required to dry out an old structure. I am confident that that explanation is correct and now the house is warm and comfortable.

13 hours ago, saveasteading said:

Is the stone not attractive?

It's all covered in layers of old plaster. The house has had a chequered history. Started, around 1840, as a pair of farm workers cottages, stone walls on ground floor and cob upper walls. In the 1970s it was knocked into one and the cob walls removed. Unsound stone walls were replaced with concrete block walls and new roof trusses and concrete tiles added.

[Roger440]

15 hours ago, SteamyTea said:

This is often said, but I have not seen any evidence that it is more breathable than OPC based pointing.

 

 

Theres heaps of evidence! Look up the values.

 

Plus plenty of practical real world experience. Cornwall is overflowing with buggered up stone houses. The old stone building in Porth Leven harbour being a classic example. Cement motar perfect, stone face heavily eroded.

 

Had the issue on my own house. Removing cement fixed it.

 

Just repeated it again at the new place which is stone built.

 

Cement is, for practical purposes, waterproof.

 

Edited January 9 by Roger440

[Roger440]

21 hours ago, saveasteading said:

These walls breathe. sometimes more than we would want.

so any condensation should be slight, then evaporate. If it doesn't, it won't be absorbed by the hard stone but by the mortar in the central core.

Also, and I'm no expert here, skillful application of external lime pointing both encourages run off and evaporation.

 

They do. Assuming not buggered up with cement.

 

But if you move the dew point into the wall, then the wall, or just the motar if a hard stone, is going to be damp for at least a good part of the time. And a damp/wet wall is a thermal disaster. Aside from any longer term implications to the integrity.

 

I need to repoint the outside and inside of my place. Problem is, im not skilful!!!

 

I want to insulate too, but getting a clear answer on how much you can apply before you start creating problems in the wall itself is as clear as mud. The reality is, you wont know until after you have done it.

[saveasteading]

If the outer wall is substantially big, impermeable stones, then very little water will soak in. Most of that will evaporate out again and the rest won't pass the central core and will evaporate in draughts,  tend downwards or stay put.

Moisture inside the building is stopped by a vapour barrier, if fitted behind an internal stud. If the wall is bare stone then, yes  some will get through but that is an aesthetic choice and compromise.

[saveasteading]

2 hours ago, Roger440 said:

Theres heaps of evidence

I started looking. What I found quickly was plenty of comments but nothing scientific. It's there though.

Lime let's water in and out again. Cement doesn't.

 

The skill is to make the lime the best shape to shed rain  but stipple for maximum evaporation.....something like that anyway.

[SteamyTea]

6 hours ago, Roger440 said:

Theres heaps of evidence! Look up the values.

I have been looking for years, if you have some links to the numbers please share.

 

6 hours ago, Roger440 said:

Porth Leven

Porthleven, a place I know so well.

[Gone West]

11 hours ago, Roger440 said:

Cement is, for practical purposes, waterproof.

So a cement rendered stone wall will keep rain out, as long as it's not got cracks.

[SteamyTea]

2 minutes ago, Gone West said:

So a cement rendered stone wall will keep rain out, as long as it's not got cracks.

I think it depends on the cement chemistry, the sand ratio and any additives.

 

I think this is where the confusion comes from.  Chemically there is not a lot of difference between OPC and limes.

 

[Gone West]

9 minutes ago, SteamyTea said:

I think it depends on the cement chemistry, the sand ratio and any additives.

Presumably a waterproof additive would solve the problem.