What to do about an uninsulated stairwell (that we do not have space to actually insulate)?

[Garald]

  On 12/12/2022 at 17:36, DamonHD said:

I have used aerogel to good effect in my own home, in several varieties:

 

https://www.earth.org.uk/note-on-Spacetherm-aerogel-thermal-insulation.html

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Thanks! It looks like even 2cm total of this (probably all we have to play with, given that there's also 1cm of plasterboard; see the picture) would help, even though they would not bring the wall up to standards. I'll talk to my architect.

 

  On 12/12/2022 at 18:32, Radian said:

You need to perform a condensation risk on that wall. As a poorly insulated surface amongst better insulated surfaces and other warmed spaces, it will be a surface that acts like an unintentional dehumidifier in you home.

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Will insulating with space-gel solve that issue as well, or will it create new issues in that direction?

 

  On 12/12/2022 at 17:36, DamonHD said:

Blinds are unlikely enough IMHO to be air-tight enough to be much good to retain heat.  To keep sun/heat it out:

 

https://www.earth.org.uk/towards-a-LZC-home.html#reflblinds

 

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Thanks, this is interesting. But surely I want a minimum of light to be reflected back out during the winter?  (If only curtains were easily convertible from winter to summer, like duvets...)

[Garald]

  On 12/12/2022 at 18:32, Radian said:

You need to perform a condensation risk on that wall. 

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How would I do that?

[DamonHD]

  On 12/12/2022 at 19:04, Garald said:

Thanks, this is interesting. But surely I want a minimum of light to be reflected back out during the winter?  (If only curtains were easily convertible from winter to summer, like duvets...)

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There's unlikely to be enough potential solar gain in winter to be significant: the insulation value of an extra layer of material probably outweighs it.

 

Rgds

 

Damon

[DamonHD]

  On 12/12/2022 at 19:04, Garald said:

Will insulating with space-gel solve that issue as well, or will it create new issues in that direction?

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It should help.

 

Rgds

 

Damon

[Garald]

  On 12/12/2022 at 21:28, DamonHD said:

There's unlikely to be enough potential solar gain in winter to be significant: the insulation value of an extra layer of material probably outweighs it.

 

Rgds

 

Damon

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Then the question arises: why do I have a window?

 

(The answer is actually clear in this case: since the cat toilet will be here, I will presumablebe opening this window briefly on a daily basis! Because of PIV, that should help with humidity without being a total disaster as far as heat is concerned, no?)

[Radian]

  On 12/12/2022 at 19:51, Garald said:

 

How would I do that?

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I didn't read anywhere what your wall makeup was. It looks like around 0.5m solid masonry, but what's on the other side? Fresh air or another building? If you can identify these parameters then you can use a simple online calculator like this one to get an idea of condensation risk e.g.

 

 

 

[SteamyTea]

  On 11/12/2022 at 23:36, Garald said:

heat loss from that staircase alone is about 650W

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At what temperature difference?

Watts is power, kWh is energy.

So while this small area may be uninsulated, it is probably going to be better than a window.

[Garald]

  On 13/12/2022 at 10:54, Radian said:

 

I didn't read anywhere what your wall makeup was. It looks like around 0.5m solid masonry, but what's on the other side? Fresh air or another building?

 

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There's another window up to a certain height, and then it stops:

 

 

 

(Mine is the red-brick building.)

 

At any rate, the architect says (I translate, summarise and paraphrase):

 

*The fact that we have positive-input ventilation (PIV) and [thus] have hot fresh air means that the aerogel proposition is not really suitable for our case;

[NB - I didn't quite understand why this is a reason]

* Aerogel plaster does not have a good enough R;

* Aerogel plaque is too risky for the workers (the resulting dust is very much an irritant and we don't know its toxicity). Its an option only if it comes precut to the exact dimensions.

 

She says she's already thought of all options (displacing the staircase, insulating from outside, from the inside, with different materials...). In the end, she proposes two options:

- "feutre de laine tendu" [NB: this is literally "stretched wool felt" - what would the technical term be?], which insulates and perspires, but is also expensive;

- simply installing a small portable electric heater in that space in case of great cold.

 

[Garald]

  On 13/12/2022 at 13:00, SteamyTea said:

At what temperature difference?

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20 degrees (= 18C - (-2)C). That's the old estimate, before I realised that Grzegorz/Grégoire had sneakily managed to insulate the short wall. We can also insulate under the staircase, though that's less important, since as you can see that adjoins a neighbouring building (which may or may not be heated regularly).

 

Let me redo the computations: I was going for average height 3.8, total length of walls 3.5, and a U value of 2.11, with a U value of 1.4 for the windows (this is probably too low for this double-glazed windows - I should set this to a higher value for the double glazing that has remained from the previous renovation, and to the manufacturer's value (probably lower than 1.4) for the new double-glazing). I was getting about 650W, counting a ventilation loss of 41W and a roof loss of 30W.

 

Let us assume the short wall to be properly insulated now (not sure the same thickness was applied as elsewhere, but let us say), and assume that the first meter or so of the long wall adjoins a properly heated space (not sure it's always properly heated, but then we could in fact insulate under the stairs, and at any rate it looks like a bit more than 1m). Also, the window is a bit smaller than I thought - it can't be more than 0.8*2 = 1.6m^2. The average height of the long wall is really at most 3+1.8/2 = 3.9, from which we subtract 1m. The long wall is 2.45m long. Then we have, assuming 2.20 for the window and 0.23 for the insulated part:

 

(3*1.3-1.6)*0.23+1.6*2.20+(3.9-1)*2.45*2.11 = 19.040..

 

So, we really have a heat loss of 19.041*20 = about 380W, which once you add ventilation loss and roof loss, ends up being more like 450W. About 300W of it comes from the long wall. 

 

Edited December 13, 2022 by Garald

[Garald]

So, where can I get aerospace blankets cut to size, for a parallelogram that is about 2m tall and 2.5m wide? (At 5m^2, the cost will be non-trivial, so this better work.) And is it really not a good idea with positive-input ventilation?

[Radian]

Or you tile it with Vacupor® NT-B2-S https://www.morganthermalceramics.com/media/4113/vacupor-nt-b2-s-data-sheet-english-v2.pdf

[Garald]

  On 13/12/2022 at 14:17, Radian said:

Or you tile it with Vacupor® NT-B2-S https://www.morganthermalceramics.com/media/4113/vacupor-nt-b2-s-data-sheet-english-v2.pdf

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The problem with vacuum products is that one needs to protect them with a layer we don't have the space for. Besides, one definitely can't cut those to size, so they are not great for irregularly shaped spaces.

[Radian]

  On 13/12/2022 at 14:25, Garald said:

The problem with vacuum products is that one needs to protect them with a layer we don't have the space for. Besides, one definitely can't cut those to size, so they are not great for irregularly shaped spaces.

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The protective layer could be as thin as you like though - 4mm plywood perhaps? And they come in small pieces that you tile to fit the space. Just a thought.

 

When you said about using a small electric heater I would remind you that a purely resistive heater is very inefficient if that's all it's doing. As a bit of lateral thinking, is there anything you can put under the stairs that draws electrical power and does useful work for you at the same time? A fridge or freezer would be one example or the dehumidifier I suggested previously. All electrical power ends up as heat. You could even put a bunch of graphics cards to work mining cryptocurrencies and make some money from it.

[Garald]

  On 13/12/2022 at 14:50, Radian said:

When you said about using a small electric heater I would remind you that a purely resistive heater is very inefficient if that's all it's doing.

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Right, I know, I just reminded the architect of that.

 

  On 13/12/2022 at 14:50, Radian said:

 

 

As a bit of lateral thinking, is there anything you can put under the stairs that draws electrical power and does useful work for you at the same time? A fridge or freezer would be one example or the dehumidifier I suggested previously. All electrical power ends up as heat. You could even put a bunch of graphics cards to work mining cryptocurrencies and make some money from it.

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.... and yes, I've explained to her that a computer is basically a space heater that computes. 

[Garald]

Is this the sort of thing I should be looking into? It seems meant for industrial use.

 

https://local.armacell.com/fileadmin/cms/corporate/en/onepager_armagel/Downloads/technical-datasheet/ArmaGelHT_Technical_Datasheet_French.pdf

[Radian]

  On 13/12/2022 at 15:17, Garald said:

Is this the sort of thing I should be looking into? It seems meant for industrial use.

 

https://local.armacell.com/fileadmin/cms/corporate/en/onepager_armagel/Downloads/technical-datasheet/ArmaGelHT_Technical_Datasheet_French.pdf

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Industrial use refers to the very high temperatures it will withstand. You might be paying a premium for something unnecessary I imagine.

 

Have you looked at aerogel insulating plaster This would appear to have a thermal conductivity of 0.03W/(mK) so a 20mm thickness would have a U-value of around 1.5 W/(m²K) I still don't understand your wall makeup. The aerial photo looks like bricks but the plan makes it seem about 500mm deep. Is it two full bricks deep?

[Garald]

  On 13/12/2022 at 16:05, Radian said:

Have you looked at aerogel insulating plaster This would appear to have a thermal conductivity of 0.03W/(mK) so a 20mm thickness would have a U-value of around 1.5 W/(m²K)

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Yes, we did (Fixit, in fact). The architect said it does not have a good performance for the tiny space we have to work with, but that may just mean it's not up to norms. We are not going to be up to norms on that wall anyhow - we are just trying to get by.

 

  On 13/12/2022 at 16:05, Radian said:

The aerial photo looks like bricks but the plan makes it seem about 500mm deep. Is it two full bricks deep?

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Good question. Let me ask.

[Adsibob]

  On 13/12/2022 at 14:50, Radian said:

When you said about using a small electric heater I would remind you that a purely resistive heater is very inefficient if that's all it's doing. As a bit of lateral thinking, is there anything you can put under the stairs that draws electrical power and does useful work for you at the same time? A fridge or freezer would be one example or the dehumidifier I suggested previously. All electrical power ends up as heat.

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How about putting your hot water tank under the stairs, going for one that doesn’t have the highest insulation level and accepting you will lose some heat from it.

[saveasteading]

  On 12/12/2022 at 19:04, Garald said:

2cm total of this (probably all we have to play with

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2cm is a lot more than nothing. How about covering it with a 4mm board (cement board for example) rather than plasterboard?

Thicker insulation where you can.

[Garald]

  On 14/12/2022 at 00:44, Adsibob said:

How about putting your hot water tank under the stairs, going for one that doesn’t have the highest insulation level and accepting you will lose some heat from it.

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That might have not been a bad idea, but we are so far along that my architect will quite possibly murder me if I suggest this. At any rate, we are going for an integrated heat pump+water tank model, and there isn't enough space for the combination there. (Also, even the internal elements of a heat pump produce some noise, and I prefer not to have them right there.)