Insulating from the outside: wood fibre vs rockwool vs perforated polystyrene

[Garald]

7 minutes ago, Iceverge said:

Ok. I'm going to take a leap here and say that there was no proper Airtightness measures taken with the buildup. The comment about the deliberate weakness in the envelope doesn't bode particularly well for the rest of the gig.

 

Again, I am translating conversations, this time in the distant past. "Deliberate weakness" is my term; what I mean is that there are supposed to be outlets near the windows (which I have never been able to find).

My general impression is that the contractor did a decent job overall, and that he took care of measures that are standard (e.g. vapor barriers; yes, I know that has nothing to do with airtightness). For the last year, I've been hiring specialists for this and that, with the secondary goal being to keep track of how well the contractor did things. So far, the verdict seems to be: not as well as a specialist but well within the range of what one expects from general contractors who do a bit of everything.

 

The fake architect, however, was incompetent; I am pretty sure she must have failed high school physics. She seems to have coasted for well over a decade on things she has picked up at trade fairs, at two architecture studios she was an intern at in the 90s (thank you Google) and in the course of her long practice as a fake architect.

 

I take the first thing I have to do is get a proper blowdoor test done. What then?

[Garald]

For what it is worth, I am still in touch with the contractor (whom I have tried to lead gently to the conclusion that the person he's worked with for a decade is an impostor, but he seems to refuse to admit it, even though it's quite easy to check things online once one has a suspicion). He also thinks I should put insulation outside the north wall, and says: (paraphrase) "I have no idea why [the fake architect] was so insistent on insulating from the inside. Obviously insulating on the north side would be better, and it need not be that difficult or expensive." (Not to mention that it's the courtyard side, so it shouldn't be that hard to get a permit.) Reasons given by him: goodbye to thermal bridging, better insulation, etc.

 

No matter whom we pay to do the external insulation, they will add enough of (wood fibre, rock wool, polystyrene, what have you) to give an extra R=4. The reason is that this is now the standard in France (or was it R=3.8?), and so it's what they are used to work with, and they can also not take responsability for whatever exists, etc. So that's a constant. TL;DR: no matter what I do there, I'll end up with a total R well above R=6, _not taking into account the effect of reflective insulation_.

[SteamyTea]

5 minutes ago, Garald said:

I take the first thing I have to do is get a proper blowdoor test done. What then

Rectify the leaks as well as you can.

 

As you have forced ventilation (I seem to remember), you do not need to worry too much about what we call 'window trickle vents'.

[Garald]

1 minute ago, SteamyTea said:

Rectify the leaks as well as you can.

 

As you have forced ventilation (I seem to remember), you do not need to worry too much about what we call 'window trickle vents'.

 

I have PIV (positive-input ventilation). What I keep calling 'outlets' is what I would have expected to look like "window trickle vents", except I cannot find any! The air being gently pumped into the building has to leave *somewhere*.

Edited October 19 by Garald

[SteamyTea]

Just now, Garald said:

What I keep calling 'outlets' is what I would have expected to look like "window trickle vents", except I cannot find any

You may not have any.

We also have 'air bricks', usually under a floor, for ventilation.

 

3 minutes ago, Garald said:

Reasons given by him: goodbye to thermal bridging, better insulation, etc.

He is right.

[Garald]

5 minutes ago, SteamyTea said:

He is right.

 

Right, I was giving this as plausible evidence that he is reasonably competent and tolerably honest.

[Garald]

Here is what one can find outside the kitchen window and a bathroom window (and nowhere else AFAIK). I think these vents were already there before the renovations. I have no idea if whether they are still active or of how they would work. 

[Garald]

A visiting ventilation guy couldn't find the ventilation exits, but, after talking in the phone with the old contractor, I found the exits in the new windows - they are well hidden at the top:

 

As for the windows installed ten years ago by the previous owners - I'm not sure. Perhaps these little indentations at the top and bottom are it? There shouldn't be cobwebs, though.

 

Apparently I'm supposed to keep the handles of the skylights down so that there's a ventilation exit there too. Not sure what would happen during heavy rains. Also, noise comes in that way...

 

At any rate, I'm going to have an airtightness test done - I just got a quote and it's reasonable.

[Iceverge]

Keep us posted. 

 

I'm guessing 4ach50. 

[Mike]

A few observations:

 

On 19/10/2024 at 09:56, Iceverge said:

What you've effectively ended up with is 50mm of Hemp insulation between battens,decoupled from the solid wall, giving I would estimate a U Value of about 1 W/m²K. It's lightly there's some wind washing behind the insulation too. 

That's very disappointing, and something a good contractor should have spotted as a problem, irrespective of the 'architect'. At a guess, they aren't RGE qualified? I'd choose one that was for any further work - or a different one, if they are.

 

On 19/10/2024 at 00:44, Garald said:

I am considering insulating from the outside as well

Sounds like a good plan to boost the insulation. I'd consider wood fibre and Rockwool, though would prefer cork to either if the budget would stretch that far (it's a 'good' thermal & acoustic insulator, breathable, fire-resistant, non-toxic, & pretty solid - but expensive).

 

And certainly improve airtightness as much as possible.

 

On 19/10/2024 at 13:06, Garald said:

phase shift

Thermal phase shift (decrement delay) is a useful concept in connection with summer heating where the insulation makes up most of the material between inside and outside - for example in loft rooms - though having the PIV pumping in warm outside summer air would probably nullify any benefit. Where stone / brick / block makes up most of the thickness, that material will dominate the calculation.

 

Where it's useful, in France 10hrs+ is considered a useful target. I did calculate it for my 145mm hemp-insulated mansard and, from memory, it was around 9 hours ignoring the timber sarking; with the sarking it was very much longer.

 

On 19/10/2024 at 00:44, Garald said:

Ubakus

Ubakus isn't useful for calculating moisture risk; it uses the old Glaser method which only considers a single point in time. Condensation in the insulation is only a problem if it remains as water for an extended period, and Glaser tells you nothing about that. Nor does it take into account the adsorption / desorption of water vapour that is particularly pronounced (and beneficial) in many natural insulations, including Biofib Trio, and absent from most (all?) non-natural insulations.

 

Edited October 25 by Mike

[Iceverge]

7 minutes ago, Mike said:

Ubakus isn't useful for calculating moisture risk; it uses the old Glaser method which only considers a single point in time. Condensation in the insulation is only a problem if it remains as water for an extended period, and Glaser tells you nothing about that. Nor does it take into account the adsorption / desorption of water vapour that is particularly pronounced (and beneficial) in many natural insulations, including Biofib Trio, and absent from most (all?) non-natural insulations.

Very true. 

 

I alter with the exterior temperature quite a lot to get a more realistic feel for worst case scenario. 

[Garald]

10 hours ago, Iceverge said:

10 hours ago, Mike said:

A few observations:

 

That's very disappointing, and something a good contractor should have spotted as a problem, irrespective of the 'architect'. At a guess, they aren't RGE qualified? I'd choose one that was for any further work - or a different one, if they are.

 

As I said, it’s probably a total U of about 2, even if one doesn’t believe in any of the data given by the reflective insulation’s manufacturer; the reflective insulation has 4cm’s worth of natural-fibre backing, which must be doing *something*; add to that 5cm of BioFib Trio.

 

As for the contractor :

- he says that insulating that side from the inside was always the « architect »’s idea, against his (and my) better judgement;

- the « architect » assured me two years ago that he was about to get his RGE certification, but, a few months ago, after many phone calls from my dude, he admitted he hadn’t got it yet. So, I’ll get no subsidies (which weren’t much anyhow, but that’s one more good reason to be annoyed). Now, he did sign a document clearly stating he had RGE certification, and that he’d have to pay a fine amounting to 10% of all energy-efficiency work if he didn’t - I could easily turn him in if I wanted to. I already asked both the tax office and the local agency to check on that, since he was taking a while to reply, so I can’t be said to fail to report.

 

My current attitude: one enemy is enough; it’s best to keep in talking terms with the contractor, so that he gives me accurate further information on what he has done, but I’ll do all further work with specialists, who, moreover, double-check on what he has done. That has been my policy for the last year, in fact. 

 

10 hours ago, Mike said:

 

Sounds like a good plan to boost the insulation. I'd consider wood fibre and Rockwool, though would prefer cork to either if the budget would stretch that far (it's a 'good' thermal & acoustic insulator, breathable, fire-resistant, non-toxic, & pretty solid - but expensive).

Right. I’ve been using cork myself to do some DIY improvements (insulating a metal door, and also the space under a rafter; there had originally been an air gap there - one of the last things the contractor did was admit his mistake and block that with silicone; that can’t give much of an R, so I did what I could, adding cork strips).

 

10 hours ago, Mike said:

 

And certainly improve airtightness as much as possible.

I’ll have a blow door test done by professionals next Wednesday.

 

10 hours ago, Mike said:

 

Thermal phase shift (decrement delay) is a useful concept in connection with summer heating where the insulation makes up most of the material between inside and outside - for example in loft rooms - though having the PIV pumping in warm outside summer air would probably nullify any benefit. Where stone / brick / block makes up most of the thickness, that material will dominate the calculation.

Right - the insulator who advocated wood fibre visited and said that thermal mass was not so important in my case (because it’s a masonry wall facing north, with some insulation added on the inside). He said perforated polystyrene would be enough (I paraphrase him: « this is not a tall building- by the time the firemen come it will have burnt anyhow »). I asked him for three quotes - perforated polystyrene (permeable to water Vapor), rock wool and wood fibre.

 

10 hours ago, Mike said:

 

Where it's useful, in France 10hrs+ is considered a useful target. I did calculate it for my 145mm hemp-insulated mansard and, from memory, it was around 9 hours ignoring the timber sarking; with the sarking it was very much longer.

I’ll keep that in mind for the attic ceiling; the attic does get hot in summer. The insulation there is mostly that left by the previous owners - only the parts close to the new skylights (which have outside shades, don’t worry) got redone by the contractor. In the long run, I have to decide whether I want to just redo the roof insulation or raise the roof (which probably implies redoing it altogether).

 

10 hours ago, Mike said:

 

Ubakus isn't useful for calculating moisture risk; it uses the old Glaser method which only considers a single point in time. Condensation in the insulation is only a problem if it remains as water for an extended period, and Glaser tells you nothing about that. Nor does it take into account the adsorption / desorption of water vapour that is particularly pronounced (and beneficial) in many natural insulations, including Biofib Trio, and absent from most (all?) non-natural insulations.

 

What would be a better simulator?

[SteamyTea]

Good to know that the building trade in France is as useless/fraudulent as it is here.

[Iceverge]

21 minutes ago, Garald said:

As I said, it’s probably a total U of about 2, even if one doesn’t believe in any of the data given by the reflective insulation’s manufacturer; the reflective insulation has 4cm’s worth of natural-fibre backing, which must be doing *something*; add to that 5cm of BioFib Trio.

 

 

I think there's a little confusion better U values and R values. A U value of 2 W/m²K would be the same as an R value of 0.5m²K/W.

 

In any case I would be slow to attribute too much to the layers of multifoil without some accurate third party testing. 

 

21 minutes ago, Garald said:

the « architect » assured me two years ago that he was about to get his RGE certification

I thought your architect was a she?  Did you change? 

 

21 minutes ago, Garald said:

 

 

21 minutes ago, Garald said:

Right - the insulator who advocated wood fibre visited and said that thermal mass was not so important in my case (because it’s a masonry wall facing north, with some insulation added on the inside). He said perforated polystyrene would be enough (I paraphrase him: « this is not a tall building- by the time the firemen come it will have burnt anyhow »). I asked him for three quotes - perforated polystyrene (permeable to water Vapor), rock wool and wood fibre.

 

Ask him for his decrement delay) phase shift calculations.

 

With a masonry wall and any insulation it'll be totally fine regardless of what kind of insulation he uses. The heat protection advantages of woodfiber ( which I like) is only really apparent in roofs with minimal space to insulate). For most new build applications a thick layer of mineral wool and some plasterboard will perform just fine. 

 

EPS in an urban situation or area that may be fire prone isn't robust enough in my opinion.  Some wayward youth will be able set fire to your house with a lighter. Something they can't do with rockwool. 

 

 

 

 

 

 

 

 

 

 

Edited October 26 by Iceverge

[Garald]

40 minutes ago, Iceverge said:

 

I think there's a little confusion better U values and R values. A U value of 2 W/m²K would be the same as an R value of 0.5m²K/W.

Right, sorry, I meant an R of 2.

 

40 minutes ago, Iceverge said:

 

40 minutes ago, Iceverge said:

In any case I would be slow to attribute too much to the layers of multifoil without some accurate third party testing. 
 

Agreed. Well, it’s foil with layers of conventional natural fibre insulation, but still.
 

40 minutes ago, Iceverge said:

 

I thought your architect was a she?  Did you change? 
 

The « architect » is a she, the contractor is a he. 
 

40 minutes ago, Iceverge said:

 

 

 

Ask him for his decrement delay) phase shift calculations.

 

With a masonry wall and any insulation it'll be totally fine regardless of what kind of insulation he uses. The heat protection advantages of woodfiber ( which I like) is only really apparent in roofs with minimal space to insulate). For most new build applications a thick layer of mineral wool and some plasterboard will perform just fine.

 

 

 

 

 

 

 

 

EPS in an urban situation or area that may be fire prone isn't robust enough in my opinion.  Some wayward youth will be able set fire to your house with a lighter. Something they can't do with rockwool. 

 

 

 

 

 

 

 

 

 

 

 

 

Completely agreed. What I really need is a reasonable quote for rock wool. 

[Garald]

52 minutes ago, SteamyTea said:

Good to know that the building trade in France is as useless/fraudulent as it is here.

Where there is money, there’s temptation. At least there are norms and penalties. Let’s see what my (real) lawyer will be able to do.

[Garald]

Now the problem is of course that my lawyer needs a postal address for the "architect", and she has closed her Paris office. I have her phone, her e-mail, her sister's professional address (her sister, a radiologist, is involved in presenting her as an architect - in fact she introduced her as such to the contractor), her ex-husband's LinkedIn, etc., but a postal address for her seems hard to find (on purpose, obviously). There has to be a way...

[Mike]

On 26/10/2024 at 11:41, Garald said:

What would be a better simulator?

WUFI, however i's not cheap and not straightforward, so normally only used by a consultant and when risks are thought to be high high. Which is why people generally use rules of thumb or manufacturer's recommendations instead.

 

[Garald]

All right - the airtightness people came today with a big fan.

 

The overall airtightness was much better than expected (here) - right in the middle of the acceptable range for *new build*, I was told. Apparently the house scored 0.5 or 0.6... something? At however many pascals? I'll get the diagnostics soon (today I'd hope - I mean, I just sent them the second half of the payment) and post them in a new thread.

 

The most serious leakage come from a bedroom window that doesn't close tightly at the top (I was told to call a carpenter). There was also leakage in some odd places here and there:

- an unused chimney (of course it's covered by a metal door, but that's not enough; I'll just get one of those woollen plugs that I've got in the other chimney, the one that I could in principle use; it's cheaper than having it sealed, and I was told it would do nicely).

- the top of an outside door (I had weatherstripped the sides and the bottom, but forgot the top), and also a bit of the bottom where the weatherstripe got bent - apparently that was detectable;

- those hidden mini-doors to access water pipes and ventilation engines behind walls and false ceilings - I was told that was detectable but minor and I shouldn't worry;

- an irregular opening (400cm^2?) in the garage that allows air to go from the garage to the space behind walls, false ceilings, etc - I'll have to call someone whose profession I had never heard of (I take the English equivalent would be "plasterer"?)

- a small hole in a bathroom floor through which radiator pipes go

- bits that confirmed that the contractor, while certainly competent overall, is a jack-of-all-trades whose collaborators are sometimes sloppy:

 * (this frightened me a bit) there is a small surface in the attic ceiling, hidden behind two beams, where the insulation is *completely exposed*; thank goodness it's rockwool and not fibreglass or something nastier; I'll need to cover this ASAP for many reasons;

 * some joints need silicon or acrylic (I was told silicon is best for bathrooms and kitchens, and acrylic is best for other rooms);

 * there's a bit of leakage in some new baseboard along the attic staircase - a visiting insulator had already pointed out that that was amateurishly done; I was told I can leave that alone for now;

 * there's a bit of leakage around light switches in the attic (as you remember, the attic was completely redone); I or an electrcian would need to replace the concave thingies behind the switches by higher-quality concave thingies (or let them be).

 

I was told I can fix most of these things myself with acrylic, silicon, cork and glue (I have a lot of 1cm- and 2cm-thick leftover cork in the garage).

 

The conclusions I was given verbally were that

- I'm well within the airtightness range where

 * double flux makes sense, though the exact settings would be determined later, possibly after a second test once I had fixed the minor issues listed above;

 * I can get something-something certification if other things are up to standard (something-something is a French something that is less strict than Passivhaus; no mention was made of Passivhaus standards)

- I should talk to a double-flux expert to see what sort of double-flux system can be made to fit in my place. Recall that the contractor said that it wouldn't be possible because the conduits were too narrow.

 

Oh, I also was told that the attic ceiling insulation (which dates back to the former owners for the most part; I didn't have it redone completely - some rotten parts aroudn the new velux was changed by new rockwool) was thermically good but had no air barrier, and so there's airflow within the ceiling; I should be ok by sealing the weak points around joints so that doesn't leak air inside the house. The guys doing the test said that redoing the ceiling insulation up to today's standards, with an air barrier, would come at a significant cost (I knew that) and was not indispensable. I had already decided I would postpone that to the indefinite future when I do some structural work on the roof (raising it, say).

 

I guess all of this sounds normal?

Edited 15 hours ago by Garald

[SteamyTea]

3 hours ago, Garald said:

Apparently the house scored 0.5 or 0.6.

If that is the @50Pa score, it is unbelievably good for an old place.

[Garald]

46 minutes ago, SteamyTea said:

If that is the @50Pa score, it is unbelievably good for an old place.

Well, it's an old place all of whose walls just got covered with new insulation from the inside (I know, I know, that can cause issues - I'm considering insulating from the outside as well on the north side, as you know, but that's another story), with all work done reasonably properly by a pretty decent general contractor (water vapour layer, fire-proof panel, triple coat of paint, the works). Oh and of course it's solid masonry from the early 1930s.

 

46 minutes ago, SteamyTea said:

If that is the @50Pa score, it is unbelievably good for an old place.

 

Edited 11 hours ago by Garald

[Mike]

2 hours ago, SteamyTea said:

5 hours ago, Garald said:

Apparently the house scored 0.5 or 0.6.

If that is the @50Pa score, it is unbelievably good for an old place.

The French new-build standard (q4) requires  ≤ 0.6 m3/h.m² at 4pa. The area used is also different from the UK test; in the UK the full area of the heated envelope is used, the French version excludes the ground floor - presumably because it's expected to be solid & non-leaking. Ignoring the difference in area and using the LABC cheat-sheet (https://www.labc.co.uk/news/dont-feel-pressurised-air-permeability-testing) that would be in the region of  2.77 to 3.28 @ 50pa. Which is still not bad, considering no particular attention was paid to the topic.

 

6 hours ago, Garald said:

There was also leakage in some odd places here and there

That's very useful - sounds like it would be fairly easy to fix many of those. Don't ignore the ones that let air in behind walls and false ceilings, even if minor. They are still ways that moist air might be able to reach cool surfaces where condensation could therefore be caused, especially if the air is being pressured though them by the PIV system.

 

6 hours ago, Garald said:

I guess all of this sounds normal?

It's not surprising for the nature of the house. I'd certainly have a chat with a reputable MVHR expert & see what they say. If it's feasible, and if budget allows, I'd choose a unit from the Passivhaus database.

[Garald]

2 minutes ago, Mike said:

The French new-build standard (q4) requires  ≤ 0.6 m3/h.m² at 4pa. The area used is also different from the UK test; in the UK the full area of the heated envelope is used, the French version excludes the ground floor - presumably because it's expected to be solid & non-leaking. Ignoring the difference in area and using the LABC cheat-sheet (https://www.labc.co.uk/news/dont-feel-pressurised-air-permeability-testing) that would be in the region of  2.77 to 3.28 @ 50pa. Which is still not bad, considering no particular attention was paid to the topic.

 

 

I’ve forgotten how many Pascals it was, but I was told that the leakage was half the maximum required for new build. So it sounds like it was better than the above. Hopefully I’ll get everything in writing and post.

[Garald]

5 minutes ago, Mike said:

 

 

It's not surprising for the nature of the house. I'd certainly have a chat with a reputable MVHR expert & see what they say. If it's feasible, and if budget allows, I'd choose a unit from the Passivhaus database.

Does the Church of Passivhaus have an MVHR mission in France ?

[Mike]

7 minutes ago, Garald said:

Does the Church of Passivhaus have an MVHR mission in France ?

At least one - https://www.propassif.fr/. But the database in international - https://database.passivehouse.com/en/components/list/ventilation_small? - and Efficiency Ratio is the key number.