Garald

Sigh. Peru and Chile are nowadays classified as upper-middle and high-income countries, respectively, but their level of institutionality, regulation, human development, etc., lag behind what you would expect from either label (though, again, Peru clearly lags Chile, as you might expect). On paper, Peru has become much wealthier since the horror years of the 80s and 90s (in 1990, annual inflation reached 7650%), but in reality... in some respects, there's barely a development. Or at least there has been a very slow recovery. This is in part for ideological reasons: the "Chilean model" (small state) has become dominant, even as Chileans become increasingly critical of it. Peru is certainly much more *stable*, economically, than in the 80s, and the middle class is a larger minority of the population than it used to be. (That includes the "emergent middle classes", whose living standards are in many ways clearly under those of the working class in developed countries, especially in terms of access to education and health care; they care very much about them, however, and many of them do care about things like energy efficiency, building standards, etc. - I was just talking to my brother about it.) To be fair to Chile, science there has developed to a very respectable level in the last 35 years. However, it's not an industrialized country in the sense that Mexico and Brazil are (a fact that plenty of people abroad forget simply because they are only too aware of the huge parts of the population in both countries that were left behind); it's still mostly an exporter of raw materials. That's true also of Peru, only more so. OK, I hope that was enough of a nutshell.

I take you mean for new build, not for retrofit. Bear with me - you are about to learn things that you'll never find useful. CLS isn't produced in Peru (though it is in Chile). In general, 1. wood is not a common primary building material in Peru outside the literal rainforest, 2. Peru is not a softwood country, though it is a hardwood country. More on 2: Peru est omnis divisum in partes tres: coastal desert, highlands, rainforest. No need to comment on the desert (... where Lima is located). The highlands have long been seriously deforested. The rainforest is, well, full of wood, often fine wood, very irresponsibly managed on the whole. There isn't really such a thing as large commercial softwood plantations AFAIK. Now, what you can do (in fact it's not uncommon in the older parts of the district I grew up in) is use wood to build a lighter addition on top of an existing flat roof. That can be quite a nice project though it won't be cheap (... except you may get away with not hiring a civil engineer, or your engineer may simply have very little work to do). I guess one would use one of the less expensive hardwoods, e.g., tornillo de la selva (Cedrelinga cateniformis, lambda of about 0.15-0.18, ChatGPT tells me, though it may have made that one up) - I can't imagine having so much money as to build entire rooms in cedarwood (lambda = 0.12-0.14). (ChatGPT chips in to say it's not that pricey, and that it's compensated for being easier to work with; that was not the impression I got from 'my' carpenter - can't ask him now, as he unfortunately died of COVID.) Oh, I think eucalyptus (a legacy from a now deprecated early-20th century attempt at reforestation) is sometimes used for building in the highlands, but it's a tricky wood to use, isn't it? PS. The *really* old skool way to build an addition of an existing building is quincha (daub-and-wattle). It actually has very reasonable anti-seismic properties if done properly, but it's not very durable (though I think there are now modern versions that are carefully engineered... and of course also not cheap). It's a material of the past now - it's preserved when possible. PPS. ChatGPT has just pointed me towards a Peruvian timber company - and here's what I found on it as one of the first hits: https://www.earthsight.org.uk/news/timberleaks/robinosn-lumber-timber-trade-peru-maderera-bozovich

Oh, you’d be surprised. All insulation materials are imported, often from Europe, and so they cost more than they do there: transportation, tariffs, etc. Yes, you can walk into a shop and buy a rockwool panel, but it will be easily more than twice the price in France. What is cheaper is labor (meaning “joiners and masons who may be clever but will figure it out together with you”) and local materials. But, as you see, the latter doesn’t seem that useful in this context - perlite has limited applications (will talk to producers). I should talk to some hipsters to see whether I can convince them to consider producing hemp insulation eventually. There’s also a city where you can build in beautiful volcanic stone with a decent lambda, but the said city will be covered in lava sooner or later.

Sure, but what about insulation? Quite frankly I wouldn’t be surprised if good insulation + enough double-glazed skylights all but eliminated the need for heating, except on the odd cloudy day. Would need to do some calculations.

Right, he told an anecdote… let me find it. It’s from when he chartered a ship to take Spanish refugees to Chile when the fascist side was about to win. Bah, resource curse. It has diversified since the first time I was there (1991) but it’s not like it produces everything it needs or nearly. Part of the problem is that cork takes decades to mature (apparently?) and part of it is that Chile has *NO* insulation requirements (neither do Peru, Bolivia, etc.) even though it can get quite chilly. Being physically uncomfortable is part of their national character. Oh, in winter, in the Peruvian highlands, you *want* solar gain - and there’s a lot to be had. People are experimenting with Trombe walls. As I said: very blue skies and lots of solar radiation in winter.

Right, everybody wears alpaca sweaters, which are nice enough. The problem is really at night, as everybody seems to prefer really scratchy blankets. The logical step is to use duvet covers, but my mother tells me that her father tried to explain how that works n times and never managed to get himself understood. Oh well. In the meantime - there seem to be importers for the usual materials, which at least means *some* people are insulating. But it's a shame that no insulation products seem to be produced in the country (other than perlite). I guess one could insulate using the cheapest kind of sheep wool, but that's a bug magnet. There's no real reason why plant fiber insulation can't be produced. As I said, in the highlands as opposed to Lima, insulation is really a need, not a want - but it's a need that goes unfulfilled. It's a public-health issue more than an efficiency issue - very few people have central heating. The potential for solar gain is huge (up there, the cold season is the sunny season) but at least that's starting to be explored. I hope Chile finally gets around to producing cork insulation at some point (they have cork trees since the 40s or 50s, or so Neruda says, but then plenty of things in his memoirs are made up).

@SteamyTea Sorry ChatGPT is so wordy. Does its assessment now sound sensible? I'd be interested to know where it goes wrong-ish or completely wrong. (I've been toying with AI for other purposes, and it has been interesting to observe what it can and cannot do.) What it also says on insulating with perlite pressed boards on the outside: What if you insulate outside instead? You keep every millimetre of floor space. Thermal bridges at floor slabs and partitions are easier to lap over. The wall stays warmer, pushing any condensation plane out into the perlite where it can dry. Pressed perlite boards can be fixed to the exterior with a polymer-modified lime render, adding only 5 mm more thickness than the indoor version. You just need shadow gaps or slim drips to protect the render nose from the persistent garúa.

With any of these you still need a mineral render or ventilated cladding plus flashing, but you gain higher R in less thickness and better freeze-thaw durability. Panels vs loose perlite—thermal hit and suitability So a board is ~25 % less insulating per centimetre, but it eliminates settlement, is easy to dowel-fix, and can be factory-treated for water repellence—essential on façades. Form Typical λ (W m⁻¹ K⁻¹) Why different? Good for… Loose granules 0.040–0.045 Air pockets undisturbed Filling cavities inside double-wythe masonry or pre-cast panels Pressed boards 0.055–0.060 Portland-cement or starch binder bridges some pores Exterior or interior retro-insulation where you need a continuous sheet

Key points Use only factory-siliconised boards or loose granules; raw perlite can absorb 30-70 % of its weight in liquid water. Provide a 5–10 mm ventilated drainage gap above lintels and at the base so any condensate or drizzle that bypasses the render can escape. Seal penetrations (flashing brackets, conduits) with compressible mineral wool backer rod and a vapour-open sealant. Under Lima’s “garúa” (heavy mist) the render surface may stay at 100 % RH for days, but liquid water load is tiny, so a hydrophobic board remains near its declared λ. Would I still specify perlite in the Andean highlands? Probably not as the primary insulation layer. Thermal demand is 3–4 × higher (winter nights below 0 °C at 3 000 m). Loose perlite (λ ≈ 0.044 W m⁻¹ K⁻¹) would need ≥ 30 cm to hit the U-values now recommended for health and comfort. Perlite Institute Summer rains are intense and freeze–thaw cycles common. A hygroscopic insulation that sits outside the waterproof layer risks saturation and spalling during cold snaps. ChimuadventuresWikipedia What works better at altitude Material λ (W m⁻¹ K⁻¹) Pros in highlands Cons Rock/mineral-wool façade boards 0.033 Non-combustible, moisture-tolerant, λ ~40 % better than perlite, proven ETICS details Heavier than EPS; cost > EPS High-density EPS (graphite) 0.030 Very light, cheap, closed-cell so no capillary uptake Combustible; UV-sensitive; must be rendered quickly Wood-fibre boards with lime render 0.038 Carbon-negative, vapour-open, good hygrothermal buffer Needs perfect detailing to avoid decay; limited Peruvian supply

Further query to ChatGPT: "OK, but why were you recommending it for use in Lima? How would you deal with the issues mentioned above - particularly for outside insulation? Would you still recommend it in the highlands, where more insulation is needed and it rains much more? What would you use instead? Remember that, while it essentially never rains properly in Lima, it drizzles, and winters are clammy. Also, how much worse is the lambda of perlite panels, as opposed to loose perlite? Are panels more appropriate for outside insulation?" Why I suggested perlite for Lima in the first place Lima’s building-physics challenge is unusual: air is damp and chilly for four months, yet real rainfall is almost zero (≈ 6-50 mm year⁻¹). RedditInca Expert Because there is no driving rain to wash through the façade, you can afford an insulation that is vapour open, non-hygroscopic once treated, fire-safe and low-embodied-energy—all true of hydrophobised expanded-perlite. In that mild-load climate the modest R-value penalty is acceptable, and the system remains fully mineral (no foam plastics that can off-gas or burn). How to make perlite work as exterior insulation in Lima Layer (outside → inside) Purpose & detailing tips ➊ Thin polymer-modified lime-cement basecoat on mesh Water-shedding skin; vapour-open. Keep cracks < 1 mm with alkali-resistant glass mesh. ➋ Hydrophobic perlite insulation board (λ ≈ 0.056 W m⁻¹ K⁻¹) Chosen grade must meet <0.15 kg m⁻² h⁻½ water-absorption per ISO 15148. ResearchGateepg.science.cmu.ac.th ➌ Bed of cement–polymer adhesive or mechanical anchors Full-surface trowel bond on rendered masonry; 5–6 screw anchors m⁻² on concrete. ➍ Existing rendered block or brick Provide a reasonably flat plane; patch holes that might let grains leak. ➎ Interior lime plaster (optional vapour retarder paint) Keeps the wall airtight; still lets occasional inward drying.

Here are ChatGPT o3's answers to these queries. Usual warning: ChatGPT bullshits a lot (and makes up references); in this case, however, it seems to acknowledge real concerns with its own previous suggestions, once it's queried appropriately. Note (after Googling): there do seem to be at least one or two legitimate insulation businesses in the relevant country producing and selling perlite insulation panels; perlite insulation also seems to be a thing elsewhere, though some folks use it within plaster, which reduces its performance greatly. 1. What is expanded-perlite insulation? Raw perlite is a volcanic glass that “pops” (expands 10-20 ×) when it is flashed to ≈ 850-900 °C. The expanded granules are light (≈ 50–120 kg m⁻³), non-combustible, and trap a lot of still air, giving a loose-fill R-value of about 2.7 per inch (≈ 0.39 m² K W⁻¹ per cm). 2. Why you don’t see it very often in walls Issue Consequence for a wall build-up Moderate R/inch At 2.7/in you need ~200 mm to reach the same U-value that 100 mm of polyisocyanurate gives. Thicker walls mean more framing, detailing and cost. Loose granules Inside a stud cavity they can sift through wiring holes or service gaps, and field reports show some settlement after thermal cycling despite manufacturers’ claims to the contrary. Hearth.com Forums HomePerlite Institute Dust & handling Pouring or blowing dry perlite is messy; dust masks are mandatory and the jobsite must be sealed. No structural capacity Boards made with perlite/gypsum exist, but the loose fill that gives the best λ-value provides zero racking or compressive strength, so an extra sheathing layer is usually required. Code familiarity & price/R 3. Interior vs. exterior placement Location Typical problems with perlite Interior stud bay Needs an air-tight liner to stop grains leaking; must also add a vapour retarder on the warm side because perlite is hygroscopic. Cavity of double-wythe brick / concrete-block Traditional niche where it does work: the masonry keeps it dry, gravity keeps it in place, and fire rating is excellent. Perlite InstituteW.L. Tucker Exterior insulation layer (EIFS or render) Exposed to driving rain. Unless the granules are silicone-treated, they can wick water and lose most of their thermal resistance; wet perlite is also heavy and can burden the cladding sub-frame. Builders already know how to use fiberglass, mineral wool and foam boards that deliver higher R per euro, so perlite rarely wins a cost-benefit comparison in mainstream housing. 5. Energy and climate footprint of expansion Boundary Reported energy use Furnace gas only (flash-expansion) 1.5 – 2.0 MBtu t⁻¹ → 1.6 – 2.1 MJ kg⁻¹. Perlite Institute Typical natural-gas plant (gas + blower power) 6.5 Nm³ gas m⁻³ finished product ⇒ ≈ 80 – 250 MJ m⁻³, depending on final bulk density. amit-online.de Cradle-to-gate (ICE database, includes mining & transport) ≈ 10 MJ kg⁻¹ for expanded perlite. Green Building Encyclopaedia For comparison, extruded polystyrene (XPS) comes in at ~70 MJ kg⁻¹, so perlite’s embodied energy is an order of magnitude lower, even if you take the higher cradle-to-gate figure. 6. Bottom line Perlite is fire-safe, inert, low-embodied-energy and great for niche uses (masonry cores, chimneys, cryogenic vessels). In framed walls it is held back by: Thickness penalty (low R/inch) Moisture sensitivity unless specially treated and detailed Installation hassles (dust, containment, potential settlement) That is why modern residential envelopes tend to favour denser mineral wool or foam boards outside the sheathing, and why perlite remains a specialty rather than a mainstream wall insulation choice.

Simply because I'm having trouble falling asleep, I started to simultaneously (a) play around with ChatGPT (b) fantasize about possible improvements to the family home - in the duller, non-darkest part of a South American country. I should explain conditions there - temperatures don't go under 10C, so nobody has heating; that would be all right, except modern brick construction comes with zero insulation (unlike older adobe construction, which unfortunately tends to fall apart during earthquakes). So, during a couple of months in 'winter' (humid, sunless, no proper rain - more of a nasty autumn) inside temperatures drop to 15Cish and people feel mildly miserable (or bury themselves under piles of scratchy blankets). Any improvements to that situation would be a want, not a need, but still. So, within a pile over overly self-assured verbiage, ChatGPT gave me an actual fact unknown to me - namely, that the said country produces lots of perlite, which can be used for insulation - whether from the inside or from the outside. Can you confirm that? Note that mortar-perlite mixtures have much worse performance than, well, plain expanded perlite. What issues are involved in using the latter to insulate a place from the outside? (Would one need to hire someone highly skilled who might not exist?)

Update: ISOVEO just answered: - yes, they can line all the skylights with 2cm cork within the plasterboard... and charge me 1300 eur more for it (OK, there's lots of skylights, but still); - to my question of whether we wouldn't need an airtight membrane outside the insulation in addition to the vapor-proof membrane below the insulation, they answer: "L’air doit circuler sous la toiture, mais pas dans l’isolant bien sur. Il ne circule pas dans l’isolant car nous prenons soin de ne pas laisser de passage d’air là où nous posons l’isolant. Nous veillons à bien calfeutrer partout avec l’isolant. Enfin, votre toiture protège de la pluie et à moins de déposer la toiture, il n’est pas possible d’installer un pare pluie qui se situe au-dessus des liteaux." TF;DR: no such thing is needed, in part because it's not really possible (without undoing the roof, which would cost a fortune) and in part because they take care of "calfeutrer" (literally: caulking; meaning filling a space so that it is impermeable) everything with the insulating material. (In fact, they had told me verbally before that that's why they prefer to work with wood fibre rathern than cork.) Does that make any sense? I'll try to coax a more reasonable quote from elsewhere.

Aha - how do you do that? (Can it be a DIY job?) At any rate, as I said, the plan is shelved now in my case - not enough land.

I get the feeling that here they are standard enough that the basic measures to be taken are agreed upon. https://conseils.xpair.com/consulter_savoir_faire/puits-canadien-ventilation-double-flux/description_puits_canadien.htm#part-1237 Reading a bit more - it seems this is not a possibility for me; the coop simply doesn't have enough land (you need to fit straight 25m-long tubes somewhere; some say 50m are better).

I'll try to talk in the next few years to people here who have one installed. (It's a fairly common thing in France among reasonably eco-conscious people.) In my case, it's something to consider doing 5-10 years in the future (or the next time we need to rip up the courtyard, whichever is sooner). I take it's out there in the fruity fringe in the UK?

That’s what I went for!

Understood. (The insulation company just sent me an Ubakus model - I can do that myself in a second, and so can anybody else. WUFI sounds a bit trickier - don't know whether they handle that themselves.) What about, um, keeping any water that gets past the tiles from dripping its way past the insulation? Does the airtightness membrane also take care of that?

Come to think of it: what would be wrong with just having expanded cork *exposed*, without a plaster finish, at least in sections of the ceiling? On top of that, one would still need an airtight membrane (and a watertight membrane? - or can one membrane fulfil both roles? I think the crucial thing would really be to keep water from filtering down...). By "sections of the ceiling" I really have in mind the lower part of the ceiling in half the attic - the part that is my home office. If I did that to the bathroom or my girlfriend's home office, she would murder me with an axe (or whatever vegans use to murder). (Would dust get in expanded cork's interstices? I have allergies.)

Well, around the windows, I can put as much cork as I want. The minimal spacing between windows is 10cm. Right now the insulation between pairs of windows close together is as thick as elsewhere (which is idiotic and not what was planned: it makes one hit one's head); I think 5cm should suffice, no? If an insulation company tries to overcharge me for it, I can tell them I can buy the cork and paste it myself. There's no magic to it, no? All one needs is cork (expanded or not - would it matter?), glue and a cutter.

Come to think of it, those spots you mention might be even more critical when it comes to sound insulation (since sound, again, finds the weakest point - and the skylights themselves are double-glazed; one might hope, but I can't know, that the frame is made so that it is not the weakest point itself). In that case, the thing to do might be just to put a few cm of cork around them, behind the plasterboard. Probably a wiser choice than putting PIR, say, which would insulate more but do nothing for noise.

On liege24: who on earth charges so much for two *samples*? https://www.liege24.fr/shop/42-echantillons-de-liege/1161-eacutecorce-de-liege-decoratif-mural-virgin-amp-cameleon---ensemble-dechantillons---2-pcs/ Elsewhere, prices are more reasonable - see, e.g., https://www.toutleliege.com/22-les-decos-double-epaisseur-6-mm-et-plus Or yet again https://magasindeliege.fr/liege-mural-echantillons-virgin-river.html Wonder how to compare the quality in an objective way.

Right, I've thought about that. Is there any solution to that? (In a future society, maybe windows would be surrounded by a layer of vacuum insulation, but I doubt a random insulation person who is trying to charge me twice what he should would agree to it.)

Oh, I solved my first-floor noise problem (expensively!) by having a new set of sliding windows (heavy single glazing, high transparency) installed 15cm away from existing double-glazed windows (which had good specs, but were not top-of-the-line; the fake architect got in the way of that, unfortunately). So: outer set sliding sideways, inner set opening inwards. But that's not what I meant! These are skylights, which open by tilting. Aha? What do you mean? I can share pictures (and a plan) if that helps.

Ah sorry, meant 15cm! Test for what - for the look?