A rammed earth wall and a pane of electrochromic glass tend to arrive in the same sentence about materials that tell a story. It is a nice sentence and it hides the interesting part, because those two surfaces behave in almost opposite ways once they are installed. One is heavy, breathable and effectively permanent. The other is a laminated electrical device with a service life, a warranty and a supply chain behind it.
Key takeaways
- Cement production accounts for roughly 7% of global CO2 emissions, according to the IEA.
- Published embodied carbon for unstabilised rammed earth sits far below fired brick, but cement stabilisation erodes much of that advantage.
- Berkeley Lab modelling put perimeter zone energy savings from electrochromic glazing at 10% to 20% in commercial buildings.
- The best known smart glass manufacturer filed for Chapter 11 in April 2024, which is a supply risk worth pricing in.
Earth and clay, the oldest surface and the most oversold
Earth walls are having a genuine revival, and the reasons given for it are often the weakest ones available. The strong arguments are physical. Compacted earth has serious thermal mass, so it damps the daily temperature swing rather than resisting heat transfer the way insulation does. Clay and lime finishes are hygroscopic, meaning they take up and release water vapour, which softens humidity peaks in bathrooms and kitchens instead of letting them condense on the coldest surface in the room.
The carbon argument is real but conditional. Published life cycle figures put unstabilised rammed earth in the region of 20 to 40 kg of CO2 equivalent per cubic metre, against roughly 120 to 180 for concrete blockwork and 200 to 300 for fired clay brick. Add cement to stabilise the mix, which most contemporary specifications do, and the figure climbs steeply. Peer-reviewed work on cement-stabilised rammed earth shows embodied energy rising more or less linearly with cement content. An earth wall with 8% cement in it is still a decent choice. It is not the number quoted in the brochure.
Two practical notes we would not skip. A load-bearing earth wall is a structural element and needs an engineer, not a finish specification. And a clay plaster over plasterboard gives you the surface and the vapour behaviour without the mass, which is frequently the honest solution in an apartment.
Concrete, the material we stopped seeing
Concrete is the second most used substance on earth after water, and cement making produces around 7% of global CO2 emissions on the IEA’s accounting. Most of that is not fuel. It is the chemistry itself, since turning limestone into clinker releases carbon dioxide whatever heats the kiln, which is why the sector is so hard to abate.
| Wall material | Indicative embodied carbon | What it gives a room |
|---|---|---|
| Unstabilised rammed earth | 20 to 40 kg CO2e per m3 | Mass, humidity buffering, visible strata |
| Cement-stabilised rammed earth | Substantially higher, rising with cement content | Same look, greater durability, weaker carbon case |
| Concrete blockwork | 120 to 180 kg CO2e per m3 | Speed, predictability, acoustic weight |
| Fired clay brick | 200 to 300 kg CO2e per m3 | Longevity, texture, repairability |
Ranges this wide are ranges for a reason. They shift with transport distance, with local grid intensity and with the assumptions of whoever ran the assessment. We use them for ordering choices, never for a single-figure claim in a client presentation.
Smart glass, a performance product with a company history attached
Electrochromic glazing changes tint when a small voltage is applied, so a window can be dimmed rather than shaded. The performance case is well documented. Modelling by Lawrence Berkeley National Laboratory found perimeter zone primary energy reductions of roughly 10% to 20% in commercial buildings with a high window-to-wall ratio, with peak demand reductions of 20% to 30% when the glazing was paired with daylighting controls. Those are conditional figures tied to orientation, climate and control strategy, not a property of the glass on its own.
The commercial history is the part rarely mentioned in design coverage. View Inc, once the best capitalised name in the category, filed for Chapter 11 in April 2024 and emerged as a private company the following month. Specifying an electrically active façade component means accepting a dependency on a manufacturer being around in fifteen years to supply a replacement pane and a controller. That is a legitimate reason to prefer external shading in some projects, and it has nothing to do with aesthetics.
Choosing for the story you actually want
Materials communicate through wear, and wear is where most specifications go wrong. Lime and clay accept a scuff and absorb it into the surface. Polished plaster records every knock permanently. Timber greys, patinates and can be sanded. Electrochromic glass looks identical in year one and year ten, which is precisely its appeal in a corporate interior and precisely why it feels inert in a home.
If you want a room that reads as handled and lived in, choose surfaces that improve with contact and accept that they will need touching up. If you want a room that stays exactly as delivered, choose engineered products and budget for eventual replacement rather than repair. Both are defensible. Confusing the two produces the interiors that look tired within a year, which is the same tension we described when writing about the role texture plays in a scheme.
Questions this raises
Can rammed earth be used in a wet climate?
Yes, with detailing. The old rule about a good hat and good boots still applies: generous roof overhangs and a raised, impermeable plinth keep driving rain and rising damp off the wall. Without those, erosion is a question of when.
Does clay plaster genuinely help with humidity?
It buffers rather than controls. A clay or lime finish moderates short-term swings in vapour pressure, which is helpful in a bathroom used twice a day. It is not a substitute for extraction, and no finish material is.
Is smart glass worth it in a house?
Rarely, on cost per square metre alone. It earns its place where shading is impractical, on a large west-facing glazed area with no external structure to hang a blind from. Elsewhere, external shutters and a decent low-emissivity double glazing unit deliver most of the comfort benefit for a fraction of the outlay.
The materials worth living with tend to be the ones that record time rather than resist it. That is a preference, not a rule, and it is the one we would defend across a clay wall, a brick pier and a plain concrete floor alike.
Interested in the philosophy behind surfaces that age?
There is a whole aesthetic tradition built on accepting wear rather than hiding it.
Sources: International Energy Agency, cement sector emissions share; published life cycle assessment ranges for earthen and masonry wall materials, including work on embodied energy in cement-stabilised rammed earth, where embodied energy rises with cement content; E. S. Lee, M. Yazdanian and S. E. Selkowitz, “The energy-savings potential of electrochromic windows in the US commercial buildings sector”, Lawrence Berkeley National Laboratory, LBNL-54966, 2004; court and company filings on View Inc’s Chapter 11 petition of April 2024 and its emergence as a private company in May 2024. Embodied carbon figures are indicative ranges that vary by study, transport distance and grid intensity. Updated August 2026.
