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Nendo’s Block-Wall House in Karuizawa, Japan, uses a long, angled screen to give its extensively glazed home privacy beside a rural road. The screen—not the entire house—is made with CO2-SUICOM, a specialty concrete described as hardening by reacting with carbon dioxide. New Atlas reported the project on April 17, 2024, relaying the material explanation and cost estimate from Kajima Corporation.
What is the Block-Wall House?
The Block-Wall House is a residence by Japanese design studio Nendo in Karuizawa, Nagano Prefecture. Its extensive glazing opens the house to its surroundings, but the rural road nearby creates a privacy challenge. Nendo’s response is an angled screen that is intended to let residents look out while making it harder for passersby to see inside.
New Atlas reported that the screen consists of approximately 2,000 blocks arranged in parallel rows to form five walls with a combined length of 110 m (360 ft). These are figures reported by the publication, not independently verified measurements. The screen is the feature made with CO2-SUICOM; the reporting does not say that the house itself is built from this concrete. New Atlas’s April 17, 2024 project report describes the design and its roadside setting.
How does the CO2-SUICOM screen work?
New Atlas attributes CO2-SUICOM to Kajima Corporation and its collaborators Chugoku Electric Power Co, Denka, and Landes Co. In the explanation relayed by New Atlas, Kajima says more than half of the cement is replaced with γ-C2S, a material that reacts with CO2 rather than water to harden. The concrete is then cured in a CO2-rich environment, where carbon dioxide is trapped as it hardens.
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This describes the material’s reported formulation and curing process. It does not, by itself, establish how much CO2 the screen stores over its life or whether its overall emissions are lower than a conventional wall after production, transport, installation, and end-of-life impacts are counted. The New Atlas report does not provide an independently reviewed lifecycle analysis or a quantified CO2 uptake figure. The report attributes the process description to Kajima.
What the reported cost does—and does not—tell you
A Kajima representative told New Atlas in its April 2024 report that CO2-SUICOM cost about three times as much to produce as standard concrete used in Japan at that time. The article also said work to reduce the cost was underway. This is a dated, Japan-specific production-cost estimate—not a current quote, an installed-cost comparison, or evidence of the material’s present availability. The report gives no newer price.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What can be concluded about its climate performance?
The project shows how a specialty concrete can be used in an architectural element with a clear functional purpose: screening a glazed home from a nearby road. Kajima’s reported process uses CO2 during curing, but the available project coverage does not quantify stored carbon or establish a whole-project carbon balance. It is therefore not enough to call the house, or even the full screen, carbon-negative.
For a construction decision, meaningful comparison would require evidence on lifecycle emissions for an equivalent application, the amount and permanence of CO2 uptake, structural performance, curing requirements, supply, and installed cost. The New Atlas article does not provide comparable figures for those measures. Its account of strength is favorable in general terms, but does not supply independent test results.
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