Microsoft builds its first datacenters with cross-laminated timber

Oct. 31, 2024 — Microsoft said it is building two datacenters in northern Virginia with cross-laminated timber to cut how much steel and concrete they use, which it called one of the first hyperscale uses of engineered wood in a U.S. datacenter. Here's what happened, what it cost, and what went wrong.

Cost and outcome (as of Oct. 31, 2024)

Outcome: The hybrid mass timber, steel and concrete design "is estimated to significantly reduce the embodied carbon footprint of two new datacenters by 35 percent compared to conventional steel construction, and 65 percent compared to typical precast concrete," Microsoft said. (Microsoft Source, Oct. 31, 2024)
Cost: No project cost was given. Microsoft says CLT "still commands a premium," adding 5 to 10 percent to material costs for a single-family home on average, but can be cost-effective on large projects through faster construction. (Microsoft Source, Oct. 31, 2024)
Status: Under construction when announced.

How it's built

CLT, typically spruce, pine or Douglas fir, is made by gluing three to nine layers of timber in alternate directions and pressing them into a panel, Microsoft explains. Unlike steel, which deforms faster in high heat, CLT forms a char layer that insulates the structure. (Microsoft Source, Oct. 31, 2024)

In the Virginia buildings, the CLT replaces part of the thick concrete normally used in floors and ceilings, with a thin concrete layer on top for durability and waterproofing. Microsoft says the result is a much lighter building that needs far less steel. Prefabricated off-site, the panels install faster and more safely than corrugated steel, said structural engineer David Swanson. "We're constantly trying to validate the suitability of these novel materials for use in a datacenter environment," he said, to make sure "they're going to be safe, they're going to be resilient." (Microsoft Source, Oct. 31, 2024)

Gensler designed the two datacenters and Thornton Tomasetti worked with it, according to the article. "They can almost be like a market mover," Thornton Tomasetti's Thomas Hooker said of Microsoft. (Microsoft Source, Oct. 31, 2024)

Why Microsoft is doing it

Microsoft has pledged to be carbon negative by 2030. In May 2024 it reported a 6.3 percent cut in direct emissions over three years, but a 30.9 percent rise in indirect emissions driven by datacenter growth and hardware, the feature says. "It's an all-hands-on-deck task," said Jim Hanna, who leads datacenter sustainability. (Microsoft Source, Oct. 31, 2024)

Other levers include low-carbon requirements in construction contracts, a requirement that select high-volume suppliers use 100 percent carbon-free electricity by 2030, and its Climate Innovation Fund, which had committed $761 million. Microsoft says it uses CarbonCure at select U.S. datacenters and plans to pilot small amounts of Prometheus Materials' low-carbon cement in the Virginia buildings. (Microsoft Source, Oct. 31, 2024)

The feature cites the World Economic Forum for steel accounting for about 7 percent of global carbon emissions and cement about 8 percent. Microsoft built its Silicon Valley headquarters with CLT in 2021, its first large-scale use of the material. On steel, it has invested in Stegra, formerly H2 Green Steel, which is building a hydrogen-based steel plant in northern Sweden. "We have to be system thinkers across the entire value chain," Hanna said. "That's what makes it hard, but certainly not impossible." (Microsoft Source, Oct. 31, 2024)

What went wrong

Estimates, not measurements. The 35% and 65% figures are estimates for buildings still under construction. (Microsoft Source, Oct. 31, 2024)
Only part of the concrete goes. CLT displaces a portion of the floor and ceiling concrete, and the design still uses steel and a concrete topping. (Microsoft Source, Oct. 31, 2024)
Cost is generic. The only cost figure, a 5–10% material premium, is for a single-family home, not these datacenters. Not all building trades have experience with CLT, Microsoft notes. (Microsoft Source, Oct. 31, 2024)
What we don't know yet: whether the buildings are finished, and the measured embodied carbon once complete.

Our follow-up question for Microsoft

Are the two Virginia CLT datacenters complete, and what embodied-carbon reduction was measured?

Sources

Microsoft Source, “Microsoft builds first datacenters with wood to slash carbon emissions,” Oct. 31, 2024. news.microsoft.com

Disclosure: [not in copy] Editor placeholder