It’s wood. It’s Passive House. It’s the “Goldilocks density.”

Boston is getting a “CLT Cellular Passive House Demonstration Project” that pushes every TreeHugger button.

Building with wood is a great way to avoid upfront carbon emissions (AKA embodied carbon) in construction; Passive House is the best way to avoid operating carbon emissions. Multifamily housing at “missing middle” or “Goldilocks” densities is the way to build sustainable cities.

© Generate Architecture + Technologies

That's why this project by Generate Architecture + Technologies, partnered with developer Placetailor pushes so many buttons, it does it all.

As a winner of the 2018 Wood Innovation Grant from the U.S. Forest Service, Generate has been developing a catalogue of tech-enabled and replicable kit-of-parts building solutions which utilize mass timber—a sustainable engineered wood product—to address the region’s twin pressures of increased urban density and carbon footprint reduction.

© Generate Architecture + Technologies

The building is the first of what is supposed to be”a pre-packaged concept that real estate developers can use for rapid deployment of CLT in mid-rise apartment buildings.” That's pretty hard to do when you are given a triangular site, but they have managed to pull it off with 14 units, a mix of unit types, from studios to fully accessible units to family accommodation.

Being a former real estate developer myself, I am impressed with the approach taken by John Klein and the Generate team, telling a group of them that “mid-rise buildings that use CLT can be built quicker, with less labor, and at a lower cost than using traditional construction materials. That really gets a real estate developer’s attention.”

© Generate Architecture + Technologies

This is actually funny, reading that in 2019, because a dozen years ago it's exactly what Andrew Waugh and Anthony Thistleton told a real estate developer in London with the building that started the CLT revolution. He was convinced, so they got to build their CLT building as long as they covered all the wood with drywall so that none of the tenants would know that it was wood. Now of course, the look of the wood is part of the pitch. But many developers are risk-adverse and they want to know the answers to these kinds of questions:

Where in the building should you use CLT? How do you design apartment units to be compatible with CLT panels? How is the structure of the building engineered? How do you design for fire protection and acoustics? And perhaps most important to them: How much will it all cost?

That's why this project is so interesting, in that it will demonstrate how it can be done in a North American context, where developers are not used to smaller, Euro-style buildings and the codes are quite different.

© Generate Architecture + Technologies

For example, it's harder to build small buildings in North America compared to much of Europe, because the building codes demand two means of exit and fire-separated stairs whether it is 5 storeys or 50 storeys; it takes up a lot of space in a little building. I wish there could be some experimentation there as well.

Passive House First is the best way to get to zero carbon

The building “features a CLT rooftop canopy to easily mount solar panels.” But a great benefit of Passive House efficiency is that you don't need a lot of them; the demand side is so low. Going the next step net zero gets really easy.

But one of the biggest sources of emissions in our cities is not our buildings, it's the getting between buildings, the emissions from driving. That's why we need buildings like this everywhere, dense enough to support public transportation and local shopping. They have reduced upfront emissions, reduced operating emissions and reduced transportation emissions. There's a lot more going on here than just wood construction.