Commercial, Mass Timber, Multifamily, Sustainability

CLT Passive House Demonstration Project

Model C mass timber building exterior during day

Model C mass timber building exterior street view

CLT Passive House Demonstration Project interior

Model C residential mass timber interior

Cross Laminated Timber Makes Its Boston Debut

The Model-C demonstration project at 201 Hampden is a mass timber, mid-rise, multifamily, and certified Passive House building that shows how cross-laminated timber systems can be leveraged to meet complex design and sustainability goals.

The five-story mixed-use demonstration project is Boston’s first full cross-laminated timber (CLT) building, housing fourteen residential units and a ground floor co-working space open to its Lower Roxbury neighborhood.

The Model-C demonstration project is the result of a collaboration between MIT start-up Generate and Boston-based design-build firm Placetailor. Both firms are committed to using wood construction to address multifamily housing shortages in dense, urban environments while meeting ambitious sustainable development goals.

John Klein

CEO of Generate

Mass timber buildings - like Model-C - have the ability to tackle climate change [and] are also mid-rise to accommodate urban density.”

A kit of parts.

The project demonstrates the “Model-C” building system – a kit-of-parts assembly constructed from prefabricated CLT building panels – the result of a collaboration that unites Generate’s expertise in mass timber with Placetailor’s expertise in high performance assemblies, including insulation and air-sealing that qualify buildings for high-performance, zero carbon, and Passive House.

While Model-C was originally developed as an optimal system for mid-rise multifamily buildings, its kit-of-parts assembly is intended to easily adapt to diverse site parameters and taller building applications. “We were looking at manufacturers, species, grades of product, ensuring the spans that you’re looking at as a system can accommodate the program, but also give you a high performing building,” said John Klein of Generate.

Generate and Placetailor have carefully documented the development of the Model-C demonstration project, and they are committed to releasing project calculations and performance data to the public prior to the 2021 International Building Code updates, which will permit high rise applications of mass timber. “If we want to get to a zero-carbon world in the next decade, we have to show people how to do it in detail,” said Colin Booth, Placetailor’s Director of Strategy. “We want to share as much of this project as possible and as transparently as possible. We have cost information to share, performance and system specs, large batch energy modeling, all of this information to help people understand how we’re doing what we’re doing,” he said.

Wood Use

201 Hampden’s Model-C building system will be delivered in prefabricated modules, reducing both construction schedules and waste. Klein describes the CLT system as a regularized ‘structural chassis’ that provides strong wall alignment and efficient load transfers. 201 Hampden’s wood construction maximizes the use of its irregular urban lot, optimizes solar panel orientation, and offers different unit mixes on the interior. The building’s exposed CLT panels provide excellent thermal and acoustic insulation; stacked in tall plate heights, they give interior spaces a clean and modern, yet warm and spacious feel.

Environmental Impact

The Model-C demonstration project was designed to operate at net-zero carbon, which is achieved by calculating both the building’s embodied energy and its operational energy, and offsetting any annual excess energy use through carbon offset purchases. The building is Passive House certified and meets the Boston Department of Neighborhood Development’s Zero Emission Standards. The building’s CLT system is paired with natural mineral wool insulation, roof-mounted solar panels, and generous daylighting.

While steel and concrete materials release their embodied carbon during manufacturing, CLT’s wood fibers store embodied carbon through the lifecycle of the building. “You get into mass timber, you’re looking at serious carbon sequestration,” said Placetailor’s Booth. “We knew getting to a larger scale, CLT was the next frontier.”

201 Hampden is scheduled to begin construction in spring 2021.