A new building design using CLT is designed to provide housing while reducing carbon emissions.
In a move intended to bring down CO2 emissions while streamlining the construction of cost-effective urban housing, Generate, an AEC technology company, assembled a coalition of industry leaders to develop the Tallhouse, an adaptable catalog of integrated design systems for carbon-conscious, high-density urban housing, focused on the structural use of mass timber.
The coalition includes Buro Happold Engineering, Niles Bolton Associates, Consigli Construction, Code Red Consultants, Olifant Market Development, Urbanica Development and Arup Engineering.
The Tallhouse, comprising a catalog of four mass timber structural systems, illustrates a range of mass timber design options, all digitally engineered to address the need to build more quickly, sustainably and cost-effectively.
The four structural options offered by the Tallhouse are: A hybrid steel/cross-laminated timber (CLT) structure; A mass timber post, beam and plate structure; A hybrid light-gauge metal/CLT structure; and a full CLT plate honeycomb structure.
To evaluate each design, the team developed a Carbon Data Analysis tool, which validated significant savings in CO2 emissions associated with building materials (“embodied” emissions). Emissions ranged from 14 to 52 percent.
The Tallhouse, as a catalog of systems, is intended to accelerate and encourage the adoption of easily digitized and sustainable materials. By displaying the CO2 emissions associated with each building component, these systems aim to increase transparency on the implications of different design options, raising carbon-awareness, while permitting project stakeholders to adopt innovative materials economically.
“Already, we are designing individual mass timber projects relying on these digital systems, which are now starting to go up in Boston,” says John Klein, CEO of Generate and project leader.
“But the Tallhouse catalog was developed with the specific intent of at once enabling our cities to achieve their ambitious CO2 footprint reduction goals, and to meet growing demand for affordable, biophilic housing.”
The Tallhouse building systems are designed for 8 to 18 stories, in anticipation of the upcoming 2021 U.S. Tallwood Codes, which will allow construction of up to 18 stories in the 2021 International Building Code.
The systems are designed as a replicable kit of parts that accommodates most U.S., Canadian and European manufacturers’ products and transportation logistics. While the majority of the structural systems are standardized, their external bays are adaptable to custom site profiles, and can be articulated to meet a vast array of unique architectural designs.
To reduce costs, these structural bays are driven by the use of five-ply cross-laminated timber in the floor systems, also offering a reduced construction schedule from rapid assembly.
To maximize savings, the four systems were approached from an integrated design standpoint, with a prefabricated panelized exterior wall system, modular bathroom and modular kitchens, and prefabricated mechanical, electrical and plumbing assemblies.
Generate is devoted to the digitalization of the AEC industry, and has been working towards the development of a digital platform that will streamline the design, manufacturing and assembly of buildings, while increasing transparency on the different implications of building materials and systems.
The Tallhouse catalog will serve to reduce risk in the deployment of sustainable systems, aiding policy makers in the difficult decisions regarding use of building materials, through precise and pre-vetted data on different, code-compliant systems.
The U.S. Northeast is home to the highest percentage of sustainably managed timber in North America, but its large tracts of working forests are threatened by competitive losses in other forest products industries, such as pulp and paper. Timber offers a unique chance to bring new value to U.S. forests, as a long-lived forest product manufactured with wood species endemic to the U.S. Northeast. Unlike pulp and paper, long-lived forest products such as mass timber building materials have much longer timelines in keeping CO2 stored in the wood after harvest. The carbon storage in the building further contributes to mass timber’s reduced GWP.
By replacing—or hybridizing—conventional construction materials with timber, the Tallhouse will help offset near-term emissions by greatly reducing emissions from the manufacture of materials, while storing carbon in the timber structure over the lifetime of buildings.
The Tallhouse team is currently implementing these systems in over 1 million square feet of construction in the U.S., and is looking for additional developers interested in adapting these pre-engineered systems. The design images and plan in the team’s package reflect early design concepts for the adaptation of an affordable, high-density and biophilic Tallhouse system in Boston.
This work has been generously supported by the National Science Foundation, the US Department of Agriculture, the Softwood Lumber Board, the Binational Softwood Lumber Council and the Commonwealth of Massachusetts.
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