The Task Group on Combustible Construction is in the process of evaluating a proposed code change request related to buildings of encapsulated mass timber construction (EMTC). As part of the analysis of the code change request, an impact analysis is required that includes a cost-benefit analysis.
Hanscomb was hired to provide a cost-benefit analysis and to compare the estimated value of the following:
1. The cost of constructing a building of mass timber (unprotected) versus a building constructed of encapsulated mass timber (e.g. mass timber protected with a double layer of Type X gypsum board) versus a traditional concrete and steel building.
2. The time to build a building of mass timber construction (unprotected) versus a building of encapsulated mass timber construction versus a traditional concrete and steel building.
3. The annual maintenance costs of building of mass timber construction versus a building of encapsulated mass timber construction versus a traditional concrete and steel building.
For the purposes of this study two sets of conceptual floor plans and elevations have been created:
1. A 12 storey building with a Group C major occupancy (residential) where each storey is 6,000 m2 in floor area.
2. A 12 storey building with a Group D major occupancy (office) where each storey is 7,200 m2 in floor area.
Canadian Conference on Building Science and Technology
On tall wood buildings, mass timber elements including CLT, NLT, glulam, and other engineered
components absolutely need to be protected from excessive wetting during construction. This requirement precludes the use of many conventional cladding systems unless the building is fully hoarded during construction.
The building enclosure and façade of UBC Tallwood House consists of an innovative prefabricated steel stud rainscreen curtain-wall assembly that is pre-insulated, pre-clad, and has factory installed windows. Design of connections and air and water sealing of panel joints and interfaces was carefully considered given the tall wood structure they were designed to protect. While steel studs were utilized in the panelized structure, feasible curtain-wall designs were also developed and prototyped for wood-framing, CLT, and precast concrete as part of the project.
Looking ahead, there will continue to be innovation in design and construction of fast and durable facades for taller wood buildings. New prefabricated panel designs incorporating CLT panels and connection technologies from unitized curtainwall systems are already being developed for the “next tallest” wood buildings in North America.