• Current construction and energy codes and standards in the USA treat mass timber walls and roofs as having thermal transmission resistance properties similar to frame and insulation constructed building components. This is scientifically incorrect.
  • Mass timber has natural thermal storage and release properties that puts it in a completely different class of building materials. The inaccurate thermal properties of mass timer that are in current codes and standards is a major detriment to the use of mass timber for construction. This means it significantly impairs the use of this building product that has major carbon capture and sequestration characteristics that would make a major contribution to reducing carbon release to the atmosphere from both construction and building occupancy and use.
  • IMTA is under contract with THE Oak Ridge National Laboratory (ORNL) for ORNL to produce the technical data needed to propose code & standards changes to assign realistic thermal characteristics to mass timber used in building construction.
  • The basic research has been completed and published by ORNL. The research demonstrated the following:

(For geeks:)

  • ‘Stick built walls with insulation’ work by providing resistance to thermal flow. Mass timber provides thermal inertia, meaning that it works by retaining and releasing thermal energy (heat) rather than only providing resistance to the flow of thermal energy. This means that mass timber works differently than ‘Stick built walls with insulation’, so using the characteristics of ‘Stick built walls with insulation’ is inaccurate in rating mass timber floors, walls and roofs.
  • Results of this difference in the way mass timber works compared to ‘Stick built walls with insulation’ were shown to include:
  • annual energy savings with mass timber walls as compared to the baseline lightweight walls depending on the climate zones were up to 22%,
  • lightweight walls with extreme insulation level (R-100 continuous insulation) saved less cooling energy as the mass timber walls,
  • when the focus is on lowering the cooling energy use, more insulation is not necessarily the solution but instead adding thermal mass,
  • mass timber walls efficiently shifted heating and cooling energy demand to other hours away from the peak demand hour, thus helping the electricity supply grid,
  • the peak demand for heating and cooling energy was 30%–50% lower with mass timber depending on the month and location,
  • mass timber walls improved thermal comfort by reducing the uncomfortable hours by up to 46%.
  • Summary of Results: Mass timber walls use less heating and cooling, provide more hours of comfortable temperatures, and reduce the amount of peak electricity natural gas that has to be produced and transmitted by electric and natural gas utilities.
  • The next phase of the Research is needed to verify that the computer model, i.e., the set of calculations needed to design a structure using walls with thermal inertia rather than walls with resistance to heat flow, is accurate.
  • The next phase the IMTA Project is three-fold:
  1. field test verification of the model and publication of the model and supporting data for its use,
  2. development and presentation of the proposals for modifications to national and international codes and standards committees to eliminate the current major impediment to this use of mass timber in building construction nationwide, and
  3. outreach to the members of the greater wood products industry (WPI) to help make the information and results of IMTA’s activities available and usable by the entire WPI, and to increase the national, regional and local support for state and federal construction design and permitting agencies to implement the results throughout the construction industry in the USA.
  • The results of implementation of the IMTA work products will increase the utilization of mass timber in building construction with all the related benefits to the wood products industry and the environment.

The International Mass Timber Alliance (IMTA) is a 5-year old, all-volunteer, non-profit registered in the State of Tennessee. Its members are from the mass timber industry, primarily log building manufacturers and their suppliers. The Board of Directors is the operating entity of IMTA. IMTA works under its registered bylaws.

Mass Timber Building Talking Points after the Elevator Pitch

  • Stick built walls with insulation’ work by providing resistance to thermal flow. Mass timber provides thermal inertia, meaning that it works by retaining and releasing thermal energy (heat) rather than only providing resistance to the flow of thermal energy.
  • Mass timber walls, through their inherent thermal inertia, actually store heating and cooling energy produced inside the structure rather than only slowing energy transfer to the outside environment.
  • Mass walls transfer heat between the building material and the environment inside and outside the building.
  • Mass wood walls not only flatten peak energy demand vs. frame walls, they provide superior carbon sequestering. They stored carbon during their growth, they do not require the carbon releasing energy for mining, they do not require the amount of carbon releasing energy for their manufacturing or the carbon releasing energy (and labor) of constructing multiple layers of the building envelope (walls, roof, floors), and they use less carbon releasing energy during their useful lives.
  • Mass wood surfaces moderate relative humidity as well as temperature, and it does so without providing an opportunity for condensation.
  • Mass wall builders have evolved with all construction trades to understand the importance of controlling air leakage, and properly built mass walls are as tight, or tighter than lightweight frame walls.
  • The improved comfort of the mass wall occupant is a significant impact of this method and material of construction.
  • Combine all of this with the potential market for using mass wood (e.g., 3-ply CLT) in off-site production (e.g., pre-cut panels, pods, or modules) of residential designs, it is critical to impact the mindset of authorities having jurisdiction to use a different metric to approve mass walls for single family dwellings, duplexes, townhouses, hotels, apartments, and more.