The Stretch Energy Code is being adopted by more and more municipalities across Massachusetts since it arrived as part of the Building Code appendix in 2009. Over 100 of the state’s municipalities have adopted the code and the state is on track for full adoption within the next 12-24 months. Additionally, almost all of the state’s population centers have already adopted and are enforcing the Stretch Energy Code. While the Stretch Energy Code addresses a wide range of building types (residential / commercial) & building size; this article will focus specifically on commercial buildings 100,000 sf and larger.
The goal of the Code is to promote energy conservation above current building Code (Mass 8th Edition) and foreshadow increased energy performance requirements by later revisions of the building code. For new construction 100,000sf and larger, the Stretch Energy Code requires the design and construction to be 20% more energy efficient than building code (780 CMR) baseline (ASHRAE 90.1 Appendix G).
Compliance with the code is not difficult, overbearing, and ideally won’t change the design intent or approach of the project… it just requires the right approach.
Do:
• Understand the Code Baseline (per ASHRAE 90.1 Appendix G)
The team (architect/engineer/owner) needs to understand what the project will be compared/
modeled against. For example, the maximum allowable percentage of glazing for the baseline is
40%. Therefore, when the building design has more than 40% glazing, the overall design must
make-up for the increased energy / load imposed by the additional glazing.
• Understand where the Building Energy is Consumed
Similar to the 80/20 rule; the majority of the energy consumed by building comes from a limited
amount of variables. Typically, the largest consumers for energy include lights, space heating,
and cooling. Drilling down through the building envelope analysis can provide clarity on the
relative impact of each component (roof, skylight, windows, wall, etc.). This is key when
determining recommendations to optimize the proposed design to reduce the environmental load
and associated energy required to offset those loads.
• Understand the Project Budget The budget is the end-game for the project and needs to be understood and respected. Understanding (and discussing) the project budget can alleviate wasted cycles of design and analysis across all disciplines. Every project has a budget. If you’re told otherwise, you’re already off track.
Don’t:
• Sacrifice the Program and/or Architectural Vision The 20% energy efficiency increase requirement over the baseline is often readily achievable
without adversely affecting the project’s original space program or architectural vision (materiality and/or façade). There may be upgrades necessary in insulation values, architectural detailing and/or buy-in from the owner/developer with regards to lighting power densities, but nothing significant (yet…).
• Apply Band-Aids without Optimizing the Building Design First If the initial modeling analysis indicates that the building isn’t meeting the Stretch Energy Code
requirements, avoid throwing the ‘Green Design’ kit of parts at the project – including double façades, triple pane glass, green roofs, active exterior shading elements, PV, wind turbines, etc. Each of these has their own place in design, but not as band-aids on your project. They often increase the overall cost/complexity of the project without addressing the root design issue with the building for the lack of compliance. Optimize the building first, and then apply additional green measures and renewables.
Fortunately our industry has a lot of synergistic activities and formalities engaged over the past 5-10 years ranging from LEED, BREEAM, and the AIA 2030 Challenge outside of the government’s code mandates. Each of these in their own way is focused on reducing energy/carbon footprint, improving the occupied environment, and minimizing waste.
The Stretch Energy Code is the tip of the iceberg for Code compliance for energy over the next 20 years. With an ever increasing focus on energy costs, bottom-line management, and corporate/institutional mandates on energy – the collaboration across the design team will become more and more important
to achieve success. We’re quickly entering a period of where these factors will strongly influence the building architecture in additional to the systems and equipment.
Chad A. Wisler (PE LEED AP BD+C) is Managing Principal at Vanderweil Engineers in Boston.