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Stretch Energy Code and Opt-In Municipal Stretch Energy Code Comments

September 14, 2022

Written By Yve Torrie, Director of Climate, Energy & Resilience

A Better City has been closely watching the Department of Energy Resources (DOER’s) update to the Massachusetts Stretch Energy Code and the development of the Municipal Opt-In Specialized Stretch Energy Code. Our blogpost from April 2022 summarized our comments to the codes’ straw proposal, released in February 2022. DOER received over 1,200 comments to the straw proposal and on June 24^th, 2022, released draft code language that included:

• A summary document explaining the Stretch Energy Code and Specialized Opt-in Code Language
• Residential Low-Rise Stretch Energy Code and Specialized Opt-in Code Language (red line of applicable code sections)
• Commercial and Other Stretch Energy Code and Specialized Opt-in Code Language (red line of applicable code sections)

Comments on the draft language were due on August 12^th. Thanks to the detailed input from many members, we were able to submit robust comments that included both technical and broader concerns and recommendations.

Our technical concerns and recommendations followed the structure of the codes themselves and are summarized below:

1. Thermal Energy Demand Intensity (TEDI) Limits (C401.2)

• A Better City members believe the TEDI limits have been set very low and will be difficult to achieve based on their experience and a review of BERDO data from over 200 newer energy efficient buildings (built after 2005), where thermal energy demands were much higher than the TEDI limits. A Better City therefore recommended heating and cooling data from existing energy efficient and best in practice sustainable buildings in the region be analyzed to determine achievable TEDI limits.
  
  

2. Building Electrification (C401.4)

• A Better City members acknowledged that 100% electrification requirements for curtain wall buildings means 100% of peak heating demand will need to be met by heat pumps which could mean installing a lot more equipment just to keep the building warm on the coldest days. A Better City therefore recommended some flexibility on the electrification requirements that could allow large commercial buildings to determine the most cost-effective and lowest emission path to comply with the code. We also recommended a required reduction in fuel use could be used as an alternative. For example, a percentage fossil fuel reduction could be proposed, like 90%, to be consistent with Boston and what DOER has asked through the MEPA process.
  
  

3. Partial Space Heating Electrification (C401.4.1)

• A Better City members suggested water-to-water heat pumps, and the use of the exhaust heat pumps with appropriate provisions be considered as options, or that the specifications be kept general. A Better City therefore recommended that section C401.4.1 permit 25% of the peak heating load in energy intensive building types (healthcare, laboratories, etc.) to be provided by water-to-water heat pumps that recover internal energy from the building. We also recommended that another option be permitted to allow buildings to use the exhaust heat pumps with appropriate provisions.
  
  

4. Curtain Wall and Envelope Backstop Requirements (402.1.5.2)

• A Better City members said that backstop requirements can, in some cases, contradict the goals of reducing building energy consumption, and that the current methodology used in Massachusetts to calculate envelope backstop has limited flexibility and does not consider orientation, shading, or advanced technologies. A Better City therefore recommended DOER provide the basis for the derating factors. We also recommended that a greater emphasis be made on modifying the methodology to promote an integrated design process that allows for increased flexibility under the performance energy modeling pathway to achieve the goals of the envelope backstop, continue the use of high-performance fenestration systems, and encourage new technologies and methods to reduce building energy consumption.
  
  

5. Air Leakage Measurement (C402.5)

• A Better City members said the stretch code requires air leakage testing that is not feasible or practical in large buildings. They support the UA provision and thermal bridge accounting and think that the addition of envelope commissioning should be a sufficient package of envelope regulations. A Better City therefore recommended DOER consider envelope commissioning, or air leakage testing on a smaller scale, on a single floor for example, instead of the current air leakage measurement requirements.
  
  

6. Air Leakage Compliance (C402.5.2)

• A Better City members expressed concern around the inclusion of “air leakage shall be tested by an approved third party,” as typically members rely on the contractor and glass manufacturer to do field mockups and testing to attain the ASTM (American Society for Testing and Materials) Standard. A Better City therefore requested additional clarity on the air leakage testing scope and what constitutes an approved third party for air leakage testing.
  
  

7. Building Envelope Verification (C402.5.2.3)

• A Better City members expressed concern around the inclusion of “The installation of the continuous air barrier shall be verified by the code official, a registered design professional or approved agency,” as they suggested it is not practical to get agency and code officials out to the site as quickly and as frequently as this would require. A Better City therefore recommended DOER clarify that the project’s architect (a registered design professional) is sufficient for continuous air barrier verification.
  
  

8. Economizers (C403.5)

• A Better City members said there is no economizer mode for a dedicated outside air system as it is essentially always in economizer mode. A Better City therefore recommended removing this item from the list.
  
  

9. Ventilation Requirements (C403.7)

• A Better City members said the TEDI limits mean envelope tightness will need to be greatly improved but that one unintended consequence of this will be new construction with reduced outdoor air intake which can lead to poor air quality and health issues for occupants. A Better City therefore recommended that DOER consult public health officials and that the Stretch Code include ventilation requirements to ensure TEDI limits do not inadvertently worsen indoor air quality. For healthcare buildings governed by 170.62.1, we suggest the limit be 100% of ventilation rates or at least allow for greater ventilation rates in the event of public health needs.
  
  

10. Minimize Reheat (C403.7.1)

• A Better City members said that exception 2 does not work for laboratories as this section will require two systems, which is highly problematic for buildings whose uses change frequently. A Better City therefore recommended revising this section to exempt systems where at least 25% of the makeup air is supplied to Class 3 and 4 exhaust systems, as well as exhaust exempt from heat recovery requirements as defined in C403.7.5.
  
  

11. Energy Recovery Systems (C403.7.5)

• A Better City members said that exhaust classification for energy recovery should not preclude combining exhaust sources with corresponding designation as required by ASHRAE 62.1. A Better City therefore recommended clarifying that exhaust classification for energy recovery does not preclude combining exhaust sources with corresponding designation.
  
  

12. Alterations (C503.1)

• A Better City members are seeking clarity on alterations that include the replacement of basic systems that result in the reduction of carbon emissions. A Better City would therefore like clarity on alterations that include the replacement of basic systems that result in a carbon emissions reduction.
  
  

13. Change of Use or Occupancy (C505.1)

• A Better City members said embodied energy is increasingly being recognized as a more important source of emissions than operational energy and that a significant reduction in embodied emissions can be achieved by re-purposing existing buildings. A Better City therefore recommended that this section allow more lenient envelope upgrades.
  
  

14. Mixed Fuel Building Pathway (CC105.2)

• A Better City members said that the Specialized Code requires mitigation of emissions from mixed fuel buildings with on-site renewable energy but that meeting the rated capacity requirements may not be possible given the need for equipment on the roof of buildings. A Better City therefore recommended that rather than set a percentage minimum, more flexibility should be allowed starting with a potential solar area that deducts actual areas for circulation, MEP equipment, overrides, etc. A Better City also recommended that actual rooftop space studies be performed. For healthcare buildings, A Better City recommended following the language of ASHRAE 189.3 for solar readiness for healthcare buildings.
  
  

Broader concerns and recommendations provided in our comment letter are also summarized below:

15. Grid Reliability, Capacity, Resiliency, and Affordability
    • A Better City members have expressed concern about the impact that the updated Stretch Energy Code and new Municipal Opt-In Specialized Stretch Energy Code could have on electrical grid reliability, capacity, resiliency, and affordability once adopted. A Better City therefore recommended DOER commission and publish a study on the impact that the incremental electrification of the building (and transportation) sectors may have on grid reliability, capacity, resiliency, and affordability, and the steps that the state and utilities must take to keep up with increasing demands for an affordable and reliable clean energy supply within buildings.
      
      

16. Site vs. Source Energy for Building Performance Calculations

• A Better City members said that while developing the new commercial code compliance pathway, TEDI, DOER used site energy usage intensity (EUI) as the key metric but have suggested that source energy usage intensity would be a better indicator of total GHG emitted by a new building. A Better City therefore recommended DOER consider the use of source energy intensity for building performance calculations.
  
  

17. Central Plant Energy

• A Better City members said the Code does not seem to consider buildings supplied by utilities from a central plant where products such as electricity, steam, and chilled water can be procured regardless of the generation source. A Better City therefore recommended DOER consider buildings supplied by a central plan for the production of electricity, steam and chilled water.
  
  

18. Health Care Building Modeling and Code Compliance

• A Better City members said a healthcare building has not been modelled for these requirements, and that hospitals and other energy intensive buildings will need to follow the Relative Performance Compliance Pathway that requires compliance with certain elements that are difficult and/or impossible to meet. A Better City therefore recommended DOER model the changes required for hospitals before requiring compliance by this unique building type and requested that DOER confirm that healthcare buildings, following 401.2.1 (3), do NOT need to comply with TEDI.

A Better City will remain engaged throughout this process. Please reach out to Yve Torrie with any comments and questions.