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Don’t Get Squashed by Your Building’s Carbon Footprint

By Patrick Murphy, PE, LEED AP BD+C, CPHC
October 20, 2021

A growing list of cities have implemented carbon emissions limits on existing buildings in the last four years, targeting the largest source of emissions within cities and aligning their policies with climate commitments like the 2015 Paris Climate Accords.  With only about 1% of commercial floor area renovated or built new each year, achieving zero emissions in buildings city-wide via energy codes won’t result in making all buildings net zero across cities by 2050.  Instead, by utilizing emissions limits targeting all large buildings, these cities can focus all building owners on reducing their emissions over the next thirty years to achieve zero emissions before it’s too late.  Buildings that exceed emissions limits may be subject to large annual penalties based on how much their emissions exceed the allowance. Now, building design professionals and building owners need to determine how to transition large existing buildings, and even new buildings, to net zero emissions over the coming years to achieve these carbon emissions goals and avoid penalties.


The general approach to these laws sets carbon targets for existing buildings that decrease over time, with all existing large buildings achieving net zero emissions by 2050. These policies are the most impactful initiative to curb cities’ carbon emissions and their buildings’ contributions to climate change.

New York and Boston previously only required large buildings (over 20,000 sf in Boston, for example) to report their energy consumption to the City and to conduct periodic energy audits; now, however, carbon emissions limits are set on a square-footage basis for different types of buildings, with higher limits for more energy-intensive uses such as lab and healthcare facilities.  These emissions limits will decrease every five years and ultimately go to zero emissions by 2050. Buildings that exceed their annual emissions limit will be subject to alternative compliance payments that could easily rise to tens or hundreds of thousands of dollars each year.


The large buildings you design, own, or operate in these cities will need to steadily reduce their emissions over the next three decades to avoid penalties.  Even new, code-compliant buildings may exceed the emissions limits within the first ten or twenty years of operation. Older, less-efficient buildings may need to take action now to remain in compliance when the ordinances go into effect (typically in 2025).


On a new 71,000 sf lab in NYC, we utilized preliminary design energy modeling to determine the risk for emissions penalties for different HVAC system options.  While the overall design was intended to be very efficient and far better than code, we studied two HVAC system options: one with fossil fuel boilers, and one with electric heat pumps.  While the project is expected to initially avoid penalties regardless of the HVAC system selection, eventually the emissions limits catch up with the fossil fuel option in 2035, while the all-electric option should avoid penalties for the life of the system (see below).  


Thankfully, as the local electrical grid becomes cleaner over the next thirty years, buildings will benefit from some automatic electricity emissions reductions. In most cases, however, that won’t be enough to remain below the limits for the life of the building or systems, so strategies that cut emissions even faster will need to be pursued. 

Building owners can reduce emissions and avoid penalties by carrying out energy efficiency improvements; switching to clean, fossil-fuel-free heating systems; and/or installing or purchasing clean energy and carbon offsets. Owners of a portfolio of buildings can also balance their overall portfolio against the limit. All owners can plan to take advantage of capital renewal and equipment replacement projects in the coming decade to position their building to avoid these penalties.  The best way to find the right path for your building is to consult a qualified engineer.