The Vornado team has gained countless lessons-learned on their decarbonization planning journey. The following are essential insights from the project team:

Insights from the energy model

The predictive energy model revealed that while the renovations to the building will yield significant energy and carbon reductions, the energy consumption from tenant spaces, such as computer and plug loads, must also be significantly reduced and intelligently managed to drive down the carbon intensity of the building (and reduce/eliminate exposure to LL97 through the 2030 compliance period).

While every effort was made to ensure that the model reflects the design team’s best understanding of the building’s existing conditions and future usage, the modeled energy consumption, energy cost, and carbon emission estimates will likely vary from the actual energy, cost, and carbon of the building after construction. This is due to variables such as weather, occupancy, building operation and maintenance, changes in energy rates, changes in carbon emission coefficients, and energy uses not covered by the modeling scope.

Underscoring the importance of an iterative design process

In the first iteration of the decarbonization strategy, the Vornado team approached the project with an all-or-nothing electrification mindset. They found that the strategies that achieve the deepest levels of decarbonization through fully eliminating district steam and co-generation waste heat as heating sources may not be practical nor cost efficient to implement in such a complex existing building. So, they went back to the drawing board.

In the second iteration of the project, a more holistic strategy emphasizing the following core principles was developed:

• Re-use existing infrastructure (i.e., piping and ductwork) where possible
• Recovery wasted heat from internal loads
• Electrify heating loads affordably with heat pumps
• Compress space requirements for electrification equipment/systems
• Dispatch thermally stored energy to shift and smooth loads to promote grid flexibility

Resource Efficient Electrification framework: With these guiding principles, the Vornado team developed a new strategy that follows the  Resource Efficient Decarbonization Framework, which JB&B refers to as “Reduce, Recycle, Electrify”. Phasing, cost compression, and space compression were prioritized so that measures are more likely to be installed and scaled to other Vornado properties.

Key takeaways on the broader decarbonization decision-making process

• Invest in a Calibrated Energy Model – In large and complex buildings, building owners should commission a decarbonization study with an investment-grade calibrated energy model. Energy models should be custom built to the building’s unique characteristics, ensuring the analysis of retrofits are accurate and adds confidence to decision making. An energy model is a flexible tool that captures interactivity of all systems and ensures the strategies and measures studied have realistic energy and carbon reduction projections.
• Just Because It’s Feasible Doesn’t Mean It’s Practical – Anything is possible in an energy model. Technical teams must be aware that building ownership teams care about more than just the energy and carbon results from the model. Strategies must be practical in real-world scenarios and should aim to re-use existing infrastructure where possible, minimize disruption, use space efficiently, and compress costs as much as possible. Technical teams must be prepared to show building owners how a particular measure will be installed practically.
• Don’t Expect 5–7 Year Paybacks on Decarbonization Measures – Deep decarbonization measures will likely have long paybacks. This is due to high upfront costs of electrification technology, supporting infrastructure, and invasive retrofitting. Working against these high-efficient electric systems is the price of electricity, which is 5 to 6 times more expensive per unit of energy than natural gas. Simple payback analyses are unable to capture the true value of decarbonization investments, including non-energy benefits. Ownership teams have to adjust their payback expectations when considering deep decarbonization measures. 
• Technological Innovation Isn’t the Only Innovation – There is new and exciting technology out there that has the potential to revolutionize the way we electrify buildings, but in the meantime, there are innovative approaches to electrifying buildings today with currently available technology. Purposeful dispatch of thermal energy sources and optimization for scalability, practicality, and affordability are innovative strategies. 
• Conditioning Exhaust Air – Recycling waste heat from exhaust air streams isn’t a new idea, but using the refrigeration cycle to extract and lift heat from exhaust air streams to serve heating loads is a new and innovative concept. Essentially, by air conditioning the exhaust air, like traditionally avoided toilet exhaust, heat can be recovered and lifted to higher temperatures by a heat pump to offset heating loads. The reverse is also true in the summertime, where exhaust air can serve as a heat rejection medium for the chilled water production of chiller plants. 
• Potential of Low Temperature Hot Water in Existing Chilled Water Coils – Low temperature hot water enables heat recovery and air source heat pumps to have a big impact, but reconfiguring all comfort heating systems in existing buildings to be low temperature is difficult and costly. The following approach offers a more practical alternative:
• Partially electrify high temperature hot water systems (i.e., perimeter systems) with water-source heat pumps and condenser heat recovery. This allows existing distribution infrastructure to stay in place – critical to wider spread of heat pump adoption. 
• Transition air handling unit steam or hot water coils to low temperature, which can be served by air source heat pumps. The cost and scope of coil replacements is much more manageable than replacing all heating systems with low temperature hot water infrastructure. In some cases, existing chilled water coils can be used with low temperature hot water and become a modified change-over coil, negating the cost of replacement. 
• Operations Team Integration: These decarbonization strategies are new and complex. Existing operations teams must be part of the design and implementation of these systems and training is of critical importance. A system that is designed to be low-carbon will not be successful if it is not operated per the design intent and understood thoroughly by those operating them. 
• Disruption and Phasing: Some of the best decarbonization strategies are also some of the most disruptive. Phasing must be based upon several factors including the rate of grid decarbonization, leasing turnover cycles, capital planning cycles, and equipment nearing its end of useful life.