Key to HSP’s strategy was understanding how to meet aggressive climate targets while addressing the practical objectives of their tenants—stable temperatures, fresh air, and reliable equipment—without placing too much onus on tenants to devise their own solutions or diligently manage their own consumption. To devise this approach, HSP divided building systems into three distinct spheres of ownership and influence. The first sphere encompasses the heating, cooling, and air distribution equipment under tenant control (e.g., radiators, fan coil units, etc.). The second sphere includes equipment commonly installed and maintained by the landlord, but controlled by the tenant (e.g., air conditioning units). The third sphere covers the core building infrastructure, under full control of the landlord, like cooling towers, boiler plants, and primary air handling units. This framework identified a major opportunity area in which to address carbon and energy goals: equipment supplied by the landlord but controlled by the tenant. Given this, the core objective was to create a scenario in which the landlord provides the solid grounding—such as the thermal network—for tenants to condition their spaces most efficiently. With this core functionality in place, tenants are afforded efficient systems performance simply by occupying the space and tapping into the building infrastructure. Incidentally, projected long term savings will be dependent on tenant plug loads and equipment fit-outs. The potential saving values displayed above are based on best-case scenario and CLCPA carbon projections.

As floors are phased in and more tenants take advantage of the thermal network, the amount of energy recycled across the building increases, incrementally improving the efficiency of 345 Hudson. By 2035, once fully implemented, whole-building energy use would be expected to drop by more than 30%. Total building carbon emissions would fall 90%, compared to a pre-retrofit baseline, with reductions increasing towards 100% as New York’s electric grid becomes fully renewable. These reductions reflect both emissions avoided by capturing 11GWh of waste heat currently rejected by the building (e.g., via cooling towers), and via the application of high-efficiency heat pumps. With a fully deployed thermal network and energy recovery ventilation, modeling reflects a scenario in which only 4 GWh of energy would be rejected. Notably, post-retrofit peak heating and cooling loads would fall dramatically—by 92 and 63% respectively—reflecting the significant benefits of capturing, sharing, and recycling heat across floors. The thermal network is key to electrifying buildings via heat pumps, as it reduces floor-level energy demand, allowing for smaller capacity heat pump systems.

345 Hudson’s 10-year deployment plan first targets improvements to the building’s core infrastructure, then phases in tenant retrofits, floor by floor. Select vacant floors will be retrofitted up front, with the hope of providing showcases to prospective tenants and their engineering staff to witness engineering solutions applied in practice—a critical step in moving the market given the systems’ novelty in New York. From there, additional floors will be phased in during periods of tenant turnover. As the project progresses floor by floor and use of the thermal network expands, heat pumps will supplant existing packaged terminal units and efficiency will improve dramatically. Updated floors will effectively become energy producers engaging in intra- floor heat exchange, rather than receivers of linear energy supply, benefiting the overall system. By 2025, HSP aims to connect the ambient loop at 345 Hudson to the neighboring building at 555 Greenwich, to share loads as needed and take advantage of its geothermal system. By 2030, the building will operate using only electricity, and take full advantage of the fully formed thermal network across all floors. With all floors connected, the thermal inertia (the energy stored within the hydronic network itself) of the whole building will often be substantial enough to store or release energy in response to changing utility rates or renewable energy generation—importing or exporting heat energy when needed, particularly during peak demand conditions. Reactive to grid demands, this solution allows the building to become an asset to the grid rather than simply a consumer.