High Rise / Low Carbon Partner Profile: 345 Hudson

Introduction

With a bold plan that imports expertise from a highly efficient Nordic model, Hudson Square Properties (HSP) is looking to fully decarbonize their commercial building portfolio—starting with 345 Hudson. While novel for the U.S. market, the HSP roadmap utilizes thermal networking techniques vetted across decades in other regions. Rather than rely on the innovation of new technologies, this approach innovates through design. In effect, the HSP innovation is in how they look at building systems—using familiar parts to create a unique, inexpensive, and highly efficient system to deliver the high-quality office environments that today’s tenants demand.

About

HSP is among the inaugural cohort of real estate partners convened by New York State Energy & Research Development Agency for their Empire Building Challenge, a public-private partnership with leading real estate groups to decarbonize New York’s existing building stock by designing and implementing innovative tall-building cold-climate retrofits, tackling systemic market barriers, and attracting the world’s top solutions providers to the New York market. The challenge’s first cohort of partners collectively represent more than 130 million square feet of New York real estate, and a massive influence over regional energy demand. If fully retrofitted to HSP’s level of peak load reduction, the combined impact would enable New York City to shut down the Astoria 5 coal power plant. In January of 2022, New York State Governor Kathy Hochul announced the awarding of $20 million to HSP and three other real estate partners for their innovative proposals for high-rise low-carbon retrofits. This profile explores how HSP’s 345 Hudson retrofit meets the EBC’s key objectives: significantly reducing building Energy Use Intensity (EUI), removing on-site fossil fuel combustion, producing a low-cost, high-value, replicable solution, engaging leading international solutions providers, and eliminating market barriers.

Project Highlights

Approach

The foundational innovation in HSP’s retrofit strategy at 345 Hudson is to see heat not as something to be ejected in summer and supplied in winter, but as a resource to be shared among different spaces year-round. For large portions of a typical year, many offices heat some spaces while simultaneously cool others, with separate heating and cooling systems working independently to add heat to the former and remove heat from the latter. The HSP model provides an integrated system that allows these spaces to share that heat—not just within an individual floor, but between different floors in the same building, and even between buildings, dramatically improving energy performance. Importantly, HSP’s approach can be applied in phases on a floor-by-floor or tenant-by-tenant basis, working with rather than against the natural lease turnover cycle, spreading costs across the term of their project and taking advantage of already planned capital expenditures.

Project Overview

Like many pre-war buildings in Manhattan, Inwood Park Apartments (IPA) grappled with aging infrastructure and operating systems that impacted residents’ comfort and costs. Additionally, the historic property faced impending penalties from local building energy laws.

Struggling to understand what was needed to comply with NYC’s Local Law 97 (LL97), the medium-sized housing cooperative conducted an independent energy audit. The building also contacted NYC Accelerator and received free advice on LL97 compliance strategies, help prioritizing building energy upgrades, and access to technical resources and tools. With NYC Accelerator’s support, IPA made energy-saving improvements and is working toward LL97 compliance for 2024 and beyond.

The Opportunity

IPA’s historic roof and original heating system were reaching the end of their life span, causing uneven temperatures across the building. With potential LL97 penalties looming in 2025, the housing cooperative reached out to NYC Accelerator for help making energy-saving improvements to its roof, boiler, and lighting. IPA aimed to increase resident comfort and temperature control while lowering energy consumption.

System Innovations

The thermal network proposed for 345 Hudson consists of a repurposed condenser water loop, or thermal spine, running vertically from floor to floor. From this thermal spine, hydronic loops run outwards within each floor, allowing for efficient local energy exchanges between zones, using water as a medium. The result is a highly efficient, self-regulating network designed to reach a temperature close to the desired operative level by capitalizing on the natural variability in temperatures across zones and floors. From this balanced state, floor-level water-source heat pumps, connected to thermal spine, cool or heat on demand, at critical junctures closest to the receiving zones. Note that the thermal network’s stable temperature range levels the playing field, providing a solid foundation for optimal heat pump operating conditions, relative to highly fluctuating outdoor temperatures. Water will then be run through high-temperature active chilled beams, ceiling mounted heating/cooling coils supplied with water from the thermal network. Floors are conditioned as air flows across the coils. Low-temperature hydronic radiators connected to the thermal network provide additional heating and cooling capacity at the perimeters of each floor. A high energy recovery Dedicated Outdoor Air System (DOAS) on the rooftop provides fresh air to the chilled beams, which induces additional airflow across the coils. Nearly 90% of the energy from exhaust air is recaptured and used to temper incoming air.

Project Team

Owner/Operator: Hudson Square Properties (Norges Bank, Trinity Church Wall Street, Hines) Consulting Engineer: Urbs | Urban Systems Heat Pump Manufacturer: Energy Machines Engineer of Record: Jaros, Baum & Bolles Thermal AI Integration: Noda Transition Risk Insurance: Willis Towers Watson Control Software: Modio Energy Storage Analyst: Blueprint Power Carbon Reduction Certification: International Finance Corporation

The Road Ahead

HSP’s 10-year deployment plan for 345 Hudson first targets improvements to the building’s core infrastructure, then phases in tenant retrofits, floor by floor. First, the primary air handling unit will be replaced with a high energy recovery DOAS system, followed by installation of the thermal spine and a building management system. As the project progresses floor by floor and use of the thermal network expands, heat pumps will supplant existing packaged terminal units. Updated floors will effectively become energy producers engaging in intra-floor heat exchange, rather than receivers of linear energy supply, benefiting the overall system. Looking beyond 345 Hudson, HSP seeks to replicate the same set of solutions across their whole portfolio, a process that will see increasing returns to scale as local trades and service providers are familiarized with new technologies, international supply chains are strengthened, and innovative market actors enter the New York market—key objectives of NYSERDA’s Empire Building Challenge.

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