RUHL TecDesign × Rockrose · 200 Water Street Project

Closed-loop heat recovery for a 31-story Manhattan residence

200 Water Street Ventilation Retrofit

Rebalancing airflow, recovering exhaust energy, and creating a scalable path toward Local Law 97 compliance for large multifamily buildings.

See how it works View impact data

541,000

sq ft

31 floors · 576 residential units

26%

energy reduction

ventilation retrofit vs. baseline

664

tCO₂e/yr saved

annual ventilation retrofit impact

weeks

kickoff to closeout

Engineering approach

Reduce, recover, modernize.

Fix pressure imbalance and recover exhaust energy before scaling HVAC.

Reduce Loads

Cut heating and cooling demand before adding larger systems.

Recover Heat

Transfer exhaust energy to incoming outdoor air without mixing streams.

Modernize HVAC

Coordinate air handling, heat recovery, and staged water-source heat pump.

The challenge

Multiple roof exhaust systems operated continuously without heat recovery or supply coordination, producing a 284% negative-pressure regime and high infiltration losses through doors, windows, and façade leakage.

The solution

Centralized exhaust and dedicated outdoor-air supply units connected by a closed-loop refrigerant heat recovery circuit, with water-source heat pump only when recovered heat cannot meet setpoints.

Organizations

Project leadership, funding, technology, and support.

RUHL TecDesign

Lead MEP design engineering

Rockrose

Owner / development partner

NYSERDA

Heat Recovery Program funding

This project is supported by the German Federal Ministry for Economic Affairs and Energy as part of the Renewable Energy Solutions Programme of the German Energy Solutions Initiative.

German Energy Agency (dena)

The German Energy Agency (dena) is a centre of excellence for the applied energy transition and climate protection. dena studies the challenges of building a climate-neutral society and supports the German government in achieving its energy and climate policy objectives. Since its foundation in 2000, dena has worked to develop and implement solutions and bring together national and international partners from politics, industry, the scientific community and all parts of society. dena is a project enterprise and a public company owned by the German federal government. dena's shareholder is the Federal Republic of Germany.

Learn more

German Energy Solutions Initiative

With the aim of positioning German technologies and know-how worldwide, the German Energy Solutions Initiative of the Federal Ministry for Economic Affairs and Energy (BMWE) supports suppliers of climate-friendly energy solutions in opening up foreign markets. The focus lies on renewable energies, energy efficiency, smart grids and storage, as well as technologies such as power-to-gas and fuel cells. Aimed in particular at small and medium-sized enterprises, the German Energy Solutions Initiative supports participants through measures to prepare market entry as well as to prospect, develop and secure new markets.

Learn more

Renewable Energy Solutions Programme (RES Programme)

With the RES programme, the German Energy Solutions Initiative of the Federal Ministry for Economic Affairs and Energy (BMWE) helps German companies in the renewable energy and energy efficiency sectors enter new markets. Within the framework of the programme, reference plants are installed and marketed with the support of the German Energy Agency (dena). Information and training activities help ensure a sustainable market entry and demonstrate the quality of climate-friendly technologies made in Germany.

Learn more

System strategy

Airflow rebalanced to reduce infiltration losses.

The proposed system reduces excessive exhaust, increases coordinated supply air, and moves the building toward balanced/slight positive pressure.

Exhaust Airflow

exhaust reduced and consolidated

CFM

Baseline74,780 CFM

After Retrofit21,480 CFM

Supply Airflow

supply increased to support slight positive pressure

CFM

Baseline26,330 CFM

After Retrofit28,316 CFM

284% negative pressure → balanced / slight positive

Ventilation losses collapse when exhaust and supply air are coordinated.

Closed-Loop Run-Around Heat Recovery

R454B air–refrigerant–air circuit transfers sensible energy between exhaust and supply air without direct mixing.

Centralized Exhaust + Dedicated Supply

Existing roof exhaust streams are consolidated into paired exhaust and 100% outdoor-air supply units.

Water-Source Heat Pump

Heat pump acts as a secondary stage only when heat recovery alone cannot meet supply-air setpoints.

Implementation

Roadmap to Net Zero

A phased view of the broader retrofit strategy, including supporting controls and adaptation measures.

Balance + Recover

Reduce apartment exhaust airflow, recover roof exhaust energy, add reversible WSHP and low-temp hot/chilled water storage; optional ASHP can inject heat into ITEN™.

Wastewater Recovery

Recover heat from the internal sewer system with water-source heat pumps and low-temperature energy storage.

DHW Low/Mid Zones

Introduce booster heat pump DHW for low- and mid-zones using high-temperature storage to reduce summer steam boiler operation.

DHW High Zone

Extend booster heat pump DHW to the high zone and use rooftop condensing boilers for heat injection into ITEN™.

Boiler Cascade

Install rooftop condensing boiler cascade using existing gas service and dismantle second-floor steam boilers.

Public Sewer Connection

Connect wastewater heat recovery to the public sewer system with WSHPs and low-temperature storage.

Supporting measures: BMS upgrades, smart automation, hydronic optimization, solid-state heat pump replacement, app-based room control, and demand-based primary flow control.

Adaptation measures: building envelope optimization with sun protection screens to manage climate-related cooling load increases.

Measured impact

Clear evidence for builders, owners, and engineers.

11.9M

kBtu/yr saved

annual ventilation retrofit energy savings

~72%

heat recovery effectiveness

closed-loop system

CO₂ Emissions vs. LL97 Limits

Baseline and projected retrofit emissions shown against the same Local Law 97 thresholds.

50% projected CO₂ reduction

Projected Energy Use: Baseline vs. Retrofit

A simple before/after view using the energy values from the project data.

58% reduction in energy use

Baseline Energy Use45,919,715 MBtu/year

Expected Energy Use After Retrofit19,179,665 MBtu/year

010M20M30M40M50M MBtu/year

Emission Reduction Waterfall

Bridge from baseline emissions to projected retrofit emissions. Yellow bars start at the previous level and step down to the final retrofit value.

Units: tCO₂e/year

4,000

3,000

2,000

1,000

Emissions (tCO₂e/year)

3,154

Baseline Emissions

553

Ventilation Initiatives

733

ITEN™ + Heat Pump

DHW Electrification

Smart Controls

101

Sun Protection Film

Additional ECM Margin

1,586

Projected Retrofit

Emission pathway measures

Broader ECM reference from the project data: Exhaust Air Energy Recovery + Balancing: 853 tons · ITEN™ + Heat Pump + Wastewater HR: 1,068 tons · DHW Booster Heat Pumps: 93 tons · Smart Automation + Hydronics: 67 tons · Building Envelope Optimization: 148 tons.

What RUHL delivers

A replicable retrofit model for multifamily decarbonization.

RUHL's scope connects decarbonization roadmaps, engineering integration, and measurement frameworks for heat recovery, ventilation balance, hydronic optimization, and heat pump integration.

Decarbonization Roadmaps

Engineering & Integration

Measurement & Verification

Heat Recovery + HVAC Modernization