The Challenge

The corporate headquarters building has been spending significant money cooling and heating outside air for ventilation, all while knowing that the outside air could no longer be considered “fresh air” due to high levels of air pollution. Further, numerous studies show poor indoor air quality (IAQ) directly impacts people’s productivity, and recent studies from Harvard and Lawrence Berkeley Labs have shown high carbon dioxide levels alone can cause a 50% decline in cognitive performance. Given the important financial decisions being made in the building, not to mention the health benefits, maintaining good air quality is a high priority.

The building management team identified a solution that would not only reduce energy consumption of ventilation, but also reduce the flow of outside air pollution and actively monitor and manage air quality in the building.

The Building

Constructed in the 1980s, the global corporate headquarters building is located in the heart of Manhattan, New York, NY. The 1.35 million square foot building has 44 floors of office space and a maximum occupancy of 6,863. Considered Class A office space, the building achieved a LEED Gold rating in 2013, and is Energy Star certified. Critical banking activities occur inside, and so excellent indoor air quality is important to ensure maximal cognitive performance.

New York City is considered a non-attainment zone by the EPA, which means it often has a high concentration of unhealthy ozone.

In addition, this area of New York has a lot of traffic, which generates ultrafine particles and combustion gases. Reducing the intake of these outdoor pollutants into the building is highly desirable.

This project demonstrated both energy savings and an improvement in IAQ immediately upon completion.”

Marc Hourican, PE
Syska Hennessy

HVAC System Overview

The heating, ventilation, and air conditioning (HVAC) system uses 16 air handling units (AHU) all located on the 7th and 28th floors, which are then connected to the rest of the floors via vertical risers through the building. (see Figure 2)

The AHUs are inline-supply mixed air type. Inline return air fans direct air into a plenum return to the AHUs while outside air is introduced through a louvered façade next to each AHU. Outside air and return air dampers regulate the mixed air.

All AHUs on-site have a dual outside air damper array:

  • Minimum outside air actuated dampers (2 actuators per damper)
  • Maximum (economizer) actuated dampers (6 actuators per damper)

Both actuator arrays are proportionally actuated and controlled by the building management system (BMS).

The M&V data and third-party IAQ testing resulted in a high level of accountability by the project team.”

Marc Hourican, PE
Syska Hennessy

Building Management System Overview

The building has a Siemens Apogee BMS that monitors and controls the HVAC systems. An example of a typical control dashboard for the AHU is shown in Figure 3.

The BMS also monitors the building chillers, fans, and energy usage. Chillers located on the 7th floor provide chilled water to all the VAV AHUs on the 7th and 28th floors that condition all the return air and outside air introduced to the AHUs on the 7th and 28th floors.

The Project

The kickoff began with a site survey by the enVerid team of the building mechanical layout and identification of potential locations for integrating the HLR 1000E systems. The team took snapshot baseline measurements of CO2 and reviewed current energy usage and metering. The number of HLR modules needed and the resulting outside air reduction were calculated according to ASHRAE Standard 62.1 Indoor Air Quality Procedure (IAQP) for a typical office building.

The site survey assessed the spaces that are cooled and heated (including stairways and closeted spaces), and documented the existing hydronic systems, power meters and all VAV and AHU interactions in the building, including dampers, sensors and exhaust systems.

The survey measured and planned for the positioning and installation of the HLR modules, ensuring that they would fit. In this phase, the team also checked for wireless connectivity options and suggested connection points to the BMS.

Accurately managing outside air intake is critically important for an accurate evaluation of the energy savings. Test and Balance measurements were performed by a third party certified company for a variety of damper positions for both outside air and return air. The building was originally designed for 20% outside air (as a percentage of total supply air), but with HLR modules cleaning the air, only 3% outside air was required to maintain good IAQ. Because the building has relatively little exhaust, 3% outside airflow was sufficient to maintain positive pressure in the building.

HLR Module Placement

The 7th floor mechanical room has space for an array of 10 HLR 1000E modules on both the north and south sides of the floor, next to the return air fans of the AHUs (see Figures 4 and 5). This placement allowed for the HLR modules to clean the return air before it entered the AHUs.

Since the HLR modules are installed in a plenum, no ductwork is required for the HLR module’s indoor air inlet or clean air outlet. The only duct connectivity required from each array is the exhaust duct, which connects to existing exhaust louvers on the façade, enabling the captured contaminants to be released outside the building when the HLR modules automatically regenerate their sorbents.

The north side of the 28th floor has an array of 20 HLR 1000E modules between the AHUs (see Figures 6 and 7)

Like the 7th floor, the HLR modules are installed in a plenum, so no ductwork is required for the HLR modules’ indoor air inlets and clean air outlets. The only duct connectivity required from each array is for the exhaust, which connects to existing exhaust louvers on the façade and allows the captured contaminants to be released outside the building when the HLR modules regenerate their sorbent.

The electrical service on the 7th and 28th floors was obtained from existing sources identified by the building engineering team.

The HLR module controls were integrated with the building through the central BMS in coordination with the building team. Using BACnet, the HLR modules exchange information with the BMS, such as operational status and outside air damper position.


In the installation phase, the enVerid project team selected and supervised electrical and mechanical subcontractors with the customer’s approval. 40 HLR modules in total were installed in the building’s mechanical rooms. A slip-stream of return air from the plenum is drawn into the HLR module by its integrated ECM fans, and after going through the sorbent cartridges, the scrubbed air goes back into return air plenum. Air from the plenum is also used for regeneration. Regeneration exhaust from the HLR is ducted to an existing exhaust duct or pressure relief in each mechanical room. Figure 8 shows the adsorption and regeneration paths.

Post-installation, the enVerid project team continues to work with the building management team to optimize energy, IAQ and environmental comfort.

Energy and Air Quality Measurements

Using HLR Technology, the building can take advantage of ASHRAE 62.1 Indoor Air Quality Procedure (IAQP) instead of using the ASHRAE 62.1 Ventilation Rate Procedure (VRP). VRP relies solely on outside air ventilation to maintain IAQ, whereas the IAQP allows for the use of sorbent-based indoor air cleaning which thereby reduces the required outside airflow and the corresponding energy consumption on the HVAC systems.

Energy savings for cooling were measured by comparing chiller consumption trends on the BMS when (a) HLR systems were in operation and there was reduced outside airflow, versus (b) when the HLR systems were off and the mechanical systems operated with the outside air damper open to design conditions. Similarly, during the winter, the BMS trend data on steam and gas consumption for heating is used to compare energy consumption with and without the HLR modules operating.

For indoor air quality (IAQ), contaminant concentrations were measured prior to the HLR operation, then again after the HLR module had been installed and running for at least one week. Indoor air quality monitoring was performed per US Environmental Protection Agency (EPA) standards and the results were analyzed and certified by an independent lab (PRISM Analytical Technologies).

This investigation included environmental and indoor air quality sampling of temperature, relative humidity, carbon dioxide (CO2), carbon monoxide, ozone, a full scan of speciated (separated by species) volatile organic compounds (VOCs), including aldehydes (e.g., formaldehyde) and TVOC, as well as particulate matter with aerodynamic size of less than 1, 2.5, 4, 7, and 10 μm (PM 1, PM 2.5, PM 4, PM 7 , PM 10 ). These include all the contaminants of concern (COC) found in office buildings. The investigation included sampling throughout the building at six different locations (figures 9, 10 and 11). Instruments used were calibrated before each use and functioned within the limits of performance specifications appropriate for pollutants measured in indoor environments.

The Energy Savings Impact

803 Ton Reduction in Peak HVAC Load

The HLR system reduced peak HVAC load by 803 tons. This savings impacts the “demand charges” on the building utility bill, which in many locations has a major impact on the overall cost of electricity. In fact, the building expects to save $135,000 per year in electricity demand charges. Furthermore, reducing the load should extend the life of the existing HVAC systems and when the building replaces the HVAC equipment in the future, the peak capacity required will be 803 tons less, providing significant savings in capital expense. At $2,000/ton for a chilled water system, the building could save $1,606,000 in capital expense on HVAC equipment in the future.

Energy Savings of over $400,000 per Year

The energy savings for reducing outside air in this building equates to 456,656 kWh annually in cooling energy, and 4,680,867 kBTU in heating energy. To ensure the accuracy of these numbers, these annual savings are calculated using an energy model that incorporates hourly temperature and humidity data for New York City, and uses the same HVAC system set points and building operating parameters as those implemented in the client’s headquarters building.

Energy Savings Verification Methodology

The underlying principle of validating the savings projections is to demonstrate that measured energy impact closely matches the calculated energy impact under a variety of known conditions. This section shows the measured savings from the summer of 2017, and then compares these to the calculated results for the same period of time, using the same weather data and building setpoints. Measurements were performed by metering energy trending data (as explained earlier).

Measurements were taken with and without HLR modules in operation. The first phase of the “Measurement and Verification” (M&V) during July to mid-August reduced daytime outside air by 55,000 CFM when using HLR modules. The second phase of the M&V started in late-August and reduced daytime outside air by 132,000 CFM when using HLR modules, based on ventilation rate calculations using the ASHRAE 62.1 Indoor Air Quality Procedure. The weather during the second phase was unseasonably cool (enthalpy less than 27) by that point and the building was operating in economizer mode, when outside air reduction no longer saves energy. Nevertheless, it was possible to assess the calculator’s accuracy using the first phase data. Figure 12 shows the measured daily energy usage, excluding economizer days, when the outside air was reduced by just 55,000 CFM.

Validation Results

Since the building operations were most consistent from 8am – 5pm, the daily energy data from this time period was used to do a comparison between the measured energy savings and the energy calculator’s results. Figure 13 displays measured data of daily HVAC energy consumption between 8am-5pm during the first phase of M&V. Table 2 shows energy calculator results using the same building operating parameters and setpoints, the same 8-5pm time period, and using years in which the July-August temperatures and humidity were similar.

The calculator projected savings resulted in remarkably similar result: 5,194 kWh – within 2% of the measured data of 5,301 kWh. The analysis highlights the accuracy of the calculator, giving confidence in its projection of future savings.

Water Savings of $10,361 per Year

The HVAC system was also able to conserve on cooling tower makeup water but a separate water meter wasn’t available, so this information was not included in the overall project savings. However, based on standard calculations, the building should be using 3,043,000 fewer gallons of water and saving $10,361 in water charges.

Earned a $60,544 Energy Rebate

The local electric utility offers rebates for energy efficiency projects which resulted in a rebate of $60,544.

Additional Savings:

  • Filters: An 85% reduction in outside air can extend the lifetime of the outside air filters by 2-4x. Outside air often passes through high efficiency filters, requiring significant fan power. By reducing outside air volumes, HLR modules can also create meaningful fan energy savings. These savings were not metered and therefore not included in the above energy savings analysis.
  • Reduced Corrosion: A reduction in outside air intake provides several secondary benefits that include extending the useful life of the existing mechanical equipment and ductwork.

Indoor Air Quality Results

The results shown below represent data from both onsite electronic gas sensors and independent lab analysis of air samples collected in six different locations in the building.

Inorganics: Inorganic compounds like carbon dioxide and carbon monoxide were kept well below thresholds. Particulate matter of various sizes was found to be at very low levels inside the building (Table 3) although outdoor concentrations were high (25 µg/m 3 ). This was expected as higher efficiency MERV 17 filters are used in the building. These filters, also known as HEPA filters, are specified to remove >99.97% of small particle sizes. This includes but is not limited to carcinogenic materials, bacteria, and viruses that are within the size range. Reducing the outdoor air to a minimum and turning the HLR modules on will decrease particle loading on the filters. This will lead to extended life of the filters, as well as a reduction in fan energy given that HEPA filters created a significant resistance to air flow.

Impact on ozone (O3) levels is particularly notable. Indoor ozone measured concentrations when the outside air was at the conventional setting (and the HLR modules were off) reached 15 ppb. Measured ozone concentrations outdoors reached 150 ppb. Reducing the outdoor air by turning on the HLR modules significantly reduced indoor ozone levels (see Figure 14). This represents a meaningful health benefit since ozone levels as low as 20 ppb have been shown to increase mortality, and statistical approaches suggest that “safe O3 levels would be lower than 10 ppb.” (Bell et. al. 2006)

Organics: Lab analysis included a full breakdown by VOC molecular species, including those identified by the U.S. Green Building Council (USGBC) as contaminants of concern. The results, shown in Table 4 below, demonstrate the air scrubbing effectiveness of the HLR Technology.

Mixtures of Concern (MOC), introduced as part of ASHRAE Standard 62.1-2016 IAQP, are two or more hazardous substances that have similar toxicological effect on the same target organ or system. Their combined effect should be considered additive as exposure to low concentrations of MOC may cause adverse effects to human health 4 . Table 5 shows the identified MOC and the organ-impact related characteristics of each COC.

To meet ASHRAE compliance, the ratio of the measured concentration of each contaminant to its exposure limit is determined, and the sum of these ratios for each MOC group should not be greater than one. The result of these calculations is shown in the bottom row of Table 5. The sum of each mixture is below 1, and therefore meet the limit of the MOC guidelines from ASHRAE.

Additional IAQ benefits of using HLR modules

In a dense, polluted city like New York City, reducing the outdoor air is beneficial to reduce the intake of outdoor generated pollutants such as particulate matter and ozone. In addition, there are other implications for reducing outdoor air that are related to indoor air quality.

  • In harsh weather conditions, if the building is not able to maintain comfort conditions (unusual heat wave or cold front), typically the building will be run with very little outside air. Having the HLR modules running with minimum damper position will maintain the comfort of the building’s occupants while also maintaining indoor air quality under such conditions.
  • In cold temperatures (around 28˚F), the building HVAC system’s “freeze stat” will command the outside air to be shut. A freeze stat is a temperature sensing device that gets triggered when it is cold to prevent HVAC coils from freezing, resulting in permanent damage. By using HLR modules, the reduced outside air is less likely to trigger these conditions and therefore positive pressure can still be maintained and air quality can be maintained with the combination of air cleaning and some outside air.
  • In the event of a bio-terrorism attack outside, an emergency protocol shuts down the outside damper. Having the HLR system in place can help maintain IAQ even during such emergencies, with no outside air.


The corporate headquarters building turned to enVerid for a solution to save on energy costs, reduce greenhouse gas emissions, and maintain a healthy, productive indoor environment.

Installation of 40 HLR modules was completed in June 2017, and a summer measurement and verification confirmed the projected energy savings and the excellent indoor air quality achieved.

Results: Reduced HVAC capacity, Improved Energy Efficiency and Indoor Air Quality (IAQ)

  • 803 tons reduction in HVAC cooling peak load
  • $403,000 energy cost savings annually
  • 1,361 metric tons annual reduction in greenhouse gases
  • $10,361 in water and wastewater savings
  • $60,544 utility rebate
  • Extended particulate filter life
  • All COC and MOC are maintained at a healthy level
  • Reduced influx of outside pollution
  • Better indoor air comfort
  • 85% reduction in outside air (IAQP using HLR Technology vs. VRP)

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Building Owner & Tenant: Major Financial Services Firm
Climate Zone: 4A
Deployed: June 2017
Location: Manhattan, New York, NY
Industry: Financial services
Employees: Over 50,000
Revenue: Over $35 billion
Challenges: Help client reach energy efficiency goal of reducing energy emissions by 15%, and specifically in 44-story global headquarters building.
Solution: 40 enVerid HLR 1000E modules to scrub air of contaminants and reduce volume of outside air ventilation required.


  • 803 tons reduction in HVAC cooling peak load
  • $403,000 annual energy cost savings
  • $10,361 in water savings
  • $60,544 utility rebate
  • 1,361 metric ton reduction in greenhouse gases
  • Extended particulate filter life
  • All contaminants of concern (COC) maintained at a healthy level
  • 85% average reduction in outside air (IAQP using HLR Technology vs. VRP)
  • Reduced intake of outside pollution