The Building

The historic building in Fort Myers, FL, formerly a small museum, was renovated and more than doubled in size to accommodate office space and meeting rooms. The original floorplan of 8,246 ft2 was entirely renovated, except for the restrooms, bringing the total size to 21,848 ft2 . The owner decided to target LEED Gold certification, under LEED v4 BD+C for new construction and renovations.

HVAC Energy Optimization Measures

TLC Engineering designed the HVAC using Variable Refrigerant Flow (VRF) systems and a pair of high-efficiency Dedicated Outdoor Air Systems (DOAS). This HVAC design, combined with all the other energy saving measures related to lighting, windows and building construction, is enabling them to apply for 12 energy optimization LEED points relative to an ASHRAE 90.1-compliant baseline design.

To earn more LEED points, HVAC Load Reduction (HLR) modules were added to the design. HLR modules clean indoor air of contaminants, and thereby reduce the amount of outside air required for ventilation in accordance with the ASHRAE 62.1 Indoor Air Quality Procedure (IAQP). Based on IAQP calculations for this building, TLC added two HLR 1000E-R modules to be installed on the rooftop. With this new design, the two DOAS systems were modified to treat a mix of return air and outside air. Figure 1 shows a comparison of the two design schematics.

The Impact of HLR Modules

Energy Savings

The HLR modules reduce the total outside airflow by 2,282 CFM. This results in an incremental $4,000 annual energy savings * on an already highly-efficient HVAC system. The building is expected to be open 8am-6pm, 7 days per week, with outside air assumed to be shut off at night, so HLR savings are based on daytime hours only.

The incremental energy savings is 7.4% above the original LEED design, and brings the total energy savings to 37% relative to the baseline.

I have been extremely impressed with the energy efficiency impact of HLR technology. I plan to recommend this technology for all HVAC designs to cost effectively achieve additional LEED points.”

Alyssa Faircloth
LEED Green Associate, CPB Energy Service Engineer TLC Engineering for Architecture, Inc.

First cost savings

By using HLR modules, TLC engineering reduced the overall cost of the HVAC system because the HLR module installed cost is less than the following estimated savings on other HVAC equipment and installation:

  • Eliminated DCV: $36,000 deduct
  • Lower capacity DOAS systems: $29,000 deduct

Total savings on other HVAC system costs: $65,000 savings

Although the owner chose not to, an ERV could have been removed from the design while still complying with ASHRAE 90.1 and LEED. This was due to the percentage of outside air on one of the DOAS systems falling out of the range that requires an ERV. Eliminating this ERV would have produced another $2,000 in savings.

By specifying HLR modules, we are reducing the first cost capital expenditures for our client, while simultaneously giving them a more energy efficient HVAC solution. The extra LEED points, the reduced intake of outside air pollution, and the intelligent IAQ management are extra benefits that essentially come for free.”

Carmine Rende Jr.
PE, CEM, LEED AP, CSDPE, CxA Associate / Senior Project Engineer TLC Engineering for Architecture, Inc

Intelligent Indoor Air Quality (IAQ) Management

Just like the thermostat revolutionized temperature control in buildings, HLR modules are doing the same for IAQ. Rather than provide the owner with a static ventilation scheme, TLC’s use of HLR modules enables the building to have actively managed indoor air quality. HLR modules can respond to the changing conditions of IAQ by increasing or decreasing air cleaning. Ultimately, this project received an Honorable Mention for the 2021 National ASHRAE Technology Awards, Public Assembly.

LEED points

LEED points that are being applied are:

  • Energy optimization
    • 2 points
  • EQ Enhanced Indoor Air Quality Strategies
    • 1 point for CO2 monitoring
    • 1 point for Exemplary performance
  • EQ Indoor Air Quality Assessment
    • 2 points for IAQ testing

View as PDF

Featured in the August, 2021 edition of ASHRAE Journal

Challenges: Improve HVAC energy consumption to meet LEED Gold Certification
Solution: Two enVerid HLR modules installed on rooftop to scrub air of contaminants and reduce the amount of outside air ventilation required


  • $65,000 savings on HVAC systems
  • Eliminated DCV
  • Lower Capacity DOAS
  • $4,000 per year energy savings
  • Extended particulate filter life
  • 46% less outside airflow needed
  • Energy Optimization: 2
  • EQ Enhanced IAQ Strategies: 2
  • EQ IAQ Assessment: 2
  • Achieved LEED v4 Gold
  • ASHRAE National Technology Award, Public Assembly Honorable Mention 2021