The Department of Defense (DoD) has a large inventory of older, inefficient multizone heating, ventilation, and air conditioning (HVAC) equipment, that remains in service due to the high cost and facility disruption of system change out to modern technology. The objective of this project was to promote awareness and facilitate implementation of a low-cost, non-invasive controls retrofit for multizone air handling systems as an interim solution for improving energy efficiency of existing systems that can incur savings while delaying system replacement.

Technology Description

A previously demonstrated HVAC retrofit (ESTCP project EW-201152) converts constant volume multizone air handling systems to variable volume for energy savings. This current project makes that retrofit accessible through full spectrum implementation support tools and outreach activities. The stakeholder vetted products include: a fact sheet, a technical note, a pitch briefing, a scoping guide, a savings estimator, procurement package templates, a commissioning guide, and on-line training. Results were published on the Whole Building Design Guide, in industry journals, and presented at technical conferences. Potential DoD users were informed of available resources. These efforts support decision makers in fully evaluating the technology and implementing rapidly and successfully.

Demonstration Results

The project met all performance objectives by obtaining constructive review and enthusiastic feedback from pertinent reviewers throughout the process of developing implementation support tools and conducting outreach to interested parties. Many people are taking steps to implement. Modeling of the retrofit impact for typical applications showed a very favorable three to five year simple payback. This project cost only a fraction of potential agency-wide annual savings and positions the DoD for significant efficiency success.

Implementation Issues

The COVID pandemic shifted the project schedule and approach due to travel restrictions and team members occupied with the COVID response. The technical journal peer review and quality control coordination of the suite of implementation documents proved challenging but tractable. Project implementers need funding and time to adopt the technology.


Bush, J., Westervelt, E., Clark, B., Schwenk, D., Battisti, C., Morton, B., and H. FitzHenry, June 2022. Multizone to Variable Volume HVAC Controls Retrofit – Design and Implementation Suite. Whole Building Design Guide, https://www.wbdg.org/ffc/army-coe/design-guides.  

Westervelt, E., Battisti, C., Morton, B., and D. Schwenk, Feb 2021. Multizone Air Handler Controls Retrofit for Energy Efficiency, ASHRAE Transactions – 2021 Virtual Conference, Vol 127, Part 1, VC-21-C009.

Westervelt, E., and C. Battisti, Mar 2021. Upgrades for HVAC Systems. The Military Engineer, Pgs. 50-51.

Westervelt, E., Bush, J., and D. Schwenk, September 2022. Exploring a Multizone to Variable Volume HVAC Controls Retrofit ASHRAE Journal, Vol. 64, No. 9 Pgs. 32-47.

  • HVAC Controls,

  • Technology Transfer,

  • Air Handling Unit (AHU),