How Smart HVAC Design Transformed a Historic D.C. Building for Modern Living

Overview

Originally built in the 1930s for the U.S. Department of Agriculture’s Cotton Division, the long-vacant Cotton Annex in Washington, D.C. was transformed by Carmel Partners into a modern office-to-apartment building—preserving its character while meeting today’s performance and energy standards through a thoughtful HVAC retrofit for this historic building.

JCM Associates led the HVAC design and coordination for the project, involving Havtech early to ensure the system approach was aligned with the building’s complex retrofit needs.

Challenge

The project required a flexible, energy-efficient HVAC system that preserved leasable space and met strict design and code requirements. Challenges included limited space for equipment and ductwork, aging infrastructure, and the need to comply with D.C.’s Building Energy Performance Standards (BEPS), while maintaining cost efficiency.

Solution

Havtech recommended a hybrid system combining Daikin Emerion VRV units and Rebel rooftop units. The VRV system’s modular layout and small-diameter refrigerant piping allowed for flexible zoning and installation within the building’s existing framework. Daikin Rebel rooftop units delivered high-efficiency air handling in a compact footprint, eliminating the need for extensive structural changes or mechanical rooms. Additionally, native controls simplified BAS integration reducing the need for third-party coordination during commissioning.

Conclusion

The Cotton Annex project demonstrates how a well-executed HVAC strategy can overcome retrofit challenges and deliver long-term results. The system preserves space, lowers energy and maintenance costs, and enhances tenant comfort while supporting code compliance and future-ready infrastructure.