Retrofit-first engineering
We evaluate existing systems before recommending full replacement.
Critical-environment experience
Our work is planned around occupied hospitals, laboratories, and operational facilities.
Controlled execution
Access, electrical work, controls, startup, and balancing are coordinated as one retrofit plan.
Verified performance
Airflow, controls, speed, alarms, and restart behavior are checked before project closeout.
12,000 CFM | 7-Hour Window
Hospital Return Fan Retrofit for OR Support
Two ECM fans, custom duct transitions, a new control panel, and stable return airflow delivered under active hospital conditions.
30-Ton RTU | 7 Hours Onsite
Live Rooftop HVAC Replacement
Existing equipment removed, curb prepared, new RTU lifted into place, duct transitions fabricated, and the system commissioned within one onsite window.
2-Coil System Rebuilt as 3 Coils
Hospital Chilled-Water Coil Section Retrof
When like-for-like replacement would not fit, GRR redesigned the coil section around actual access, piping, drainage, and service conditions.
Hospital & OR Ventilation
Ventilation upgrades planned around limited shutdown windows.
EC Fan Array Retrofits
High-efficiency EC technology with project-specific energy-saving potential.
Commercial HVAC Modernization
of office towers, schools, and industrial facilities
Emergency HVAC Replacement
24/7 response for fan or system failure in critical spaces.
1. Assess
Existing airflow, equipment condition, access, controls, and shutdown limits.
2. Engineer
Retrofit configuration, equipment selection, transitions, controls, and installation sequence.
3. Coordinate
Facility access, electrical work, controls, balancing, and startup.
4. Install
Field execution planned around operational constraints.
5. Verify
Airflow, controls, alarms, restart, and system performance.
“GRR’s team handled our AHU retrofit in one of the busiest wings of the hospital with incredible precision. They worked around patient schedules, coordinated seamlessly with infection control, and finished on time. The new EC fan array immediately improved airflow balance and reduced our energy load by almost 25%. It’s a major upgrade we actually felt the same week."
“We had been postponing a fan wall replacement for years due to the risks involved with downtime. GRR designed a phased installation that let us keep the labs operational the entire time. Their engineering insight and responsiveness were exceptional. The end result was quieter operation and easier maintenance access — exactly what our staff needed.”
Weill Cornell Medicine
Director of Facilities Operations
“Our research buildings needed serious ventilation modernization after several system failures. GRR provided a clear plan, transparent communication, and flawless execution. What impressed me most was how they adjusted to site constraints without delays. The retrofit exceeded expectations in both energy performance and reliability.”