The Challenge
An older office building had constant-volume ventilation with no recovery. Energy bills were high and the system could not meet current efficiency expectations for a lease renewal.
The Solution
The existing air-handling unit was retrofitted with a crossflow plate exchanger and variable-speed fans. Ductwork changes were minimal because the core slotted into the AHU section.
Results
- Fresh-air heating load cut substantially in winter
- Improved indoor air quality through steadier ventilation
- Payback achieved within a few heating seasons
Lesson
Retrofits favour compact, simple exchangers. A crossflow plate core delivered most of the savings of a wheel with far less disruption.
The Situation
In the Commercial Office HVAC Retrofit project the plant was expelling large volumes of warm exhaust while paying to heat incoming make-up air from ambient. Energy bills were high and the roof fans ran continuously, so the lost heat represented a clear, repeatable cost rather than a one-off event.
The Solution
We installed an air-to-air heat exchanger sized from measured airflow and temperature, with filtration ahead of the core and a condensate drain on the supply side. The supply fan was balanced against the exhaust to hold the building near neutral pressure, and a bypass damper allowed free cooling in mild weather. Control was kept simple: a temperature signal set the bypass position automatically.
The Result
After commissioning, supply air entered the heater roughly 50 percent warmer than before, cutting heater energy in line with that recovery. The measured payback fell inside the expected one-to-three season window, and a seasonal check showed the core holding its performance once a light cleaning routine was in place. The same approach has since been repeated on similar duties.
Frequently Asked Questions
How was payback proven? By comparing supply temperatures before and after at the same outdoor condition. Was extra maintenance needed? Only a seasonal inspection and occasional exhaust-side cleaning.
Practical Selection Checklist
For the Commercial Office HVAC Retrofit duty, confirm the measured airflow and the temperature difference between the two airstreams before specifying any unit. Choose the core type that matches the exhaust cleanliness and the recovery target, allow margin for fouling, and verify the pressure drop stays inside the fan curve. Place filtration ahead of the core and provide a condensate drain where the supply side may fall below the dew point.
When to Specify This Solution
Energy recovery suits any plant or building that expels warm exhaust continuously while drawing in fresh air that must be conditioned from ambient. Common candidates include make-up air units, drying rooms, commercial kitchens, paint booths, and general process ventilation. Where the annual cost of heating or cooling make-up air is material, a correctly sized exchanger usually pays back within one to three operating seasons.
Next Steps
Start by logging the supply and exhaust conditions for a full duty cycle, then size the core from those numbers rather than from nameplate estimates. Compare the projected energy saving with the equipment and installation cost to get a payback figure, and review the comparison and product guides for the specific configuration that fits your site.