Recovery in the Whole Building
A building's energy use is an energy balance: gains (people, equipment, sun) minus losses (envelope, ventilation). Recovery attacks the ventilation loss directly.
The Ventilation Load
Ventilation brings in untreated outside air, so it adds both a heating load in winter and a cooling load in summer. Recovery moves that energy back before the coil sees it.
Quantify the Impact
If recovery removes 70 percent of the ventilation load, the coil, plant, and distribution are all sized smaller. That cuts both capital and running cost.
Standards Context
EN 16798 and ASHRAE 90.1 set recovery expectations because this lever is so effective at the whole-building scale.
Before You Start
A successful Heat Recovery and Building Energy Balance project begins with measurement. Record the supply and exhaust airflow rates, the temperatures on each side, and the hours the system runs per year. Note any contaminants in the exhaust and the available space for the core and ductwork. These figures decide both the type of exchanger and whether the payback makes sense.
Step-by-Step
First, choose the exchanger type from the air cleanliness and recovery target. Second, size the core using the measured airflow and the log-mean temperature difference, leaving margin for fouling. Third, lay out the duct path so the exhaust is filtered before the core and the supply side has drainage if it may condense. Fourth, add a bypass for free cooling and wire the fans to a simple control. Finally, commission the unit and record baseline temperatures.
Verification
After startup, compare the pre- and post-installation supply temperatures at the same outdoor condition. A steady recovery of 50 percent or more confirms correct sizing. Re-check each season and clean the exhaust side when the recovered temperature begins to fall, because fouling quietly erodes performance over time.
Frequently Asked Questions
Do I need a bypass? In most climates yes, so the system can free-cool when outdoor air is mild. How is sizing done? From measured airflow and the log-mean temperature difference, not from estimates.
Practical Selection Checklist
For the Heat Recovery and Building Energy Balance 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.