| Parameter | Without ERV | With ERV | Unit |
|---|
This DOAS sizing calculator estimates a dedicated outdoor air system from occupancy and design conditions. Enter building area, space type, diversity, ventilation rates, summer and winter outdoor conditions, supply temperatures, and energy recovery effectiveness; the tool returns total outdoor air CFM, design occupants, total and sensible cooling coil capacity, heating coil MBH, and the cooling tons an ERV saves.
A DOAS conditions ventilation air separately from space sensible cooling, which improves humidity control and pairs well with fan coils, VRF, chilled beams, or radiant systems. The summary table contrasts the system with and without energy recovery so the value of an ERV is clear.
| Quantity | Equation |
|---|---|
| Outdoor air (62.1) | Vbz = Rp · Pz + Ra · Az |
| Total coil load | BTU/hr = 4.5 × CFM × Δh (BTU/lb) |
| Sensible coil load | BTU/hr = 1.08 × CFM × ΔT (°F) |
| ERV-conditioned air | T‑leaving = T‑OA − ε · (T‑OA − T‑exhaust) |
Outdoor air follows ASHRAE 62.1-2019 (Vbz = Rp·Pz + Ra·Az). Total coil capacity uses the enthalpy form, where 4.5 = 60 min/hr × 0.075 lb/ft³ standard density; sensible capacity uses the 1.08 factor. Moist-air enthalpy is h = 0.240·T + W·(1061 + 0.444·T). Energy recovery applies the device effectiveness ε to the outdoor-to-exhaust difference in temperature and humidity before the coil, reducing both cooling and heating loads.