Every ventilator gets a score from 0 to 100% built from five factors, which maps onto the 5-point rating shown on the site (a 0% score would be 1.5 stars; a perfect score, 5). Each factor is scored against fixed reference points, not against the other products in the list, so adding a new model never moves another model’s rating. Ventilators are grouped by type: single-room ductless units, whole-house ERVs and whole-house HRVs. The two whole-house groups share the same scales; single-room units have their own scales for efficiency and value, since they move far less air.
| Factor | Measures | Weight |
|---|---|---|
| Heat recovery | sensible recovery efficiency | 25% |
| Efficiency | airflow per watt | 15% |
| Value | price per cfm of airflow | 25% |
| Quiet | noise in sones | 10% |
| Warranty | warranty length | 25% |
Where the numbers come from
For whole-house units, airflow, sensible recovery efficiency and power come from the Home Ventilating Institute (HVI) certified products directory where the unit is listed, and otherwise from the maker’s spec sheet. Single-room units are rarely in the HVI directory, so their figures come from the maker’s datasheet or manual. Noise, filters, defrost and warranty come from the maker’s spec sheet, manual or product page. Prices are checked at Amazon, the maker’s own store and other retailers, and the lowest is used.
The factors
Heat recovery is the sensible recovery efficiency at 32 °F and the lowest listed airflow: the share of the heat in the outgoing air that ends up in the incoming air. 55% scores zero and 85% full marks.
Efficiency is the rated airflow divided by the power draw at that airflow, on a log scale, so doubling the cfm per watt always counts the same. For whole-house units, airflow and power are taken at 0.4 in of static pressure: 0.7 cfm per watt scores zero and 2.5 full marks. For single-room units, airflow and power are taken at top speed: 1 cfm per watt scores zero and 8 full marks.
Value is the current price divided by the rated airflow, on a log scale, so halving the price per cfm always counts the same. For whole-house units, $20 per cfm scores zero and $5 full marks. For single-room units, $40 per cfm scores zero and $6 full marks. Units sold as a pair are scored on the pair’s price and combined airflow.
Quiet is the maker’s noise rating in sones: 3 sones scores zero and 0.3 sones full marks.
Warranty is the maker’s warranty on the unit: 1 year scores zero and 7 years full marks. A longer warranty on the core alone is listed but not scored.
What isn’t scored
Core type (ERV or HRV), install type, frost protection, filter rating, ENERGY STAR and HVI certification, core and motor warranties beyond the unit warranty, and release date are listed but not scored.
Missing data
If a figure isn’t published, that factor gets the neutral middle score (50) and the product page marks it as estimated. The exception is warranty: a maker that doesn’t publish one gets no warranty counted, so that factor scores zero, the same as the shortest warranty on the scale, and is marked estimated.
Ties and discontinued models
Products are ranked by score within each group. Discontinued models stay listed but rank below every current model and can be hidden with the “Hide discontinued” filter.