🔎 Filter Products
SRE / ASRE / FID filters apply to ERV & HRV products only — setting them will exclude exhaust and whole house fans. For ERV/HRV, CFM + SRE + ASRE must all be met within a single rating row.
📖 Whole House Fan Attic Ventilation — §150.1(c)12(B)
- Energy Code rule: at least 1 ft² of attic vent net free area (NFVA) per 750 CFM of rated whole house fan airflow — or the manufacturer's specified free vent area if greater. (2022 & 2025 Energy Code §150.1(c)12(B); prescriptive requirement in Climate Zones 8–14 per Table 150.1-A.)
- Rated airflow basis: use the airflow listed in the HVI Certified Products Directory (rated at 0.1" w.g.). Only HVI-listed whole house fans may be installed for prescriptive compliance.
- Use NFVA, not gross: deduct screen/louver/grille losses — use the vent manufacturer's published net free area, not the rough opening.
- Building code minimum still applies: CRC §R806.2 requires attic NFVA ≥ 1/150 of attic floor area (1/300 with qualifying high/low vent split). The installed venting must satisfy the larger of the two requirements.
- Exceptions: WHFs ducted directly outside are exempt from the attic-vent requirement; dwellings ≤ 500 ft² CFA are exempt from WHF requirements entirely.
- Forms: installer documents on CF2R-MCH-02-E; performance-path projects require HERS verification of WHF airflow & fan efficacy per RA3.9 (CF3R-MCH-31b-H).
🏠 Required Attic NFVA Calculator
Required NFVA (sq in) = (Rated WHF CFM ÷ 750) × 144 [rounded up]
📖 How to Use — RA3.7-1 Watt Draw Interpolation (ERV/HRV)
- Find your product in the Product Search tab using the model number from your CF1R or field documentation.
- Open the Ratings Table on the product card. Identify two rated airflow points (CFM) that bracket your field-measured airflow — one below and one above.
- Enter Point A (the lower CFM row): type its CFM value and corresponding Watt value from the table.
- Enter Point B (the higher CFM row): type its CFM value and corresponding Watt value from the table.
- Enter your Field CFM — the actual measured airflow from the field test. The calculator will interpolate the expected watt draw at that airflow.
⚡ RA3.7-1 — Watt Draw Interpolation
W_field = W_A + (W_B − W_A) × (CFM_field − CFM_A) / (CFM_B − CFM_A)
📖 How to Use — RA3.7-2 SRE Interpolation (ERV/HRV)
- Find your product in the Product Search tab using the model number from your CF1R or field documentation.
- Open the Ratings Table on the product card. Identify two rated airflow points (CFM) that bracket your field-measured airflow — one below and one above.
- Enter Point A (the lower CFM row): type its CFM value and corresponding SRE% from the table.
- Enter Point B (the higher CFM row): type its CFM value and corresponding SRE% from the table.
- Enter your Field CFM — the actual measured airflow from the field test. The calculator will interpolate the expected SRE at that airflow.
📊 RA3.7-2 — SRE Interpolation
SRE_field = SRE_A + (SRE_B − SRE_A) × (CFM_field − CFM_A) / (CFM_B − CFM_A)
📋 HVI Certified Products Directory
Section III (HRV/ERV) and Section I (exhaust & supply fans) of the HVI Certified Products Directory are the authoritative sources for HVI-certified products and the rated airflow basis for Title 24 whole house fan compliance.
Open HVI Directory →Click Model Details on any listing for full product information including additional rating points and certifications.
🗄️ CEC MAEDBS Appliance Database
The California Energy Commission's Modernized Appliance Efficiency Database System lists whole house fans and residential exhaust fans with rated airflow, watts, and efficiency. Exhaust and whole house fan data in this tool was exported from MAEDBS.
Open MAEDBS Search →Note: for 2022/2025 prescriptive WHF compliance, rated airflow is determined from the HVI Certified Products Directory, not MAEDBS.