M1505.4 Whole-House Mechanical Ventilation System
The whole house mechanical ventilation system shall provide outdoor air at a continuous rate as determined in accordance with Table M1505.4.3(1) or Equation 15-1.
Exception: The whole-house mechanical ventilation system is permitted to operate intermittently where the system has controls that enable operation for not less than 25 percent of each 4-hour segment and the ventilation rate prescribed in Table M1505.4.3(1) is multiplied by the factor determined in accordance with Table M1505.4.3(2).
CONTINUOUS WHOLE-HOUSE MECHANICAL VENTILATION SYSTEM AIRFLOW RATE REQUIREMENTS
| DWELLING UNIT FLOOR AREA (square feet) | NUMBER OF BEDROOMS | ||||
| 0 — 1 | 2 — 3 | 4 — 5 | 6 — 7 | > 7 | |
| Airflow in CFM | |||||
| < 1,500 | 30 | 45 | 60 | 75 | 90 |
| 1,501 — 3,000 | 45 | 60 | 75 | 90 | 105 |
| 3,001 — 4,500 | 60 | 75 | 90 | 105 | 120 |
| 4,501 — 6,000 | 75 | 90 | 105 | 120 | 135 |
| 6,001 — 7,500 | 90 | 105 | 120 | 135 | 150 |
| > 7,500 | 105 | 120 | 135 | 150 | 165 |
For SI: 1 square foot = 0.0929 m2, 1 cubic foot per minute = 0.0004719 m3/s.
INTERMITTENT WHOLE-HOUSE MECHANICAL VENTILATION RATE FACTORSa, b
| RUN-TIME PERCENTAGE IN EACH 4-HOUR SEGMENT | 25% | 33% | 50% | 66% | 75% | 100% |
| Factora | 4 | 3 | 2 | 1.5 | 1.3 | 1.0 |
- For ventilation system run time values between those given, the factors are permitted to be determined by interpolation.
- Extrapolation beyond the table is prohibited.
Local exhaust systems shall be designed to have the capacity to exhaust the minimum airflow rate determined in accordance with Table M1505.4.4.
MINIMUM REQUIRED LOCAL EXHAUST RATES FOR ONE- AND TWO-FAMILY DWELLINGS
| AREA TO BE EXHAUSTED | EXHAUST RATES |
| Kitchens | 100 cfm intermittent or 25 cfm continuous |
| Bathrooms-Toilet Rooms | Mechanical exhaust capacity of 50 cfm intermittent or 20 cfm continuous |
For SI: 1 cubic foot per minute = 0.0004719 m3/s.